FFsscckk -- TThhee UUNNIIXX||-- FFiillee SSyysstteemm CChheecckk PPrrooggrraamm _M_a_r_s_h_a_l_l _K_i_r_k _M_c_K_u_s_i_c_k Computer Systems Research Group Computer Science Division Department of Electrical Engineering and Computer Science University of California, Berkeley Berkeley, CA 94720 _T_. _J_. _K_o_w_a_l_s_k_i Bell Laboratories Murray Hill, New Jersey 07974 _A_B_S_T_R_A_C_T This document reflects the use of _f_s_c_k with the 4.2BSD and 4.3BSD file system organization. This is a revision of the original paper written by T. J. Kowalski. File System Check Program (_f_s_c_k) is an inter- active file system check and repair program. _F_s_c_k uses the redundant structural information in the UNIX file system to perform several consistency checks. If an inconsistency is detected, it is reported to the operator, who may elect to fix or ignore each inconsistency. These inconsistencies result from the permanent interruption of the file system updates, which are performed every time a file is modified. Unless there has been a hard- ware failure, _f_s_c_k is able to repair corrupted file systems using procedures based upon the order in which UNIX honors these file system update requests. The purpose of this document is to describe the normal updating of the file system, to discuss the possible causes of file system corruption, and to present the corrective actions implemented by _f_s_c_k_. Both the program and the interaction between the program and the operator are ----------- |-UNIX is a trademark of Bell Laboratories. This work was done under grants from the National Science Foundation under grant MCS80-05144, and the Defense Advance Research Projects Agency (DoD) under Arpa Order No. 4031 monitored by Naval Elec- tronic System Command under Contract No. N00039-82-C-0235. SMM:3-2 The UNIX File System Check Program described. Revised October 7, 1996 The UNIX File System Check Program SMM:3-3 TTAABBLLEE OOFF CCOONNTTEENNTTSS 11.. IInnttrroodduuccttiioonn 22.. OOvveerrvviieeww ooff tthhee ffiillee ssyysstteemm 2.1. Superblock 2.2. Summary Information 2.3. Cylinder groups 2.4. Fragments 2.5. Updates to the file system 33.. FFiixxiinngg ccoorrrruupptteedd ffiillee ssyysstteemmss 3.1. Detecting and correcting corruption 3.2. Super block checking 3.3. Free block checking 3.4. Checking the inode state 3.5. Inode links 3.6. Inode data size 3.7. Checking the data associated with an inode 3.8. File system connectivity AAcckknnoowwlleeddggeemmeennttss RReeffeerreenncceess 44.. AAppppeennddiixx AA 4.1. Conventions 4.2. Initialization 4.3. Phase 1 - Check Blocks and Sizes 4.4. Phase 1b - Rescan for more Dups 4.5. Phase 2 - Check Pathnames 4.6. Phase 3 - Check Connectivity 4.7. Phase 4 - Check Reference Counts 4.8. Phase 5 - Check Cyl groups 4.9. Cleanup SMM:3-4 The UNIX File System Check Program 11.. IInnttrroodduuccttiioonn This document reflects the use of _f_s_c_k with the 4.2BSD and 4.3BSD file system organization. This is a revision of the original paper written by T. J. Kowalski. When a UNIX operating system is brought up, a consis- tency check of the file systems should always be performed. This precautionary measure helps to insure a reliable envi- ronment for file storage on disk. If an inconsistency is discovered, corrective action must be taken. _F_s_c_k runs in two modes. Normally it is run non-interactively by the sys- tem after a normal boot. When running in this mode, it will only make changes to the file system that are known to always be correct. If an unexpected inconsistency is found _f_s_c_k will exit with a non-zero exit status, leaving the sys- tem running single-user. Typically the operator then runs _f_s_c_k interactively. When running in this mode, each problem is listed followed by a suggested corrective action. The operator must decide whether or not the suggested correction should be made. The purpose of this memo is to dispel the mystique sur- rounding file system inconsistencies. It first describes the updating of the file system (the calm before the storm) and then describes file system corruption (the storm). Finally, the set of deterministic corrective actions used by _f_s_c_k (the Coast Guard to the rescue) is presented. 22.. OOvveerrvviieeww ooff tthhee ffiillee ssyysstteemm The file system is discussed in detail in [Mckusick84]; this section gives a brief overview. 22..11.. SSuuppeerrbblloocckk A file system is described by its _s_u_p_e_r_-_b_l_o_c_k. The super-block is built when the file system is created (_n_e_w_f_s(8)) and never changes. The super-block contains the basic parameters of the file system, such as the number of data blocks it contains and a count of the maximum number of files. Because the super-block contains critical data, _n_e_w_f_s replicates it to protect against catastrophic loss. The _d_e_f_a_u_l_t _s_u_p_e_r _b_l_o_c_k always resides at a fixed offset from the beginning of the file system's disk partition. The _r_e_d_u_n_d_a_n_t _s_u_p_e_r _b_l_o_c_k_s are not referenced unless a head crash or other hard disk error causes the default super- block to be unusable. The redundant blocks are sprinkled throughout the disk partition. Within the file system are files. Certain files are distinguished as directories and contain collections of pointers to files that may themselves be directories. Every file has a descriptor associated with it called an _i_n_o_d_e. The UNIX File System Check Program SMM:3-5 The inode contains information describing ownership of the file, time stamps indicating modification and access times for the file, and an array of indices pointing to the data blocks for the file. In this section, we assume that the first 12 blocks of the file are directly referenced by val- ues stored in the inode structure itself|-. The inode struc- ture may also contain references to indirect blocks contain- ing further data block indices. In a file system with a 4096 byte block size, a singly indirect block contains 1024 further block addresses, a doubly indirect block contains 1024 addresses of further single indirect blocks, and a triply indirect block contains 1024 addresses of further doubly indirect blocks (the triple indirect block is never needed in practice). In order to create files with up to 2|^32 bytes, using only two levels of indirection, the minimum size of a file system block is 4096 bytes. The size of file system blocks can be any power of two greater than or equal to 4096. The block size of the file system is maintained in the super- block, so it is possible for file systems of different block sizes to be accessible simultaneously on the same system. The block size must be decided when _n_e_w_f_s creates the file system; the block size cannot be subsequently changed with- out rebuilding the file system. 22..22.. SSuummmmaarryy iinnffoorrmmaattiioonn Associated with the super block is non replicated _s_u_m_- _m_a_r_y _i_n_f_o_r_m_a_t_i_o_n. The summary information changes as the file system is modified. The summary information contains the number of blocks, fragments, inodes and directories in the file system. 22..33.. CCyylliinnddeerr ggrroouuppss The file system partitions the disk into one or more areas called _c_y_l_i_n_d_e_r _g_r_o_u_p_s. A cylinder group is comprised of one or more consecutive cylinders on a disk. Each cylin- der group includes inode slots for files, a _b_l_o_c_k _m_a_p describing available blocks in the cylinder group, and sum- mary information describing the usage of data blocks within the cylinder group. A fixed number of inodes is allocated for each cylinder group when the file system is created. The current policy is to allocate one inode for each 2048 bytes of disk space; this is expected to be far more inodes than will ever be needed. All the cylinder group bookkeeping information could be placed at the beginning of each cylinder group. However if this approach were used, all the redundant information would ----------- |-The actual number may vary from system to system, but is usually in the range 5-13. SMM:3-6 The UNIX File System Check Program be on the top platter. A single hardware failure that destroyed the top platter could cause the loss of all copies of the redundant super-blocks. Thus the cylinder group bookkeeping information begins at a floating offset from the beginning of the cylinder group. The offset for the _i_+_1st cylinder group is about one track further from the beginning of the cylinder group than it was for the _ith cylinder group. In this way, the redundant information spirals down into the pack; any single track, cylinder, or platter can be lost without losing all copies of the super-blocks. Except for the first cylinder group, the space between the begin- ning of the cylinder group and the beginning of the cylinder group information stores data. 22..44.. FFrraaggmmeennttss To avoid waste in storing small files, the file system space allocator divides a single file system block into one or more _f_r_a_g_m_e_n_t_s. The fragmentation of the file system is specified when the file system is created; each file system block can be optionally broken into 2, 4, or 8 addressable fragments. The lower bound on the size of these fragments is constrained by the disk sector size; typically 512 bytes is the lower bound on fragment size. The block map associ- ated with each cylinder group records the space availability at the fragment level. Aligned fragments are examined to determine block availability. On a file system with a block size of 4096 bytes and a fragment size of 1024 bytes, a file is represented by zero or more 4096 byte blocks of data, and possibly a single fragmented block. If a file system block must be fragmented to obtain space for a small amount of data, the remainder of the block is made available for allocation to other files. For example, consider an 11000 byte file stored on a 4096/1024 byte file system. This file uses two full size blocks and a 3072 byte fragment. If no fragments with at least 3072 bytes are available when the file is created, a full size block is split yielding the necessary 3072 byte fragment and an unused 1024 byte fragment. This remaining fragment can be allocated to another file, as needed. 22..55.. UUppddaatteess ttoo tthhee ffiillee ssyysstteemm Every working day hundreds of files are created, modi- fied, and removed. Every time a file is modified, the oper- ating system performs a series of file system updates. These updates, when written on disk, yield a consistent file system. The file system stages all modifications of criti- cal information; modification can either be completed or cleanly backed out after a crash. Knowing the information that is first written to the file system, deterministic pro- cedures can be developed to repair a corrupted file system. To understand this process, the order that the update The UNIX File System Check Program SMM:3-7 requests were being honored must first be understood. When a user program does an operation to change the file system, such as a _w_r_i_t_e, the data to be written is copied into an internal _i_n_-_c_o_r_e buffer in the kernel. Nor- mally, the disk update is handled asynchronously; the user process is allowed to proceed even though the data has not yet been written to the disk. The data, along with the inode information reflecting the change, is eventually writ- ten out to disk. The real disk write may not happen until long after the _w_r_i_t_e system call has returned. Thus at any given time, the file system, as it resides on the disk, lags the state of the file system represented by the in-core information. The disk information is updated to reflect the in-core information when the buffer is required for another use, when a _s_y_n_c(2) is done (at 30 second intervals) by _/_e_t_c_/_u_p_d_a_t_e(8), or by manual operator intervention with the _s_y_n_c(8) command. If the system is halted without writing out the in-core information, the file system on the disk will be in an inconsistent state. If all updates are done asynchronously, several serious inconsistencies can arise. One inconsistency is that a block may be claimed by two inodes. Such an inconsistency can occur when the system is halted before the pointer to the block in the old inode has been cleared in the copy of the old inode on the disk, and after the pointer to the block in the new inode has been written out to the copy of the new inode on the disk. Here, there is no deterministic method for deciding which inode should really claim the block. A similar problem can arise with a multiply claimed inode. The problem with asynchronous inode updates can be avoided by doing all inode deallocations synchronously. Consequently, inodes and indirect blocks are written to the disk synchronously (_i_._e_. the process blocks until the infor- mation is really written to disk) when they are being deal- located. Similarly inodes are kept consistent by syn- chronously deleting, adding, or changing directory entries. 33.. FFiixxiinngg ccoorrrruupptteedd ffiillee ssyysstteemmss A file system can become corrupted in several ways. The most common of these ways are improper shutdown proce- dures and hardware failures. File systems may become corrupted during an _u_n_c_l_e_a_n _h_a_l_t. This happens when proper shutdown procedures are not observed, physically write-protecting a mounted file system, or a mounted file system is taken off-line. The most common operator procedural failure is forgetting to _s_y_n_c the system SMM:3-8 The UNIX File System Check Program before halting the CPU. File systems may become further corrupted if proper startup procedures are not observed, e.g., not checking a file system for inconsistencies, and not repairing inconsis- tencies. Allowing a corrupted file system to be used (and, thus, to be modified further) can be disastrous. Any piece of hardware can fail at any time. Failures can be as subtle as a bad block on a disk pack, or as bla- tant as a non-functional disk-controller. 33..11.. DDeetteeccttiinngg aanndd ccoorrrreeccttiinngg ccoorrrruuppttiioonn Normally _f_s_c_k is run non-interactively. In this mode it will only fix corruptions that are expected to occur from an unclean halt. These actions are a proper subset of the actions that _f_s_c_k will take when it is running interac- tively. Throughout this paper we assume that _f_s_c_k is being run interactively, and all possible errors can be encoun- tered. When an inconsistency is discovered in this mode, _f_s_c_k reports the inconsistency for the operator to chose a corrective action. A quiescent|= file system may be checked for structural integrity by performing consistency checks on the redundant data intrinsic to a file system. The redundant data is either read from the file system, or computed from other known values. The file system mmuusstt be in a quiescent state when _f_s_c_k is run, since _f_s_c_k is a multi-pass program. In the following sections, we discuss methods to dis- cover inconsistencies and possible corrective actions for the cylinder group blocks, the inodes, the indirect blocks, and the data blocks containing directory entries. 33..22.. SSuuppeerr--bblloocckk cchheecckkiinngg The most commonly corrupted item in a file system is the summary information associated with the super-block. The summary information is prone to corruption because it is modified with every change to the file system's blocks or inodes, and is usually corrupted after an unclean halt. The super-block is checked for inconsistencies involv- ing file-system size, number of inodes, free-block count, and the free-inode count. The file-system size must be larger than the number of blocks used by the super-block and the number of blocks used by the list of inodes. The file- system size and layout information are the most critical pieces of information for _f_s_c_k. While there is no way to actually check these sizes, since they are statically ----------- |= I.e., unmounted and not being written on. The UNIX File System Check Program SMM:3-9 determined by _n_e_w_f_s, _f_s_c_k can check that these sizes are within reasonable bounds. All other file system checks require that these sizes be correct. If _f_s_c_k detects cor- ruption in the static parameters of the default super-block, _f_s_c_k requests the operator to specify the location of an alternate super-block. 33..33.. FFrreeee bblloocckk cchheecckkiinngg _F_s_c_k checks that all the blocks marked as free in the cylinder group block maps are not claimed by any files. When all the blocks have been initially accounted for, _f_s_c_k checks that the number of free blocks plus the number of blocks claimed by the inodes equals the total number of blocks in the file system. If anything is wrong with the block allocation maps, _f_s_c_k will rebuild them, based on the list it has computed of allocated blocks. The summary information associated with the super-block counts the total number of free blocks within the file sys- tem. _F_s_c_k compares this count to the number of free blocks it found within the file system. If the two counts do not agree, then _f_s_c_k replaces the incorrect count in the summary information by the actual free-block count. The summary information counts the total number of free inodes within the file system. _F_s_c_k compares this count to the number of free inodes it found within the file system. If the two counts do not agree, then _f_s_c_k replaces the incorrect count in the summary information by the actual free-inode count. 33..44.. CChheecckkiinngg tthhee iinnooddee ssttaattee An individual inode is not as likely to be corrupted as the allocation information. However, because of the great number of active inodes, a few of the inodes are usually corrupted. The list of inodes in the file system is checked sequentially starting with inode 2 (inode 0 marks unused inodes; inode 1 is saved for future generations) and pro- gressing through the last inode in the file system. The state of each inode is checked for inconsistencies involving format and type, link count, duplicate blocks, bad blocks, and inode size. Each inode contains a mode word. This mode word describes the type and state of the inode. Inodes must be one of six types: regular inode, directory inode, symbolic link inode, special block inode, special character inode, or socket inode. Inodes may be found in one of three SMM:3-10 The UNIX File System Check Program allocation states: unallocated, allocated, and neither unal- located nor allocated. This last state suggests an incor- rectly formated inode. An inode can get in this state if bad data is written into the inode list. The only possible corrective action is for _f_s_c_k is to clear the inode. 33..55.. IInnooddee lliinnkkss Each inode counts the total number of directory entries linked to the inode. _F_s_c_k verifies the link count of each inode by starting at the root of the file system, and descending through the directory structure. The actual link count for each inode is calculated during the descent. If the stored link count is non-zero and the actual link count is zero, then no directory entry appears for the inode. If this happens, _f_s_c_k will place the disconnected file in the _l_o_s_t_+_f_o_u_n_d directory. If the stored and actual link counts are non-zero and unequal, a directory entry may have been added or removed without the inode being updated. If this happens, _f_s_c_k replaces the incorrect stored link count by the actual link count. Each inode contains a list, or pointers to lists (indi- rect blocks), of all the blocks claimed by the inode. Since indirect blocks are owned by an inode, inconsistencies in indirect blocks directly affect the inode that owns it. _F_s_c_k compares each block number claimed by an inode against a list of already allocated blocks. If another inode already claims a block number, then the block number is added to a list of _d_u_p_l_i_c_a_t_e _b_l_o_c_k_s. Otherwise, the list of allocated blocks is updated to include the block number. If there are any duplicate blocks, _f_s_c_k will perform a partial second pass over the inode list to find the inode of the duplicated block. The second pass is needed, since without examining the files associated with these inodes for correct content, not enough information is available to determine which inode is corrupted and should be cleared. If this condition does arise (only hardware failure will cause it), then the inode with the earliest modify time is usually incorrect, and should be cleared. If this happens, _f_s_c_k prompts the operator to clear both inodes. The opera- tor must decide which one should be kept and which one should be cleared. _F_s_c_k checks the range of each block number claimed by an inode. If the block number is lower than the first data block in the file system, or greater than the last data block, then the block number is a _b_a_d _b_l_o_c_k _n_u_m_b_e_r. Many bad blocks in an inode are usually caused by an indirect block that was not written to the file system, a condition which can only occur if there has been a hardware failure. The UNIX File System Check Program SMM:3-11 If an inode contains bad block numbers, _f_s_c_k prompts the operator to clear it. 33..66.. IInnooddee ddaattaa ssiizzee Each inode contains a count of the number of data blocks that it contains. The number of actual data blocks is the sum of the allocated data blocks and the indirect blocks. _F_s_c_k computes the actual number of data blocks and compares that block count against the actual number of blocks the inode claims. If an inode contains an incorrect count _f_s_c_k prompts the operator to fix it. Each inode contains a thirty-two bit size field. The size is the number of data bytes in the file associated with the inode. The consistency of the byte size field is roughly checked by computing from the size field the maximum number of blocks that should be associated with the inode, and comparing that expected block count against the actual number of blocks the inode claims. 33..77.. CChheecckkiinngg tthhee ddaattaa aassssoocciiaatteedd wwiitthh aann iinnooddee An inode can directly or indirectly reference three kinds of data blocks. All referenced blocks must be the same kind. The three types of data blocks are: plain data blocks, symbolic link data blocks, and directory data blocks. Plain data blocks contain the information stored in a file; symbolic link data blocks contain the path name stored in a link. Directory data blocks contain directory entries. _F_s_c_k can only check the validity of directory data blocks. Each directory data block is checked for several types of inconsistencies. These inconsistencies include directory inode numbers pointing to unallocated inodes, directory inode numbers that are greater than the number of inodes in the file system, incorrect directory inode numbers for ``..'' and ``....'', and directories that are not attached to the file system. If the inode number in a directory data block references an unallocated inode, then _f_s_c_k will remove that directory entry. Again, this condition can only arise when there has been a hardware failure. _F_s_c_k also checks for directories with unallocated blocks (holes). Such directories should never be created. When found, _f_s_c_k will prompt the user to adjust the length of the offending directory which is done by shortening the size of the directory to the end of the last allocated block preceeding the hole. Unfortunately, this means that another Phase 1 run has to be done. _F_s_c_k will remind the user to rerun fsck after repairing a directory containing an unallo- cated block. SMM:3-12 The UNIX File System Check Program If a directory entry inode number references outside the inode list, then _f_s_c_k will remove that directory entry. This condition occurs if bad data is written into a direc- tory data block. The directory inode number entry for ``..'' must be the first entry in the directory data block. The inode number for ``..'' must reference itself; e.g., it must equal the inode number for the directory data block. The directory inode number entry for ``....'' must be the second entry in the directory data block. Its value must equal the inode number for the parent of the directory entry (or the inode number of the directory data block if the directory is the root directory). If the directory inode numbers are incor- rect, _f_s_c_k will replace them with the correct values. If there are multiple hard links to a directory, the first one encountered is considered the real parent to which ``....'' should point; _f_s_c_k recommends deletion for the subsequently discovered names. 33..88.. FFiillee ssyysstteemm ccoonnnneeccttiivviittyy _F_s_c_k checks the general connectivity of the file sys- tem. If directories are not linked into the file system, then _f_s_c_k links the directory back into the file system in the _l_o_s_t_+_f_o_u_n_d directory. This condition only occurs when there has been a hardware failure. AAcckknnoowwlleeddggeemmeennttss I thank Bill Joy, Sam Leffler, Robert Elz and Dennis Ritchie for their suggestions and help in implementing the new file system. Thanks also to Robert Henry for his edito- rial input to get this document together. Finally we thank our sponsors, the National Science Foundation under grant MCS80-05144, and the Defense Advance Research Projects Agency (DoD) under Arpa Order No. 4031 monitored by Naval Electronic System Command under Contract No. N00039-82-C-0235. (Kirk McKusick, July 1983) I would like to thank Larry A. Wehr for advice that lead to the first version of _f_s_c_k and Rick B. Brandt for adapting _f_s_c_k to UNIX/TS. (T. Kowalski, July 1979) RReeffeerreenncceess [Dolotta78] Dolotta, T. A., and Olsson, S. B. eds., _U_N_I_X _U_s_e_r_'_s _M_a_n_u_a_l_, _E_d_i_t_i_o_n _1_._1, January 1978. The UNIX File System Check Program SMM:3-13 [Joy83] Joy, W., Cooper, E., Fabry, R., Leffler, S., McKusick, M., and Mosher, D. 4.2BSD System Manual, _U_n_i_v_e_r_s_i_t_y _o_f _C_a_l_i_f_o_r_n_i_a _a_t _B_e_r_k_e_l_e_y, _C_o_m_p_u_t_e_r _S_y_s_t_e_m_s _R_e_s_e_a_r_c_h _G_r_o_u_p _T_e_c_h_n_i_c_a_l _R_e_p_o_r_t #4, 1982. [McKusick84] McKusick, M., Joy, W., Leffler, S., and Fabry, R. A Fast File System for UNIX, _A_C_M _T_r_a_n_s_a_c_t_i_o_n_s _o_n _C_o_m_p_u_t_e_r _S_y_s_t_e_m_s _2, 3. pp. 181-197, August 1984. [Ritchie78] Ritchie, D. M., and Thompson, K., The UNIX Time-Sharing System, _T_h_e _B_e_l_l _S_y_s_- _t_e_m _T_e_c_h_n_i_c_a_l _J_o_u_r_n_a_l 5577, 6 (July-August 1978, Part 2), pp. 1905-29. [Thompson78] Thompson, K., UNIX Implementation, _T_h_e _B_e_l_l _S_y_s_t_e_m _T_e_c_h_n_i_c_a_l _J_o_u_r_n_a_l 5577, 6 (July-August 1978, Part 2), pp. 1931-46. SMM:3-14 The UNIX File System Check Program 44.. AAppppeennddiixx AA -- FFsscckk EErrrroorr CCoonnddiittiioonnss 44..11.. CCoonnvveennttiioonnss _F_s_c_k is a multi-pass file system check program. Each file system pass invokes a different Phase of the _f_s_c_k pro- gram. After the initial setup, _f_s_c_k performs successive Phases over each file system, checking blocks and sizes, path-names, connectivity, reference counts, and the map of free blocks, (possibly rebuilding it), and performs some cleanup. Normally _f_s_c_k is run non-interactively to _p_r_e_e_n the file systems after an unclean halt. While preen'ing a file sys- tem, it will only fix corruptions that are expected to occur from an unclean halt. These actions are a proper subset of the actions that _f_s_c_k will take when it is running interac- tively. Throughout this appendix many errors have several options that the operator can take. When an inconsistency is detected, _f_s_c_k reports the error condition to the opera- tor. If a response is required, _f_s_c_k prints a prompt mes- sage and waits for a response. When preen'ing most errors are fatal. For those that are expected, the response taken is noted. This appendix explains the meaning of each error condition, the possible responses, and the related error conditions. The error conditions are organized by the _P_h_a_s_e of the _f_s_c_k program in which they can occur. The error conditions that may occur in more than one Phase will be discussed in ini- tialization. 44..22.. IInniittiiaalliizzaattiioonn Before a file system check can be performed, certain tables have to be set up and certain files opened. This section concerns itself with the opening of files and the initialization of tables. This section lists error condi- tions resulting from command line options, memory requests, opening of files, status of files, file system size checks, and creation of the scratch file. All the initialization errors are fatal when the file system is being preen'ed. _C ooppttiioonn?? _C is not a legal option to _f_s_c_k; legal options are -b, -c, -y, -n, and -p. _F_s_c_k terminates on this error condition. See the _f_s_c_k(8) manual entry for further detail. ccaannnnoott aalllloocc NNNNNN bbyytteess ffoorr bblloocckkmmaapp ccaannnnoott aalllloocc NNNNNN bbyytteess ffoorr ffrreeeemmaapp ccaannnnoott aalllloocc NNNNNN bbyytteess ffoorr ssttaatteemmaapp ccaannnnoott aalllloocc NNNNNN bbyytteess ffoorr llnnccnnttpp The UNIX File System Check Program SMM:3-15 _F_s_c_k's request for memory for its virtual memory tables failed. This should never happen. _F_s_c_k terminates on this error condition. See a guru. CCaann''tt ooppeenn cchheecckklliisstt ffiillee:: _F The file system checklist file _F (usually _/_e_t_c_/_f_s_t_a_b) can not be opened for reading. _F_s_c_k terminates on this error condition. Check access modes of _F. CCaann''tt ssttaatt rroooott _F_s_c_k's request for statistics about the root directory ``/'' failed. This should never happen. _F_s_c_k terminates on this error condition. See a guru. CCaann''tt ssttaatt _F CCaann''tt mmaakkee sseennssee oouutt ooff nnaammee _F _F_s_c_k's request for statistics about the file system _F failed. When running manually, it ignores this file system and continues checking the next file system given. Check access modes of _F. CCaann''tt ooppeenn _F _F_s_c_k's request attempt to open the file system _F failed. When running manually, it ignores this file system and con- tinues checking the next file system given. Check access modes of _F. _F:: ((NNOO WWRRIITTEE)) Either the -n flag was specified or _f_s_c_k's attempt to open the file system _F for writing failed. When running manu- ally, all the diagnostics are printed out, but no modifica- tions are attempted to fix them. ffiillee iiss nnoott aa bblloocckk oorr cchhaarraacctteerr ddeevviiccee;; OOKK You have given _f_s_c_k a regular file name by mistake. Check the type of the file specified. Possible responses to the OK prompt are: YES ignore this error condition. NO ignore this file system and continues checking the next file system given. UUNNDDEEFFIINNEEDD OOPPTTIIMMIIZZAATTIIOONN IINN SSUUPPEERRBBLLOOCCKK ((SSEETT TTOO DDEEFFAAUULLTT)) The superblock optimization parameter is neither OPT_TIME nor OPT_SPACE. SMM:3-16 The UNIX File System Check Program Possible responses to the SET TO DEFAULT prompt are: YES The superblock is set to request optimization to mini- mize running time of the system. (If optimization to minimize disk space utilization is desired, it can be set using _t_u_n_e_f_s(8).) NO ignore this error condition. IIMMPPOOSSSSIIBBLLEE MMIINNFFRREEEE==_D IINN SSUUPPEERRBBLLOOCCKK ((SSEETT TTOO DDEEFFAAUULLTT)) The superblock minimum space percentage is greater than 99% or less then 0%. Possible responses to the SET TO DEFAULT prompt are: YES The minfree parameter is set to 10%. (If some other percentage is desired, it can be set using _t_u_n_e_f_s(8).) NO ignore this error condition. IIMMPPOOSSSSIIBBLLEE IINNTTEERRLLEEAAVVEE==_D IINN SSUUPPEERRBBLLOOCCKK ((SSEETT TTOO DDEEFFAAUULLTT)) The file system interleave is less than or equal to zero. Possible responses to the SET TO DEFAULT prompt are: YES The interleave parameter is set to 1. NO ignore this error condition. IIMMPPOOSSSSIIBBLLEE NNPPSSEECCTT==_D IINN SSUUPPEERRBBLLOOCCKK ((SSEETT TTOO DDEEFFAAUULLTT)) The number of physical sectors per track is less than the number of usable sectors per track. Possible responses to the SET TO DEFAULT prompt are: YES The npsect parameter is set to the number of usable sectors per track. NO ignore this error condition. One of the following messages will appear: MMAAGGIICC NNUUMMBBEERR WWRROONNGG NNCCGG OOUUTT OOFF RRAANNGGEE CCPPGG OOUUTT OOFF RRAANNGGEE NNCCYYLL DDOOEESS NNOOTT JJIIVVEE WWIITTHH NNCCGG**CCPPGG SSIIZZEE PPRREEPPOOSSTTEERROOUUSSLLYY LLAARRGGEE TTRRAASSHHEEDD VVAALLUUEESS IINN SSUUPPEERR BBLLOOCCKK and will be followed by the message: _F:: BBAADD SSUUPPEERR BBLLOOCCKK:: _B UUSSEE --bb OOPPTTIIOONN TTOO FFSSCCKK TTOO SSPPEECCIIFFYY LLOOCCAATTIIOONN OOFF AANN AALLTTEERRNNAATTEE The UNIX File System Check Program SMM:3-17 SSUUPPEERR--BBLLOOCCKK TTOO SSUUPPPPLLYY NNEEEEDDEEDD IINNFFOORRMMAATTIIOONN;; SSEEEE ffsscckk((88)).. The super block has been corrupted. An alternative super block must be selected from among those listed by _n_e_w_f_s (8) when the file system was created. For file systems with a blocksize less than 32K, specifying -b 32 is a good first choice. IINNTTEERRNNAALL IINNCCOONNSSIISSTTEENNCCYY:: _M _F_s_c_k's has had an internal panic, whose message is specified as _M. This should never happen. See a guru. CCAANN NNOOTT SSEEEEKK:: BBLLKK _B ((CCOONNTTIINNUUEE)) _F_s_c_k's request for moving to a specified block number _B in the file system failed. This should never happen. See a guru. Possible responses to the CONTINUE prompt are: YES attempt to continue to run the file system check. Often, however the problem will persist. This error condition will not allow a complete check of the file system. A second run of _f_s_c_k should be made to re- check this file system. If the block was part of the virtual memory buffer cache, _f_s_c_k will terminate with the message ``Fatal I/O error''. NO terminate the program. CCAANN NNOOTT RREEAADD:: BBLLKK _B ((CCOONNTTIINNUUEE)) _F_s_c_k's request for reading a specified block number _B in the file system failed. This should never happen. See a guru. Possible responses to the CONTINUE prompt are: YES attempt to continue to run the file system check. It will retry the read and print out the message: TTHHEE FFOOLLLLOOWWIINNGG SSEECCTTOORRSS CCOOUULLDD NNOOTT BBEE RREEAADD:: _N where _N indicates the sectors that could not be read. If _f_s_c_k ever tries to write back one of the blocks on which the read failed it will print the message: WWRRIITTIINNGG ZZEERROO''EEDD BBLLOOCCKK _N TTOO DDIISSKK where _N indicates the sector that was written with zero's. If the disk is experiencing hardware problems, the problem will persist. This error condition will not allow a complete check of the file system. A sec- ond run of _f_s_c_k should be made to re-check this file system. If the block was part of the virtual memory buffer cache, _f_s_c_k will terminate with the message ``Fatal I/O error''. SMM:3-18 The UNIX File System Check Program NO terminate the program. CCAANN NNOOTT WWRRIITTEE:: BBLLKK _B ((CCOONNTTIINNUUEE)) _F_s_c_k's request for writing a specified block number _B in the file system failed. The disk is write-protected; check the write protect lock on the drive. If that is not the prob- lem, see a guru. Possible responses to the CONTINUE prompt are: YES attempt to continue to run the file system check. The write operation will be retried with the failed blocks indicated by the message: TTHHEE FFOOLLLLOOWWIINNGG SSEECCTTOORRSS CCOOUULLDD NNOOTT BBEE WWRRIITTTTEENN:: _N where _N indicates the sectors that could not be writ- ten. If the disk is experiencing hardware problems, the problem will persist. This error condition will not allow a complete check of the file system. A sec- ond run of _f_s_c_k should be made to re-check this file system. If the block was part of the virtual memory buffer cache, _f_s_c_k will terminate with the message ``Fatal I/O error''. NO terminate the program. bbaadd iinnooddee nnuummbbeerr DDDDDD ttoo ggiinnooddee An internal error has attempted to read non-existent inode _D_D_D. This error causes _f_s_c_k to exit. See a guru. 44..33.. PPhhaassee 11 -- CChheecckk BBlloocckkss aanndd SSiizzeess This phase concerns itself with the inode list. This section lists error conditions resulting from checking inode types, setting up the zero-link-count table, examining inode block numbers for bad or duplicate blocks, checking inode size, and checking inode format. All errors in this phase except IINNCCOORRRREECCTT BBLLOOCCKK CCOOUUNNTT and PPAARRTTIIAALLLLYY TTRRUUNNCCAATTEEDD IINNOODDEE are fatal if the file system is being preen'ed. UUNNKKNNOOWWNN FFIILLEE TTYYPPEE II==_I ((CCLLEEAARR)) The mode word of the inode _I indicates that the inode is not a special block inode, special character inode, socket inode, regular inode, symbolic link, or directory inode. Possible responses to the CLEAR prompt are: YES de-allocate inode _I by zeroing its contents. This will always invoke the UNALLOCATED error condition in Phase 2 for each directory entry pointing to this inode. The UNIX File System Check Program SMM:3-19 NO ignore this error condition. PPAARRTTIIAALLLLYY TTRRUUNNCCAATTEEDD IINNOODDEE II==_I ((SSAALLVVAAGGEE)) _F_s_c_k has found inode _I whose size is shorter than the number of blocks allocated to it. This condition should only occur if the system crashes while in the midst of truncating a file. When preen'ing the file system, _f_s_c_k completes the truncation to the specified size. Possible responses to SALVAGE are: YES complete the truncation to the size specified in the inode. NO ignore this error condition. LLIINNKK CCOOUUNNTT TTAABBLLEE OOVVEERRFFLLOOWW ((CCOONNTTIINNUUEE)) An internal table for _f_s_c_k containing allocated inodes with a link count of zero cannot allocate more memory. Increase the virtual memory for _f_s_c_k. Possible responses to the CONTINUE prompt are: YES continue with the program. This error condition will not allow a complete check of the file system. A sec- ond run of _f_s_c_k should be made to re-check this file system. If another allocated inode with a zero link count is found, this error condition is repeated. NO terminate the program. _B BBAADD II==_I Inode _I contains block number _B with a number lower than the number of the first data block in the file system or greater than the number of the last block in the file system. This error condition may invoke the EEXXCCEESSSSIIVVEE BBAADD BBLLKKSS error con- dition in Phase 1 (see next paragraph) if inode _I has too many block numbers outside the file system range. This error condition will always invoke the BBAADD//DDUUPP error condi- tion in Phase 2 and Phase 4. EEXXCCEESSSSIIVVEE BBAADD BBLLKKSS II==_I ((CCOONNTTIINNUUEE)) There is more than a tolerable number (usually 10) of blocks with a number lower than the number of the first data block in the file system or greater than the number of last block in the file system associated with inode _I. Possible responses to the CONTINUE prompt are: SMM:3-20 The UNIX File System Check Program YES ignore the rest of the blocks in this inode and con- tinue checking with the next inode in the file system. This error condition will not allow a complete check of the file system. A second run of _f_s_c_k should be made to re-check this file system. NO terminate the program. BBAADD SSTTAATTEE DDDDDD TTOO BBLLKKEERRRR An internal error has scrambled _f_s_c_k's state map to have the impossible value _D_D_D. _F_s_c_k exits immediately. See a guru. _B DDUUPP II==_I Inode _I contains block number _B that is already claimed by another inode. This error condition may invoke the EEXXCCEESS-- SSIIVVEE DDUUPP BBLLKKSS error condition in Phase 1 if inode _I has too many block numbers claimed by other inodes. This error con- dition will always invoke Phase 1b and the BBAADD//DDUUPP error condition in Phase 2 and Phase 4. EEXXCCEESSSSIIVVEE DDUUPP BBLLKKSS II==_I ((CCOONNTTIINNUUEE)) There is more than a tolerable number (usually 10) of blocks claimed by other inodes. Possible responses to the CONTINUE prompt are: YES ignore the rest of the blocks in this inode and con- tinue checking with the next inode in the file system. This error condition will not allow a complete check of the file system. A second run of _f_s_c_k should be made to re-check this file system. NO terminate the program. DDUUPP TTAABBLLEE OOVVEERRFFLLOOWW ((CCOONNTTIINNUUEE)) An internal table in _f_s_c_k containing duplicate block numbers cannot allocate any more space. Increase the amount of vir- tual memory available to _f_s_c_k. Possible responses to the CONTINUE prompt are: YES continue with the program. This error condition will not allow a complete check of the file system. A sec- ond run of _f_s_c_k should be made to re-check this file system. If another duplicate block is found, this error condition will repeat. NO terminate the program. The UNIX File System Check Program SMM:3-21 PPAARRTTIIAALLLLYY AALLLLOOCCAATTEEDD IINNOODDEE II==_I ((CCLLEEAARR)) Inode _I is neither allocated nor unallocated. Possible responses to the CLEAR prompt are: YES de-allocate inode _I by zeroing its contents. NO ignore this error condition. IINNCCOORRRREECCTT BBLLOOCCKK CCOOUUNNTT II==_I ((_X sshhoouulldd bbee _Y)) ((CCOORRRREECCTT)) The block count for inode _I is _X blocks, but should be _Y blocks. When preen'ing the count is corrected. Possible responses to the CORRECT prompt are: YES replace the block count of inode _I with _Y. NO ignore this error condition. 44..44.. PPhhaassee 11BB:: RReessccaann ffoorr MMoorree DDuuppss When a duplicate block is found in the file system, the file system is rescanned to find the inode that previously claimed that block. This section lists the error condition when the duplicate block is found. _B DDUUPP II==_I Inode _I contains block number _B that is already claimed by another inode. This error condition will always invoke the BBAADD//DDUUPP error condition in Phase 2. You can determine which inodes have overlapping blocks by examining this error con- dition and the DUP error condition in Phase 1. 44..55.. PPhhaassee 22 -- CChheecckk PPaatthhnnaammeess This phase concerns itself with removing directory entries pointing to error conditioned inodes from Phase 1 and Phase 1b. This section lists error conditions resulting from root inode mode and status, directory inode pointers in range, and directory entries pointing to bad inodes, and directory integrity checks. All errors in this phase are fatal if the file system is being preen'ed, except for directories not being a multiple of the blocks size and extraneous hard links. RROOOOTT IINNOODDEE UUNNAALLLLOOCCAATTEEDD ((AALLLLOOCCAATTEE)) The root inode (usually inode number 2) has no allocate mode bits. This should never happen. Possible responses to the ALLOCATE prompt are: SMM:3-22 The UNIX File System Check Program YES allocate inode 2 as the root inode. The files and directories usually found in the root will be recovered in Phase 3 and put into _l_o_s_t_+_f_o_u_n_d. If the attempt to allocate the root fails, _f_s_c_k will exit with the mes- sage: CCAANNNNOOTT AALLLLOOCCAATTEE RROOOOTT IINNOODDEE. NO _f_s_c_k will exit. RROOOOTT IINNOODDEE NNOOTT DDIIRREECCTTOORRYY ((RREEAALLLLOOCCAATTEE)) The root inode (usually inode number 2) is not directory inode type. Possible responses to the REALLOCATE prompt are: YES clear the existing contents of the root inode and real- locate it. The files and directories usually found in the root will be recovered in Phase 3 and put into _l_o_s_t_+_f_o_u_n_d. If the attempt to allocate the root fails, _f_s_c_k will exit with the message: CCAANNNNOOTT AALLLLOOCCAATTEE RROOOOTT IINNOODDEE. NO _f_s_c_k will then prompt with FFIIXX Possible responses to the FIX prompt are: YES replace the root inode's type to be a directory. If the root inode's data blocks are not directory blocks, many error conditions will be produced. NO terminate the program. DDUUPPSS//BBAADD IINN RROOOOTT IINNOODDEE ((RREEAALLLLOOCCAATTEE)) Phase 1 or Phase 1b have found duplicate blocks or bad blocks in the root inode (usually inode number 2) for the file system. Possible responses to the REALLOCATE prompt are: YES clear the existing contents of the root inode and real- locate it. The files and directories usually found in the root will be recovered in Phase 3 and put into _l_o_s_t_+_f_o_u_n_d. If the attempt to allocate the root fails, _f_s_c_k will exit with the message: CCAANNNNOOTT AALLLLOOCCAATTEE RROOOOTT IINNOODDEE. NO _f_s_c_k will then prompt with CCOONNTTIINNUUEE. Possible responses to the CONTINUE prompt are: YES ignore the DDUUPPSS//BBAADD error condition in the root inode and attempt to continue to run the file system check. The UNIX File System Check Program SMM:3-23 If the root inode is not correct, then this may result in many other error conditions. NO terminate the program. NNAAMMEE TTOOOO LLOONNGG _F An excessively long path name has been found. This usually indicates loops in the file system name space. This can occur if the super user has made circular links to directo- ries. The offending links must be removed (by a guru). II OOUUTT OOFF RRAANNGGEE II==_I NNAAMMEE==_F ((RREEMMOOVVEE)) A directory entry _F has an inode number _I that is greater than the end of the inode list. Possible responses to the REMOVE prompt are: YES the directory entry _F is removed. NO ignore this error condition. UUNNAALLLLOOCCAATTEEDD II==_I OOWWNNEERR==_O MMOODDEE==_M SSIIZZEE==_S MMTTIIMMEE==_T _t_y_p_e==_F ((RREEMMOOVVEE)) A directory or file entry _F points to an unallocated inode _I. The owner _O, mode _M, size _S, modify time _T, and name _F are printed. Possible responses to the REMOVE prompt are: YES the directory entry _F is removed. NO ignore this error condition. DDUUPP//BBAADD II==_I OOWWNNEERR==_O MMOODDEE==_M SSIIZZEE==_S MMTTIIMMEE==_T _t_y_p_e==_F ((RREEMMOOVVEE)) Phase 1 or Phase 1b have found duplicate blocks or bad blocks associated with directory or file entry _F, inode _I. The owner _O, mode _M, size _S, modify time _T, and directory name _F are printed. Possible responses to the REMOVE prompt are: YES the directory entry _F is removed. NO ignore this error condition. ZZEERROO LLEENNGGTTHH DDIIRREECCTTOORRYY II==_I OOWWNNEERR==_O MMOODDEE==_M SSIIZZEE==_S MMTTIIMMEE==_T DDIIRR==_F ((RREEMMOOVVEE)) A directory entry _F has a size _S that is zero. The owner _O, mode _M, size _S, modify time _T, and directory name _F are SMM:3-24 The UNIX File System Check Program printed. Possible responses to the REMOVE prompt are: YES the directory entry _F is removed; this will always invoke the BAD/DUP error condition in Phase 4. NO ignore this error condition. DDIIRREECCTTOORRYY TTOOOO SSHHOORRTT II==_I OOWWNNEERR==_O MMOODDEE==_M SSIIZZEE==_S MMTTIIMMEE==_T DDIIRR==_F ((FFIIXX)) A directory _F has been found whose size _S is less than the minimum size directory. The owner _O, mode _M, size _S, modify time _T, and directory name _F are printed. Possible responses to the FIX prompt are: YES increase the size of the directory to the minimum directory size. NO ignore this directory. DDIIRREECCTTOORRYY _F LLEENNGGTTHH _S NNOOTT MMUULLTTIIPPLLEE OOFF _B ((AADDJJUUSSTT)) A directory _F has been found with size _S that is not a mul- tiple of the directory blocksize _B. Possible responses to the ADJUST prompt are: YES the length is rounded up to the appropriate block size. This error can occur on 4.2BSD file systems. Thus when preen'ing the file system only a warning is printed and the directory is adjusted. NO ignore the error condition. DDIIRREECCTTOORRYY CCOORRRRUUPPTTEEDD II==_I OOWWNNEERR==_O MMOODDEE==_M SSIIZZEE==_S MMTTIIMMEE==_T DDIIRR==_F ((SSAALLVVAAGGEE)) A directory with an inconsistent internal state has been found. Possible responses to the FIX prompt are: YES throw away all entries up to the next directory bound- ary (usually 512-byte) boundary. This drastic action can throw away up to 42 entries, and should be taken only after other recovery efforts have failed. NO skip up to the next directory boundary and resume read- ing, but do not modify the directory. The UNIX File System Check Program SMM:3-25 BBAADD IINNOODDEE NNUUMMBBEERR FFOORR ``..'' II==_I OOWWNNEERR==_O MMOODDEE==_M SSIIZZEE==_S MMTTIIMMEE==_T DDIIRR==_F ((FFIIXX)) A directory _I has been found whose inode number for `.' does does not equal _I. Possible responses to the FIX prompt are: YES change the inode number for `.' to be equal to _I. NO leave the inode number for `.' unchanged. MMIISSSSIINNGG ``..'' II==_I OOWWNNEERR==_O MMOODDEE==_M SSIIZZEE==_S MMTTIIMMEE==_T DDIIRR==_F ((FFIIXX)) A directory _I has been found whose first entry is unallo- cated. Possible responses to the FIX prompt are: YES build an entry for `.' with inode number equal to _I. NO leave the directory unchanged. MMIISSSSIINNGG ``..'' II==_I OOWWNNEERR==_O MMOODDEE==_M SSIIZZEE==_S MMTTIIMMEE==_T DDIIRR==_F CCAANNNNOOTT FFIIXX,, FFIIRRSSTT EENNTTRRYY IINN DDIIRREECCTTOORRYY CCOONNTTAAIINNSS _F A directory _I has been found whose first entry is _F. _F_s_c_k cannot resolve this problem. The file system should be mounted and the offending entry _F moved elsewhere. The file system should then be unmounted and _f_s_c_k should be run again. MMIISSSSIINNGG ``..'' II==_I OOWWNNEERR==_O MMOODDEE==_M SSIIZZEE==_S MMTTIIMMEE==_T DDIIRR==_F CCAANNNNOOTT FFIIXX,, IINNSSUUFFFFIICCIIEENNTT SSPPAACCEE TTOO AADDDD ``..'' A directory _I has been found whose first entry is not `.'. _F_s_c_k cannot resolve this problem as it should never happen. See a guru. EEXXTTRRAA ``..'' EENNTTRRYY II==_I OOWWNNEERR==_O MMOODDEE==_M SSIIZZEE==_S MMTTIIMMEE==_T DDIIRR==_F ((FFIIXX)) A directory _I has been found that has more than one entry for `.'. Possible responses to the FIX prompt are: YES remove the extra entry for `.'. NO leave the directory unchanged. BBAADD IINNOODDEE NNUUMMBBEERR FFOORR ``....'' II==_I OOWWNNEERR==_O MMOODDEE==_M SSIIZZEE==_S MMTTIIMMEE==_T DDIIRR==_F ((FFIIXX)) A directory _I has been found whose inode number for `..' SMM:3-26 The UNIX File System Check Program does does not equal the parent of _I. Possible responses to the FIX prompt are: YES change the inode number for `..' to be equal to the parent of _I (``....'' in the root inode points to itself). NO leave the inode number for `..' unchanged. MMIISSSSIINNGG ``....'' II==_I OOWWNNEERR==_O MMOODDEE==_M SSIIZZEE==_S MMTTIIMMEE==_T DDIIRR==_F ((FFIIXX)) A directory _I has been found whose second entry is unallo- cated. Possible responses to the FIX prompt are: YES build an entry for `..' with inode number equal to the parent of _I (``....'' in the root inode points to itself). NO leave the directory unchanged. MMIISSSSIINNGG ``....'' II==_I OOWWNNEERR==_O MMOODDEE==_M SSIIZZEE==_S MMTTIIMMEE==_T DDIIRR==_F CCAANNNNOOTT FFIIXX,, SSEECCOONNDD EENNTTRRYY IINN DDIIRREECCTTOORRYY CCOONNTTAAIINNSS _F A directory _I has been found whose second entry is _F. _F_s_c_k cannot resolve this problem. The file system should be mounted and the offending entry _F moved elsewhere. The file system should then be unmounted and _f_s_c_k should be run again. MMIISSSSIINNGG ``....'' II==_I OOWWNNEERR==_O MMOODDEE==_M SSIIZZEE==_S MMTTIIMMEE==_T DDIIRR==_F CCAANNNNOOTT FFIIXX,, IINNSSUUFFFFIICCIIEENNTT SSPPAACCEE TTOO AADDDD ``....'' A directory _I has been found whose second entry is not `..'. _F_s_c_k cannot resolve this problem. The file system should be mounted and the second entry in the directory moved else- where. The file system should then be unmounted and _f_s_c_k should be run again. EEXXTTRRAA ``....'' EENNTTRRYY II==_I OOWWNNEERR==_O MMOODDEE==_M SSIIZZEE==_S MMTTIIMMEE==_T DDIIRR==_F ((FFIIXX)) A directory _I has been found that has more than one entry for `..'. Possible responses to the FIX prompt are: YES remove the extra entry for `..'. NO leave the directory unchanged. The UNIX File System Check Program SMM:3-27 _N IISS AANN EEXXTTRRAANNEEOOUUSS HHAARRDD LLIINNKK TTOO AA DDIIRREECCTTOORRYY _D ((RREEMMOOVVEE)) _F_s_c_k has found a hard link, _N, to a directory, _D. When preen'ing the extraneous links are ignored. Possible responses to the REMOVE prompt are: YES delete the extraneous entry, _N. NO ignore the error condition. BBAADD IINNOODDEE _S TTOO DDEESSCCEENNDD An internal error has caused an impossible state _S to be passed to the routine that descends the file system direc- tory structure. _F_s_c_k exits. See a guru. BBAADD RREETTUURRNN SSTTAATTEE _S FFRROOMM DDEESSCCEENNDD An internal error has caused an impossible state _S to be returned from the routine that descends the file system directory structure. _F_s_c_k exits. See a guru. BBAADD SSTTAATTEE _S FFOORR RROOOOTT IINNOODDEE An internal error has caused an impossible state _S to be assigned to the root inode. _F_s_c_k exits. See a guru. 44..66.. PPhhaassee 33 -- CChheecckk CCoonnnneeccttiivviittyy This phase concerns itself with the directory connec- tivity seen in Phase 2. This section lists error conditions resulting from unreferenced directories, and missing or full _l_o_s_t_+_f_o_u_n_d directories. UUNNRREEFF DDIIRR II==_I OOWWNNEERR==_O MMOODDEE==_M SSIIZZEE==_S MMTTIIMMEE==_T ((RREECCOONNNNEECCTT)) The directory inode _I was not connected to a directory entry when the file system was traversed. The owner _O, mode _M, size _S, and modify time _T of directory inode _I are printed. When preen'ing, the directory is reconnected if its size is non-zero, otherwise it is cleared. Possible responses to the RECONNECT prompt are: YES reconnect directory inode _I to the file system in the directory for lost files (usually _l_o_s_t_+_f_o_u_n_d). This may invoke the _l_o_s_t_+_f_o_u_n_d error condition in Phase 3 if there are problems connecting directory inode _I to _l_o_s_t_+_f_o_u_n_d. This may also invoke the CONNECTED error condition in Phase 3 if the link was successful. NO ignore this error condition. This will always invoke the UNREF error condition in Phase 4. SMM:3-28 The UNIX File System Check Program NNOO lloosstt++ffoouunndd DDIIRREECCTTOORRYY ((CCRREEAATTEE)) There is no _l_o_s_t_+_f_o_u_n_d directory in the root directory of the file system; When preen'ing _f_s_c_k tries to create a _l_o_s_t_+_f_o_u_n_d directory. Possible responses to the CREATE prompt are: YES create a _l_o_s_t_+_f_o_u_n_d directory in the root of the file system. This may raise the message: NNOO SSPPAACCEE LLEEFFTT IINN // ((EEXXPPAANNDD)) See below for the possible responses. Inability to create a _l_o_s_t_+_f_o_u_n_d directory generates the message: SSOORRRRYY.. CCAANNNNOOTT CCRREEAATTEE lloosstt++ffoouunndd DDIIRREECCTTOORRYY and aborts the attempt to linkup the lost inode. This will always invoke the UNREF error condition in Phase 4. NO abort the attempt to linkup the lost inode. This will always invoke the UNREF error condition in Phase 4. lloosstt++ffoouunndd IISS NNOOTT AA DDIIRREECCTTOORRYY ((RREEAALLLLOOCCAATTEE)) The entry for _l_o_s_t_+_f_o_u_n_d is not a directory. Possible responses to the REALLOCATE prompt are: YES allocate a directory inode, and change _l_o_s_t_+_f_o_u_n_d to reference it. The previous inode reference by the _l_o_s_t_+_f_o_u_n_d name is not cleared. Thus it will either be reclaimed as an UNREF'ed inode or have its link count ADJUST'ed later in this Phase. Inability to create a _l_o_s_t_+_f_o_u_n_d directory generates the message: SSOORRRRYY.. CCAANNNNOOTT CCRREEAATTEE lloosstt++ffoouunndd DDIIRREECCTTOORRYY and aborts the attempt to linkup the lost inode. This will always invoke the UNREF error condition in Phase 4. NO abort the attempt to linkup the lost inode. This will always invoke the UNREF error condition in Phase 4. NNOO SSPPAACCEE LLEEFFTT IINN //lloosstt++ffoouunndd ((EEXXPPAANNDD)) There is no space to add another entry to the _l_o_s_t_+_f_o_u_n_d directory in the root directory of the file system. When preen'ing the _l_o_s_t_+_f_o_u_n_d directory is expanded. Possible responses to the EXPAND prompt are: YES the _l_o_s_t_+_f_o_u_n_d directory is expanded to make room for the new entry. If the attempted expansion fails _f_s_c_k prints the message: SSOORRRRYY.. NNOO SSPPAACCEE IINN lloosstt++ffoouunndd DDIIRREECCTTOORRYY and aborts the attempt to linkup the lost inode. This will always invoke the UNREF error condition in Phase The UNIX File System Check Program SMM:3-29 4. Clean out unnecessary entries in _l_o_s_t_+_f_o_u_n_d. This error is fatal if the file system is being preen'ed. NO abort the attempt to linkup the lost inode. This will always invoke the UNREF error condition in Phase 4. DDIIRR II==_I_1 CCOONNNNEECCTTEEDD.. PPAARREENNTT WWAASS II==_I_2 This is an advisory message indicating a directory inode _I_1 was successfully connected to the _l_o_s_t_+_f_o_u_n_d directory. The parent inode _I_2 of the directory inode _I_1 is replaced by the inode number of the _l_o_s_t_+_f_o_u_n_d directory. DDIIRREECCTTOORRYY _F LLEENNGGTTHH _S NNOOTT MMUULLTTIIPPLLEE OOFF _B ((AADDJJUUSSTT)) A directory _F has been found with size _S that is not a mul- tiple of the directory blocksize _B (this can reoccur in Phase 3 if it is not adjusted in Phase 2). Possible responses to the ADJUST prompt are: YES the length is rounded up to the appropriate block size. This error can occur on 4.2BSD file systems. Thus when preen'ing the file system only a warning is printed and the directory is adjusted. NO ignore the error condition. BBAADD IINNOODDEE _S TTOO DDEESSCCEENNDD An internal error has caused an impossible state _S to be passed to the routine that descends the file system direc- tory structure. _F_s_c_k exits. See a guru. 44..77.. PPhhaassee 44 -- CChheecckk RReeffeerreennccee CCoouunnttss This phase concerns itself with the link count informa- tion seen in Phase 2 and Phase 3. This section lists error conditions resulting from unreferenced files, missing or full _l_o_s_t_+_f_o_u_n_d directory, incorrect link counts for files, directories, symbolic links, or special files, unreferenced files, symbolic links, and directories, and bad or duplicate blocks in files, symbolic links, and directories. All errors in this phase are correctable if the file system is being preen'ed except running out of space in the _l_o_s_t_+_f_o_u_n_d directory. UUNNRREEFF FFIILLEE II==_I OOWWNNEERR==_O MMOODDEE==_M SSIIZZEE==_S MMTTIIMMEE==_T ((RREECCOONNNNEECCTT)) Inode _I was not connected to a directory entry when the file system was traversed. The owner _O, mode _M, size _S, and mod- ify time _T of inode _I are printed. When preen'ing the file is cleared if either its size or its link count is zero, otherwise it is reconnected. SMM:3-30 The UNIX File System Check Program Possible responses to the RECONNECT prompt are: YES reconnect inode _I to the file system in the directory for lost files (usually _l_o_s_t_+_f_o_u_n_d). This may invoke the _l_o_s_t_+_f_o_u_n_d error condition in Phase 4 if there are problems connecting inode _I to _l_o_s_t_+_f_o_u_n_d. NO ignore this error condition. This will always invoke the CLEAR error condition in Phase 4. ((CCLLEEAARR)) The inode mentioned in the immediately previous error condi- tion can not be reconnected. This cannot occur if the file system is being preen'ed, since lack of space to reconnect files is a fatal error. Possible responses to the CLEAR prompt are: YES de-allocate the inode mentioned in the immediately pre- vious error condition by zeroing its contents. NO ignore this error condition. NNOO lloosstt++ffoouunndd DDIIRREECCTTOORRYY ((CCRREEAATTEE)) There is no _l_o_s_t_+_f_o_u_n_d directory in the root directory of the file system; When preen'ing _f_s_c_k tries to create a _l_o_s_t_+_f_o_u_n_d directory. Possible responses to the CREATE prompt are: YES create a _l_o_s_t_+_f_o_u_n_d directory in the root of the file system. This may raise the message: NNOO SSPPAACCEE LLEEFFTT IINN // ((EEXXPPAANNDD)) See below for the possible responses. Inability to create a _l_o_s_t_+_f_o_u_n_d directory generates the message: SSOORRRRYY.. CCAANNNNOOTT CCRREEAATTEE lloosstt++ffoouunndd DDIIRREECCTTOORRYY and aborts the attempt to linkup the lost inode. This will always invoke the UNREF error condition in Phase 4. NO abort the attempt to linkup the lost inode. This will always invoke the UNREF error condition in Phase 4. lloosstt++ffoouunndd IISS NNOOTT AA DDIIRREECCTTOORRYY ((RREEAALLLLOOCCAATTEE)) The entry for _l_o_s_t_+_f_o_u_n_d is not a directory. Possible responses to the REALLOCATE prompt are: YES allocate a directory inode, and change _l_o_s_t_+_f_o_u_n_d to reference it. The previous inode reference by the _l_o_s_t_+_f_o_u_n_d name is not cleared. Thus it will either be The UNIX File System Check Program SMM:3-31 reclaimed as an UNREF'ed inode or have its link count ADJUST'ed later in this Phase. Inability to create a _l_o_s_t_+_f_o_u_n_d directory generates the message: SSOORRRRYY.. CCAANNNNOOTT CCRREEAATTEE lloosstt++ffoouunndd DDIIRREECCTTOORRYY and aborts the attempt to linkup the lost inode. This will always invoke the UNREF error condition in Phase 4. NO abort the attempt to linkup the lost inode. This will always invoke the UNREF error condition in Phase 4. NNOO SSPPAACCEE LLEEFFTT IINN //lloosstt++ffoouunndd ((EEXXPPAANNDD)) There is no space to add another entry to the _l_o_s_t_+_f_o_u_n_d directory in the root directory of the file system. When preen'ing the _l_o_s_t_+_f_o_u_n_d directory is expanded. Possible responses to the EXPAND prompt are: YES the _l_o_s_t_+_f_o_u_n_d directory is expanded to make room for the new entry. If the attempted expansion fails _f_s_c_k prints the message: SSOORRRRYY.. NNOO SSPPAACCEE IINN lloosstt++ffoouunndd DDIIRREECCTTOORRYY and aborts the attempt to linkup the lost inode. This will always invoke the UNREF error condition in Phase 4. Clean out unnecessary entries in _l_o_s_t_+_f_o_u_n_d. This error is fatal if the file system is being preen'ed. NO abort the attempt to linkup the lost inode. This will always invoke the UNREF error condition in Phase 4. LLIINNKK CCOOUUNNTT _t_y_p_e II==_I OOWWNNEERR==_O MMOODDEE==_M SSIIZZEE==_S MMTTIIMMEE==_T CCOOUUNNTT==_X SSHHOOUULLDD BBEE _Y ((AADDJJUUSSTT)) The link count for inode _I, is _X but should be _Y. The owner _O, mode _M, size _S, and modify time _T are printed. When preen'ing the link count is adjusted unless the number of references is increasing, a condition that should never occur unless precipitated by a hardware failure. When the number of references is increasing under preen mode, _f_s_c_k exits with the message: LLIINNKK CCOOUUNNTT IINNCCRREEAASSIINNGG Possible responses to the ADJUST prompt are: YES replace the link count of file inode _I with _Y. NO ignore this error condition. UUNNRREEFF _t_y_p_e II==_I OOWWNNEERR==_O MMOODDEE==_M SSIIZZEE==_S MMTTIIMMEE==_T ((CCLLEEAARR)) Inode _I, was not connected to a directory entry when the file system was traversed. The owner _O, mode _M, size _S, and modify time _T of inode _I are printed. When preen'ing, this SMM:3-32 The UNIX File System Check Program is a file that was not connected because its size or link count was zero, hence it is cleared. Possible responses to the CLEAR prompt are: YES de-allocate inode _I by zeroing its contents. NO ignore this error condition. BBAADD//DDUUPP _t_y_p_e II==_I OOWWNNEERR==_O MMOODDEE==_M SSIIZZEE==_S MMTTIIMMEE==_T ((CCLLEEAARR)) Phase 1 or Phase 1b have found duplicate blocks or bad blocks associated with inode _I. The owner _O, mode _M, size _S, and modify time _T of inode _I are printed. This error cannot arise when the file system is being preen'ed, as it would have caused a fatal error earlier. Possible responses to the CLEAR prompt are: YES de-allocate inode _I by zeroing its contents. NO ignore this error condition. 44..88.. PPhhaassee 55 -- CChheecckk CCyyll ggrroouuppss This phase concerns itself with the free-block and used-inode maps. This section lists error conditions resulting from allocated blocks in the free-block maps, free blocks missing from free-block maps, and the total free- block count incorrect. It also lists error conditions resulting from free inodes in the used-inode maps, allocated inodes missing from used-inode maps, and the total used- inode count incorrect. CCGG _C:: BBAADD MMAAGGIICC NNUUMMBBEERR The magic number of cylinder group _C is wrong. This usually indicates that the cylinder group maps have been destroyed. When running manually the cylinder group is marked as need- ing to be reconstructed. This error is fatal if the file system is being preen'ed. BBLLKK((SS)) MMIISSSSIINNGG IINN BBIITT MMAAPPSS ((SSAALLVVAAGGEE)) A cylinder group block map is missing some free blocks. During preen'ing the maps are reconstructed. Possible responses to the SALVAGE prompt are: YES reconstruct the free block map. NO ignore this error condition. The UNIX File System Check Program SMM:3-33 SSUUMMMMAARRYY IINNFFOORRMMAATTIIOONN BBAADD ((SSAALLVVAAGGEE)) The summary information was found to be incorrect. When preen'ing, the summary information is recomputed. Possible responses to the SALVAGE prompt are: YES reconstruct the summary information. NO ignore this error condition. FFRREEEE BBLLKK CCOOUUNNTT((SS)) WWRROONNGG IINN SSUUPPEERRBBLLOOCCKK ((SSAALLVVAAGGEE)) The superblock free block information was found to be incor- rect. When preen'ing, the superblock free block information is recomputed. Possible responses to the SALVAGE prompt are: YES reconstruct the superblock free block information. NO ignore this error condition. 44..99.. CClleeaannuupp Once a file system has been checked, a few cleanup functions are performed. This section lists advisory mes- sages about the file system and modify status of the file system. _V ffiilleess,, _W uusseedd,, _X ffrreeee ((_Y ffrraaggss,, _Z bblloocckkss)) This is an advisory message indicating that the file system checked contained _V files using _W fragment sized blocks leaving _X fragment sized blocks free in the file system. The numbers in parenthesis breaks the free count down into _Y free fragments and _Z free full sized blocks. ********** RREEBBOOOOTT UUNNIIXX ********** This is an advisory message indicating that the root file system has been modified by _f_s_c_k_. If UNIX is not rebooted immediately, the work done by _f_s_c_k may be undone by the in- core copies of tables UNIX keeps. When preen'ing, _f_s_c_k will exit with a code of 4. The standard auto-reboot script dis- tributed with 4.3BSD interprets an exit code of 4 by issuing a reboot system call. ********** FFIILLEE SSYYSSTTEEMM WWAASS MMOODDIIFFIIEEDD ********** This is an advisory message indicating that the current file system was modified by _f_s_c_k_. If this file system is mounted or is the current root file system, _f_s_c_k should be halted and UNIX rebooted. If UNIX is not rebooted immediately, the work done by _f_s_c_k may be undone by the in-core copies of SMM:3-34 The UNIX File System Check Program tables UNIX keeps.