506 lines
15 KiB
Groff
506 lines
15 KiB
Groff
.\" -*- nroff -*-
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.\" Copyright 1993, 1994, 1995 by Theodore Ts'o. All Rights Reserved.
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.\" This file may be copied under the terms of the GNU Public License.
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.\"
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.TH E2FSCK 8 "@E2FSPROGS_MONTH@ @E2FSPROGS_YEAR@" "E2fsprogs version @E2FSPROGS_VERSION@"
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.SH NAME
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e2fsck \- check a Linux ext2/ext3/ext4 file system
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.SH SYNOPSIS
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.B e2fsck
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[
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.B \-pacnyrdfkvtDFV
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]
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[
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.B \-b
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.I superblock
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]
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[
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.B \-B
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.I blocksize
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]
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[
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.BR \-l | \-L
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.I bad_blocks_file
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]
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[
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.B \-C
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.I fd
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]
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@JDEV@[
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@JDEV@.B \-j
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@JDEV@.I external-journal
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@JDEV@]
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[
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.B \-E
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.I extended_options
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]
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[
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.B \-z
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.I undo_file
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]
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.I device
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.SH DESCRIPTION
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.B e2fsck
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is used to check the ext2/ext3/ext4 family of file systems.
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For ext3 and ext4 filesystems that use a journal, if the system has been
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shut down uncleanly without any errors, normally, after replaying the
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committed transactions in the journal, the file system should be
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marked as clean. Hence, for filesystems that use journalling,
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.B e2fsck
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will normally replay the journal and exit, unless its superblock
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indicates that further checking is required.
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.PP
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.I device
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is a block device (e.g.,
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.IR /dev/sdc1 )
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or file containing the file system.
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.PP
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Note that in general it is not safe to run
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.B e2fsck
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on mounted filesystems. The only exception is if the
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.B \-n
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option is specified, and
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.BR \-c ,
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.BR \-l ,
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or
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.B -L
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options are
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.I not
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specified. However, even if it is safe to do so, the results printed by
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.B e2fsck
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are not valid if the filesystem is mounted. If
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.B e2fsck
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asks whether or not you should check a filesystem which is mounted,
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the only correct answer is ``no''. Only experts who really know what
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they are doing should consider answering this question in any other way.
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.PP
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If
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.B e2fsck
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is run in interactive mode (meaning that none of
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.BR \-y ,
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.BR \-n ,
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or
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.BR \-p
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are specified), the program will ask the user to fix each problem found in the
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filesystem. A response of 'y' will fix the error; 'n' will leave the error
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unfixed; and 'a' will fix the problem and all subsequent problems; pressing
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Enter will proceed with the default response, which is printed before the
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question mark. Pressing Control-C terminates e2fsck immediately.
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.SH OPTIONS
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.TP
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.B \-a
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This option does the same thing as the
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.B \-p
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option. It is provided for backwards compatibility only; it is
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suggested that people use
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.B \-p
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option whenever possible.
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.TP
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.BI \-b " superblock"
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Instead of using the normal superblock, use an alternative superblock
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specified by
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.IR superblock .
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This option is normally used when the primary superblock has been
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corrupted. The location of backup superblocks is dependent on the
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filesystem's blocksize, the number of blocks per group, and features
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such as
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.BR sparse_super .
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.IP
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Additional backup superblocks can be determined by using the
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.B mke2fs
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program using the
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.B \-n
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option to print out where the superblocks exist, supposing
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.B mke2fs
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is supplied with arguments that are consistent with the filesystem's layout
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(e.g. blocksize, blocks per group,
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.BR sparse_super ,
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etc.).
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.IP
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If an alternative superblock is specified and
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the filesystem is not opened read-only, e2fsck will make sure that the
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primary superblock is updated appropriately upon completion of the
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filesystem check.
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.TP
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.BI \-B " blocksize"
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Normally,
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.B e2fsck
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will search for the superblock at various different
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block sizes in an attempt to find the appropriate block size.
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This search can be fooled in some cases. This option forces
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.B e2fsck
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to only try locating the superblock at a particular blocksize.
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If the superblock is not found,
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.B e2fsck
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will terminate with a fatal error.
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.TP
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.B \-c
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This option causes
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.B e2fsck
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to use
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.BR badblocks (8)
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program to do a read-only scan of the device in order to find any bad
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blocks. If any bad blocks are found, they are added to the bad block
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inode to prevent them from being allocated to a file or directory. If
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this option is specified twice, then the bad block scan will be done
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using a non-destructive read-write test.
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.TP
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.BI \-C " fd"
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This option causes
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.B e2fsck
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to write completion information to the specified file descriptor
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so that the progress of the filesystem
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check can be monitored. This option is typically used by programs
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which are running
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.BR e2fsck .
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If the file descriptor number is negative, then absolute value of
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the file descriptor will be used, and the progress information will be
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suppressed initially. It can later be enabled by sending the
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.B e2fsck
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process a SIGUSR1 signal.
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If the file descriptor specified is 0,
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.B e2fsck
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will print a completion bar as it goes about its business. This requires
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that e2fsck is running on a video console or terminal.
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.TP
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.B \-d
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Print debugging output (useless unless you are debugging
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.BR e2fsck ).
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.TP
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.B \-D
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Optimize directories in filesystem. This option causes e2fsck to
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try to optimize all directories, either by reindexing them if the
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filesystem supports directory indexing, or by sorting and compressing
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directories for smaller directories, or for filesystems using
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traditional linear directories.
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.IP
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Even without the
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.B \-D
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option,
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.B e2fsck
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may sometimes optimize a few directories --- for example, if
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directory indexing is enabled and a directory is not indexed and would
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benefit from being indexed, or if the index structures are corrupted
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and need to be rebuilt. The
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.B \-D
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option forces all directories in the filesystem to be optimized. This can
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sometimes make them a little smaller and slightly faster to search, but
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in practice, you should rarely need to use this option.
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.IP
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The
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.B \-D
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option will detect directory entries with duplicate names in a single
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directory, which e2fsck normally does not enforce for performance reasons.
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.TP
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.BI \-E " extended_options"
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Set e2fsck extended options. Extended options are comma
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separated, and may take an argument using the equals ('=') sign. The
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following options are supported:
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.RS 1.2i
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.TP
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.BI ea_ver= extended_attribute_version
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Set the version of the extended attribute blocks which
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.B e2fsck
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will require while checking the filesystem. The version number may
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be 1 or 2. The default extended attribute version format is 2.
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.TP
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.BI journal_only
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Only replay the journal if required, but do not perform any further checks
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or repairs.
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.TP
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.BI fragcheck
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During pass 1, print a detailed report of any discontiguous blocks for
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files in the filesystem.
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.TP
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.BI discard
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Attempt to discard free blocks and unused inode blocks after the full
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filesystem check (discarding blocks is useful on solid state devices and sparse
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/ thin-provisioned storage). Note that discard is done in pass 5 AFTER the
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filesystem has been fully checked and only if it does not contain recognizable
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errors. However there might be cases where
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.B e2fsck
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does not fully recognize a problem and hence in this case this
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option may prevent you from further manual data recovery.
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.TP
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.BI nodiscard
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Do not attempt to discard free blocks and unused inode blocks. This option is
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exactly the opposite of discard option. This is set as default.
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.TP
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.BI no_optimize_extents
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Do not offer to optimize the extent tree by eliminating unnecessary
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width or depth. This can also be enabled in the options section of
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.BR /etc/e2fsck.conf .
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.TP
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.BI optimize_extents
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Offer to optimize the extent tree by eliminating unnecessary
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width or depth. This is the default unless otherwise specified in
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.BR /etc/e2fsck.conf .
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.TP
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.BI inode_count_fullmap
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Trade off using memory for speed when checking a file system with a
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large number of hard-linked files. The amount of memory required is
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proportional to the number of inodes in the file system. For large file
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systems, this can be gigabytes of memory. (For example, a 40TB file system
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with 2.8 billion inodes will consume an additional 5.7 GB memory if this
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optimization is enabled.) This optimization can also be enabled in the
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options section of
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.BR /etc/e2fsck.conf .
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.TP
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.BI no_inode_count_fullmap
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Disable the
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.B inode_count_fullmap
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optimization. This is the default unless otherwise specified in
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.BR /etc/e2fsck.conf .
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.TP
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.BI readahead_kb
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Use this many KiB of memory to pre-fetch metadata in the hopes of reducing
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e2fsck runtime. By default, this is set to the size of two block groups' inode
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tables (typically 4MiB on a regular ext4 filesystem); if this amount is more
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than 1/50th of total physical memory, readahead is disabled. Set this to zero
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to disable readahead entirely.
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.TP
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.BI bmap2extent
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Convert block-mapped files to extent-mapped files.
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.TP
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.BI fixes_only
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Only fix damaged metadata; do not optimize htree directories or compress
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extent trees. This option is incompatible with the -D and -E bmap2extent
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options.
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.TP
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.BI unshare_blocks
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If the filesystem has shared blocks, with the shared blocks read-only feature
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enabled, then this will unshare all shared blocks and unset the read-only
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feature bit. If there is not enough free space then the operation will fail.
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If the filesystem does not have the read-only feature bit, but has shared
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blocks anyway, then this option will have no effect. Note when using this
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option, if there is no free space to clone blocks, there is no prompt to
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delete files and instead the operation will fail.
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.IP
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Note that unshare_blocks implies the "-f" option to ensure that all passes
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are run. Additionally, if "-n" is also specified, e2fsck will simulate trying
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to allocate enough space to deduplicate. If this fails, the exit code will
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be non-zero.
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.RE
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.TP
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.B \-f
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Force checking even if the file system seems clean.
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.TP
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.B \-F
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Flush the filesystem device's buffer caches before beginning. Only
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really useful for doing
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.B e2fsck
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time trials.
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@JDEV@.TP
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@JDEV@.BI \-j " external-journal"
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@JDEV@Set the pathname where the external-journal for this filesystem can be
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@JDEV@found.
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.TP
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.BI \-k
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When combined with the
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.B \-c
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option, any existing bad blocks in the bad blocks list are preserved,
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and any new bad blocks found by running
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.BR badblocks (8)
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will be added to the existing bad blocks list.
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.TP
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.BI \-l " filename"
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Add the block numbers listed in the file specified by
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.I filename
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to the list of bad blocks. The format of this file is the same as the
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one generated by the
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.BR badblocks (8)
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program. Note that the block numbers are based on the blocksize
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of the filesystem. Hence,
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.BR badblocks (8)
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must be given the blocksize of the filesystem in order to obtain correct
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results. As a result, it is much simpler and safer to use the
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.B -c
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option to
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.BR e2fsck ,
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since it will assure that the correct parameters are passed to the
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.B badblocks
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program.
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.TP
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.BI \-L " filename"
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Set the bad blocks list to be the list of blocks specified by
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.IR filename .
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(This option is the same as the
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.B \-l
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option, except the bad blocks list is cleared before the blocks listed
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in the file are added to the bad blocks list.)
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.TP
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.B \-n
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Open the filesystem read-only, and assume an answer of `no' to all
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questions. Allows
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.B e2fsck
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to be used non-interactively. This option
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may not be specified at the same time as the
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.B \-p
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or
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.B \-y
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options.
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.TP
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.B \-p
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Automatically repair ("preen") the file system. This option will cause
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.B e2fsck
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to automatically
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fix any filesystem problems that can be safely fixed without human
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intervention. If
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.B e2fsck
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discovers a problem which may require the system administrator
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to take additional corrective action,
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.B e2fsck
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will print a description of the problem and then exit with the value 4
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logically or'ed into the exit code. (See the \fBEXIT CODE\fR section.)
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This option is normally used by the system's boot scripts. It may not
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be specified at the same time as the
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.B \-n
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or
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.B \-y
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options.
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.TP
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.B \-r
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This option does nothing at all; it is provided only for backwards
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compatibility.
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.TP
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.B \-t
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Print timing statistics for
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.BR e2fsck .
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If this option is used twice, additional timing statistics are printed
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on a pass by pass basis.
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.TP
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.B \-v
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Verbose mode.
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.TP
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.B \-V
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Print version information and exit.
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.TP
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.B \-y
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Assume an answer of `yes' to all questions; allows
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.B e2fsck
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to be used non-interactively. This option
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may not be specified at the same time as the
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.B \-n
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or
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.B \-p
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options.
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.TP
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.BI \-z " undo_file"
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Before overwriting a file system block, write the old contents of the block to
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an undo file. This undo file can be used with e2undo(8) to restore the old
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contents of the file system should something go wrong. If the empty string is
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passed as the undo_file argument, the undo file will be written to a file named
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e2fsck-\fIdevice\fR.e2undo in the directory specified via the
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\fIE2FSPROGS_UNDO_DIR\fR environment variable.
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WARNING: The undo file cannot be used to recover from a power or system crash.
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.SH EXIT CODE
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The exit code returned by
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.B e2fsck
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is the sum of the following conditions:
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.br
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\ 0\ \-\ No errors
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.br
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\ 1\ \-\ File system errors corrected
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.br
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\ 2\ \-\ File system errors corrected, system should
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.br
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\ \ \ \ be rebooted
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.br
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\ 4\ \-\ File system errors left uncorrected
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.br
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\ 8\ \-\ Operational error
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.br
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\ 16\ \-\ Usage or syntax error
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.br
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\ 32\ \-\ E2fsck canceled by user request
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.br
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\ 128\ \-\ Shared library error
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.br
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.SH SIGNALS
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The following signals have the following effect when sent to
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.BR e2fsck .
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.TP
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.B SIGUSR1
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This signal causes
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.B e2fsck
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to start displaying a completion bar or emitting progress information.
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(See discussion of the
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.B \-C
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option.)
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.TP
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.B SIGUSR2
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This signal causes
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.B e2fsck
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to stop displaying a completion bar or emitting progress information.
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.SH REPORTING BUGS
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Almost any piece of software will have bugs. If you manage to find a
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filesystem which causes
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.B e2fsck
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to crash, or which
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.B e2fsck
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is unable to repair, please report it to the author.
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.PP
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Please include as much information as possible in your bug report.
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Ideally, include a complete transcript of the
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.B e2fsck
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run, so I can see exactly what error messages are displayed. (Make sure
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the messages printed by
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.B e2fsck
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are in English; if your system has been
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configured so that
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.BR e2fsck 's
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messages have been translated into another language, please set the the
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.B LC_ALL
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environment variable to
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.B C
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so that the transcript of e2fsck's output will be useful to me.)
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If you
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have a writable filesystem where the transcript can be stored, the
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.BR script (1)
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program is a handy way to save the output of
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.B e2fsck
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to a file.
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.PP
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It is also useful to send the output of
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.BR dumpe2fs (8).
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If a specific inode or inodes seems to be giving
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.B e2fsck
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trouble, try running the
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.BR debugfs (8)
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command and send the output of the
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.BR stat (1u)
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command run on the relevant inode(s). If the inode is a directory, the
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.B debugfs
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.I dump
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command will allow you to extract the contents of the directory inode,
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which can sent to me after being first run through
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.BR uuencode (1).
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The most useful data you can send to help reproduce
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the bug is a compressed raw image dump of the filesystem, generated using
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.BR e2image (8).
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See the
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.BR e2image (8)
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man page for more details.
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.PP
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Always include the full version string which
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.B e2fsck
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displays when it is run, so I know which version you are running.
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.SH ENVIRONMENT
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.TP
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.BI E2FSCK_CONFIG
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Determines the location of the configuration file (see
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.BR e2fsck.conf (5)).
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.SH AUTHOR
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|
This version of
|
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.B e2fsck
|
|
was written by Theodore Ts'o <tytso@mit.edu>.
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.SH SEE ALSO
|
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.BR e2fsck.conf (5),
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.BR badblocks (8),
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.BR dumpe2fs (8),
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.BR debugfs (8),
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.BR e2image (8),
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.BR mke2fs (8),
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.BR tune2fs (8)
|