e2fsck – check a Linux second extended file system
e2fsck is used to check a Linux second extended file system (ext2fs).E2fsck also supports ext2 filesystems countaining a journal, which are also sometimes known as ext3 filesystems, by first applying the journal to the filesystem before continuing with normal e2fsckprocessing. After the journal has been applied, a filesystem will normally be marked as clean. Hence, for ext3 filesystems,e2fsck will normally run the journal and exit, unless its superblock indicates that further checking is required.
- This option does the same thing as the -p option. It is provided for backwards compatibility only; it is suggested that people use -p option whenever possible.
- -b superblock
- Instead of using the normal superblock, use an alternative superblock specified by superblock. This option is normally used when the primary superblock has been corrupted. The location of the backup superblock is dependent on the filesystem’s blocksize. For filesystems with 1k blocksizes, a backup superblock can be found at block 8193; for filesystems with 2k blocksizes, at block 16384; and for 4k blocksizes, at block 32768.
- Additional backup superblocks can be determined by using the mke2fs program using the -n option to print out where the superblocks were created. The -b option to mke2fs, which specifies blocksize of the filesystem must be specified in order for the superblock locations that are printed out to be accurate.
- If an alternative superblock is specified and the filesystem is not opened read-only, e2fsck will make sure that the primary superblock is updated appropriately upon completion of the filesystem check.
- -B blocksize
- Normally, e2fsck will search for the superblock at various different block sizes in an attempt to find the appropriate block size. This search can be fooled in some cases. This option forces e2fsck to only try locating the superblock at a particular blocksize. If the superblock is not found, e2fsck will terminate with a fatal error.
- This option causes e2fsck to run the badblocks(8) program to find any blocks which are bad on the filesystem, and then marks them as bad by adding them to the bad block inode. If this option is specified twice, then the bad block scan will be done using a non-destructive read-write test.
- This option causes e2fsck to write completion information to the specified file descriptor so that the progress of the filesystem check can be monitored. This option is typically used by programs which are running e2fsck. If the file descriptor specified is 0, e2fsck will print a completion bar as it goes about its business. This requires that e2fsck is running on a video console or terminal.
- Print debugging output (useless unless you are debugging e2fsck).
- Optimize directories in filesystem. This option causes e2fsck to try to optimize all directories, either by reindexing them if the filesystem supports directory indexing, or by sorting and compressing directories for smaller directories, or for filesystems using traditional linear directories.
- -E extended_options
- Set e2fsck extended options. Extended options are comma separated, and may take an argument using the equals (‘=’) sign. The following options are supported:
- Assume the format of the extended attribute blocks in the filesystem is the specified version number. The version number may be 1 or 2. The default extended attribute version format is 2.
- Force checking even if the file system seems clean.
- Flush the filesystem device’s buffer caches before beginning. Only really useful for doing e2fsck time trials.
- -j external-journal
- Set the pathname where the external-journal for this filesystem can be found.
- -l filename
- Add the block numbers listed in the file specified by filename to the list of bad blocks. The format of this file is the same as the one generated by the badblocks(8) program. Note that the block numbers are based on the blocksize of the filesystem. Hence, badblocks(8) must be given the blocksize of the filesystem in order to obtain correct results. As a result, it is much simpler and safer to use the -c option to e2fsck, since it will assure that the correct parameters are passed to the badblocks program.
- -L filename
- Set the bad blocks list to be the list of blocks specified by filename. (This option is the same as the -l option, except the bad blocks list is cleared before the blocks listed in the file are added to the bad blocks list.)
- Open the filesystem read-only, and assume an answer of `no’ to all questions. Allows e2fsck to be used non-interactively. (Note: if the -c, -l, or -L options are specified in addition to the -n option, then the filesystem will be opened read-write, to permit the bad-blocks list to be updated. However, no other changes will be made to the filesystem.)
- Automatically repair (“preen”) the file system without any questions.
- This option does nothing at all; it is provided only for backwards compatibility.
- This option will byte-swap the filesystem so that it is using the normalized, standard byte-order (which is i386 or little endian). If the filesystem is already in the standard byte-order, e2fsck will take no action.
- This option will byte-swap the filesystem, regardless of its current byte-order.
- Print timing statistics for e2fsck. If this option is used twice, additional timing statistics are printed on a pass by pass basis.
- Verbose mode.
- Print version information and exit.
- Assume an answer of `yes’ to all questions; allows e2fsck to be used non-interactively.
The exit code returned by e2fsck is the sum of the following conditions:
0 – No errors
1 – File system errors corrected
2 – File system errors corrected, system should
4 – File system errors left uncorrected
8 – Operational error
16 – Usage or syntax error
32 – E2fsck canceled by user request
128 – Shared library error
The following signals have the following effect when sent to e2fsck.
- This signal causes e2fsck to start displaying a completion bar. (See discussion of the -C option.)
- This signal causes e2fsck to stop displaying a completion bar.