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E2FSCK(8)		    System Manager's Manual		     E2FSCK(8)

NAME
       e2fsck -	check a	Linux ext2/ext3/ext4 file system

SYNOPSIS
       e2fsck  [  -pacnyrdfkvtDFV ] [ -b superblock ] [	-B blocksize ] [ -l|-L
       bad_blocks_file ] [ -C fd ] [ -j	external-journal ] [  -E  extended_op-
       tions ] [ -z undo_file ]	device

DESCRIPTION
       e2fsck is used to check the ext2/ext3/ext4 family of file systems.  For
       ext3 and	ext4 filesystems that use a journal, if	the  system  has  been
       shut  down  uncleanly without any errors, normally, after replaying the
       committed transactions  in the  journal,	 the  file  system  should  be
       marked  as clean.   Hence, for filesystems that use journalling,	e2fsck
       will normally replay the	journal	and exit, unless its superblock	 indi-
       cates that further checking is required.

       device  is a block device (e.g.,	/dev/sdc1) or file containing the file
       system.

       Note that in general it is not safe to run e2fsck on  mounted  filesys-
       tems.  The only exception is if the -n option is	specified, and -c, -l,
       or -L options are not specified.	  However, even	if it is  safe	to  do
       so,  the	 results  printed by e2fsck are	not valid if the filesystem is
       mounted.	  If e2fsck asks whether or not	you should check a  filesystem
       which  is mounted, the only correct answer is ``no''.  Only experts who
       really know what	they are doing should consider answering this question
       in any other way.

       If  e2fsck  is run in interactive mode (meaning that none of -y,	-n, or
       -p are specified), the program will ask the user	to  fix	 each  problem
       found  in  the  filesystem.   A response	of 'y' will fix	the error; 'n'
       will leave the error unfixed; and 'a' will fix the problem and all sub-
       sequent	problems;  pressing  Enter  will  proceed with the default re-
       sponse, which is	printed	before the question mark.  Pressing  Control-C
       terminates e2fsck immediately.

OPTIONS
       -a     This  option  does  the same thing as the	-p option.  It is pro-
	      vided 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 su-
	      perblock 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	block-
	      size.   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  su-
	      perblocks	 were created.	 The -b	option to mke2fs, which	speci-
	      fies 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 su-
	      perblock	 is  updated  appropriately  upon  completion  of  the
	      filesystem check.

       -B blocksize
	      Normally,	e2fsck will search for the superblock at various  dif-
	      ferent  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 particu-
	      lar blocksize.  If the superblock	is not found, e2fsck will ter-
	      minate with a fatal error.

       -c     This  option  causes  e2fsck to use badblocks(8) program to do a
	      read-only	scan of	the device in order to find  any  bad  blocks.
	      If any bad blocks	are found, they	are added to the bad block in-
	      ode to prevent them from being allocated to a file or directory.
	      If  this option is specified twice, then the bad block scan will
	      be done using a non-destructive read-write test.

       -C fd  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  pro-
	      grams  which  are	running	e2fsck.	 If the	file descriptor	number
	      is negative, then	absolute value of the file descriptor will  be
	      used, and	the progress information will be suppressed initially.
	      It can later be enabled by sending the e2fsck process a  SIGUSR1
	      signal.	If  the	 file  descriptor  specified is	0, e2fsck will
	      print a completion bar as	it goes	about its business.  This  re-
	      quires that e2fsck is running on a video console or terminal.

       -d     Print   debugging	 output	 (useless  unless  you	are  debugging
	      e2fsck).

       -D     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 filesys-
	      tems using traditional linear directories.

	      Even without the -D option, e2fsck may sometimes optimize	a  few
	      directories  ---	for  example, if directory indexing is enabled
	      and a directory is not indexed and would benefit from being  in-
	      dexed,  or  if the index structures are corrupted	and need to be
	      rebuilt.	The -D option forces all directories in	the filesystem
	      to  be optimized.	 This can sometimes make them a	little smaller
	      and slightly faster to  search,  but  in	practice,  you	should
	      rarely need to use this option.

	      The -D option will detect	directory entries with duplicate names
	      in a single directory, which e2fsck normally  does  not  enforce
	      for performance reasons.

       -E extended_options
	      Set  e2fsck  extended options.  Extended options are comma sepa-
	      rated, and may take an argument using  the  equals  ('=')	 sign.
	      The following options are	supported:

		   ea_ver=extended_attribute_version
			  Set  the  version  of	 the extended attribute	blocks
			  which	 e2fsck	 will  require	while	checking   the
			  filesystem.	The version number may be 1 or 2.  The
			  default extended attribute version format is 2.

		   journal_only
			  Only replay the journal if required, but do not per-
			  form any further checks or repairs.

		   fragcheck
			  During  pass	1, print a detailed report of any dis-
			  contiguous blocks for	files in the filesystem.

		   discard
			  Attempt to discard  free  blocks  and	 unused	 inode
			  blocks  after	 the full filesystem check (discarding
			  blocks is useful on solid state devices and sparse /
			  thin-provisioned storage). Note that discard is done
			  in pass  5  AFTER  the  filesystem  has  been	 fully
			  checked and only if it does not contain recognizable
			  errors. However there	might be  cases	 where	e2fsck
			  does not fully recognize a problem and hence in this
			  case this option may prevent you from	further	manual
			  data recovery.

		   nodiscard
			  Do not attempt to discard free blocks	and unused in-
			  ode blocks. This option is exactly the  opposite  of
			  discard option. This is set as default.

		   readahead_kb
			  Use this many	KiB of memory to pre-fetch metadata in
			  the hopes of reducing	e2fsck runtime.	  By  default,
			  this	is  set	to the size of two block groups' inode
			  tables (typically 4MiB on a  regular	ext4  filesys-
			  tem);	 if  this  amount is more than 1/50th of total
			  physical memory, readahead is	disabled.  Set this to
			  zero to disable readahead entirely.

		   bmap2extent
			  Convert block-mapped files to	extent-mapped files.

		   fixes_only
			  Only fix damaged metadata; do	not optimize htree di-
			  rectories or compress	extent trees.  This option  is
			  incompatible with the	-D and -E bmap2extent options.

       -f     Force checking even if the file system seems clean.

       -F     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.

       -k     When combined with the -c	option,	any existing bad blocks	in the
	      bad blocks list are preserved, and any new bad blocks  found  by
	      running  badblocks(8)  will  be added to the existing bad	blocks
	      list.

       -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  filesys-
	      tem 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.)

       -n     Open  the	 filesystem read-only, and assume an answer of `no' to
	      all questions.  Allows  e2fsck  to  be  used  non-interactively.
	      This  option  may	not be specified at the	same time as the -p or
	      -y options.

       -p     Automatically repair ("preen") the  file	system.	  This	option
	      will  cause  e2fsck to automatically fix any filesystem problems
	      that can be safely fixed without human intervention.  If	e2fsck
	      discovers	 a  problem which may require the system administrator
	      to take additional corrective action, e2fsck will	 print	a  de-
	      scription	 of  the  problem and then exit	with the value 4 logi-
	      cally or'ed into the exit	code.  (See the	 EXIT  CODE  section.)
	      This  option  is normally	used by	the system's boot scripts.  It
	      may not be specified at the same time as the -n or -y options.

       -r     This option does nothing at all; it is provided only  for	 back-
	      wards compatibility.

       -t     Print  timing  statistics	 for  e2fsck.	If this	option is used
	      twice, additional	timing statistics are printed  on  a  pass  by
	      pass basis.

       -v     Verbose mode.

       -V     Print version information	and exit.

       -y     Assume  an answer	of `yes' to all	questions; allows e2fsck to be
	      used non-interactively.  This option may not be specified	at the
	      same time	as the -n or -p	options.

       -z undo_file
	      Before  overwriting  a file system block,	write the old contents
	      of the block to an undo file.  This undo file can	be  used  with
	      e2undo(8)	 to restore the	old contents of	the file system	should
	      something	go wrong.  If  the  empty  string  is  passed  as  the
	      undo_file	 argument,  the	 undo  file  will be written to	a file
	      named e2fsck-device.e2undo in the	directory  specified  via  the
	      E2FSPROGS_UNDO_DIR environment variable.

	      WARNING: The undo	file cannot be used to recover from a power or
	      system crash.

EXIT CODE
       The exit	code returned by e2fsck	is the sum  of	the  following	condi-
       tions:
	    0	 - No errors
	    1	 - File	system errors corrected
	    2	 - File	system errors corrected, system	should
		   be rebooted
	    4	 - File	system errors left uncorrected
	    8	 - Operational error
	    16	 - Usage or syntax error
	    32	 - E2fsck canceled by user request
	    128	 - Shared library error

SIGNALS
       The following signals have the following	effect when sent to e2fsck.

       SIGUSR1
	      This  signal  causes e2fsck to start displaying a	completion bar
	      or emitting progress information.	 (See discussion of the	-C op-
	      tion.)

       SIGUSR2
	      This signal causes e2fsck	to stop	displaying a completion	bar or
	      emitting progress	information.

REPORTING BUGS
       Almost any piece	of software will have bugs.  If	you manage to  find  a
       filesystem  which  causes e2fsck	to crash, or which e2fsck is unable to
       repair, please report it	to the author.

       Please include as much information as  possible	in  your  bug  report.
       Ideally,	 include a complete transcript of the e2fsck run, so I can see
       exactly what error messages are displayed.   (Make  sure	 the  messages
       printed by e2fsck are in	English; if your system	has been configured so
       that e2fsck's messages have  been  translated  into  another  language,
       please  set  the	the LC_ALL environment variable	to C so	that the tran-
       script of e2fsck's output will  be  useful  to  me.)   If  you  have  a
       writable	 filesystem  where the transcript can be stored, the script(1)
       program is a handy way to save the output of e2fsck to a	file.

       It is also useful to send the output of dumpe2fs(8).  If	a specific in-
       ode  or	inodes	seems to be giving e2fsck trouble, try running the de-
       bugfs(8)	command	and send the output of the stat(1u) command run	on the
       relevant	 inode(s).  If the inode is a directory, the debugfs dump com-
       mand will allow you to extract the contents  of	the  directory	inode,
       which  can  sent	 to me after being first run through uuencode(1).  The
       most useful data	you can	send to	help reproduce the bug is a compressed
       raw  image dump of the filesystem, generated using e2image(8).  See the
       e2image(8) man page for more details.

       Always include the full version string which e2fsck displays when it is
       run, so I know which version you	are running.

AUTHOR
       This version of e2fsck was written by Theodore Ts'o <tytso@mit.edu>.

SEE ALSO
       e2fsck.conf(5),	 badblocks(8),	dumpe2fs(8),  debugfs(8),  e2image(8),
       mke2fs(8), tune2fs(8)

E2fsprogs version 1.43.4	 January 2017			     E2FSCK(8)

NAME | SYNOPSIS | DESCRIPTION | OPTIONS | EXIT CODE | SIGNALS | REPORTING BUGS | AUTHOR | SEE ALSO

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