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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
	      backup superblocks is dependent on the  filesystem's  blocksize,
	      the  number of blocks per	group, and features such as sparse_su-
	      per.

	      Additional backup	superblocks can	be  determined	by  using  the
	      mke2fs  program  using  the -n option to print out where the su-
	      perblocks	exist, supposing mke2fs	 is  supplied  with  arguments
	      that  are	 consistent  with the filesystem's layout (e.g.	block-
	      size, blocks per group, sparse_super, etc.).

	      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.

		   no_optimize_extents
			  Do not offer to optimize the extent tree  by	elimi-
			  nating unnecessary width or depth.  This can also be
			  enabled in the options section of /etc/e2fsck.conf.

		   optimize_extents
			  Offer	to optimize the	extent tree by eliminating un-
			  necessary  width  or depth.  This is the default un-
			  less otherwise specified in /etc/e2fsck.conf.

		   inode_count_fullmap
			  Trade	off using memory for  speed  when  checking  a
			  file	system	with  a	 large	number	of hard-linked
			  files.  The amount of	 memory	 required  is  propor-
			  tional  to  the number of inodes in the file system.
			  For large file systems, this	can  be	 gigabytes  of
			  memory.   (For  example, a 40TB file system with 2.8
			  billion inodes will consume  an  additional  5.7  GB
			  memory if this optimization is enabled.)  This opti-
			  mization can also be enabled in the options  section
			  of /etc/e2fsck.conf.

		   no_inode_count_fullmap
			  Disable  the inode_count_fullmap optimization.  This
			  is  the  default  unless  otherwise	specified   in
			  /etc/e2fsck.conf.

		   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.

		   unshare_blocks
			  If the filesystem has	shared blocks, with the	shared
			  blocks read-only feature enabled, then this will un-
			  share	all shared blocks and unset the	read-only fea-
			  ture bit. If there is	not enough free	space then the
			  operation  will  fail.   If  the filesystem does not
			  have the  read-only  feature	bit,  but  has	shared
			  blocks anyway, then this option will have no effect.
			  Note when using this option, if  there  is  no  free
			  space	 to clone blocks, there	is no prompt to	delete
			  files	and instead the	operation will fail.

			  Note that unshare_blocks implies the "-f" option  to
			  ensure  that	all  passes  are run. Additionally, if
			  "-n" is also specified, e2fsck will simulate	trying
			  to  allocate	enough	space  to deduplicate. If this
			  fails, the exit code will be non-zero.

       -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.

ENVIRONMENT
       E2FSCK_CONFIG
	      Determines  the  location	 of  the   configuration   file	  (see
	      e2fsck.conf(5)).

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 1.45.6	  March	2020			     E2FSCK(8)

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

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