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DEBUGFS(8) DEBUGFS(8)
NAME
debugfs - ext2/ext3 file system debugger
SYNOPSIS
debugfs [ -Vwci ] [ -b blocksize ] [ -s superblock ] [ -f cmd_file ] [ -R request ] [ -d
data_source_device ] [ device ]
DESCRIPTION
The debugfs program is an interactive file system debugger. It can be used to examine and
change the state of an ext2 file system.
device is the special file corresponding to the device containing the ext2 file system
(e.g /dev/hdXX).
OPTIONS
-w Specifies that the file system should be opened in read-write mode. Without this
option, the file system is opened in read-only mode.
-c Specifies that the file system should be opened in catastrophic mode, in which the
inode and group bitmaps are not read initially. This can be useful for filesystems
with significant corruption, but because of this, catastrophic mode forces the
filesystem to be opened read-only.
-i Specifies that device represents an ext2 image file created by the e2image program.
Since the ext2 image file only contains the superblock, block group descriptor,
block and inode allocation bitmaps, and the inode table, many debugfs commands will
not function properly. Warning: no safety checks are in place, and debugfs may
fail in interesting ways if commands such as ls, dump, etc. are tried without spec-
ifying the data_source_device using the -d option. debugfs is a debugging tool.
It has rough edges!
-d data_source_device
Used with the -i option, specifies that data_source_device should be used when
reading blocks not found in the ext2 image file. This includes data, directory,
and indirect blocks.
-b blocksize
Forces the use of the given block size for the file system, rather than detecting
the correct block size as normal.
-s superblock
Causes the file system superblock to be read from the given block number, instead
of using the primary superblock (located at an offset of 1024 bytes from the begin-
ning of the filesystem). If you specify the -s option, you must also provide the
blocksize of the filesystem via the -b option.
-f cmd_file
Causes debugfs to read in commands from cmd_file, and execute them. When debugfs
is finished executing those commands, it will exit.
-R request
Causes debugfs to execute the single command request, and then exit.
-V print the version number of debugfs and exit.
SPECIFYING FILES
Many debugfs commands take a filespec as an argument to specify an inode (as opposed to a
pathname) in the filesystem which is currently opened by debugfs. The filespec argument
may be specified in two forms. The first form is an inode number surrounded by angle
brackets, e.g., <2>. The second form is a pathname; if the pathname is prefixed by a for-
ward slash ('/'), then it is interpreted relative to the root of the filesystem which is
currently opened by debugfs. If not, the pathname is interpreted relative to the current
working directory as maintained by debugfs. This may be modified by using the debugfs
command cd.
COMMANDS
This is a list of the commands which debugfs supports.
bmap filespec logical_block
Print the physical block number corresponding to the logical block number logi-
cal_block in the inode filespec.
cat filespec
Dump the contents of the inode filespec to stdout.
cd filespec
Change the current working directory to filespec.
chroot filespec
Change the root directory to be the directory filespec.
close Close the currently open file system.
clri file
Clear the contents of the inode file.
dump [-p] filespec out_file
Dump the contents of the inode filespec to the output file out_file. If the -p
option is given set the owner, group and permissions information on out_file to
match filespec.
expand_dir filespec
Expand the directory filespec.
feature [fs_feature] [-fs_feature] ...
Set or clear various filesystem features in the superblock. After setting or
clearing any filesystem features that were requested, print the current state of
the filesystem feature set.
find_free_block [count [goal]]
Find the first count free blocks, starting from goal and allocate it.
find_free_inode [dir [mode]]
Find a free inode and allocate it. If present, dir specifies the inode number of
the directory which the inode is to be located. The second optional argument mode
specifies the permissions of the new inode. (If the directory bit is set on the
mode, the allocation routine will function differently.)
freeb block [count]
Mark the block number block as not allocated. If the optional argument count is
present, then count blocks starting at block number block will be marked as not
allocated.
freei filespec
Free the inode specified by filespec.
help Print a list of commands understood by debugfs(8).
icheck block ...
Print a listing of the inodes which use the one or more blocks specified on the
command line.
imap filespec
Print the location of the inode data structure (in the inode table) of the inode
filespec.
init_filesys device blocksize
Create an ext2 file system on device with device size blocksize. Note that this
does not fully initialize all of the data structures; to do this, use the mke2fs(8)
program. This is just a call to the low-level library, which sets up the
superblock and block descriptors.
kill_file filespec
Deallocate the inode filespec and its blocks. Note that this does not remove any
directory entries (if any) to this inode. See the rm(1) command if you wish to
unlink a file.
lcd directory
Change the current working directory of the debugfs process to directory on the
native filesystem.
ln filespec dest_file
Create a link named dest_file which is a link to filespec. Note this does not
adjust the inode reference counts.
logdump [-acs] [-b<block>] [-i<filespec>] [-f<journal_file>] [output_file]
Dump the contents of the ext3 journal. By default, the journal inode as specified
in the superblock. However, this can be overridden with the -i option, which uses
an inode specifier to specify the journal to be used. A file containing journal
data can be specified using the -f option. Finally, the -s option utilizes the
backup information in the superblock to locate the journal.
The -a option causes the logdump program to print the contents of all of the
descriptor blocks. The -b option causes logdump to print all journal records that
are refer to the specified block. The -c option will print out the contents of all
of the data blocks selected by the -a and -b options.
ls [-l] [-d] [-p] filespec
Print a listing of the files in the directory filespec. The -l flag will list
files using a more verbose format. The -d flag will list deleted entries in the
directory. The -p flag will list the files in a format which is more easily
parsable by scripts, as well as making it more clear when there are spaces or other
non-printing characters at the end of filenames.
modify_inode filespec
Modify the contents of the inode structure in the inode filespec.
mkdir filespec
Make a directory.
mknod filespec [p|[[c|b] major minor]]
Create a special device file (a named pipe, character or block device). If a char-
acter or block device is to be made, the major and minor device numbers must be
specified.
ncheck inode_num ...
Take the requested list of inode numbers, and print a listing of pathnames to those
inodes.
open [-w] [-e] [-f] [-i] [-c] [-b blocksize] [-s superblock] device
Open a filesystem for editing. The -f flag forces the filesystem to be opened even
if there are some unknown or incompatible filesystem features which would normally
prevent the filesystem from being opened. The -e flag causes the filesystem to be
opened in exclusive mode. The -b, -c, -i, -s, and -w options behave the same as
the command-line options to debugfs.
pwd Print the current working directory.
quit Quit debugfs
rdump directory destination
Recursively dump directory and all its contents (including regular files, symbolic
links, and other directories) into the named destination which should be an exist-
ing directory on the native filesystem.
rm pathname
Unlink pathname. If this causes the inode pointed to by pathname to have no other
references, deallocate the file. This command functions as the unlink() system
call.
rmdir filespec
Remove the directory filespec.
setb block [count]
Mark the block number block as allocated. If the optional argument count is
present, then count blocks starting at block number block will be marked as allo-
cated.
set_block_group bgnum field value
Modify the block group descriptor specified by bgnum so that the block group
descriptor field field has value value.
seti filespec
Mark inode filespec as in use in the inode bitmap.
set_inode_field filespec field value
Modify the inode specified by filespec so that the inode field field has value
value. The list of valid inode fields which can be set via this command can be
displayed by using the command: set_inode_field -l
set_super_value field value
Set the superblock field field to value. The list of valid superblock fields which
can be set via this command can be displayed by using the command: set_super_value
-l
show_super_stats [-h]
List the contents of the super block and the block group descriptors. If the -h
flag is given, only print out the superblock contents.
stat filespec
Display the contents of the inode structure of the inode filespec.
testb block [count]
Test if the block number block is marked as allocated in the block bitmap. If the
optional argument count is present, then count blocks starting at block number
block will be tested.
testi filespec
Test if the inode filespec is marked as allocated in the inode bitmap.
undel <inode num> [pathname]
Undelete the specified inode number (which must be surrounded by angle brackets) so
that it and its blocks are marked in use, and optionally link the recovered inode
to the specified pathname. The e2fsck command should always be run after using the
undel command to recover deleted files.
Note that if you are recovering a large number of deleted files, linking the inode
to a directory may require the directory to be expanded, which could allocate a
block that had been used by one of the yet-to-be-undeleted files. So it is safer
to undelete all of the inodes without specifying a destination pathname, and then
in a separate pass, use the debugfs link command to link the inode to the destina-
tion pathname, or use e2fsck to check the filesystem and link all of the recovered
inodes to the lost+found directory.
unlink pathname
Remove the link specified by pathname to an inode. Note this does not adjust the
inode reference counts.
write source_file out_file
Create a file in the filesystem named out_file, and copy the contents of
source_file into the destination file.
ENVIRONMENT VARIABLES
DEBUGFS_PAGER, PAGER
The debugfs(8) program always pipes the output of the some commands through a pager
program. These commands include: show_super_stats, list_directory,
show_inode_info, list_deleted_inodes, and htree_dump. The specific pager can
explicitly specified by the DEBUGFS_PAGER environment variable, and if it is not
set, by the PAGER environment variable.
Note that since a pager is always used, the less(1) pager is not particularly
appropriate, since it clears the screen before displaying the output of the command
and clears the output the screen when the pager is exited. Many users prefer to
use the less(1) pager for most purposes, which is why the DEBUGFS_PAGER environment
variable is available to override the more general PAGER environment variable.
AUTHOR
debugfs was written by Theodore Ts'o <tytso AT mit.edu>.
SEE ALSO
dumpe2fs(8), tune2fs(8), e2fsck(8), mke2fs(8)
E2fsprogs version 1.41.3 October 2008 DEBUGFS(8)
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On Apache
Under GNU General Public License
2012-05-25 20:13 @38.107.179.239 Crawled by CCBot/1.0 (+http://www.commoncrawl.org/bot.html)