DEBUGFS linux command manual
DEBUGFS(8) DEBUGFS(8)
NAME
debugfs - ext2/ext3 file system debugger
SYNOPSIS
debugfs [ -b blocksize ] [ -s superblock ] [ -f cmd_file ] [ -R
request ] [ -V ] [ [ -w ] [ -c ] [ -i ] [ 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 ini-
tially. 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 alloca-
tion 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. debugfs is a debugging tool. It has
rough edges!
-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, rather than the default (1). If you give a -s
option, you must also give a -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 brack-
ets, e.g., <2>. The second form is a pathname; if the pathname is
prefixed by a forward 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 logical_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] filspec 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 allo-
cate 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 per-
missions 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 block-
size. 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] [-i] [-f] [out-
put_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] 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.
modify_inode filespec
Modify the contents of the inode structure in the inode file-
spec.
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 character 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] [-f] [-i] [-c] [-b blocksize] [-s superblock] device
Open a filesystem for editing. The -w flag causes the filesys-
tem to be opened for writing. The -f flag forces the filesys-
tem to be opened even if there are some unknown or incompatible
filesystem features which would normally prevent the filesystem
from being opened. The -c, -b, -i, and -s options behave the
same as those to debugfs itself.
pwd Print the current working directory.
quit Quit debugfs
rdump directory destination
Recursively dump directory and all its contents (including reg-
ular files, symbolic links, and other directories) into the
named destination which should be an existing directory on the
native filesystem.
rm pathname
Unlink pathname. If this causes the inode pointed to by path-
name 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 allocated.
seti filespec
Mark inode filespec as in use in the inode bitmap.
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 dis-
played 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 file-
spec.
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.
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 com-
mands 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 .
SEE ALSO
dumpe2fs(8), e2fsck(8), mke2fs(8)
E2fsprogs version 1.35 February 2004 DEBUGFS(8)