debugfs - ext2 file system debugger
debugfs [ -b blocksize ] [ -s superblock ] [ -f cmd_file ] [ -R request ] [ -V ] [ [ -w ]
[ -c ] [ -i ] [ device ] ]
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
-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. debugfs is
a debugging tool. It has rough edges!
Forces the use of the given block size for the file system, rather than detecting
the correct block size as normal.
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.
Causes debugfs to read in commands from cmd_file, and execute them. When debugfs
is finished executing those commands, it will exit.
Causes debugfs to execute the single command request, and then exit.
-V print the version number of debugfs and exit.
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
This is a list of the commands which debugfs supports.
Dump the contents of the inode filespec to stdout.
Change the current working directory to filespec.
Change the root directory to be the directory filespec.
close Close the currently open file system.
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
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
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
initialize 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.
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.
Change the current working directory of the debugfs process to directory on the
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 [-ac] [-b<block>] [-i<inode>] [-f<journal_file>] [output_file]
Dump the contents of the ext3 journal.
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
Modify the contents of the inode structure in the inode 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
ncheck inode_num ...
Take the requested list of inode numbers, and print a listing of pathnames to those
open [-w] [-f] [-i] [-c] [-b blocksize] [-s superblock] device
Open a filesystem for editing. The -w flag causes the filesystem to be opened for
writing. 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 -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 regular files, symbolic
links, and other directories) into the named destination which should be an exist-
ing directory on the native filesystem.
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
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-
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 displayed by using the command: set_super_value
List the contents of the super block and the block group descriptors. If the -h
flag is given, only print out the superblock contents.
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.
Test if the inode filespec is marked as allocated in the inode bitmap.
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.
debugfs was written by Theodore Ts'o <email@example.com>.
dumpe2fs(8), e2fsck(8), mke2fs(8)
E2fsprogs version 1.32 November 2002 DEBUGFS(8)