debugfs
DEBUGFS(8) DEBUGFS(8)
NAME
debugfs - ext2 file system debugger
SYNOPSIS
debugfs [ -b blocksize ] [ -s superblock ] [ -f cmd_file ]
[ -R request ] [ -V ] [ [ -w ] [ -c ] [ -i ] [ device ] ]
DESCRIPTION
The debugfs program is a file system debugger. It can be
used to examine and change the state of an ext2 file sys
tem.
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 inter
esting 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, also give a
-b option.
-f cmd_file
Causes debugfs to read in commands from cmd_file,
and execute them. When debugfs is finished execut
ing 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.
COMMANDS
debugfs is an interactive debugger. It understands a num
ber of commands.
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 file
spec.
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 out
put 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 filesys
tem features that were requested, print the current
state of the filesystem feature set.
find_free_block [goal]
Find the first free block, 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
Mark the block number block 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.
initialize device blocksize
Create an ext2 file system on device with device
size blocksize. Note that this does not fully ini
tialize 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.
ln filespec dest_file
Create a link named dest_file which is a link to
filespec. Note this does not adjust the inode ref
erence counts.
ls [-l] filespec
Print a listing of the files in the directory file
spec.
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, charac
ter 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 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 filesys
tem 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
rm pathname
Unlink pathname. If this causes the inode pointed
to by pathname to have no other references, deallo
cate the file. This command functions as the
unlink() system call.
rmdir filespec
Remove the directory filespec. This function is
currently not implemented.
setb block
Mark the block number block as allocated.
seti filespec
Mark inode filespec as in use in the inode bitmap.
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
Test if the block number block is marked as allo
cated in the block bitmap.
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 destina
tion file.
lcd directory
Change the current working directory of the debugfs
process to directory on the native filesystem.
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 existing directory on the native
filesystem.
SPECIFYINGFILES
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.
AUTHOR
debugfs was written by Theodore Ts'o <tytso@mit.edu>.
SEE ALSO
dumpe2fs(8), e2fsck(8), mke2fs(8)
E2fsprogs version 1.23 August 2001 DEBUGFS(8)