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 specifying 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,
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 brackets, 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 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.
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
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 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 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 existing 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 allocated.
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.
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@mit.edu>.
