DEBUGFS

Section: Maintenance Commands (8)
Updated: July 2000
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Copyright 1993, 1994, 1995 by Theodore Ts'o. All Rights Reserved.
This file may be copied under the terms of the GNU Public License.

NAME

debugfs - ext2 file system debugger

SYNOPSIS

debugfs [ -b blocksize ] [ -s superblock ] [ -f cmd_file ] [ -R request ] [ -V ] [ [ -w ] [ -c ] [ device ] ]

DESCRIPTION

The debugfs program is a 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.
-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.

COMMANDS

debugfs is an interactive debugger. It understands a number 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 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 [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 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.
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.
ls [-l] filespec: Print a listing of the files in the directory filespec.
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 [-w] [-f] [-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, 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, deallocate 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 allocated 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 destination 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.

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.

AUTHOR

debugfs was written by Theodore Ts'o <tytso@mit.edu>.

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