1DEBUGFS(8) System Manager's Manual DEBUGFS(8)
2
6 debugfs - ext2/ext3 file system debugger
7
9 debugfs [ -Vwci ] [ -b blocksize ] [ -s superblock ] [ -f cmd_file ] [
10 -R request ] [ -d data_source_device ] [ device ]
11
13 The debugfs program is an interactive file system debugger. It can be
14 used to examine and change the state of an ext2 file system.
15 device is the special file corresponding to the device containing the
16 ext2 file system (e.g /dev/hdXX).
17
19 -w Specifies that the file system should be opened in read-write
20 mode. Without this option, the file system is opened in read-
21 only mode.
22 -c Specifies that the file system should be opened in catastrophic
24 mode, in which the inode and group bitmaps are not read ini‐
25 tially. This can be useful for filesystems with significant
26 corruption, but because of this, catastrophic mode forces the
27 filesystem to be opened read-only.
28 -i Specifies that device represents an ext2 image file created by
30 the e2image program. Since the ext2 image file only contains
31 the superblock, block group descriptor, block and inode alloca‐
32 tion bitmaps, and the inode table, many debugfs commands will
33 not function properly. Warning: no safety checks are in place,
34 and debugfs may fail in interesting ways if commands such as ls,
35 dump, etc. are tried without specifying the data_source_device
36 using the -d option. debugfs is a debugging tool. It has rough
37 edges!
38 -d data_source_device
40 Used with the -i option, specifies that data_source_device
41 should be used when reading blocks not found in the ext2 image
42 file. This includes data, directory, and indirect blocks.
43 -b blocksize
45 Forces the use of the given block size for the file system,
46 rather than detecting the correct block size as normal.
47 -s superblock
49 Causes the file system superblock to be read from the given
50 block number, rather than the default (1). If you give a -s
51 option, you must also give a -b option.
52 -f cmd_file
54 Causes debugfs to read in commands from cmd_file, and execute
55 them. When debugfs is finished executing those commands, it
56 will exit.
57 -R request
59 Causes debugfs to execute the single command request, and then
60 exit.
61 -V print the version number of debugfs and exit.
63
65 Many debugfs commands take a filespec as an argument to specify an
66 inode (as opposed to a pathname) in the filesystem which is currently
67 opened by debugfs. The filespec argument may be specified in two
68 forms. The first form is an inode number surrounded by angle brackets,
69 e.g., <2>. The second form is a pathname; if the pathname is prefixed
70 by a forward slash ('/'), then it is interpreted relative to the root
71 of the filesystem which is currently opened by debugfs. If not, the
72 pathname is interpreted relative to the current working directory as
73 maintained by debugfs. This may be modified by using the debugfs com‐
74 mand cd.
75
77 This is a list of the commands which debugfs supports.
78 bmap filespec logical_block
80 Print the physical block number corresponding to the logical
81 block number logical_block in the inode filespec.
82 cat filespec
84 Dump the contents of the inode filespec to stdout.
85 cd filespec
87 Change the current working directory to filespec.
88 chroot filespec
90 Change the root directory to be the directory filespec.
91 close Close the currently open file system.
93 clri file
95 Clear the contents of the inode file.
96 dump [-p] filspec out_file
98 Dump the contents of the inode filespec to the output file
99 out_file. If the -p option is given set the owner, group and
100 permissions information on out_file to match filespec.
101 expand_dir filespec
103 Expand the directory filespec.
104 feature [fs_feature] [-fs_feature] ...
106 Set or clear various filesystem features in the superblock.
107 After setting or clearing any filesystem features that were
108 requested, print the current state of the filesystem feature
109 set.
110 find_free_block [count [goal]]
112 Find the first count free blocks, starting from goal and allo‐
113 cate it.
114 find_free_inode [dir [mode]]
116 Find a free inode and allocate it. If present, dir specifies
117 the inode number of the directory which the inode is to be
118 located. The second optional argument mode specifies the per‐
119 missions of the new inode. (If the directory bit is set on the
120 mode, the allocation routine will function differently.)
121 freeb block [count]
123 Mark the block number block as not allocated. If the optional
124 argument count is present, then count blocks starting at block
125 number block will be marked as not allocated.
126 freei filespec
128 Free the inode specified by filespec.
129 help Print a list of commands understood by debugfs(8).
131 icheck block ...
133 Print a listing of the inodes which use the one or more blocks
134 specified on the command line.
135 imap filespec
137 Print the location of the inode data structure (in the inode ta‐
138 ble) of the inode filespec.
139 init_filesys device blocksize
141 Create an ext2 file system on device with device size blocksize.
142 Note that this does not fully initialize all of the data struc‐
143 tures; to do this, use the mke2fs(8) program. This is just a
144 call to the low-level library, which sets up the superblock and
145 block descriptors.
146 kill_file filespec
148 Deallocate the inode filespec and its blocks. Note that this
149 does not remove any directory entries (if any) to this inode.
150 See the rm(1) command if you wish to unlink a file.
151 lcd directory
153 Change the current working directory of the debugfs process to
154 directory on the native filesystem.
155 ln filespec dest_file
157 Create a link named dest_file which is a link to filespec. Note
158 this does not adjust the inode reference counts.
159 logdump [-acs] [-b<block>] [-i<filespec>] [-f<journal_file>] [out‐
161 put_file]
162 Dump the contents of the ext3 journal. By default, the journal
163 inode as specified in the superblock. However, this can be
164 overridden with the -i option, which uses an inode specifier to
165 specify the journal to be used. A file containing journal data
166 can be specified using the -f option. Finally, the -s option
167 utilizes the backup information in the superblock to locate the
168 journal.
169 The -a option causes the logdump program to print the contents
171 of all of the descriptor blocks. The -b option causes logdump
172 to print all journal records that are refer to the specified
173 block. The -c option will print out the contents of all of the
174 data blocks selected by the -a and -b options.
175 ls [-l] [-d] filespec
177 Print a listing of the files in the directory filespec. The -l
178 flag will list files using a more verbose format. The -d flag
179 will list deleted entries in the directory.
180 modify_inode filespec
182 Modify the contents of the inode structure in the inode file‐
183 spec.
184 mkdir filespec
186 Make a directory.
187 mknod filespec [p|[[c|b] major minor]]
189 Create a special device file (a named pipe, character or block
190 device). If a character or block device is to be made, the
191 major and minor device numbers must be specified.
192 ncheck inode_num ...
194 Take the requested list of inode numbers, and print a listing of
195 pathnames to those inodes.
196 open [-w] [-e] [-f] [-i] [-c] [-b blocksize] [-s superblock] device
198 Open a filesystem for editing. The -f flag forces the filesys‐
199 tem to be opened even if there are some unknown or incompatible
200 filesystem features which would normally prevent the filesystem
201 from being opened. The -e flag causes the filesystem to be
202 opened in exclusive mode. The -b, -c, -i, -s, and -w options
203 behave the same as the command-line options to debugfs.
204 pwd Print the current working directory.
206 quit Quit debugfs
208 rdump directory destination
210 Recursively dump directory and all its contents (including regu‐
211 lar files, symbolic links, and other directories) into the named
212 destination which should be an existing directory on the native
213 filesystem.
214 rm pathname
216 Unlink pathname. If this causes the inode pointed to by path‐
217 name to have no other references, deallocate the file. This
218 command functions as the unlink() system call.
219 rmdir filespec
221 Remove the directory filespec.
222 setb block [count]
224 Mark the block number block as allocated. If the optional argu‐
225 ment count is present, then count blocks starting at block num‐
226 ber block will be marked as allocated.
227 set_block_group bgnum field value
229 Modify the block group descriptor specified by bgnum so that the
230 block group descriptor field field has value value.
231 seti filespec
233 Mark inode filespec as in use in the inode bitmap.
234 set_inode_field filespec field value
236 Modify the inode specified by filespec so that the inode field
237 field has value value. The list of valid inode fields which can
238 be set via this command can be displayed by using the command:
239 set_inode_field -l
240 set_super_value field value
242 Set the superblock field field to value. The list of valid
243 superblock fields which can be set via this command can be dis‐
244 played by using the command: set_super_value -l
245 show_super_stats [-h]
247 List the contents of the super block and the block group
248 descriptors. If the -h flag is given, only print out the
249 superblock contents.
250 stat filespec
252 Display the contents of the inode structure of the inode file‐
253 spec.
254 testb block [count]
256 Test if the block number block is marked as allocated in the
257 block bitmap. If the optional argument count is present, then
258 count blocks starting at block number block will be tested.
259 testi filespec
261 Test if the inode filespec is marked as allocated in the inode
262 bitmap.
263 unlink pathname
265 Remove the link specified by pathname to an inode. Note this
266 does not adjust the inode reference counts.
267 write source_file out_file
269 Create a file in the filesystem named out_file, and copy the
270 contents of source_file into the destination file.
271
273 DEBUGFS_PAGER, PAGER
274 The debugfs(8) program always pipes the output of the some com‐
275 mands through a pager program. These commands include:
276 show_super_stats, list_directory, show_inode_info,
277 list_deleted_inodes, and htree_dump. The specific pager can
278 explicitly specified by the DEBUGFS_PAGER environment variable,
279 and if it is not set, by the PAGER environment variable.
280 Note that since a pager is always used, the less(1) pager is not
282 particularly appropriate, since it clears the screen before dis‐
283 playing the output of the command and clears the output the
284 screen when the pager is exited. Many users prefer to use the
285 less(1) pager for most purposes, which is why the DEBUGFS_PAGER
286 environment variable is available to override the more general
287 PAGER environment variable.
288
290 debugfs was written by Theodore Ts'o <tytso@mit.edu>.
291
293 dumpe2fs(8), e2fsck(8), mke2fs(8)
294E2fsprogs version 1.40.2 July 2007 DEBUGFS(8)