1gfs2_edit(8) System Manager's Manual gfs2_edit(8)
2
6 gfs2_edit - Display, print or edit GFS2 or GFS internal structures.
7
10 gfs2_edit [OPTION]... [DEVICE]
11
14 The gfs2_edit command is a tool used to examine, edit or display inter‐
15 nal data structures of a GFS2 or GFS file system. The gfs2_edit com‐
16 mand can be run interactively, as described below in INTERACTIVE MODE.
17 Caution: Several options of the gfs2_edit command alter the file system
19 metadata and can cause file system corruption. These options should be
20 used with great care.
21
24 -p [struct | block] [blocktype] [blockalloc [val]] [blockbits]
25 [blockrg] [find sb|rg|rb|di|in|lf|jd|lh|ld|ea|ed|lb|13|qc] [field
26 <field> [val]]
27 Print a gfs2 data structure in human-readable format to stdout.
28 You can enter either a block number or a data structure name.
29 Block numbers may be specified in hex (e.g., 0x10) or decimal
30 (e.g., 16).
31 You can specify the following well-known locations with the -p
33 option.
34 sb, superblock - Print the superblock.
36 root - Print the root directory.
38 master - Print the master system directory.
40 jindex - Print the journal index system directory.
42 per_node - Print the per_node system directory.
44 inum - Print the system inum file.
46 statfs - Print the system statfs file.
48 rindex, rgindex - Print the resource group index system file.
50 rg X - Print the resource group information for RG X (zero-
52 based).
53 rgs - Print the resource group information.
55 quota - Print the contents of the system quota file.
57 identify - Identify a data block rather than print the block's
59 contents.
60 size - Print the device size information.
62 journalX - Print the contents of journal X, where X is a journal
64 number from 0 to <the number of journals in your file system -
65 1>. Only the journal headers and journal descriptors are
66 dumped. For journal descriptors, this option prints out every
67 file system block number logged in that section of the journal.
68 The actual journaled blocks are not printed.
69 If you specify a block number rather than a structure name,
71 gfs2_edit will print out a breakdown of the structure for that
72 block. For example: gfs2_edit -p sb will print the superblock,
73 but so does gfs2_edit -p 0x10 and gfs2_edit -p 16.
74 If you specify -p without a block or structure name, gfs2_edit
76 prints the superblock.
77 You can specify more than one data structure with a single -p
79 option. For example, gfs2_edit -p inum statfs /dev/sda1 prints
80 the system inum file and the system statfs file on /dev/sda1.
81 Optionally, you may specify the keyword blocktype to print out
83 the gfs2 block type for the specified block. Valid gfs2 block
84 types are: 0 (Clump), 1 (Superblock), 2 (Resource Group Header),
85 3 (Resource Group Bitmap), 4 (Dinode), 5 (Indirect Block), 6
86 (Leaf), 7 (Journaled data), 8 (Log Header), 9 (Log descriptor),
87 10 (Extended attribute), 11 (Eattr Data), 12 (Log Buffer), 13
88 (Invalid), and 14 (Quota Change).
89 Optionally, you may specify the keyword blockalloc with an
91 optional value to assign. If no value is specified, the block‐
92 alloc keyword will print the block allocation type for the spec‐
93 ified block. Valid block allocation types are: 0 (Free block),
94 1 (Data block), 2 (Unlinked block), and 3 (Metadata block). If
95 a value from 0 to 3 is specified, the resource group bitmap will
96 be changed to the new value. This may be used, for example, to
97 artificially free or allocate a block in order to test
98 fsck.gfs2's ability to detect and fix the problem.
99 Optionally, you may specify the keyword blockbits. This option
101 will locate and print the block containing the bitmap corre‐
102 sponding to the specified block.
103 Optionally, you may specify the keyword blockrg. This option
105 will locate and print the block number of the resource group
106 that holds information about the specified block.
107 You may also use gfs2_edit to find the next occurrence of a
109 metadata block of a certain type. Valid metadata types are:
110 none (unused metadata clump block), sb (superblock), rg
111 (resource group), rb (rg bitmap), di (disk inode aka dinode), in
112 (indirect block list), lf (directory leaf), jd (journaled data),
113 lh (journal log header), ld (journal log descriptor), ea
114 (extended attribute), ed (ea data block), lb (log buffer), 13
115 (unused block type 13), qc (quota change). The block AFTER the
116 one specified with -p is the starting point for the search. For
117 example, if you specify gfs2_edit -p rg 12 find rg
118 /dev/your/device, it will find the rg that follows rg 12 (nor‐
119 mally, this would be rg 13). Note, however, that since metadata
120 often appears in the journals, it could be a copy of a different
121 RG, inside a journal. Also note that gfs2_edit will only find
122 allocated metadata blocks unless the type specified is none, sb,
123 rg or rb. In other words, if you try to find a disk inode, it
124 will only find an allocated dinode, not a deallocated one.
125 Optionally, you may specify the keyword field followed by a
127 valid metadata field name. Right now, only the fields in disk
128 inodes and resource groups are allowed. If no value is speci‐
129 fied after the field, the value of the field will be printed to
130 stdout. If a value is specified, the field's value will be
131 changed. This may be used, for example, to artificially change
132 the di_size field for an inode in order to test fsck.gfs2's
133 ability to detect and fix the problem.
134 -s [structure | block]
137 Specify a starting block for interactive mode. Any of the well-
138 known locations found in the -p option may be specified. If you
139 want to start on a particular resource group, specify it in
140 quotes, e.g. -s "rg 3"
141 -h, -help, -usage
143 Print help information.
144 -c [0 | 1]
146 Use alternate color scheme for interactive mode: 0=normal (dark
147 colors on white background), or 1 (light colors on black back‐
148 ground).
149 -V Print program version information only.
151 -x Print in hex mode.
153 rg <rg> <device>
156 Print the contents of Resource Group <rg> on <device>.
157 <rg> is a number from 0 to X - 1, where X is the number of RGs.
159 rgcount <device>
161 Print the number of Resource Groups in the file system on
162 <device>.
163 rgflags <rg> [new_value] <device>
165 Print and/or modify the rg_flags value of Resource Group <rg> on
166 <device>.
167 <rg> is a number from 0 to X - 1, where X is the number of RGs.
169 If new_value is not specified, the current rg_flags value will
170 be printed but not modified. If new_value is specified, the
171 rg_flags field will be overwritten with the new value.
172 printsavedmeta <filename>
174 Print off a list of blocks from <filename> that were saved with
175 the savemeta option.
176 savemeta <device> <filename>
178 Save off the GFS2 metadata (not user data) for the file system
179 on the specified device to a file given by <filename>. You can
180 use this option to analyze file system problems without reveal‐
181 ing sensitive information that may be contained in the files.
182 This option works quickly by using the system bitmap blocks in
183 the resource groups to determine the location of all the meta‐
184 data. If there is corruption in the bitmaps, resource groups or
185 rindex file, this method may fail and you may need to use the
186 savemetaslow option. The destination file is not compressed.
187 You may want to compress it with a program such as bzip2 before
188 sending it for analysis.
189 savemetaslow <device> <filename>
191 Save off GFS2 metadata, as with the savemeta option, examining
192 every block in the file system for metadata. This option is
193 less prone to failure due to file system corruption than the
194 savemeta option, but it is extremely slow.
195 savergs <device> <filename>
197 Save off only the GFS2 resource group metadata for the file sys‐
198 tem on the specified device to a file given by <filename>.
199 restoremeta <filename> <dest device>
201 Take a file created with the savemeta option and restores its
202 contents on top of the specified destination device. WARNING:
203 When you use this option, the file system and all data on the
204 destination device is destroyed. Since only metadata (but no
205 data) is restored, every file in the resulting file system is
206 likely to be corrupt. The ONLY purpose of this option is to
207 examine and debug file system problems by restoring and examin‐
208 ing the state of the saved metadata. If the destination file
209 system is the same size or larger than the source file system
210 where the metadata was saved, the resulting file system will be
211 the same size as the source. If the destination device is
212 smaller than the source file system, gfs2_edit will restore as
213 much as it can, then quit, leaving you with a file system that
214 probably will not mount, but from which you might still be able
215 to figure out what is wrong with the source file system.
216
219 If you specify a device on the gfs2_edit command line and you specify
220 no options other than -c, gfs2_edit will act as an interactive GFS2
221 file system editor for the file system you specify. There are three
222 display modes: hex mode, structure mode and pointers mode. You use the
223 m key to switch between the modes, as described below. The modes are
224 as follows:
225 Hex mode (default)
227 Display or edit blocks of the file system in hexadecimal and
228 ascii.
229 Lines at the top indicate the currently displayed block in both
231 hex and decimal. If the block contains a GFS2 data structure,
232 the name of that structure will appear in the upper right corner
233 of the display. If the block is a well-known block, such as the
234 superblock or rindex, there will be a line to indicate what it
235 is.
236 In hex mode, you can edit blocks by pressing <enter> and enter‐
238 ing hexadecimal digits to replace the highlighted hex digits.
239 Do NOT precede the numbers with "0x". For example, if you want
240 to change the value at offset 0x60 from a 0x12 to 0xef, position
241 your cursor to offset 0x60, so that the 12 is highlighted, then
242 press <enter> and type in "ef". Press <escape> or <enter> to
243 exit edit mode.
244 In hex mode, different colors indicate different things. For
246 example, in the default color scheme, the GFS2 data structure
247 will be black, data offsets will be light blue, and actual data
248 (anything after the gfs2 data structure) will be red.
249 Structure mode
252 Decode the file system block into its GFS2 structure and display
253 the values of that structure. This mode is most useful for
254 jumping around the file system. For example, you can use the
255 arrow keys to position down to a pointer and press J to jump to
256 that block.
257 Pointers mode
260 Display any additional information appearing on the block. For
261 example, if an inode has block pointers, this will display them
262 and allow you to scroll through them. You can also position to
263 one of them and press J to jump to that block.
264
267 q or <esc>
268 The q or <escape> keys are used to exit gfs2_edit.
269 <arrow/movement keys> up, down, right, left, pg-up, pg-down, home, end
272 The arrow keys are used to highlight an area of the display.
273 The J key may be used to jump to the block that is highlighted.
274 m - Mode switch
277 The m key is used to switch between the three display modes.
278 The initial mode is hex mode. Pressing the m key once switches
279 to structure mode. Pressing it a second time switches from
280 structure mode to pointers mode. Pressing it a third time takes
281 you back to hex mode again.
282 j - Jump to block
285 The j key jumps to the block number that is currently high‐
286 lighted. In hex mode, hitting J will work when any byte of the
287 pointer is highlighted.
288 g - Goto block
291 The g key asks for a block number, then jumps there. Note that
292 in many cases, you can also arrow up so that the current block
293 number is highlighted, then press <enter> to enter a block num‐
294 ber to jump to.
295 h - Help display
298 The h key causes the interactive help display to be shown.
299 e - Extended mode
302 The e key causes gfs2_edit to switch to extended ("pointers")
303 mode.
304 c - Color scheme
307 The c key causes gfs2_edit to switch to its alternate color
308 scheme.
309 f - Forward block
312 The f key causes you to scroll forward one block. This does not
313 affect the "jump" status. In other words, if you use the f key
314 to move forward several blocks, pressing <backspace> will not
315 roll you back up.
316 <enter> - Edit value
319 The <enter> key causes you to go from display mode to edit mode.
320 If you are in hex mode and you hit enter, you can type new hex
321 values at the cursor's current location. Note: pressing <enter>
322 in structure mode allows you to enter a new value, with the fol‐
323 lowing restrictions: For gfs2 disk inodes and resource groups,
324 it will actually change the value on disk. However, inode num‐
325 bers may not be changed. For all other structures, the values
326 entered are ignored.
327 If you use the up arrow key to highlight the block number, then
329 press <enter>, you may then enter a new block number, or any of
330 the well-known block locations listed above (e.g. sb, rindex,
331 inum, rg 17, etc.) and gfs2_edit will jump to the block speci‐
332 fied. If you specify a slash character followed by a metadata
333 type, gfs2_edit will search for the next occurrence of that
334 metadata block type, and jump there. It will take you to block
335 0 if it does not find any more blocks of the specified metadata
336 type.
337 <home> If you are in pointers mode, this takes you back to the starts
340 of the pointers you are viewing. Otherwise it takes you back to
341 the superblock.
342 <backspace>
345 This takes you back to the block you were displaying before a
346 jump.
347 <space>
350 This takes you forward to the block you were displaying when you
351 hit <backspace>.
352
355 gfs2_edit /dev/roth_vg/roth_lv
356 Display and optionally edit the file system on
357 /dev/roth_vg/roth_lv
358 gfs2_edit -p sb /dev/vg0/lvol0
361 Print the superblock of the gfs2 file system located on
362 /dev/vg0/lvol0.
363 gfs2_edit -p identify 2746 2748 /dev/sda2
366 Print out what kind of blocks are at block numbers 2746 and 2748
367 on device /dev/sda2.
368 gfs2_edit -p rindex /dev/sda1
371 Print the resource group index system file located on device
372 /dev/sda1.
373 gfs2_edit savemeta /dev/sda1 /tmp/our_fs
376 Save off all metadata (but no user data) to file /tmp/our_fs.
377 gfs2_edit -p root /dev/my_vg/my_lv
380 Print the contents of the root directory in /dev/my_vg/my_lv.
381 gfs2-edit -x -p 0x3f7a /dev/sda1
384 Print the contents of block 16250 of /dev/sda1 in hex.
385 gfs2_edit -p 12345 /dev/sdc2
388 Print the gfs2 data structure at block 12345.
389 gfs2_edit rgcount /dev/sdb1
392 Print how many Resource Groups exist for /dev/sdb1.
393 gfs2_edit -p rg 17 /dev/sdb1
396 Print the contents of the eighteenth Resource Group on
397 /dev/sdb1.
398 gfs2_edit rgflags 3 /dev/sdb1
401 Print the rg_flags value for the fourth Resource Group on
402 /dev/sdb1.
403 gfs2_edit rgflags 3 8 /dev/sdb1
406 Set the GFS2_RGF_NOALLOC flag on for the fourth Resource Group
407 on /dev/sdb1.
408 gfs2_edit -p 25 blockalloc /dev/roth_vg/roth_lv
411 Print the block allocation type of block 25. May produce this
412 output: 3 (Metadata)
413 gfs2_edit -p 25 blockalloc 1 /dev/roth_vg/roth_lv
416 Change the block allocation type of block 25 to data. May pro‐
417 duce this output: 1
418 gfs2_edit -p 25 blocktype /dev/roth_vg/roth_lv
421 Print the metadata block type of block 25. May produce this
422 output: 4 (Block 25 is type 4: Dinode)
423 gfs2_edit -p 25 field di_size /dev/roth_vg/roth_lv
426 Print the di_size field of block 25. May produce this output:
427 134217728
428 gfs2_edit -x -p 25 field di_size /dev/roth_vg/roth_lv
431 Print the di_size field of block 25, in hexidecimal. May pro‐
432 duce this output: 0x8000000
433 gfs2_edit -p 25 field di_size 0x4000 /dev/roth_vg/roth_lv
436 Change the di_size field of block 25 to the hexidecimal value
437 0x4000. May produce this output: 16384
438
440 The directory code does not work well. It might be confused
441 by directory "sentinel" entries.
442 gfs2_edit(8)