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MAN page from OpenSuSE gfs2-utils-3.1.9-lp152.3.5.x86_64.rpm

gfs2_edit

Section: Maintenance Commands (8)
Index

 

NAME

gfs2_edit - Display, print or edit GFS2 or GFS internal structures.

 

SYNOPSIS

gfs2_edit[OPTION]... [DEVICE]

 

DESCRIPTION

The gfs2_edit command is a tool used to examine, edit ordisplay internal data structures of a GFS2 or GFS file system.The gfs2_edit command can be run interactively, as describedbelow in INTERACTIVE MODE.

Caution: Several options of the gfs2_edit command alter thefile system metadata and can cause file system corruption.These options should be used with great care.

 

OPTIONS

-p [struct | block] [blocktype] [blockalloc [val]] [blockbits] [blockrg] [find sb|rg|rb|di|in|lf|jd|lh|ld|ea|ed|lb|13|qc] [field <field> [val]]
Print a gfs2 data structure in human-readable format to stdout.You can enter either a block number or a data structure name. Block numbersmay be specified in hex (e.g., 0x10) or decimal (e.g., 16).

You can specify the following well-known locations with the -p option.

sb, superblock - Print the superblock.

root - Print the root directory.

master - Print the master system directory.

jindex - Print the journal index system directory.

per_node - Print the per_node system directory.

inum - Print the system inum file.

statfs - Print the system statfs file.

rindex, rgindex - Print the resource group index system file.

rg X - Print the resource group information for RG X (zero-based).

rgs - Print the resource group information.

quota - Print the contents of the system quota file.

identify - Identify a data block rather than print the block's contents.

size - Print the device size information.

journalX - Print the contents of journal X, where X is a journalnumber from 0 to <the number of journals in your file system - 1>.Only the journal headers and journal descriptors are dumped. For journaldescriptors, this option prints out every file system block number loggedin that section of the journal. The actual journaled blocks are not printed.

If you specify a block number rather than a structure name, gfs2_edit willprint out a breakdown of the structure for that block.For example: gfs2_edit -p sb will print the superblock, but so doesgfs2_edit -p 0x10 and gfs2_edit -p 16.

If you specify -p without a block or structure name, gfs2_edit prints thesuperblock.

You can specify more than one data structure with a single -p option.For example, gfs2_edit -p inum statfs /dev/sda1 prints the system inumfile and the system statfs file on /dev/sda1.

Optionally, you may specify the keyword blocktype to print out thegfs2 block type for the specified block. Valid gfs2 block types are:0 (Clump), 1 (Superblock), 2 (Resource Group Header), 3 (Resource GroupBitmap), 4 (Dinode), 5 (Indirect Block), 6 (Leaf), 7 (Journaled data),8 (Log Header), 9 (Log descriptor), 10 (Extended attribute),11 (Eattr Data), 12 (Log Buffer), 13 (Invalid), and 14 (Quota Change).

Optionally, you may specify the keyword blockalloc with anoptional value to assign. If no value is specified, the blockallockeyword will print the block allocation type for the specified block.Valid block allocation types are: 0 (Free block), 1 (Data block),2 (Unlinked block), and 3 (Metadata block). If a value from 0 to 3 isspecified, the resource group bitmap will be changed to the new value.This may be used, for example, to artificially free or allocate a blockin order to test fsck.gfs2's ability to detect and fix the problem.

Optionally, you may specify the keyword blockbits. This optionwill locate and print the block containing the bitmap corresponding tothe specified block.

Optionally, you may specify the keyword blockrg. This optionwill locate and print the block number of the resource group that holdsinformation about the specified block.

You may also use gfs2_edit to find the next occurrence of a metadatablock of a certain type. Valid metadata types are: none (unusedmetadata clump block), sb (superblock), rg (resource group),rb (rg bitmap), di (disk inode aka dinode), in (indirectblock list), lf (directory leaf), jd (journaled data),lh (journal log header), ld (journal log descriptor),ea (extended attribute), ed (ea data block), lb (log buffer),13 (unused block type 13), qc (quota change).The block AFTER the one specified with -p is the starting point forthe search. For example, if you specify gfs2_edit -p rg 12 find rg/dev/your/device, it will find the rg that follows rg 12 (normally,this would be rg 13). Note, however, that since metadata often appearsin the journals, it could be a copy of a different RG, inside a journal.Also note that gfs2_edit will only find allocated metadata blocksunless the type specified is none, sb, rg or rb. In other words, if youtry to find a disk inode, it will only find an allocated dinode, not adeallocated one.

Optionally, you may specify the keyword field followed by avalid metadata field name. Right now, only the fields in disk inodesand resource groups are allowed. If no value is specified after thefield, the value of the field will be printed to stdout. If a valueis specified, the field's value will be changed. This may be used,for example, to artificially change the di_size field for an inodein order to test fsck.gfs2's ability to detect and fix the problem.

-s [structure | block]
Specify a starting block for interactive mode. Any of the well-knownlocations found in the -p option may be specified. If you want to starton a particular resource group, specify it in quotes, e.g. -s "rg 3"
-h, -help, -usage
Print help information.
-c [0 | 1]
Use alternate color scheme for interactive mode: 0=normal (dark colors onwhite background), or 1 (light colors on black background).
-V
Print program version information only.
-x
Print in hex mode.
-z <0-9>
Compress metadata with gzip compression level 1 to 9 (default 9). 0 means no compression at all.
rg <rg> <device>
Print the contents of Resource Group <rg> on <device>.

<rg> is a number from 0 to X - 1, where X is the number of RGs.

rgcount <device>
Print the number of Resource Groups in the file system on <device>.
rgflags <rg> [new_value] <device>
Print and/or modify the rg_flags value of Resource Group <rg> on<device>.

<rg> is a number from 0 to X - 1, where X is the number of RGs.If new_value is not specified, the current rg_flags value will beprinted but not modified. If new_value is specified, the rg_flagsfield will be overwritten with the new value.

printsavedmeta <filename>
Print off a list of blocks from <filename> that were saved with the savemetaoption.
savemeta <device> <filename>
Save off the GFS2 metadata (not user data) for the file system on thespecified device to a file given by <filename>. You can use this optionto analyze file system problems without revealing sensitive informationthat may be contained in the files. This option works quickly byusing the system bitmap blocks in the resource groups to determine thelocation of all the metadata. If there is corruptionin the bitmaps, resource groups or rindex file, this method may fail andyou may need to use the savemetaslow option. The destination file iscompressed using gzip unless -z 0 is specified.
savemetaslow <device> <filename>
Save off GFS2 metadata, as with the savemeta option, examining everyblock in the file system for metadata. This option is less prone to failuredue to file system corruption than the savemeta option, but it is extremely slow. The destination file is compressed using gzip unless-z 0 is specified.
savergs <device> <filename>
Save off only the GFS2 resource group metadata for the file system on thespecified device to a file given by <filename>. The destination file iscompressed using gzip unless -z 0 is specified.
restoremeta <filename> <dest device>
Take a compressed or uncompressed file created with the savemeta option andrestores its contents on top of the specified destination device.WARNING: When you use this option, the file system and all data on thedestination device is destroyed. Since only metadata (but no data) isrestored, every file in the resulting file system is likely to be corrupt. TheONLY purpose of this option is to examine and debug file system problems byrestoring and examining the state of the saved metadata. If the destinationfile system is the same size or larger than the source file system where themetadata was saved, the resulting file system will be the same size as thesource. If the destination device is smaller than the source file system,gfs2_edit will restore as much as it can, then quit, leaving you with a filesystem that probably will not mount, but from which you might still be able tofigure out what is wrong with the source file system.

 

INTERACTIVE MODE

If you specify a device on the gfs2_edit command line and you specifyno options other than -c, gfs2_edit will act as an interactive GFS2file system editor for the file system you specify. Thereare three display modes: hex mode, structure mode and pointers mode.You use the m key to switch between the modes, as described below.The modes are as follows:
Hex mode (default)
Display or edit blocks of the file system in hexadecimal and ascii.

Lines at the top indicate the currently displayed block in both hex anddecimal. If the block contains a GFS2 data structure, the name of thatstructure will appear in the upper right corner of the display.If the block is a well-known block, such as the superblock or rindex,there will be a line to indicate what it is.

In hex mode, you can edit blocks by pressing <enter> and enteringhexadecimal digits to replace the highlighted hex digits. Do NOT precedethe numbers with "0x". For example, if you want to change the value atoffset 0x60 from a 0x12 to 0xef, position your cursor to offset 0x60,so that the 12 is highlighted, then press <enter> and type in "ef".Press <escape> or <enter> to exit edit mode.

In hex mode, different colors indicate different things.For example, in the default color scheme, the GFS2 data structure willbe black, data offsets will be light blue, and actual data (anything afterthe gfs2 data structure) will be red.

Structure mode
Decode the file system block into its GFS2 structure anddisplay the values of that structure. This mode is most useful forjumping around the file system. For example, you can use the arrow keys to position down to a pointer and press J to jump to that block.

Pointers mode
Display any additional information appearing on the block.For example, if an inode has block pointers, this will display them andallow you to scroll through them. You can also position to one of themand press J to jump to that block.

 

Interactive mode command keys:

q or <esc>
The q or <escape> keys are used to exit gfs2_edit.

<arrow/movement keys> up, down, right, left, pg-up, pg-down, home, end
The arrow keys are used to highlight an area of the display. The Jkey may be used to jump to the block that is highlighted.

m - Mode switch
The m key is used to switch between the three display modes.The initial mode is hex mode. Pressing the m key once switches tostructure mode. Pressing it a second time switches from structure modeto pointers mode. Pressing it a third time takes you back to hex mode again.

j - Jump to block
The j key jumps to the block number that is currently highlighted.In hex mode, hitting J will work when any byte of the pointer is highlighted.

g - Goto block
The g key asks for a block number, then jumps there. Note thatin many cases, you can also arrow up so that the current block numberis highlighted, then press <enter> to enter a block number to jump to.

h - Help display
The h key causes the interactive help display to be shown.

e - Extended mode
The e key causes gfs2_edit to switch to extended ("pointers") mode.

c - Color scheme
The c key causes gfs2_edit to switch to its alternate color scheme.

f - Forward block
The f key causes you to scroll forward one block. This doesnot affect the "jump" status. In other words, if you use the fkey to move forward several blocks, pressing <backspace> willnot roll you back up.

<enter> - Edit value
The <enter> key causes you to go from display mode to edit mode.If you are in hex mode and you hit enter, you can type new hex valuesat the cursor's current location. Note: pressing <enter>in structure mode allows you to enter a new value, with the followingrestrictions: For gfs2 disk inodes and resource groups, it willactually change the value on disk. However, inode numbers may not bechanged. For all other structures, the values entered are ignored.

If you use the up arrow key to highlight the block number, then press<enter>, you may then enter a new block number, or any of thewell-known block locations listed above (e.g. sb, rindex, inum, rg 17,etc.) and gfs2_edit will jump to the block specified. If you specifya slash character followed by a metadata type, gfs2_edit will search forthe next occurrence of that metadata block type, and jump there. Itwill take you to block 0 if it does not find any more blocks of thespecified metadata type.

<home>
If you are in pointers mode, this takes you back to the starts of thepointers you are viewing. Otherwise it takes you back to the superblock.

<backspace>
This takes you back to the block you were displaying before a jump.

<space>
This takes you forward to the block you were displaying when you hit<backspace>.

 

EXAMPLES

gfs2_edit /dev/roth_vg/roth_lv
Display and optionally edit the file system on /dev/roth_vg/roth_lv

gfs2_edit -p sb /dev/vg0/lvol0
Print the superblock of the gfs2 file system located on/dev/vg0/lvol0.

gfs2_edit -p identify 2746 2748 /dev/sda2
Print out what kind of blocks are at block numbers 2746 and 2748 ondevice /dev/sda2.

gfs2_edit -p rindex /dev/sda1
Print the resource group index system file located on device/dev/sda1.

gfs2_edit savemeta /dev/sda1 /tmp/our_fs
Save off all metadata (but no user data) to file /tmp/our_fs.

gfs2_edit -p root /dev/my_vg/my_lv
Print the contents of the root directory in /dev/my_vg/my_lv.

gfs2-edit -x -p 0x3f7a /dev/sda1
Print the contents of block 16250 of /dev/sda1 in hex.

gfs2_edit -p 12345 /dev/sdc2
Print the gfs2 data structure at block 12345.

gfs2_edit rgcount /dev/sdb1
Print how many Resource Groups exist for /dev/sdb1.

gfs2_edit -p rg 17 /dev/sdb1
Print the contents of the eighteenth Resource Group on /dev/sdb1.

gfs2_edit rgflags 3 /dev/sdb1
Print the rg_flags value for the fourth Resource Group on /dev/sdb1.

gfs2_edit rgflags 3 8 /dev/sdb1
Set the GFS2_RGF_NOALLOC flag on for the fourth Resource Group on /dev/sdb1.

gfs2_edit -p 25 blockalloc /dev/roth_vg/roth_lv
Print the block allocation type of block 25.May produce this output:3 (Metadata)

gfs2_edit -p 25 blockalloc 1 /dev/roth_vg/roth_lv
Change the block allocation type of block 25 to data.May produce this output:1

gfs2_edit -p 25 blocktype /dev/roth_vg/roth_lv
Print the metadata block type of block 25.May produce this output:4 (Block 25 is type 4: Dinode)

gfs2_edit -p 25 field di_size /dev/roth_vg/roth_lv
Print the di_size field of block 25.May produce this output:134217728

gfs2_edit -x -p 25 field di_size /dev/roth_vg/roth_lv
Print the di_size field of block 25, in hexidecimal.May produce this output:0x8000000

gfs2_edit -p 25 field di_size 0x4000 /dev/roth_vg/roth_lv
Change the di_size field of block 25 to the hexidecimal value 0x4000.May produce this output:16384
 

KNOWN BUGS

The directory code does not work well. It might be confused
by directory "sentinel" entries.


 

Index

NAME
SYNOPSIS
DESCRIPTION
OPTIONS
INTERACTIVE MODE
Interactive mode command keys:
EXAMPLES
KNOWN BUGS

This document was created byman2html,using the manual pages.