gfs_edit(8)gfs_edit(8)NAMEgfs_edit - Display or edit GFS internal structures.
SYNOPSISgfs_edit [OPTION]... DEVICE
DESCRIPTION
The gfs_edit command is a tool used to examine, edit or display inter‐
nal data structures of a GFS filesystem. Use at your own risk.
OPTIONS-V Print program version information only.
INTERACTIVE MODE
There are 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 number
in hex. If the block contains a GFS data structure, the name of
that structure will appear in the upper right corner of the dis‐
play. 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 enter‐
ing hexadecimal digits to replace the highlighted hex digits.
Do NOT precede the numbers with "0x". For example, if you want
to change the value at offset 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". You will automatically be
returned to display mode (Unlike gfs2_edit, you may only edit
one byte at a time.)
In hex mode, different colors indicate different things. For
example, an inode will appear white, block offsets will be light
blue, and actual data (anything after the gfs data structure)
will be red.
Structure mode
Decode the file system block into its GFS structure and display
the values of that structure. This mode is most useful for
jumping 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
and allow you to scroll through them. You can also position to
one of them and press J to jump to that block.
Interactive mode command keys:
q or <esc>
The q or <escape> keys are used to exit gfs_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 J key 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
to structure mode. Pressing it a second time switches from
structure mode to 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 high‐
lighted. 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 that
in many cases, you can also arrow up so that the current block
number is highlighted, then press <enter> to enter a block num‐
ber to jump to in hexadecimal, with no leading "0x".
h - Help display
The h key causes the interactive help display to be shown.
f or <space> - Forward block
The f key causes you to scroll forward one block.
b - Backward block
The b key causes you to scroll backward one block.
<home> - Return to superblock
The <home> key takes you back to the superblock.
<backspace>
This takes you back to the block you were displaying previously.
Unlike gfs2_edit, gfs_edit only remembers the one block you pre‐
viously viewed.
EXAMPLESgfs_edit /dev/vg0/lvol0
This will display the superblock of the gfs file system located
on /dev/vg0/lvol0 and allow you to edit.
KNOWN LIMITATIONS
Shortcomings compared to gfs2_edit
Unlike gfs2_edit, gfs_edit cannot print data structures. There
is no alternate color scheme. It does not remember multiple
block jumps, and it can not parse the rindex file and other data
structures. It only operates on file systems with the default
4K block size. It does not work with gfs2 file systems.
Since this is primarily a debugging tool and since gfs2_edit can
do more than gfs_edit can, we have no plans at this time to
enhance gfs_edit.
SEE ALSOgfs2_edit(8)gfs_edit(8)
