[Linux-cluster] unformat gfs2

[Bob Peterson]

----- Original Message -----
> It's GFS2 .
> Without any use of gfs2_grow,
> All options are equal ..
> No,
> 
> There is many many block types (http://linux.die.net/man/8/gfs2_edit),
> Do we find 4 (Dinode)? instead of for example 3 (Resource Group Bitmap)?
> 
> How we could fine bitmaps?

Hi,

To use gfs2_edit properly, you should have an understanding of how the
gfs2 file system is kept on disk. If you are a Red Hat customer, I have
several videos on the Red Hat customer portal on how to use gfs2_edit.

The dinode blocks are type 4. There are two kinds of bitmaps: bitmaps
associated with rgrps (type 2) and bitmaps that follow rgrps (type 3).
The rgrps are indexed by the rindex system file in the master directory,
and ri_length tells you how many bitmap blocks follow each rgrp block.

In newer versions (RHEL6+) there are little helper functions in gfs2_edit
that can tell you the bitmap status, and alter it. For example:

gfs2_edit -p <block number> blocktype /dev/your/device

This command will tell you the block type, for example:
# gfs2_edit -p root blocktype /dev/mpathc/scratch
4 (Block 22 is type 4: Dinode)

gfs2_edit -p <block number> blockalloc /dev/your/device
This command will tell you the current bitmap setting. The bitmap setting
may be changed to "3" (dinode) with:
gfs2_edit -p <block number> blockalloc 3 /dev/your/device

So you could write a script to do it, but again, you would have to be
careful, and work on a copy, never the original.

Regards,

Bob Peterson
Red Hat File Systems