One of the patches which slipped into 2.6.7-rc3-mm2 is one by Andreas
Dilger and others which makes it possible to resize a running ext3
filesystem on the fly. This patch has been shipped with Fedora kernels for
a little while, but has not seen a lot of wider use. That could change, of
course, if the resize patch finds its way into the mainline.
The resize patch is conceptually quite simple. It simply adds one or more
block groups which make use of extra space which, one hopes, is sitting
there idle at the end of the existing filesystem. Once the block groups
are hooked into the filesystem data structures, a simple ioctl()
call or remount will make the space available. Behind this apparent
simplicity, of course, is a significant amount of code which makes the
resize operation happen on a modern, complex filesystem in a robust
People wanting to try out resizing will need a few things:
- A kernel (such as 2.6.7-rc3-mm2) with the online resize patch
- A patch to e2fsprogs to make use of the resize capability; it is
the ext2resize SourceForge download area.
- Free disk space into which the filesystem can expand. Usually this
means that the filesystem should live in a device mapper partition which
can be expanded as well.
- A very good backup of your filesystem.
This patch and its associated documentation (or lack thereof) still require
some work before being ready for widespread deployment. Once they get
there, however, life should get easier for system administrators who,
throughout history, have routinely found out that all that "extra space"
they figured into their filesystems is never enough.
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