How to resize ext3 filesystem on RHEL 5.x

I didn't have a luck when I was looking for ext2online utility to resize ext3 filesystem online on RHEL 5.x (it is available on RHEL 4.x). Online means to resize it without requirement to unmount the filesystem. I went through the release notes but I didn't find any notes about it. Perhaps, I didn't read them carefully.

The ext2online tool can be used to resize ext2 filesystem but it has to be unmounted. The tool is able to resize ext3 filesystem online under the condition of kernel supports online resizing. More particularly, it is possible to do online enlarging only.

Alongside it, there exists another tool - resize2fs which is capable of ext2/ext3 filesystem resizing. But the filesystem has to be unmounted first. This is required on RHEL 4.x. If you try to resize a mounted ext3 filesytem on RHEL 4.x with the tool it will end with error "can't resize a mounted filesystem!".

So, how to resize ext3 filesystem on newer RHEL 5.x? Both tools belong to the e2fsprogs package which contains a set of tools for creating, checking, modifying, and correcting ext2/ext3 filesystems. On RHEL 4.x, the package contain both tools - ext2online in version 1.1.8 and resize2fs 1.35. On RHEL 5.x, it contains resize2fs only - version 1.39. The newer version supports online resizing in case of kernel supports it. Here is the summary how to resize ext2/ext3 online on RHEL platform:

1. RHEL 4.x - use ext2online tool (e2fsprogs package)
   
2. RHEL 5.x - use resize2fs tool (e2fsprogs package)

I don't consider necessary to write about these tools usage, it's simple and the tools have related man pages.