I have CentOS 5.5 installed, I have no un-partitioned space and the only ext3 partition I have is huge with lots of free space.

Can I change that partition size in order to allocate another one? I want to create new partitions in order to install another distribution there (Ubuntu).

I tried to do it through the volume administration tool in CentOS, but when I edit the partition size and confirm, it says that it is mounted in / and it needs to be un-mounted before re-sizing, which of course fails.

Any suggestion?


You should probably look at GParted; as long as you're working in Gnome it'll work without data loss. If not, there's a LiveCD/media version which lets you boot and reconfigure without involving the current OS.

Something to consider for future system setups is using LVM (man page, Wikipedia reference, additional detailed reference), which allows this kind of reallocation on the fly without special software. I'm pretty sure you can't convert an existing filesystem to LVM without rebuilding it. I use LVM on one of my home systems, and it makes adding additional physical drives pretty trivial - they just get added to the volume group, and then I allocate as needed.

  • Thanks! Great info. Please edit your answer to add some LVM link (I had to google it). – Toto Oct 2 '10 at 1:28
  • 1
    @Toto - I added the links. Sorry I didn't add them initially; for some reason I was convinced I was too new a user to be able to add more than one link. Oops :) – mlschechter Oct 2 '10 at 1:45
  • GParted has nothing to do with Gnome except for using gnome libraries; what did you have in mind with the data loss remark? – Gilles 'SO- stop being evil' Oct 2 '10 at 10:23
  • @Gilles - apologies for the poor phrasing; I was attempting to convey what you stated, in that you have to have Gnome on your system to use GParted without using the media-based version. – mlschechter Oct 3 '10 at 1:19
  • 1
    The rep limit is only 10 for posting multiple links, and I think it's actually 1 during beta, so you're good to go :) – Michael Mrozek Oct 3 '10 at 4:31

The smart and safe thing to do is to boot from a live CD and resize from the CD since the partition does not have to be mounted in that case.

Parted magic is a live CD especially made to repartition drives.

PS Take the LVM suggestion with a grain of salt. For me LVM seems to use a lot of resources. Of course YMMV.

  • I do recommend LVM for ease of management. I've never come upon any performance impact of LVM: could you elaborate on your experience (ideally with some hard data)? – Gilles 'SO- stop being evil' Oct 2 '10 at 10:22

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.