First of all a little disclaimer - although I've done this a few times and never had any problems, one should never consider resizing partitions a completely foolproof exercise. Things can go wrong. With regards to swap though, don't worry if your swap partition is destroyed as this will not harm your system - most healthy systems will not ever need swap and unlike Windows, Linux only starts using swap when it needs it and can quite easily survive without it. You can trash it and format it as many times as you like as long as it's not in use. And of course take backups of any important data first!
Resize swap partition in Red Hat Linux
- Is your swap on a logical volume (LVM)? If so then skip below to the LVM section. If not then read on:
- Download gparted (Gnome Partition Manager), burn the iso and then boot into it.
- Gparted will identify the filesystems on each partition so your target will be clearly labelled as swap.
- Reize your partitions as required. Try to minimise the overall number of resize and move operations as this can take several hours to complete.
When you reboot swap not be enabled - if you check using top (or htop) or free -m, you will see 0 mb of swap available. The reason for this is the UUID of the partition changed when it was resized by GParted, and this confuses the system when it tries to mount the volumes in /etc/fstab. The solution is to relabel your swap partition, by reformatting it as swap and specifying the correct label.
fdisk -l | grep swap
Note down the device name of your swap partition. e.g:
/dev/cciss/c0d0p3 1926 3837 15358140 82 Linux swap
Make a note of the label for the swap partition from fstab:
cat /etc/fstab | grep swap
Now format your partition as swap, specifiying the label exactly as shown in the fstab.
mkswap /dev/cciss/c0d0p3 -L SW-cciss/c0d0p3
You can then enable the swap space straight away by using swapon devicename, or just reboot and check with free -m again, and all should be ok.
Resizing swap on LVM
If your swap partition is on a logical volume it can be resized without rebooting your system. However you will need free space to extend into, if you do not have free space you will need to shrink another volume or add another physical disk into your volume group (see this post which explains how to do this).
cat /etc/fstab | grep swap /dev/VolGroup00/LogVol01 swap swap defaults 0 0
lvdisplay will show you the size of your logical volume:
lvdisplay /dev/VolGroup00/LogVol01 --- Logical volume --- LV Name /dev/VolGroup00/LogVol01 VG Name VolGroup00 LV UUID RVIFz3-B8kp-z9KV-JYtG-N997-JOQ6-ETaJaJ LV Write Access read/write LV Status available # open 1 LV Size 512.00 MB Current LE 24 Segments 1 Allocation inherit Read ahead sectors 0 Block device 253:1
To resize an LVM you need to unmount it, or in this case swapoff.
Resizing the volume to 768Mb (assuming you have the space to extend into)
lvresize /dev/VolGroup00/LogVol01 -L 768M Extending logical volume LogVol01 to 768.00 MB Logical volume LogVol01 successfully resized swapon /dev/VolGroup00/LogVol01 free -m total used free shared buffers cached Mem: 375 343 32 0 48 120 -/+ buffers/cache: 174 201 Swap: 767 0 767