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How do I change swap partition in Linux? If I currently use /dev/hda3 for swap, and I rather would like to use /dev/hda4, which steps should I go through?

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it is probably worth to create a logical partition /dev/hda5 in primary partition /dev/hda4 and use it for swap. This way, you don't have to spend the entire /dev/hda4 for swap, and can create other logical partitions in it – dmityugov Jun 2 '09 at 20:25
up vote 16 down vote accepted

Do it as root:

swapoff /dev/hda3
mkswap /dev/hda4
swapon /dev/hda4

and edit swap entry in /etc/fstab

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On the fly:

sudo swapoff /dev/hda3
sudo mkswap /dev/hda4
sudo swapon /dev/hda4

For bootime, after you have run the mkswap, edit the /etc/fstab file and the change the /dev/hda3 line accordingly.

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If you have decent amount of RAM and your applications aren't memory-intensive, you might consider using a separate file as a swap instead of the whole partition. That way you can easily select the amount of swap space you use, either by adding more swap files, or resizing existing ones.

Let's say that your swapfile will reside in root directory as /swapfile, and will have size 512 MB. To create it issue commands as root:

$ dd if=/dev/zero of=/swapfile bs=1M count=512
$ mkswap /swapfile
$ swapon /swapfile

To automatically use it after reboot, insert in /etc/fstab:

/swapfile    none    swap    defaults    0 0

Adding more swap files is as simple as creating more files (/swapfile1, /swapfileX), formatting them using mkswap and enabling using swapon. If you want to disable a swapfile, you can use command swapoff /swapfile.

As for the performance between disk and file version, it's not that terribly different. You can even use swapfile as hibernation disk in laptops (although I always use separate partition for that anyway).

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You'll need to format /dev/hda4 as swap, which I think just deletes the file system tables, then just edit /etc/fstab and point swap to /dev/hda4. Then reboot and you should be good. It goes without saying that you'll lose any data on /dev/hda4. You can use gparted as a gui for the formatting.

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You don't need to reboot Linux 2.6.x after formatting a partition, not even after changing the partition table of the disk. – drybjed Jun 2 '09 at 13:15
Good point, but I was sticking to the K.I.S.S. philosophy. – skitzot33 Jun 2 '09 at 13:40

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