Swap space not being used

[jroa]

I had several Linux distros installed on several partitions not very long ago. I decided to clean house and deleted everything except Ubuntu. Now, I have a 133GB logical partition for Ubuntu and 8GB for swap.

However, when I run free -m, it shows that I do not have any swap memory, just physical memory. I probably accidentally deleted the swap space that Ubuntu was using.

Is there a way that I can manually tie Ubuntu to this swap space, or do I need to reinstall?

Here is the output for free -m:


total used free shared buffers cached
Mem: 3016 2760 256 0 73 768
-/+ buffers/cache: 1917 1098
Swap: 0 0 0


and here is the output for parted and print:


Model: ATA Hitachi HDP72505 (scsi)
Disk /dev/sda: 500GB
Sector size (logical/physical): 512B/512B
Partition Table: msdos

Number Start End Size Type File system Flags
1 1049kB 525MB 524MB primary ext4
2 526MB 358GB 358GB primary ntfs boot
3 358GB 500GB 142GB extended lba
6 358GB 492GB 133GB logical ext4
5 492GB 500GB 8472MB logical linux-swap(v1)

[plucky]

Open a terminal and post output for
cat /etc/fstab
sudo blkid
cat /etc/initramfs-tools/conf.d/resume


Your swap partition is not being mounted.

[SeijiSensei]

In /etc/fstab you should have a line that reads


UUID=something none swap sw 0 0

If that's not there you can add it by replacing "something" with the partition's UUID that you'll see using "sudo blkid" as plucky suggests. On my machine that returns


/dev/sda3: UUID="58e6b339-eac1-4acd-a9f2-d640f9b8b8bf" TYPE="swap"

If you use the UUID method in fstab, don't include the quotation marks, just the UUID itself. The corresponding entry in my /etc/fstab is


UUID=58e6b339-eac1-4acd-a9f2-d640f9b8b8bf none swap sw 0 0

You'll need to be root to edit /etc/fstab. Use "sudo nano /etc/fstab" or some other editor instead of nano like vi.

[jroa]

Never mind, I am dumb. I thought that since I set swapon in GParted from a live USB, that it will carry over to installed Ubuntu, but apparently it does not work that way. I used GParted on the installed Ubuntu and set swapon and now my swap space is recognized.

At least I learned something new today.

Thanks anyway for your help. Will set this to solved now.

[oldfred]

If swap is mounted as above, it is normal not to see swap used especially if you have lots of RAM.

Swap is at least 10 time slower than RAM, so you really do not want to use it if you can avoid it.

Also Ubuntu may show lots of RAM in use, but that is because it also uses RAM as cache since the same task is often reused. It only frees that if needed for new tasks and then only if all new/working tasks fill RAM is swap used. With 4GB of RAM I almost never use swap. But I understand video editing can use as much RAM as you can throw at it.

[jroa]

I don't think I ever really remember seeing much swap used on my computer. Just out of curiosity, I checked it today and saw that 0 was available, and I got a little concerned. But, it is fixed now.

In fact, I currently have Chrome, AutoCAD, XP VM running netflix, terminal, and Starcraft: Brood War open all at once and am still not using swap. Although, only 206 MB of physical memory are free.

[plucky]

I used GParted on the installed Ubuntu and set swapon and now my swap space is recognized.



Did you update /etc/fstab?

If you don't,then the swap partition will not be mounted on the next reboot.