Hi,

I want to reduce my swap disk size without too much effort. Is there a way to do this on reboot with a script?

Thanks

If you want to turn off swap completely, that can be done with command "swapoff". This does not require reboot, but swap will get turned back on after reboot. You can comment out the swap line in /etc/fstab if you do not want swap to get turned on after reboots.

To reduce swap partition, you will have to use parted/fdisk.

I dont want to turn it off complete I want to reduce the amount of swap being used for example from 90Gig to 6Gig. Without the system freezing up on me.

What distribution/version are you running?

I think Ubuntu now creates/uses a swap file instead of a swap partition. Without freezing depends on what you have running on your system but you should be able to turn swap off (swapoff command). With little effort you can easily create a swap file and switch from default to a new swap file without rebooting.

If using a swap partition you can use mkswap specifying the size without having to first resize but take note of the warning. If you specify the wrong size you could overwrite data in the adjoining partition which could lead to data lose.

From the mkswap man page

" Is there a way to do this on reboot with a script?" The simple answer is yes. I've never seen anyone create one but there are some super coders at LQ that could create one I suppose. Might be some web article on making one.

In general any command or set of commands can almost always be placed in a script. Once script may be used upon completion of some task to start a new task or write changes or whatnot.


Having too much swap isn't usually a terrible thing.

Having 90GiB of it, mentioned as an example by the OP above, might be a wee bit excessive though.

Doooh! That is a bit much.

I've never tried this but I suppose one could create a new swap (file or partition), mount it then change swappiness to force new to basically take control then remove/reduce old one. I think there is some flush swap command that would insure that the old swap is almost or totally empty. Silly swap is an odd deal sometimes. Some bits get put there seemingly no matter how much ram you have.

One could use a live cd to change it or maybe single user mode to fix all of this.

Some distro's have installers or tools to do this task. I get the feeling I have tried this on Opensuse maybe or red hat.

If it were me, I'd boot to a Live CD of something (likely GPartED) and shrink the swap partition--after backing stuff up to external media, because, when you muck about with partitions, you never can predict . . . .

In these days of multi-GBs of RAM, 90GB is a bit high for a single user machine (I can't speak to a server in a thin-client environment--that's a whole nother horse). I've got 16GB RAM in this box and 4 GB swap, and swap is hardly ever touched.

Backing up your data is always sensible before messing with filesystems.

What you need to do is first unmount your present swap partition, using (enter your partition number).

Then using fdisk or similar program, alter the size of your swap partition on your disk, write it out to disk, then run (your partition number), then (your partition number).

That should have you back up & running with your newly sized swap partition.

The free space created can then be merged into a present partition, (possible risk of data loss), or, easiest option, just create a new partition, & put a file system on it, which can then be added to your /etc/fstab file.

May depend a lot on what you're doing on the system. Here I have 8GB of physical memory and 4X that in swap space and swap can still get hammered at times. Not frequently but I'd rather have the swap space than receive an "uh uh... not enough memory" message. Disk space is cheap nowadays.