I usually go with a swapfile instead of a swap partition. So, during installation I don't create that partition, and instead I add the swapfile later.
So, here's how I do it.
First, I do everything as su:
~$ su -
Password:
~#
Create the directory and the swapfile. I prefer the path /var/vm/. Others may prefer /var/swap/. To create the swapfile - you can use dd, or fallocate if you prefer that one. I use dd.
The size of the swapfile may vary on your needs. I usually go with quite a big one, so in case I want to hibernate - there will be enough room. So, on an old laptop with 3G of RAM - I'll go with 4G.
~# mkdir /var/vm && cd /var/vm
vm# dd if=/dev/zero of=./swapfile0 bs=1M count=4096 status=progress
4237295616 bytes (4,2 GB, 3,9 GiB) copied, 45 s, 94,2 MB/s
4096+0 records in
4096+0 records out
4294967296 bytes (4,3 GB, 4,0 GiB) copied, 45,6187 s, 94,1 MB/s
And set the permissions to 600:
vm# chmod 600 swapfile0
vm# ls -l swapfile0
total 4194304
-rw-------. 1 root root 4294967296 5 jan 03.14 swapfile0
Then make it an actual swapfile, turn the swap on, and check the status.
vm# mkswap swapfile0
Setting up swapspace version 1, size = 4 GiB (4294963200 bytes)
no label, UUID=<unique hash string>
vm# swapon swapfile0
vm# swapon -s
Filename Type Size Used Priority
/var/vm/swapfile0 file 4194300 0 -2
To make it mount on boot, we need to add it to /etc/fstab. So, with your favorite editor (eg. vim, vi, nano, etc)…
vm# vim /etc/fstab
And add these lines to the end of the file:
# Swapfile0
/var/vm/swapfile0 none swap defaults 0 0
Using the free command will get you information on how much swap you have and are using.
$ free -h
total used free shared buff/cache available
Mem: 2,9Gi 1,3Gi 493Mi 140Mi 1,1Gi 1,3Gi
Swap: 4,0Gi 132Mi 3,9Gi
SELinux
To make sure it works fine with SELinux, we need to set the correct context to the file: 'swap_t'.
~# semanage fcontext -a -t swapfile_t '/var/vm/swapfile0'
~# restorecon /var/vm/swapfile0
~# ls -lZ /var/vm/
total 4194304
-rw-------. 1 root root unconfined_u:object_r:swapfile_t:s0 4294967296 5 jan 03.17 swapfile0
Tuning
To tune the cache so it doesn't swap too much, you can add these settings to sysctl.conf. In some systems/distros, you can add them directly there. In others you make an xtra file that will be sourced.
On my Rocky Linux system, I use an xtra file, like this:
~# vim /etc/sysctl.d/90-swappiness.conf
Then add this content:
#
# /etc/sysctl.d/90-swappiness.conf
#
# Description:
# sysctl.conf settings for swap
#
vm.swappiness=10
vm.vfs_cache_pressure=40
vm.dirty_background_ratio=10
vm.dirty_ratio=15
Now all is good. :)
// Happy hacking… 👍
· Eric
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