linuxexpert-practice-labs/labs/lfcs/3-5-swap

LFCS 3.5: Swap space

Swap files and swap partitions, priorities, removing swap, and swappiness.

Before you start

The lab adds an empty 1 GiB spare disk, /dev/loop40 (partitions show up as /dev/loop40p1 and so on). It comes back at every boot before swap is turned on, so /etc/fstab lines for it keep working. The lab also adds a 128 MiB swap file, /var/swap.old, in use and listed in /etc/fstab.

Tasks

1. Add a 1 GiB swap file at /swapfile that's used after every reboot.
2. Add a 512 MiB swap partition on /dev/loop40 with priority 10, and give the swap file /swapfile priority 5, both after every reboot too.
3. Turn off the swap file /var/swap.old without rebooting, and remove it for good.
4. Set swappiness to 10 persistently.

Hints

• dd or fallocate, chmod 600, mkswap, swapon; swapon --show, free -h.
• fdisk, gdisk or parted (type Linux swap); mkswap, blkid. In /etc/fstab swap has mount point none, type swap, and pri= among the options; swapon -a.
• swapoff, then clean up /etc/fstab.
• sysctl vm.swappiness; a file in /etc/sysctl.d/, sysctl --system.