Ubuntu/swap

About

Newer versions of Ubuntu use a regular(ish) file for swap, rather than a partition -- so resizing it is now possible without rebooting or mucking around with fdisk.

Commands:

• swapon --show
  • Confirms the swap-file status (default is currently 2 gigabytes)
• sudo fallocate -l 4G /swap4G
  • creates a new swapfile-compatible 4 gigabyte file named /swap4G
  • Regardless of what's implied by the tldp.org instructions, you can do this before disabling the old swapfile as long as you give it a different name.
• sudo mkswap /swap4G
  • Mark the new file as a swapfile.
• sudo swapon /swap4G
  • Tell the swap system to use the new file.
• sudo swapoff /swapfile
  • Turn off usage of the given swapfile (/swapfile is the name of the default) -- but make sure you've got enough RAM free first, or have set up another swapfile!
  • Yes, you can have two swapfiles in use simultaneously.

Notes

• Linux Partition HOWTO: 9. Setting Up Swap Space
  • 2020-02-11 How to Increase Swap Size on Ubuntu (using the new swapfile instead of partitioning)
    • Note that you have to edit fstab for the change to persist after reboot.
    • Also, it's not necessary to do swapoff except to stop using a given swapfile. You can add a new swapfile at any point, and the system will use more than one swapfile concurrently.
• upgrade command for 16.04 LTS: do-release-upgrade