Difference between revisions of "Ubuntu/swap"

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Commands:
 
Commands:
* {{l/cmd|swapon}} --show
+
* <code>{{l/cmd|swapon}} --show</code>
 
** Confirms the swap-file status (default is currently 2 gigabytes)
 
** Confirms the swap-file status (default is currently 2 gigabytes)
* sudo {{l/cmd|fallocate}} -l 4G /swap4G
+
* <code>sudo {{l/cmd|fallocate}} -l 4G /swap4G</code>
 
** creates a new swapfile-compatible 4 gigabyte file named <code>/swap4G</code>
 
** creates a new swapfile-compatible 4 gigabyte file named <code>/swap4G</code>
 
** 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.
 
** 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 {{l/cmd|chmod}} 0600 /swap4G
+
* <code>sudo {{l/cmd|chmod}} 0600 /swap4G</code>
 
** Not required, but reduces warning messages and possible security holes.
 
** Not required, but reduces warning messages and possible security holes.
* sudo mkswap /swap4G
+
* <code>sudo mkswap /swap4G</code>
 
** Mark the new file as a swapfile.
 
** Mark the new file as a swapfile.
* sudo swapon /swap4G
+
* <code>sudo swapon /swap4G</code>
 
** Tell the swap system to use the new file.
 
** Tell the swap system to use the new file.
* sudo swapoff /swapfile
+
* <code>sudo swapoff /swapfile</code>
 
** Turn off usage of the given swapfile (<code>/swapfile</code> is the name of the default) -- but make sure you've got enough RAM free first, or have set up another swapfile!
 
** Turn off usage of the given swapfile (<code>/swapfile</code> is the name of the default) -- but make sure you've got enough RAM free first, or have set up another swapfile!
 
** This will take some time, depending on how full this swapfile is.
 
** This will take some time, depending on how full this swapfile is.

Latest revision as of 14:12, 2 June 2025

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 chmod 0600 /swap4G
    • Not required, but reduces warning messages and possible security holes.
  • 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!
    • This will take some time, depending on how full this swapfile is.
    • Yes, you can have two swapfiles in use simultaneously.

Then edit /etc/fstab to change the name of the swapfile you want to use. You can delete the old swapfile either before or after that, but safest to do it after.

Notes