systemd-swap

⚠️ Current code quality and commit frequency is low ⚠️

Users should migrate to systemd/zram-generator since zram should be enough in most systems

Script to manage swap on:

• zswap - Enable/Configure
• zram - Autoconfigurating for swap
• files - (sparse files for saving space, supports btrfs)
• block devices - auto find and do swapon

:information_source: It is configurable in /etc/systemd/swap.conf.

Additional terms:

• SwapFC (File Chunked) - provides a dynamic swap file allocation/deallocation

File location

/etc/systemd/swap.conf
/usr/lib/systemd/system/systemd-swap.service
/usr/bin/systemd-swap

Please don't forget to enable and start with

sudo systemctl enable --now systemd-swap

Install

• Arch Linux: in the community repo.

• Debian based distros

  git clone https://github.com/Nefelim4ag/systemd-swap.git
  cd systemd-swap
  make deb
  sudo apt install ./systemd-swap_*_all.deb

• Fedora based distros

  sudo dnf copr enable zeno/systemd-swap
  sudo dnf install systemd-swap

  or

  
  git clone https://github.com/Nefelim4ag/systemd-swap.git
  cd systemd-swap
  make rpm
  sudo dnf install ./systemd-swap-*noarch.rpm

• Manual

  Install dependencies:

  • python3 >= 3.7
  • python3 packages: systemd-python and sysv_ipc

  git clone https://github.com/Nefelim4ag/systemd-swap.git
  cd systemd-swap
  sudo make install
  
  # or into /usr/local:
  sudo make prefix=/usr/local install

About configuration

Q: Do we need to activate both zram and zswap?\ A: Nope, it's useless, as zram is a compressed RAM DISK, but zswap is a compressed "writeback" CACHE on swap file/disk. Also having both activated can lead to inverse LRU as noted here

Q: Do I need to use swapfc_force_use_loop on swapFC?\ A: Nope, as you wish really, native swapfile should work faster and it's safer in OOM condition in comparison to loop backed scenario.

Q: When would we want a certain configuration?\ A: In most cases zram is enough since it on average compresses 2-3x and is much faster than disk based swap.

Q: How many zram devices should one use? A: If you are not using an ancient kernel (pre 4.7) there's no benefit from using multiple zram devices.

Q: Can we use this to enable hibernation?\ A: Nope as hibernation wants a persistent fs blocks and wants access to swap data directly from disk, this will not work on: swapfc (without some magic of course, see #85).

Switch on systemd-swap:s automatic swap management

• Enable swapfc if wanted (note, you should never use zram and zswap at the same time)

  vim /etc/systemd/swap.conf.d/overrides.conf

  swapfc_enabled=1

• Stop any external swap:

  sudo swapoff -a

• Remove swap entry from fstab:

  vim /etc/fstab

• Remove your swap

  # For Ubuntu
  sudo rm -f /swapfile
  
  # For Centos 7 (if using a swap partition and lvm)
  lvremove -Ay /dev/centos/swap
  lvextend -l +100%FREE centos/root

• Remove swap from Grub:

  # For Ubuntu remove resume* in grub
  vim /etc/default/grub
  
  # For Centos 7 remove rd.lvm.lv=centos/swap*
  vim /etc/default/grub
  
  # For Manjaro remove resume* in grub & mkinitcpio
  vim /etc/default/grub
  vim /etc/mkinitcpio.conf

  # For Ubuntu
  update-grub
  
  # For Centos 7
  grub2-mkconfig -o /boot/grub2/grub.cfg
  
  # For Manjaro
  update-grub
  mkinitcpio -P