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systemd-swap

Code Style: Black

⚠️ 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

ℹ️ 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