Notes for my Linux installation

linux_tips.md

Configurations

Kernel modules

# /etc/modprobe.d/blacklist.conf
blacklist radeon # nvidia, i915, depends on hardware specs
blacklist iTCO_wdt # who wants watchdog on desktop tbh? (except shutdown might not work properly xD)
blacklist iTCO_vendor_support # watchdog

Boot options

loglevel=4 apparmor=1 security=apparmor nmi_watchdog=0

Swap

• swapfile: see ArchWiki for Btrfs notes

  # dd if=/dev/zero of=/swapfile bs=1M count=2048 status=progress
  # chmod 600 /swapfile
  # mkswap /swapfile
  # swapon /swapfile
  # echo "/swapfile none swap defaults 0 0" >> /etc/fstab

• zram (see more here)

  # echo "options zram num_devices=2" > /etc/modprobe.d/zram.conf

  • systemd: see ArchWiki
  • openrc: see GentooWiki
  • runit:

    # /etc/runit/core-services/03-zram.sh
    
    # ensure zram is ready
    modprobe zram
    
    # set compression algorithm
    echo zstd > /sys/block/zram0/comp_algorithm
    echo zstd > /sys/block/zram1/comp_algorithm
    
    # set disksize
    echo 2G > /sys/block/zram0/disksize
    echo 2G > /sys/block/zram1/disksize
    
    # set memory limit
    echo 2G > /sys/block/zram0/mem_limit
    echo 2G > /sys/block/zram1/mem_limit
    
    # activate swaps
    mkswap --label zram0 /dev/zram0
    mkswap --label zram1 /dev/zram1
    
    # swapon
    swapon /dev/zram0
    swapon /dev/zram1

• encrypted swap

Typical /etc/fstab

• ext4: some programs (like pyenv, Doom Emacs, ...) need stuff to be executable in /tmp

UUID=...  /      ext4  rw,relatime             0  1
UUID=...  /home  ext4  rw,relatime             0  2
UUID=...  /media ext4  rw,relatime,nofail      0  2
tmpfs     /tmp   tmpfs rw,nosuid,nodev         0  0
tmpfs     /run   tmpfs rw,nosuid,nodev,noexec  0  0

• btrfs: nested subvolumes for performance: @/var/cache/xbps, @/var/tmp, @/tmp, @/srv

# Separated subvolume for /var/log is nice for troubleshooting
UUID=...	/		        btrfs	rw,noatime,compress=zstd,ssd,space_cache,commit=120,subvol=@	        0 1
UUID=...	/home		    btrfs	rw,noatime,compress=zstd,ssd,space_cache,commit=120,subvol=@home	    0 2
UUID=...	/var/log	  btrfs	rw,noatime,compress=zstd,ssd,space_cache,commit=120,subvol=@log	      0 2
UUID=...	/.snapshots btrfs	rw,noatime,compress=zstd,ssd,space_cache,commit=120,subvol=@snapshots	0 2

UUID=...	/media		        btrfs	rw,noatime,compress=zstd,space_cache,autodefrag,commit=120,subvol=@media     0 2
UUID=...	/media/.snapshots	btrfs	rw,noatime,compress=zstd,space_cache,autodefrag,commit=120,subvol=@snapshots 0 2

# This is useful for disk overview
UUID=...	/mnt/defvol-root  btrfs rw,noatime,compress=zstd,ssd,space_cache,commit=120,subvol=/        0 2
UUID=...	/mnt/defvol-media btrfs rw,noatime,compress=zstd,space_cache,autodefrag,commit=120,subvol=/ 0 2

UUID=...	/boot		    vfat	rw,noatime,...					0 2
tmpfs     /tmp        tmpfs rw,nosuid,nodev         0 0

• voidvault has a more detailed filesystem structures.

Btrfs maintenance

• /etc/cron.weekly/btrfs-scrub (do the same with btrfs balance if using RAID)

#!/bin/sh

btrfs scrub start /

# Scrub 1 disk at a time
while btrfs scrub status / | grep running; do
	sleep 20
done

btrfs scrub start /media

• /etc/cron.weekly/fstrim

#!/bin/sh

fstrim /

• Use snapper for cron snapshots is a no-brainer
• Use btrbk for incrementally sending snapshots

Dependencies (some distros don't ship them by default or mark them as optional)

• vifm needs python3-dbus for mounting usb devices
• ranger needs python3-Pillow and ImageMagick for ueberzug and kitty image preview methods
• mpDris2 requires python3-mutagen for displaying music covers
• luakit need gst-libav, gst-plugins-base, gst-plugins-good for video playbacks.
• qutebrowser needs pdf.js (Void) / pdfjs (Arch) to open pdf files in the browser (enable c.content.pdfjs = True in config file)

Other notes

• disable coredump
• android udev rules at /etc/udev/rules.d/51-android.rules
• libvirt conf
• cron job for ssd (which is easier?? than discard)
• elogind is needed when using flatpak with apparmor installed (to get a proper $XDG_RUNTIME_DIR)
• per-user services on Void Linux
• hardening
  • disable ssh password authentication

Small fixes for things

• Alacritty might not display italic fonts correctly in terminal apps (eg. neovim). See #1977.

# Clone the alacritty repo
git clone https://github.com/alacritty/alacritty.git
cd alacritty/

# Re-compile the terminfo as normal user
tic -xe alacritty,alacritty-direct extra/alacritty.info

# Double check the result
infocmp alacritty

• Libreoffice might hang on startup because of OpenCL. Run it the 1st time with SAL_DISABLE_OPENCL=1 libreoffice then go to Tools -> OpenCL to turn it off.

Some notes for Bedrock Linux

• build all kernels' initramfs manually (since default hook will not be triggered) with dracut/mkinitcpio/... from the strata that installs grub/systemd-boot/... (for less headache)
• things to be installed on each strata
  • same fonts
  • cursor themes (set /usr/share/icons/default/index.theme for each strata too)

Knowledge from other people

@konomikitten

@nikitavoloboev

winny from @LinArcX