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Essential software for new systems

This is just a quick personal reference so I don’t have to guess and notice that I forgot something important.

Automaattinen sisällysluettelo / Automatically generated Table of Contents

• Security
• Usability
• Essential system configuration
  • Debian console
  • Terminus on Fedora
    • Terminus on Arch Linux
  • SSD
  • BTRFS
  • Swap
  • sudo
  • systemd presets
  • Debian
    • sources.list
    • /etc/apt/preferences.d/whatever
  • sshd
  • Encrypted DNS
  • /etc/xdg/autostart
  • aminda-*.{service,socket]
• Remember!
  • Accessing UEFI setup without key smashing
  • Recovering selinux policy issues

Security

• microcode - propietary, but otherwise CPU holes are going to be gaping open. Refer to tail -n +1 /sys/devices/system/cpu/vulnerabilities/*
  • Debian calls this as amd64-microcode or intel-microcode
  • Arch knows them as amd-ucode or intel-ucode and won’t load it for you, you will have to initrd /intel-ucode.img yourself instantly after linux and before initrd /initramfs-linux-lts.img…
• ufw for Deb-based or firewalld on Fedora (and Kali and Arch Linux, if you so choose in the last)
• sshguard for mitigating shared systems where others refuse to use keys
• needrestart for knowing when updates actually require services to be restarted or a kernel upgrade happens and requires reboot
  • Arch users may prefer checkservices from archlinux-contrib
• molly-guard so you won’t accidentally reboot or poweroff production rather than local machine.
• apt-listchanges changelogs are worth knowing when updating.
• apt-listbugs known bugs are especially nice when performing bigger updates.
• chrony - security demands the time to be correct, Chrony supports NTS and is proper NTP server instead of just SNTP like systemd-timesyncd.
  • alternatively configure systemd-timesyncd
• unbound - my choice for both DNSSEC validating and DNS-over-TLS, even if I had it connect to upstream dns[crypt]proxy
  • alternatively configure systemd-resolved. Simultaneously systemd-networkd may be a good idea.
• unattended-upgrades or dnf-automatic so security updates are at least downloaded if not even directly installed (see configuration and systemd units!)
  • if dnf-automatic, consider sudo systemctl enable dnf-automatic-install.{timer,service} or at least sudo systemctl enable dnf-automatic-download.{timer,service}

Usability

• nvim git tmux zsh mosh - good luck without these
• if cryptographic operations are taking ages, consider something like haveged. It’s controversial, so if there are no issues, don’t install a random number generator.
• userspace oom killer, may avoid frozen systems, much more pleasant than actually having to deal with a frozen system.
  • earlyoom
    • remember to sudo systemctl enable --now earlyoom
  • systemd-oomd
    • remember to sudo systemctl enable --now systemd-oomd
    • https://codeberg.org/Aminda/shell-things/src/branch/cxefa/etc/systemd/oomd.conf.d
• zram-tools - small compressed swap in RAM
  • Remember to check configs! Fedora: /etc/zram.conf
  • sudo systemctl enable --now zramswap.service zram-swap.service
• thermald for additional help keeping system cool, especially intel
  • sudo systemctl enable --now thermald
• vnstat - help for observing bandwidth usage
• yggdrasil - essential for getting through Carrier Grade NAT whether there is IPv6 or not. Also gives static internal IPv6 reducing need for dynamic DNS.
• tlp - for laptop power management, especially ThinkPad.
  • sudo tlp-stat | less
  • sudo systemctl enable --now tlp

Essential system configuration

Since software being present and doing nothing may not actually do anything.

Debian console

• sudo dpkg-reconfigure console-setup
  • ensure UTF-8 and select Terminus
• sudo dpkg-reconfigure keyboard-configuration
  • compose key

Terminus on Fedora

After installing the package, adjust /etc/vconsole.conf e.g.:

KEYMAP="fi"
FONT="ter-v16v"

Maybe sudo updatedb and locate ter-v16v at first though?

Terminus on Arch Linux

See Fedora, but change the FONT to "ter-132b" instead.

SSD

• sudo systemctl enable --now fstrim.timer
• check that /etc/fstab has noatime so every file access isn’t written to the disk. BTRFS filesystems should also have ssd flag.
  • NEVER ENABLE atime, relatime or norelatime under the threat of suffering especially on BTRFS. I have been doing fine without it for years, it will not help any issue, unless you want read operations to cause writes and eat space…

BTRFS

• The above applies, /etc/fstab must have noatime.
• compress=zstd:0 may be helpful. It enables zstd compression, which is an integrated feature of BTRFS, with the default compression level (3 at the time of writing). The BTRFS devs are most likely wiser than me and can provide a reasonable balance between efficiency and CPU use.
  • Alternatively compress-force=zstd:0 may be used, but that might bring extra CPU usage in compressing what cannot be compressed.
    • Test on Lumina: 20G free -> 24G free.
  • The compression will happen either the next time the file is written or can be manually triggered through sudo btrfs filesystem defragment -r "$PWD"
• For swapfiles on btrfs partition, e.g. btrfs filesystem mkswapfile --size 8G /swap

Swap

Zramswap is not enough. 8 GB everywhere may be enough, summarizing Gentoo.

No swap partition and swap file is acceptable (consider SSD)? See above for btrfs or as root

fallocate -l 8G /swap
chmod 600 /swap
mkswap /swap
swapon /swap

The /etc/fstab rule is: /swap none swap sw 0 0 and then it’s just a matter of sudo swapon -a

sudo

• https://codeberg.org/Aminda/shell-things/src/branch/cxefa/etc/sudoers.d

Consider these:

# Thanks Tails
Defaults timestamp_timeout=0
Defaults pwfeedback
Defaults lecture = always

Additionally Arch Linux should consider either

# Allow full sudo access to the group which is uncommented. The first is
# Debian.
#%sudoers ALL=(ALL:ALL) ALL
# Defaults to passwordless sudo on Debian.
#%wheel ALL=(ALL:ALL) ALL

systemd presets

You are practically guaranteed horrible time especially on Debian, unless /etc/systemd/system-preset has a whatever.preset saying disable * as some distributions consider it a good idea to autostart every installed service by default. I am unsure on whether this requires sudo systemctl daemon-reload to apply.

To return to the preset state of nothing autostarting, execute the dangerous if you don’t know what you are doing command sudo systemctl preset-all.

Debian

Remember to install apt-transport-tor!

sources.list

The mirror to use is https://deb.debian.org/debian.

/etc/apt/preferences.d/whatever

# Copied from https://www.wireguard.com/install/ (2020-01-11)
# Default priority appears to be 500, so 90 results to unstable being
# used when the package is not available anywhere else
Package: *
Pin: release a=unstable
Pin-Priority: 90

Package: *
Pin: release a=unstable-debug
Pin-Priority: 90

sshd

If nothing else, please at least

# ssh-keygen -t ed25519 -N "" -f /etc/ssh/ssh_host_ed25519_key
HostKey /etc/ssh/ssh_host_ed25519_key

LogLevel VERBOSE
PermitRootLogin prohibit-password
PasswordAuthentication no
AuthenticationMethods publickey

Encrypted DNS

• https://codeberg.org/Aminda/shell-things/src/branch/cxefa/etc/systemd/resolved.conf.d
• https://codeberg.org/Aminda/shell-things/src/branch/cxefa/etc/unbound/unbound.conf.d

/etc/xdg/autostart

Not having terminal autostarting for all users is pain.

• https://codeberg.org/Aminda/shell-things/src/branch/cxefa/etc/xdg/autostart/kgx-tmux.desktop

[Desktop Entry]
Terminal=true
Exec=kgx --command="bash --norc -c tmux"
Name=Tmux in Console
Icon=org.gnome.Console

aminda-*.{service,socket]

They workaround either me or the distribution messing things up. While at it, don’t forget /etc/sysctl.d

• https://codeberg.org/Aminda/shell-things/src/branch/cxefa/etc/systemd/system

Remember!

Not quite configuration, but I am not going to start inventing a new place for it.

Accessing UEFI setup without key smashing

• systemd: there is a systemctl reboot --firmware-setup (spotted here)
• Plasma: in systemsettings section desktop session there is a checkbox to after next boot, enter UEFI settings (via reply to that)
• Windows allows access to UEFI by pressing Shift while reboot (said here) or simply shutdown -r -t 1 -fw twice (said here).
• GNOME: in the reboot after 60 seconds menu, hold alt to get into boot options (said here)
• In boot loader the command fwsetup should take you there (said here). And anyone using either grub or systemd-bootd has probably seen the menu entry.
• efibootmgr: efibootmgr —bootnext 0000 && reboot (said or implied here)

Recovering selinux policy issues

• The Fedora advice is sudo fixfiles -B onboot, but that didn’t assist me.
• Boot with flags enforcing=0 autorelabel to temporarily have permissive mode and automatic fixing.
• What actually worked was booting with enforcing=0 and sudo restorecon -R /