Tag Archives: ubuntu

Too Good To, UNIX & Linux

Too good to #0009

1 Comment

In this episode:

  • urlwatch for new daily Ubuntu Server ISO
  • systemd-run ephemeral timers as replacement for at
  • Mozillateam Firefox on Debian
  • systemd service: ExecStartPre as root
  • gdm3 autosuspend/shutdown behaviour

urlwatch for new daily Ubuntu Server ISO

Somewhat desparate because at the time of starting this post, the (pre-beta, non-LTS, not blaming anyone) server image in question was badly broken.

---
name: Ubuntu Server Daily ISO
url: https://cdimage.ubuntu.com/ubuntu-server/daily-live/current/SHA256SUMS
filter:
  - grep: .*-live-server-amd64.iso
---

systemd-run ephemeral timers as replacement for at

Goes great with “hardened” systems that deny use of at(1).

Run a command 60 seconds from now, via the user’s private systemd (after logout only if session lingering is enabled).

systemd-run --user --on-active=60s -- logger --tag foo "Hello world"

Run a command 2 minutes from now, privileged or as a specific user via the global systemd:

sudo systemd-run --uid="${LOGNAME}" --on-active=2m -- touch /tmp/hello

Insights

systemctl --user list-timers
journalctl --user -u 'run-*.timer'
sudo systemctl list-timers
sudo journalctl -u 'run-*.timer'

Mozillateam Firefox on Debian

$ sudo tee /etc/apt/sources.list.d/mozillateam-ppa.list <<Here
deb https://ppa.launchpadcontent.net/mozillateam/ppa/ubuntu jammy main
deb-src https://ppa.launchpadcontent.net/mozillateam/ppa/ubuntu jammy main
Here

$ sudo tee /etc/apt/trusted.gpg.d/mozillateam.asc < <(curl 'https://keyserver.ubuntu.com/pks/lookup?op=get&search=0x0ab215679c571d1c8325275b9bdb3d89ce49ec21')

systemd service: ExecStartPre as root

[Service]
...
User=nonroot
Group=nonroot
ExecStartPre=+install -d /var/lib/theservice -o nonroot -g nonroot
ExecStart=/usr/sbin/theservice

See systemd.service, “special executable prefixes”.

gdm3 autosuspend/shutdown behaviour

Debian:

$ sudo apt-get install dbus-x11
$ sudo chsh -s /bin/bash Debian-gdm
$ sudo -i -u Debian-gdm
$ gsettings get org.gnome.settings-daemon.plugins.power sleep-inactive-ac-type
'suspend'
$ dbus-launch gsettings set org.gnome.settings-daemon.plugins.power sleep-inactive-ac-type nothing
$ gsettings get org.gnome.settings-daemon.plugins.power sleep-inactive-ac-type
$ exit
$ sudo chsh -s /bin/false Debian-gdm

Arch/Garuda:

$ sudo chsh -s /bin/bash gdm
$ gsettings get org.gnome.settings-daemon.plugins.power sleep-inactive-ac-type
'suspend'
$ dbus-launch gsettings set org.gnome.settings-daemon.plugins.power sleep-inactive-ac-type nothing
$ gsettings get org.gnome.settings-daemon.plugins.power sleep-inactive-ac-type
$ exit
$ sudo chsh -s /usr/bin/nologin gdm
python, Too Good To, UNIX & Linux

Too good to #0007

Disable the dynamic motd on Ubuntu and everywhere else

This is without messing around in /etc/pam.d or doing things that may be reverted by future updates. Remember to systemctl enable disable-dynamic-motd.timer.

# /etc/systemd/system/disable-dynamic-motd.timer
[Unit]
Description=Disable all the dynamic-motd scriptlets (timer)

[Timer]
OnBootSec=10
OnActiveSec=3600

[Install]
WantedBy=timers.target

# /etc/systemd/system/disable-dynamic-motd.service
[Unit]
Description=Disable all the dynamic-motd scriptlets (service)

[Service]
Type=oneshot
ExecStart=sh -c 'chmod -v -x /etc/update-motd.d/*'

Disable verbose logging on realmd.service

Problem on AD-member Linux client, realmd logs thousands of redundant messages:

Feb 01 11:11:34 kvm-28ca realmd[22302]: client using service: :1.1042
Feb 01 11:11:34 kvm-28ca realmd[22302]: holding daemon: :1.1042
Feb 01 11:11:34 kvm-28ca realmd[22302]: client gone away: :1.1042
Feb 01 11:11:34 kvm-28ca realmd[22302]: released daemon: :1.1042

Solution, disable debug logging in the systemd unit by introducing this drop-in:

# /etc/systemd/system/realmd.service.d/override.conf
[Service]
LogLevelMax=info

Sorting Debian package versions

dpkg –compare-versions is not exactly a secret, but I’ve wrapped a script around it to visualize and better wrap my head around non-straightforward naming schemes:

$ cat test.txt
2.1
2.2~pre01
1.0
2022-01.1~pre03
2.1-bugfix-foo
2.1~bugfix-foo
2.2
2022-01~foo~bar
2022-01
1.0
0
3
2022-01~foo

$ ./dpkg-sort-versions < test.txt
Sorted from lowest (oldest) to highest (latest):
0
1.0
1.0
2.1~bugfix-foo
2.1
2.1-bugfix-foo
2.2~pre01
2.2
3
2022-01~foo~bar
2022-01~foo
2022-01
2022-01.1~pre03

Script is here.

Too Good To, UNIX & Linux

Too good to #0006

1 Comment

“Sudo on demand” from TGT0003 considered more useful for downgrading privileges on the fly

#!/usr/bin/env bash

want_user=letsencrypt
am_user="$(id -un)"
printf "Running as: %s\n" "${am_user}"
if [[ "${want_user}" != "${am_user}" ]]
then
        printf "Re-executing with sudo.\n"
        exec sudo -u "${want_user}" "${0}"
fi
...

JSON export of all installed packages on Debian/Ubuntu

#!/bin/bash

function dpkg_json(){
    printf "{\n"
    format='"${Package}": { "Version": "${Version}", "Architecture": "${Architecture}", "Status": "${db:Status-Abbrev}" },\n'
    dpkg-query --show --showformat="${format}" | sed '$s/,$//'
    printf "}\n"
}

dpkg_json | jq .

Urlwatch for a new version of a package in the Ubuntu package pool

---
name: "Ubuntu Curtin package (waiting for apt-key fix)"
url: http://archive.ubuntu.com/ubuntu/pool/main/c/curtin/
filter:
  - xpath: //table//td[2]
  - html2text
  - grep: ^curtin.*\.deb$
---
Too Good To, UNIX & Linux

Too good to #0005

Prioritizing own NTP servers for systemd-timesyncd

# cat /etc/systemd/timesyncd.conf.d/timesyncd-corporate.conf 
[Time]
NTP=ntp1.example.com ntp2.example.com ntp.ubuntu.com

Test if text is empty (even if it does contain a linebreak)

Good job by: https://unix.stackexchange.com/q/386499/2028

if ! grep -q '[^[:space:]]' "${file}"; then echo "Text is empty"; fi

Watch for changes in the Gnome registry

(To reproduce manual changes, for configuration management.)

dconf watch / # (Sorry, thats all)

Trigger Debian/Ubuntu unattended-upgrade

(For testing configuration changes)

rm /var/lib/apt/periodic/*
systemctl start apt-daily.service 
systemctl start apt-daily-upgrade.service

And remember:

tail -f /var/log/unattended-upgrades/*log
Too Good To, UNIX & Linux

Too good to #0003

Linux uptime in seconds, once and for all

awk '{printf "%i\n", $1}' /proc/uptime

“Sudo on demand”, re-exec shell script with sudo if not running as root

#!/usr/bin/env bash
printf "Running as: %s\n" "$(id -un)"
[[ ${EUID} -ne 0 ]] && printf "Re-executing with sudo.\n" && exec sudo "${0}"

See also TGT0006, this is just as useful for downgrading privileges on the fly.

“When was the last time apt-get on that Debian/Ubuntu machine installed package upgrades?”

  • Reliably answering this is a lot harder than it looks, subject of countless discussions and really does need to parse /var/log/apt/history.log, which is painful.
  • The script below maintains a file /var/log/apt/lastupgrade with the last upgrade’s time stamp, for further processing.
  • Does NOT track invocations of apt-get upgrade that did not lead to package upgrades.
  • Does NOT look behind logfile rotations, which should not be a problem because it’s closely hooked to dpkg.

/usr/sbin/apt-lastupgrade:

#!/bin/bash

while IFS=: read -r key value
do
	if [[ "${key}" == 'Start-Date' ]]
	then
		upgraded=0
	elif [[ "${key}" == 'Upgrade' ]]
	then
		upgraded=1
	elif [[ "${key}" == 'End-Date' ]]
	then
		if [[ ${upgraded} -eq 1 ]]
		then
			printf -v lastupgrade "%s" "${value}"
		fi
		upgraded=0
	fi
done < /var/log/apt/history.log

if [[ -v lastupgrade ]]
then
	tee /var/log/apt/lastupgrade <<-Here
	# Timestamp of last upgrade: ${lastupgrade}
	Here
	touch -d "${lastupgrade}" /var/log/apt/lastupgrade
fi

/etc/apt/apt.conf.d/90lastupgrade:

DPkg::Post-Invoke {"/usr/bin/systemd-run --on-active=60 /usr/sbin/apt-lastupgrade || /bin/true"};

Path of running shell script, dirname for locating config files, includes etc.

me_path="$(readlink -f "${0}")"
me_dir="$(dirname "${me_path}")"
me_base="$(basename "${me_path}")"