Packages, services, and logs / Stage 3 of 13 · step 7 of 8

Upgrade a package without losing its setting

~25 min

Not running Starting usually ~20 s

Situation

An isolated machine runs a training reporter, lab-pkg-report version 1.0-1, together with the data package lab-pkg-data. Running lab-pkg-report prints the versions and the operating mode. The mode is a local setting here: /etc/lab-pkg-report.conf says mode=training. Release 2.0-1 is approved, and the archives of both packages have already been delivered to /srv/package-lab. The user keeps a note in ~/pkg-notes/report.txt.

Task

lab-pkg-report is installed and configured at version 2.0-1 — as dpkg sees it.
lab-pkg-data is installed at version 2.0-1, and lab-pkg-report's dependency is met.
Both packages' files come from release 2.0-1, and lab-pkg-report run as student prints report=2.0-1 data=2.0-1 mode=training.
/etc/lab-pkg-report.conf still says mode=training and remains the package's conffile.
The note ~/pkg-notes/report.txt is intact: same contents, owner and modes.
Other packages, APT sources and indexes, and the archives in /srv/package-lab are unchanged.

Constraints

There's no internet; no need to refresh indexes or upgrade system packages.
Don't bypass dependencies with --force-… options or edit the dpkg database by hand.
Don't remove packages together with their configuration (purge): the local setting is needed.

The tools you need are already installed. There's no internet on this machine.

Lab goals

0 of 6

lab-pkg-report is installed and configured at version 2.0-1 — not checked yet
lab-pkg-data is installed at version 2.0-1 and report's dependency is met — not checked yet
Package files come from release 2.0-1, and the program run as student prints the new report — not checked yet
/etc/lab-pkg-report.conf kept mode=training and is still the package's conffile — not checked yet
The note in ~/pkg-notes is intact with the same owner and modes — not checked yet
Other packages, APT and the supplied archives are unchanged — not checked yet

Hints

0 of 3 open · they open one at a time

Hint 1

Show the solution after 3 failed checks

Packages · picked for this lab

apt / dpkg — package management

Cheat sheet

$_ — insert into the terminal

sudo apt update && sudo apt upgrade refresh the index, then install upgrades
sudo apt install nginx install a package
sudo apt purge nginx remove a package together with its config
sudo apt autoremove --purge remove orphaned dependencies
apt-cache policy nginx package versions and which repo they come from
dpkg -L nginx which files a package brought in
dpkg -S /usr/sbin/nginx which package owns a file
sudo apt --fix-broken install install missing dependencies after a failure
sudo dpkg --configure -a finish configuring a broken dpkg run
sudo apt-mark hold nginx pin a package's version

apt is built around subcommands (apt install, apt remove, …) rather than flags of a single command; below are the main subcommands and flags. The full list is in man apt, man dpkg.

apt

bash

sudo apt update                   # refresh the package INDEX (does not install upgrades)
sudo apt upgrade                  # install available upgrades
sudo apt full-upgrade             # + remove conflicting packages (riskier)
sudo apt install nginx            # install
sudo apt install nginx=1.24\*     # a specific version
sudo apt install --reinstall nginx
sudo apt remove nginx             # remove (config files stay)
sudo apt purge nginx              # remove together with config files
sudo apt autoremove --purge       # remove orphaned dependencies
apt search keyword ; apt show nginx ; apt list --installed
apt-cache policy nginx            # available versions and which repo they come from
sudo apt-mark hold nginx          # pin a version (unhold to release it)
sudo apt download nginx           # download the .deb without installing

dpkg and repositories

bash

dpkg -l | grep nginx              # is it installed
dpkg -L nginx                     # which files the package brought in
dpkg -S /usr/sbin/nginx           # which package owns a file
sudo dpkg -i package.deb          # install a local .deb (then apt -f install)
dpkg --get-selections             # a list to carry over to another machine

# add a third-party repository (modern way, with a key):
curl -fsSL https://repo.example.com/key.gpg | sudo gpg --dearmor -o /etc/apt/keyrings/example.gpg
echo "deb [signed-by=/etc/apt/keyrings/example.gpg] https://repo.example.com stable main" \
  | sudo tee /etc/apt/sources.list.d/example.list
sudo apt update

"Could not get lock /var/lib/dpkg/lock"

apt/unattended-upgrades is already running. Wait, or find the process (ps aux | grep -E 'apt|dpkg', see processes). Do not kill dpkg mid-way.

dpkg was interrupted, "broken packages"

bash

sudo dpkg --configure -a          # finish configuring what was interrupted
sudo apt --fix-broken install     # install the missing dependencies

apt update: NO_PUBKEY / 404 / repository changed

A broken or stale source in sources.list.d/. Fix the URL or add the key (signed-by=, not the deprecated apt-key). If the Suite changed, use --allow-releaseinfo-change.

A specific version / rollback

apt-cache policy PKG shows what's available; apt install pkg=version installs it; apt-mark hold pins it. Without internet (as on a lab VM), use a proxy/mirror (apt-cacher-ng).

Free up space used by the cache

sudo apt clean (the whole cache) / autoclean (only stale files); autoremove --purge (see disk-usage).

Upgrade a package without losing its setting

Situation

Task

Constraints

Signing in is needed to start the machine

apt

dpkg and repositories

"Could not get lock /var/lib/dpkg/lock"

dpkg was interrupted, "broken packages"

apt update: NO_PUBKEY / 404 / repository changed

A specific version / rollback

Free up space used by the cache