Apt

## update /etc/apt/sources.list
sudo apt-get update
sudo apt-get check
sudo apt-get upgrade
sudo apt-get -s upgrade
sudo apt-get -u upgrade
sudo apt-get dist-upgrade
sudo apt-get -s dist-upgrade
sudo apt-get -u dist-upgrade
sudo apt-get clean
sudo apt-file update

apt-cache search foo

apt-file update
apt-file search tcl.h

apt-get install -f
dpkg --configure -a

https://www.debian.org/releases/bookworm/amd64/release-notes/ch-upgrading.html
https://www.debian.org/releases/bookworm/amd64/release-notes/ch-information.html

## Start from pure Debian
cat /etc/debian_version
lsb_release -a
apt-forktracer
sudo apt install gpgv
dpkg --audit
#dpkg --get-selections | grep 'hold$'
apt-mark showhold

## Preparing Source List
cd /etc/apt
cat sources.list | sed 's/^/#/g' | sudo tee sources_bullseye.list
cat sources.list | sed 's/^/#/g' | sed 's/bullseye/bookworm/g' | sudo tee sources_bookworm.list
cat sources_bookworm.list | sed 's/^#//g' | sudo tee sources.list

cd /etc/apt/sources.list.d
for i in *.list ; do
    cat ${i} | sed 's/^/#/g' | sudo tee ${i%.list}_bullseye.list
    cat ${i} | sed 's/^/#/g' | sed 's/bullseye/bookworm/g' | sudo tee ${i%.list}_bookworm.list
    cat ${i%.list}_bookworm.list | sed 's/^#//g' | sudo tee ${i}
done

## Upgrading Packages
sudo apt update
sudo apt -o APT::Get::Trivial-Only=true full-upgrade

sudo apt upgrade --without-new-pkgs
sudo apt full-upgrade

Available Options for Configuration Files:

1. Install the Package Maintainer's Version
   • Original configuration file is copied with post-fix '.ucf-old' to the same location
2. Keep the Local Version Currently Installed (Default)
   • Possible safest way

## Preparing for the Next Release
sudo apt list '~c'
sudo apt purge '~c'

https://www.debian.org/releases/bullseye/amd64/release-notes/ch-upgrading.html
https://www.debian.org/releases/bullseye/amd64/release-notes/ch-information.html

## Start from pure Debian
cat /etc/debian_version
lsb_release -a
apt-forktracer
dpkg --audit
dpkg --get-selections | grep 'hold$'

## Preparing Source List
cd /etc/apt
cat sources.list | sed 's/^/#/g' | sudo tee sources_buster.list
cat sources.list | sed 's/^/#/g' | sed 's/buster/bullseye/g' | sed 's/\/updates/-security/g' | sudo tee sources_bullseye.list
cat sources_bullseye.list | sed 's/^#//g' | sudo tee sources.list

cd /etc/apt/sources.list.d
for i in *.list ; do
    cat ${i} | sed 's/^/#/g' | sudo tee ${i%.list}_buster.list
    cat ${i} | sed 's/^/#/g' | sed 's/buster/bullseye/g' | sudo tee ${i%.list}_bullseye.list
    cat ${i%.list}_bullseye.list | sed 's/^#//g' | sudo tee ${i}
done

## Upgrading Packages
sudo apt update
sudo apt -o APT::Get::Trivial-Only=true full-upgrade

sudo apt upgrade --without-new-pkgs
sudo apt full-upgrade

Available Options for Configuration Files:

1. Install the Package Maintainer's Version
   • Original configuration file is copied with post-fix '.ucf-old' to the same location
2. Keep the Local Version Currently Installed (Default)
   • Possible safest way
   • New configuration file is stored with post-fix '.ucf-dist' to the same location

## Preparing for the Next Release
dpkg -l | awk '/^rc/ {print $2}'
sudo apt purge $(dpkg -l | awk '/^rc/ {print $2}')

https://unix.stackexchange.com/questions/758100/in-debian-bullseye-does-systemd-timesyncd-check-for-other-ntp-daemons
https://tracker.debian.org/news/1115332/accepted-systemd-2454-2-source-amd64-into-unstable-unstable/
https://wiki.archlinux.org/title/systemd-timesyncd

systemctl list-unit-files

## UNIT FILE                              STATE           VENDOR PRESET
## dbus-org.freedesktop.timesync1.service bad             enabled

• Debian Bullseye(11) has adopted Chrony as the default NTP service
• Debian Buster(10) used another NTP-related package systemd-timesyncd conflicting with Chrony
• The systemd-timesyncd package has been removed in this update process, but some files are not purged

#sudo apt purge systemd-timesyncd
sudo rm -f /etc/systemd/system/dbus-org.freedesktop.timesync1.service
#sudo rm -f /etc/systemd/system/sysinit.target.wants/systemd-timesyncd.service

https://www.debian.org/releases/