… is a matter of taste, but this is (part of) my list:

# For general use:
apt-get install aptitude zsh less strace psmisc rcs screen \
                rsync sshfs ntpdate host exim4-daemon-light \
                sudo file bc mlocate man cvs patch [uemacs|nano]
# For some diagnostics
apt-get install pciutils iftop tcpdump lshw
# For systems running on the "bare metal"
apt-get install smartmontools ethtool
# For server maintenance
apt-get install munin-node munin-plugins-extra sysstat
# For development use
apt-get install dpkg-dev debhelper devscripts liburi-perl \
                fakeroot build-essential autoconf bison \
                autotools-dev sharutils

At least for uemacs you need to access the /usr/local repositories. Get it by

wget -O /etc/apt/sources.list.d/usr-local-debian.list -c http://debian.usr-local.de/debian.list

/etc/apt/apt.conf.d/myconf

// APT::Cache-Limit "50331648";
APT::Default-Release "bookworm";

Aptitude::UI::Package-Status-Format "%C : %A : %D : %v : %t";
Aptitude::UI::Package-Display-Format "%c%a %M %10v =%i=> %S %10V (%D) %p";
Aptitude::UI::Package-Header-Format "%m: %d# #";

Aptitude::UI::Keybindings::ReSearch "n";
// Aptitude::UI::Keybindings::Undo "C-z,C-u,C-_";
Aptitude::UI::Keybindings::DescriptionDown "y,z";
// Aptitude::UI::Keybindings::Quit "backspace,q";

Tested with Debian 10 Buster

/etc/apt/preferences.d/99ul-pin-priorities

# /usr/local Pin Priorities
# Need to be in sync with /etc/apt/sources.list !
# Check with apt-cache policy
 
Package: *
Pin: origin deb.debian.org
Pin-Priority: 500
 
Package: *
Pin: origin security.debian.org
Pin-Priority: 500
 
# Package: *
# Pin: origin repo.dovecot.org
# Pin-Priority: 1
 
Package: *
Pin: origin *
Pin-Priority: 1

See:

• https://wiki.debian.org/AptConfiguration#apt_preferences_.28APT_pinning.29

You need to know why apt-key add is deprecated

To change the timezone of a running systems, issue

tzconfig

or¹⁾

dpkg-reconfigure tzdata

depending on your version of Debian.

For unattended installations, the following may work:

debconf-set-selections tzdata.debconf

tzdata.debconf

tzdata tzdata/Areas select Europe
# tzdata tzdata/Areas seen false
tzdata tzdata/Zones/Europe select Berlin
# tzdata tzdata/Zones/Europe seen false

For some versions of Debian, you need to add sec=sys in /etc/exports if you want to use no_root_squash

Reference: Re: NFS and no_root_squash - cannot write as root - permission denied (SOLVED)

update-locale LANG=C LC_CTYPE=de_DE LANGUAGE

locale

sudo apt-get install devscripts
apt-get source <package>
# If you start here: dpkg-source -x <package>.dsc
cd <packagedir>
# generating new changelog entry with local version suffix for distribution lenny:
export DEBEMAIL="${DEBEMAIL:-peter@foo.bar}"
export DEBFULLNAME="${DEBFULLNAME:-Peter Foobar}"
dch -l .ul~ulyana -D ulyana
dpkg-buildpackage -rfakeroot --no-sign

This works e.g. for the Clock xfce4-panal applet.

Do as root:

mkdir -vp /usr/local/share/i18n/locales/
sed -e 's/^week.*$/&\nfirst_weekday\t2/g' /usr/share/i18n/locales/en_US  > /usr/local/share/i18n/locales/en_US
locale-gen

GOSH!
Yeah - it's as easy as that. The tricky part is to what to do

References:

• mozycan's answer to "Can I make panel's calendar week start on Monday instead of Sunday?" on Reddit
• less /usr/sbin/locale-gen

Also quite interesting while not directly related to my solution:

• 0xC0000022L's answer to "Change a locale definition (as opposed to a locale setting)" on Stackexchange.

locale Xfce

This was actually tried with success on a Linux Mint 20 Ulyana, but I assume it works pretty much the same on Debian and all its derivatives

The most easy way would be to uninstall systemd-resolved, but as it is bundled with systemd which unfortunately is a crucial part of Debian meanwhile, this ist not possible.

apt install resolveconf
systemctl disable systemd-resolved
vi /etc/NetworkManager/conf.d/10-dns-resolved.conf

We need to override /usr/lib/NetworkManager/conf.d/10-dns-resolved.conf, therefore the file name does not really match its purpose²⁾:

/etc/NetworkManager/conf.d/10-dns-resolved.conf

dns=default
rc-manager=resolvconf
systemd-resolved=false

Disabling systemd-resolved in systemd and in NetworkManager propably doesn't make much of a difference after your told NetworkManager not to route DNS queries to it but for saving system resources.

References:

• man NetworkManager.conf
• Stackexchange

systemd DNS

Linux Debian