dean

Obviously these are probably in other distributions and BSD's. Debian is win though.

adjtimex

Actually reduce/stop clock drift, rather than having ntp constantly tweaking the system time. Useless on VM's obviously.

apticron

Emails you a list of packages to be updated.

Configure it via /etc/apt/listchanges.conf

cpulimit

Control max cpu usage of a process

disktype

A convenient way to show disk size, partitions, format, uuid etc etc

dstat

vmstat, iostat and ifstat all in one... with color!

eatmydata

Disables fsync, so programs that ask to sync data to disk only think they have. Dangerous as important data can be lost, but can improve performance.

ferm / shorewall

Both try to make iptables (and firewall stuff generally) more straight forward. Both happen to be in written in perl

gdebi-core

Useful for installing local packages plus deps (which you would like to draw from remote repos)

Runs like this...

gdebi local-file.deb

jq

command line json processing

libpam-ssh

Unlocks your ssh key if the password is the same as your log in. Perfect for jump boxes and xfce.

localepurge

Cleans up locales to save disk space, runs initially then runs after package installs

molly-guard

Wraps reboot and halt, so that you don't run them via ssh unless you are super sure you want to...

mtr

Useful alternative to 'traceroute' - keeps updating in real time

orphaner

Finds and helps remove 'orphaned' packages and config files

• orphaner with no options looks for anything apt considers a library
• orphaner --find-config looks for left over config files from removed packages
• orphaner --help does what you would imagine

(surprise! apt doesn't remove config files when it removes packages, remove with --purge to clean them. i.e. apt-get --purge remove foo )

parallel

Runs commands in parallel. can do quite insane stuff. Happens to be written in perl
snmp-mibs-downloader

Mibs are 'non-free', so don't forget to install them when you install net-snmp

sxid

Keeps track of setuid and setgid files

tree

Simple cli command related to 'ls'. Very handy

unattended-upgrades

(see also http://www.howtoforge.com/how-to-configure-automatic-updates-on-debian-squeeze)

Installs updates automagically.

configure via /etc/apt/apt.conf.d/50unattended-upgrades

populate /etc/apt/apt.conf.d/02periodic with something like...

// Enable the update/upgrade script (0=disable)
APT::Periodic::Enable "1";

// Do "apt-get update" automatically every n-days (0=disable)
APT::Periodic::Update-Package-Lists "1";

// Do "apt-get upgrade --download-only" every n-days (0=disable)
APT::Periodic::Download-Upgradeable-Packages "1";

// Run the "unattended-upgrade" security upgrade script
// every n-days (0=disabled)
// Requires the package "unattended-upgrades" and will write
// a log in /var/log/unattended-upgrades
APT::Periodic::Unattended-Upgrade "1";

// Do "apt-get autoclean" every n-days (0=disable)
APT::Periodic::AutocleanInterval "7";

xclip

Pipe to X windows clipboard

In your .bashrc / .bash_aliases, put:

alias setclip='xclip -selection c'
alias getclip='xclip -selection clipboard -o'

You can now use setclip and getclip, e.g:

$ echo foo | setclip $ getclip foo