Unix: Pranks that sysadmins play

link to a Network World piece on sysadmin pranks, with the alias tricks, fake DOS prompt and terminal freeze bits pulled out

Unix: Pranks that sysadmins play

Unix systems administrators tend to be very serious about their responsibilities – except when they’re not. And, when they’re not, the pranks that they play on each other and some of their more annoying users might surprise you.

TL;DR

A catalogue of classic sysadmin pranks that exploit command-line knowledge the victim doesn’t have.

Alias tricks

Redefine a common command to do something weird or break loudly:

1alias ls='echo "Segmentation fault"'      # ls now "crashes"
2alias cd='echo "Segmentation fault"'      # paired with PROMPT_COMMAND="cd"
3                                           # so every prompt prints it
4alias vi='ed'                              # forces the victim into `ed`
5alias sl='ls | rev'                        # filenames printed backwards
6                                           # (targets people who typo `ls`)
7alias pwd='cd'
8alias who='logout'

Prompt swap

Make a Unix shell look like DOS:

1export PS1='C:${PWD////}> '

Terminal freeze

Ctrl+S freezes the terminal until Ctrl+Q unfreezes it (XON/XOFF flow control). Leaves people thinking the machine hung.

Sending messages to another user’s terminal

1echo "boo" > /dev/pts/3   # appears on whoever is on pty 3

System-level mischief

  • Edit /etc/hosts to redirect a domain (e.g. map google.com to 127.0.0.1)
  • Remote-trigger the CD tray (eject) in a server room for spooky effect
  • Physically swap mice / keyboards between adjacent workstations

Bonus

The sl command is a real package — it prints an ASCII steam locomotive when you typo ls. Half prank, half punishment for sloppy typing.