These are all the useful commands I can think of right now that you don't need to have root privileges to run. Some will be useful for Werewolves, others might be useful for CtF contests, for the rest, who knows. The five most important commands in Linux are: apropos - search the manual page names and descriptions help - bash built-in commands, see bash info - readable online documentation man - an interface to the on-line reference manuals whatis - display manual page descriptions For logging in, logging out, managing a terminal, editing text files: clear - clear the terminal screen exit - exit from a session history - see your command history scp - secure copy (remote file copy program) screen - screen manager with VT100/ANSI terminal emulation sftp - secure file transfer program sleep - delay for a specified amount of time ssh - OpenSSH SSH client (remote login program) vim - Vi IMproved, a programmers text editor watch - execute a program periodically, showing output fullscreen For dealing with files and directories: cd - change directories chown - change file owner and group chgrp - change group ownership chmod - change file mode bits, e.g., such as permissions cksum - checksum and count the bytes in a file cmp - compare two files byte by byte cp - copy files and directories dd - convert and copy a file diff - compare files line by line dirname - strip last component from file name file - determine file type find - search for files in a directory hierarchy hexdump - display file contents in ascii, decimal, hexadecimal, ... ls - list directory contents md5sum - compute and check MD5 message digest mkdir - make directories mv - move (rename) files pwd - print name of current/working directory rm - remove files or directories rmdir - remove empty directories sha1sum - compute and check SHA1 message digest stat - display file or file system status touch - change file timestamps wget - The non-interactive network downloader Commands for finding and interacting with other users: finger - See some baisc user info, like that last login time groups - print the groups a user is in id - print real and effective user and group IDs sslpasswd (1ssl) - compute password hashes passwd - update user's authentication tokens users - print the user names of users currently logged in w - Show who is logged on and what they are doing who - show who is logged on whoami - print effective userid write - send a message to another user Commands for processes and understanding what's going on in the system: free - Display amount of free and used memory in the system kill - terminate a process killall - kill processes by name ps - report a snapshot of the current processes. pstree - display a tree of processes top - display Linux processes Networking commands: host - DNS lookup utility hostname - show or set the system's host name ifconfig - configure a network interface mtr - slightly fancy combination of traceroute and ping netstat - Print network connections, routing tables, etc. ping - send ICMP ECHO_REQUEST to network hosts traceroute - print the route packets trace to network host dig - DNS lookup utility Some advanced stuff for bash scripting and playing Werewolves: done - built-in for bash scripting for - built-in for bash scripting fuser - identify processes using files or sockets lsof - list open files nohup - run a command immune to hangups, with output to a non-tty nslookup - query Internet name servers interactively while - built-in for bash scripting Commands for I/O processing awk - pattern scanning and processing language cat - concatenate files and print on the standard output echo - display a line of text grep - print lines matching a pattern head - output the first part of files HEAD - Simple command line user agent less - opposite of more more - file perusal filter for crt viewing rev - reverse lines of a file or files sed - stream editor for filtering and transforming text sort - sort lines of text files strings - print the strings of printable characters in files tail - output the last part of files tee - read from standard input and write to standard output tr - translate or delete characters uniq - report or omit repeated lines Others: alias - bash built-in commands, see bash arp - manipulate the system ARP cache arping - send ARP REQUEST to a neighbour host basename - strip directory and suffix from filenames bash - GNU Bourne-Again SHell bg - bash built-in commands, see bash break - bash built-in commands, see bash bzip2 - a block-sorting file compressor, v1.0.6 cal - display a calendar comm - compare two sorted files line by line convert - Might be useful for CtF chaosreader - Might be useful for CtF cut - remove sections from each line of files date - print or set the system date and time dc - an arbitrary precision calculator df - report file system disk space usage dirs - bash built-in commands, see bash dmesg - print or control the kernel ring buffer du - estimate file space usage egrep - print lines matching a pattern eject - eject removable media env - run a program in a modified environment expect - Might be useful for CtF expand - convert tabs to spaces export - bash built-in commands, see bash false - do nothing, unsuccessfully fg - bash built-in commands, see bash fgrep - print lines matching a pattern fmt - simple optimal text formatter gawk - pattern scanning and processing language gdb - The GNU Debugger gunzip - compress or expand files gzip - compress or expand files iconv - Might be useful for CtF iftop - Might be useful for CtF jobs - bash built-in commands, see bash join - join lines of two files on a common field ln - make links between files locate - find files by name logname - print user's login name logout - bash built-in commands, see bash look - display lines beginning with a given string ltrace - Might be useful for CtF mkfifo - make FIFOs (named pipes) mmv - massive move mogrify - Might be useful for CtF nice - run a program with modified scheduling priority nl - number lines of files nm - list symbols from object files objdump - display information from object files. od - dump files in octal and other formats paste - merge lines of files pax - Might be useful for CtF pkill - look up or signal processes based on name and other at... popd - bash built-in commands, see bash pushd - bash built-in commands, see bash pv - Might be useful for CtF quota - get disk quota info readelf - Displays information about ELF files. rename - rename files renice - alter priority of running processes ripole - Might be useful for CtF sdel - secure delete select - Might be useful for CtF seq - print a sequence of numbers shred - overwrite a file to hide its contents, and optionally ... shuf - generate random permutations split - split a file into pieces strace - Might be useful for CtF su - run a command with substitute user and group ID sudo - execute a command as another user sum - checksum and count the blocks in a file suspend - bash built-in commands, see bash tac - concatenate and print files in reverse tar - an archiver tool tar - format of tape archive files tcpdump - dump traffic on a network tcpflow - Might be useful for CtF tcpick - Might be useful for CtF time - time a process timeout - run a command with a time limit times - bash built-in commands, see bash tshark - Might be useful for CtF tsort - perform topological sort tty - print the file name of the terminal connected to stdout type - bash built-in commands, see bash ulimit - bash built-in commands, see bash umask - bash built-in commands, see bash uname - print system information unzip - list, test and extract compressed files in a ZIP archive uptime - Tell how long the system has been running. uuencode - Might be useful for CtF uudecode - Might be useful for CtF valgrind - Might be useful for CtF wait - bash built-in commands, see bash wc - print newline, word, and byte counts for each file whereis - locate binary, source, and manual page files which - shows the full path of (shell) commands whois - Might be useful for CtF wireshark - Might be useful for CtF zip - package and compress (archive) files zipinfo - list detailed information about a ZIP archive