Below are compilation of few must have tools for unix which I use personally to achieve faster work completion time.
Please add to the comments if I have missed few others. Np: I’m not a UNIX administrator 🙂
tee – allows simultaneous writing to STDOUT (standard output) and a file. Great for viewing information and logging it for later.
top – the task manager of UNIX, gives a great overview of the system.
tail -f – allows you to view appended data as a file grows, great for monitoring log files on a server.
grep – Global Regular Expression Print, great for searching the system for data in files.
df – reports disk usage of current file systems.
du – reports disk usage of a certain file/directory.
less – needed to view man pages! also useful for viewing output of commands in an easily seekable manner.
vim/Emacs/nano/pico/ed – whatever your text editor of choice may be, self explanatory of why it’s needed.
lsof – to determine which processes are using a file or directory (useful when trying to figure out what is preventing a device from being umount’d)
netstat – to determine which processes are using network connections (especially useful when trying to figure out which daemon is bound to a certain port)
Perl – It is ideal for manipulating text, and since un*x operators live on text files, pipes, input and output, Perl is a great fit.
Cygwin – If you are a un*x admin and have to work on a windows box (even your desktop) having ls, rm, grep, sed, tail etc save you a lot of time when switching OS’s.
sed & awk – Quick examples are command line filtering with sed, and quick and dirty log processing with awk.
rsync – Allows simple efficient copying of files from host to host.
mtr, tcpdump and tshark – Useful for seeing what’s happening in network.
Test if TCP services are listening.
Perform transactions against plaintext protocols such as SMTP.
Quick insecure data transfers between machines.
Telnet client emulation.
Open SSH (Linux client),Putty (Windows client) – To connect to your *NIX server
python & gawk – For automating work – Scripting
htop — great for process management.
pinfo — lynx like browser for info and man pages.
xterm – A single graphical console window to allow commands to be interactively run servers over an ssh connection.
tail -f – checking logs
vmstat 1 – Gives you a great overview of system behaviour.
dstat –nocolor (overview of cpu-, disk-, net-usage)
iftop (nice dynamic overview of network traffic)
ccze (colour logfiles nicely)
ssh tunnels (can be useful once in a while; see the manual; -R)
expect (automate interactive, chatty dialogy interfaces, nice if you’re in a pinch)
SSH, FTP, NFS, NIS, LDAP, DNS, Sudo – few other tools required
Nagios, RT, ORCA, MRTG, Cacti – Exposure to open source management tools.
ufsdump, tar, cpio, (Netbackup, TSM, veritas, legato) – Few backup tools, is a plus.