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After administering Unix or Unix-like servers, what tools (command-line preferably) do you feel you cannot live without?

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42 Answers 42

rsync, especially in concert with ssh. It allows simple efficient copying of files from host to host. How did we ever cope without ssh and rsync? :-)

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ssh, Vim, htop, su, Python, ls, cd, screen, du, tar :)

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nmon

Haven't seen anyone mention this yet.

The nmon tool is designed for AIX and Linux performance specialists to use for monitoring and analyzing performance data, including:

  • CPU utilization
  • Memory use
  • Kernel statistics and run queue information
  • Disks I/O rates, transfers, and read/write ratios
  • Free space on file systems
  • Disk adapters
  • Network I/O rates, transfers, and read/write ratios
  • Paging space and paging rates
  • CPU and AIX specification
  • Top processors
  • and more

Can be run in file mode which generates a big CSV file. IBM also provide an Excel macro for parsing this and turning it in to awesome graphs, although you do need a Windows VM for that.

nagios and munin for monitoring and graphing.

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Most of these tools are made much more powerful using Bash "programmable completion" - so you can tab-complete things like commandline options, or say the name of a package with "apt-get install". It will also limit what you tab-complete for relevant files - for example, "unzip" will only complete supported archive files.

It really is the mutts - if you have never tried it you probably just need to fiddle your .bashrc:

if [ -f /etc/bash_completion ]; then
    . /etc/bash_completion
 fi

Certainly this is true on Ubuntu and Debian. You may need to get the package on some Linux distributions.

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Face it - sooner or later you'll deal with the network as well. mtr, tcpdump and tshark are really useful for seeing what's happening.

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munin is a great tool for doing capacity analysis and review, but you need to set it up before you need it. We install it as a standard part of every server install we do.

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  • rsync running over ssh to keep things consistent... in multiple directions (-gloptru[n]c)
  • Vim and vimdiff to edit with 'folding' and viewing differences in scripts, logs, etc.
  • Perl and (Ba)sh for scripting and analysis
  • cURL (and maybe Wget) for posting/fetching data from ...
  • Apache to webify them all (or at least create point-n-click admin tools)
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Learn Vim or Emacs in and out!!
For text editing
Grep
Sed
AWK


For network tools
Nmap
dig

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Perl and Vim. In that order. Anything else, I can use Perl to emulate somehow.

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All the standard commands and utilities (Bash, grep, sed, AWK, find, xargs, ssh, Vim, etc.)

  • Lsof, awesome in so many ways, I love to use it for finding open ports AND the files associated with that process.
  • Screen, for multi-session awesome.
  • Tcpdump, its funny how many application problems are really weird network issues
  • Ruby, makes more sense to me than Perl, becoming wildly popular for SA work.
  • Chef, configuration management system.
  • Capistrano, ssh in a for loop, but less crappy. And in Ruby.
  • Rake, more sensible than make.
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These are the tools I use on a daily basis (as a developer more than a system administrator)

  • zsh
  • lsof
  • ps
  • ack (or grep)
  • find
  • svn
  • Python
  • tar
  • which
  • fortune (a guy has to keep his sanity somehow)
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I love AWK as well as "for" on the command line.

Especially to build up a list of commands I want to run and then execute them all at once.

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  • vi
  • find
  • ssh
  • AWK
  • sed
  • netcat
  • tar
  • ps

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    • Bash
    • Vim
    • iostat
    • ps
    • top
    • lsof
    • strace
    • tcpdump
    • netstat
    • find
    • grep
    • Perl
    • sed
    • tail
    • dig
    • traceroute

    Where possible the GNU versions of the above over the propritary versions.

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    Some I know that I cannot live without...

    • 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 filesystems.

    • 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.

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    8  
    Another useful but little known feature of less is that you can always use the 'v' command to start editing the file you're currently looking at. Mnemonic is 'v' for 'vi'. –  dr-jan Jun 1 '09 at 14:20
    1  
    htop is a "better" version of top. –  Alexander Bird Nov 10 '11 at 5:49

    screen is a must, especially with a good .screenrc file. I have it configured to display visually which window I'm in and can move between them with Ctrl+Arrow. For a single ssh session and multiple shells, it is a life saver.

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    iotop, is a top-like program to monitor I/O accesses to your disks.

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    man - to read the man pages.

    elinks - to check google, cause I sure as hell cant remember everything.

    And attention to detail & tenacity, because without them I just waste time.

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    One tool sometimes very handy is nohup. I use it to run scripts that last for a long time using remote SSH clients.

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    pv: Displays the progress of long operations that can be redirected. http://www.ivarch.com/programs/pv.shtml

    Useful then you want to monitor something that is going to take ages, like copying/compressing a raw block device over the network (which is how I take paranoia backups of my 8Gb netbook before tinkering with anything major like tweaking with file system settings).

    Also: I'll second votes for ssh, rsync, screen, htop and netcat as mentioned by people above - all of which are more important than pv but pv had not been mentioned yet. In fact pv is often a useful addition when piping stuff to or from to netcat.

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    zsh as a shell

    It is especially efficient with grml.org's extensions/setup.

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    I use most of the tools already listed, but here's one no one has touched on yet:

    Puppet - system for automating system administration tasks

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    • atop - yet another top alternative, great for monitoring changes in processes
    • strace/ltrace - for tracking down those REALLY annoying bugs
    • ldd - track down broken library dependencies
    • cron, logrotate ;)

    Of course, beyond command line, you need Nagios/Cacti/MRTG/etc...

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    tar pipe!

    piping the output of tar to another utility, to tar running on the same box, or to tar running over SSH is my favorite old-school Unix move for moving files from one place to another.

    This also gives you the Windows-style option of copying one folder to another and ending up with all of the files in the source and destination directory.

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    A few things overlooked I wanted to mention.

    • vim -d split screen console diff that makes it very easy to see the differences in a file
    • pdsh allows you to easily run a command over as many systems as you want either serial or parallel(I am a cluster admin. I can't function without it.)
    • nmon is like top on crack. It gives you a great idea of what is going on on a system on a single screen. You can see disk I/O, network I/O CPU usage, and memory usage real time. At the very least a real fun thing to play with when profiling a system.

    Oh, and I forgot to mention, when scripting, I believe you should always use Korn. I hate Korn(Not the band. I love the band:-P) but it's literally everywhere. You can take a script and move it between Solaris, AIX and Linux and not have to worry about whether or not the admin had the decency to install Bash.

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    A couple of handy tools I haven't seen mentioned yet:

    • 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)
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    Netcat.

    • Test if TCP services are listening.
    • Perform transactions against plaintext protocols such as SMTP.
    • Quick insecure data transfers between machines.
    • Telnet client emulation.

    The network swiss army knife, as they say.

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    Some additional answers can be found in this similar question

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    Some that haven't been mentioned before:

    • head/tail
    • diff
    • pstree
    • tar
    • gzip/bzip
    • watch
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