1-800-HOSTING Blog » cli http://blog.800hosting.com Inside 1-800-HOSTING Mon, 19 Jul 2010 21:04:46 +0000 http://wordpress.org/?v=2.9.2 en hourly 1 Linux Shell Insights: Volume 2 http://blog.800hosting.com/2009/05/linux-shell-insights-volume-2/ http://blog.800hosting.com/2009/05/linux-shell-insights-volume-2/#comments Tue, 26 May 2009 23:40:14 +0000 Jonathan Kelley http://blog.800hosting.com/?p=548 My last volume Linux Shell Insights: Volume 1 had some talk on the social plane about it so here’s Volume 2. Enjoy.

Here are a few more one-liners. I also call for the assistance of our audience; if anyone has more reliable or efficient methods to accomplish the ends in this article, get involved and comment!

  1. Obtain your internet IP
    There are two ways to do this (both below.) This can be useful in bash scripts that require your IP address. It’s useful in a dynamic IP environment when handling dynamic DNS in some fashion; though can be useful in a variety of scripts in which NAT may exist making eth0 unreliable for this information.

    shell# wget -O – -q checkip.dyndns.org | grep -o “[[:digit:].]+”

    You can also use curl if it’s your tool-of-choice.

    shell# curl -s http://checkip.dydns.org/ | grep -o “[[:digit:].]+”

    If you’ve got a static IP that is directly connected to the internet; it’s best to just scrape the information out of ifconfig.

    shell# /sbin/ifconfig eth0 | grep inet | grep -o “[[:digit:].]+” | head -n 1
  2. Get Distribution Information/Version
    From time to time we get support tickets or calls asking “What distribution of Linux am I running?”. Here’s a way to ascertain this under most modern Linux distributions we offer.

    Most Linux distributions follow the “Linux Standard Base” and have a file in /etc matching *release. You can take a look by running:

    shell# cat /etc/*release

    This does the same thing if you find it easier to remember.

    shell# lsb_release –all

    NOTE: You may have to cat the file /etc/debian_version on some Debian releases.

  3. Shortcut to list all system users
    I stumbled upon this one by a typo once where you can get a peek of system users. This shouldn’t be considered authoritative, as /etc/passwd is your daddy; but it’s quick to verify the spelling of that strange developer who insists on the username supercalifragilistic_expialidocious.
    Tested on: Debian, Redhat

    shell# ~(HIT TAB TWICE HERE)
  4. Lost Plesk Password
    Here’s one of those gems that we keep close to our chest, but I’m willing to reveal it to you. If you misplace your Plesk Admin password, on UNIX it stores it in /etc/psa/.psa.shadow. This is a read-only file, changing the password here does not change it for Plesk. It’s a good way to jot your memory if you forget though.

    shell# cat /etc/psa/.psa.shadow

Continue to keep an eye out for my next list!

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]]> http://blog.800hosting.com/2009/05/linux-shell-insights-volume-2/feed/ 0 Linux Shell Insights: Volume 1 http://blog.800hosting.com/2009/05/linux-shell-insights-volume-1/ http://blog.800hosting.com/2009/05/linux-shell-insights-volume-1/#comments Wed, 06 May 2009 20:57:43 +0000 Jonathan Kelley http://blog.800hosting.com/?p=433 Hello readers,

I thought I’d share some intriguing and useful one-liners that could make your life easier on the Linux/Unix shell environment. I hope to offer a regular multi-part series for those who are fans of the Linux platform.

  1. View Physical Console via SSH
    This will view the console (and makes assumption that the console is an 80 character screen.) It’s helpful to scrape error messages that are printed to the local console. Great for when you don’t have physical access to the server and need to see the terminal; we also find it useful here by eliminating unnecessary trips to the data center floor.

    shell# sudo cat /dev/vcs1 | fold -w 80

  2. Remove multiple RPM packages by a defined pattern
    This is useful for remove all packages that are part of a common suite. This example would uninstall any package in the system with ‘php’ in the name. (Disclaimer: Check what packages contain the string prior to running this. Unpredictable results could remove system critical packages! I’d suggest this for advanced shell users only.)

    shell# yum erase `yum list installed | grep ‘php’`

  3. Reduce a file to zero bytes
    I’m sure every administrator has needed to zero out a log file taking too much space; or clear a users mail spool. Many commands involve piping /dev/null to the file or similar. The following command is probably the easiest and quickest way that many users overlook.

    shell# > file_to_wipe.txt

  4. Look at the strings stored in RAM
    This one is more for fun; though it could be used for security auditing. This command will access the system RAM and reveal text strings stored in memory. Don’t worry, this file is read-only by the kernel. You can usually find interesting data stored in memory with this command.

    shell# sudo dd if=/dev/mem | cat | strings

That’s it for now; more in this series coming soon.

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