Useful Linux (Ubuntu) Tidbits

Here are just some morsels of information about the Linux Command line, and more specifically, Ubuntu Linux Command line / system.

  • Users can be added to a group with the command:
sudo adduser <username> <groupname>

In ubuntu, the default system shell is “Dash”. That does speed up your system boot, but it also introduces problems with those scripts which are designed to run in bash, but use /bin/sh to execute. (Which is a surprising amount… this has solved many problems for me. Especially with Asterisk and freePBX.)

  • To set Ubuntu back to using bash from dash, run the following command…
cd /bin && sudo rm sh && sudo ln -s /bin/bash /bin/sh
  • To add a user to the sudoer list (the list that controls who can use “sudo”) use the command
sudo visudo
  • Add a user underneath the “# User privalage specification” comment. If you want just a bog standard sudo user, able to do all on the system, add the line:
<username>    ALL=(ALL) ALL
  • ?Fun? tip: add “insults” to the end of the list of “Defaults” in visudo, so it will look like:
Defaults        !lecture,tty_tickets,!fqdn,insults
  • The system will insult you every time you enter your sudo password wrongly. For a random example, it just gave me this when I deliberately triggered it:
You speak an infinite deal of nothing
  • In Firefox, select the address bar quickly by hitting the “F6” key.
  • Type “pwd” to get the full path to your current directory. e.g.:
kirrus@asus:~$ pwd
/home/kirrus
  • Monit is a useful program, that gives you a good way of keeping an eye on your servers, making sure they don’t run out of harddisk space, or get a high CPU load. It can either perform some function (like stopping a program from running) during high CPU, or send you a warning email.

http://debianhelp.co.uk/monit.htm (useful howto/basic guide)

http://www.tildeslash.com/monit/ (main website)

Monit is in the ubuntu repositories:

aptitude install monit

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