chmod calculator

The best that I have found for quickly calculating numerical permissions:

http://www.javascriptkit.com/script/script2/chmodcal.shtml

Remove old files

If you don't use logrotate to remove or archive old logs, here is a way to remove old logs using the -ctime directive within the bash command find.

/usr/bin/find /var/log/tomcat -name *.tgz -ctime +15 | xargs rm -rf

Mount a cdrom from the command line

To mount a cdrom (or DVD) from the command line, do the following:

#mount -t iso9660 -o ro <device> <mountedDirectory>

Example:

# mount -t iso9660 -o ro /dev/cdrom /media/cdrom

Note: make sure that /media/cdrom exists.

Configure a wireless connection from the command line

Here is how to configure a wireless network interface from the command line in Ubuntu.

http://www.stoltenow.com/archives/2006/12/ubuntu_configur.html