Linux commands

I'm starting a list of useful linux shell commands (generally "one liners") we use a lot

Image Manipulation

Resizing JPG's and changing quality setting

The first line shows how to reduce and image to 25% and quality to 50% adding "_resized" to the results filename. The second command uses Perl to apply this same command to all JPG's in the current directory.

{{{1}}}

Apply an opaque background of a specified colour to a directory of transparent PNG's

• This command requires ImageMagick to be installed
• It loops through all PNG's in the CWD and puts them in a directory called processed which must exist

<bash> perl -e 'qx "convert $_ -background #ff00ff -flatten foo/$_" for glob "*.png"' </bash>

See also

• Converting_microarray_images for bash/imagemagick image file manipulation

Network commands

Release DHCP lease

<bash> sudo dhclient -r </bash>

Obtain a new DHCP lease

<bash> sudo dhclient </bash>

Devices

fstab

Static information about the filesystems (fstab) is a configuration file that contains information of all the partitions and storage devices in your computer. It contains information of where your partitions and storage devices should be mounted and how.

<bash> cat /etc/fstab </bash>

mount

All files accessible in a Unix system are arranged in one big tree,
      the file hierarchy, rooted at /.  These files  can  be  spread  out
      over  several  devices. The mount command serves to attach the file
      system found on some device to the big file tree.