Install scp, rsync and other tools on CentOS

When you do a "minimal" install of CentOS it doesn't install things like rsync and scp by default.

To install them do;

yum install openssh-clients rsync

Unmount stale NFS mounts

If you have a stale NFS mount hanging on your system it can cause various programs and utilities to fail. A typical symptom is a hang when using the 'df' command.

In such cases you cant do umount /path/to/stale/nfs because it will say "the device is busy" or words to that effect

To fix this you can unmount it with the 'lazy' option;

umount -l /path/to/stale/nfs

If you don't expect that mount point to ever be available again (for example the nfs server was decommissioned) then make sure you adjust /etc/fstab accordingly.

Remove Subtitles and Audio tracks from MKV files

To remove unwanted audio and subtitle tracks from Matroska (mkv) files you use mkvtools; sudo apt-get install mkvtoolnix-gui Once it is installed then open up the gui (Sound & Video menu) and follow these steps; 1) In the "Input files" box on the "Input" tab browse to the mkv file you want to modify. 2) In the "Tracks, chapters and tags" box uncheck any part you want to remove (leave the stuff you want to keep checked) 3) In the "Output filename" box keep the default name or modify to suit. 4) Click "Start muxing" and wait a minute or two until it completes. Once you are done, you can delete the original file (after checking it worked of course!) and rename the new file accordingly.