dacaprice.com from fitness to technology.

The ssh_config file.

Working in an environment with hundreds of SSH servers, one appreciates the value a good ssh_config file.  I use an ssh_config file to specify specific usernames for certain hosts, as well as specifying a keepalive interval, to prevent my session from timing out.

I use the following options:

Host hostname

HostName hostname (can be an IP)

User username

ServerAliveInterval 60 (sends keepalive every 60 seconds)

For further info check out the good old man ssh_config.

How to zero out a file in Linux

Ever need to quickly clear a file out in Linux?  Maybe a log file that is growing out of control?  Rather than delete it, try this:

[dacaprice@fedora10 ~]$ > /var/log/messages

Now your messages file is empty, and the file retains its permissions.

Securely delete files in linux

I often use shred in linux, when deleting anything sensitive.  Any way I've used it has always been pretty simple and straight forward (ie shred -uvz filename).  Today I sold my old cell phone with microSD card on eBay and I wanted to get all of my data off securely.  Unfortunately, it seems shred does not know how to handle directories.  A little googling found me this:

find -type f -execdir shred -uvz '{}' \;

The find command lists every file in your present working directory and subdirectories and executes the shred command on it.  I finished up with an rm -rf * to delete any remaining directories and I was then comfortable sending the card out with the phone.