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Delete files by age on Linux

admin — Fri, 14 Aug 2009 00:34:51 +0000

Often it might be necessary to remove files older than a certain age on a Linux machine. This uses the bash programming language which is native to most Linux distributions. It can be run on a regular basis by scheduling it with the crontab, or run once to clean out old files. The time variable can be changed to suit the user’s needs, more examples can be found at the Save Lono software engineering help site.

This script removes every *.wav file older then one minute in the directory it is executed. This script is very useful and can be used with the cron daemon for regular file removal.

#!/bin/bash

find ./*.wav -type f -mmin +1 -exec rm {} \;

Also we can adjust this for days rather than minutes by changing ‘-mmin +1′ to ‘-mtime +10′. This would delete .wav files in the working directory that were older than 10 days.

More Information
provided by SaveLono.com

http://www.savelono.com/

OpenSSH Visual Host Fingerprint Representation

David Hudson — Sat, 18 Jul 2009 08:41:26 +0000

With the visual host key fingerprint, users can more easily tell whether they recognize a hex key using ssh. The secure shell remote connection program lets you connect to another machine via an encrypted connection.

Apparently, there is a setting in OpenSSH 5.1 and later for visual remote host fingerprinting. The basic concept is that it’s much easier for the human brain to notice a change in a visual pattern than in a string of hex digits. To turn it on, simply add a line that says
VisualHostKey yes to your ~/.ssh/config file. Then, when you go to SSH into a server, you’ll see a visual representation of the remote host fingerprint, in addition to the regular fingerprint, as shown below:

Example

[dhudson@attackbot ~]$ ssh myhost.com
Host key fingerprint is
07:d4:02:db:9f:70:d5:2d:7f:1b:6a:df:83:73:95:1d

+--[ RSA 2048]----+
|      ....  .. . |
|       +. ..  o .|
|      . +..    o |
|         = .   Eo|
|        S +   . B|
|         .   o oo|
|            . o o|
|             o +.|
|              o .|
+-----------------+

Search your command history in Linux

David Hudson — Mon, 13 Jul 2009 07:33:23 +0000

Push Ctrl+R (Control key held down at the same time as the R key). This will display the following in your shell:

(reverse-i-search)`’:

Type part of the command you’re searching for, for example “ls”, bash will search for matching commands. For example, it might show:

(reverse-i-search)`ls’: ls – /home/bob/

What it actually shows is going to be dependent on the commands you’ve previously entered.

Control + R again to cycle through the list.

When you do this, bash looks for the last command that you entered that contains the substring “ls”, in my case that was “ls …”. If the command that bash finds is what you’re looking for, just hit Enter to execute it. You can also edit the command to suit your current needs before executing it (use the left and right arrow keys to move through it). If you’re looking for a different command, hit Ctrl+R again to find a matching command further back in the command history. You can also continue to type a longer substring to refine the search, since searching is incremental.

Note that the sub string you enter is searched for throughout the command, not just at the beginning of the command.

/home/susan/.bash_history

The predeeding “.” indicates that it a hidden file.

If you’ve used bash for a while you might know that the commands you enter are saved in the ~/.bash_history when you log out. Next time you log in, bash automatically loads these history commands from the saved file and you can then use the up and down arrow keys to browse your command history and find the command you want rather than re-entering it.