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Get an IP address out of fail2ban jail
Removes an iptables rule created by fail2ban. This example shows how to remove a rule for an IP from the fail2ban-SSH chain. Can be used for any service monitored by fail2ban. For more on fail2ban, see http://www.fail2ban.org/wiki/index.php/Main_Page

Send a binary file as an attachment to an email
The uuencode utility will encode your file so that it can be sent as an attachment to an email. It is part of the sharutils package in RHEL/CentOS/Fedora.

diff 2 remote files

Print stack trace of a core file without needing to enter gdb interactively
This does almost the same thing as the original, but it runs the full backtrace for _all_ the threads, which is pretty important when reporting a crash for a multithreaded software, since more often than not, the signal handler is executed in a different thread than the crash happened.

Monitor the queries being run by MySQL

Watch the progress of 'dd'
dcfldd is a forensic version of dd that shows a process indicator by default.

modify a file in place with perl
changes THIS to THAT in all files matching fileglob* without using secondary files

find with high precission (nanoseconds 1/1,000,000,000s) the last changed file.
this is good for variables if you have many script created files and if you want to know which one is the last created/changed one..

Start a local web server in the current directory on a random dynamic port.

Create arbitrary big file full of zeroes but done in a second
If you want to create fast a very big file for testing purposes and you do not care about its content, then you can use this command to create a file of arbitrary size within less than a second. Content of file will be all zero bytes. The trick is that the content is just not written to the disk, instead the space for it is somehow reserved on operating system level and file system level. It would be filled when first accessed/written (not sure about the mechanism that lies below, but it makes the file creation super fast). Instead of '1G' as in the example, you could use other modifiers like 200K for kilobytes (1024 bytes), 500M for megabytes (1024 * 1024 bytes), 20G for Gigabytes (1024*1024*1024 bytes), 30T for Terabytes (1024^4 bytes). Also P for Penta, etc... Command tested under Linux.


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