All commands

Change the -p argument for the port number. See "man nmap" for different ways to specify address ranges.

Just run the command, type your password, and that's the last time you need to enter your password for that server.

This assumes that the server supports publickey authentication. Also, the permissions on your home dir are 755, and the permissions on your .ssh dir are 700 (local and remote).

If you come from a DOS background and accidentally use DOS commands often, this and others like it can be helpful. Add to your .bash_profile, or wherever you keep such things.

Insert the last argument to the previous command

this is very useful when there is a different network host to determine which are turned on or not

You'll need to make sure your xorg.conf permits a virtual screen size this big. If it doesn't then xrandr should return a suitable error message that tells you the required size.

This command creates a rar archive from all files in the current folder and names the archive after the folder name.

waste the band width

Very useful for rerunning a long command changing some arguments globally.

As opposed to ^foo^bar, which only replaces the first occurrence of foo, this one changes every occurrence.

Useful for massive files where doing a full diff would take too long. This just runs diff on the first 500 lines of each. The use of subshells to feed STDIN is quite a useful construct.

Return the current shell. It is better than print $SHELL which can sometimes return a false value.

Add @mail.com each line of a list

This open the cd rom device and close it in a loop

Check if Fail2Ban is running on the system and alert it with a message in the terminal

Create a exact mirror of the local folder "/root/files", on remote server 'remote_server' using SSH command (listening on port 22)

(all files & folders on destination server/folder will be deleted)

#!/bin/sh

_HOSTNAME=`hostname`

_HOSTTYPE=`echo $HOSTTYPE`

_MACHINETYPE=`echo $MACHTYPE`

_OSTYPE=`echo $OSTYPE`

_VENDOR=`echo $VENDOR`

_KERNEL=`uname -r | awk -F- '{print $1}'`

_GLIBC=`ls /lib/libc-*.so | awk -F- '/lib/ {print $2}' | awk -F. '{print $1"."$2}'`

_MEM=`cat /proc/meminfo | awk '/MemTotal/ {print $2 $3}'`

_CPU=`cat /proc/cpuinfo | grep 'cpu MHz' | awk '{print $4}'`

echo '=============================='

echo 'HOSTNAME ' $_HOSTNAME

echo 'HOSTTYPE ' $_HOSTTYPE

echo 'MACHINETYPE ' $_MACHINETYPE

echo 'OSTYPE ' $_OSTYPE

echo 'VENDOR ' $_VENDOR

echo 'KERNEL ' $_KERNEL

echo 'GLIBC ' $_GLIBC

echo 'MEM INFO ' $_MEM

echo 'CPU INFO ' $_CPU

echo '=============================='

This command requires the imagemagick libraries and will resize all files with the .jpg extension to a width of 1024 pixels and will keep the same proportions as the original image.

apt-get must be run as root, and it is useless to run it as your own user. So just run it as root. Saves you the "sudo !!" every time you're adding a package.

If your web server is down, this command will periodically attempt to connect to it. If the output is blank, your server is not yet up. If you see HTML, your server is up. Obviously, you need to replace the Google URL with your web server URL...

* 'watch' -- a command for re-executing a command and displaying

the output

* '-n 15' -- tells watch to redo the command every 15 seconds

* 'curl' -- a handy utility for getting the source of a web page

* '-s' -- tells curl to be silent about failing

* '--connect-timeout 10' -- Try to connect for 10 seconds