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Create a persistent connection to a machine
Create a persistent SSH connection to the host in the background. Combine this with settings in your ~/.ssh/config: Host host ControlPath ~/.ssh/master-%r@%h:%p ControlMaster no All the SSH connections to the machine will then go through the persisten SSH socket. This is very useful if you are using SSH to synchronize files (using rsync/sftp/cvs/svn) on a regular basis because it won't create a new socket each time to open an ssh connection.

Use result of the last command
\$ which python /usr/bin/python \$ ll `!!` lrwxrwxrwx 1 root root 9 2010-11-08 22:01 /usr/bin/python -> python2.6

Create a mirror of a local folder, on a remote server
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)

Quickly add user accounts to the system and force a password change on first login
This command is a bit Linux specific, as --stdin doesn't exist for passwd on many Unix machines. Further, useradd is high level in most distributions and Unix derivatives except for the Debian family of distros, where adduser would be more appropriate. The last bit, with chage, will force the user to change their password on new login.

Which processes are listening on a specific port (e.g. port 80)
swap out "80" for your port of interest. Can use port number or named ports e.g. "http"

Extract rpm package name, version and release using some fancy sed regex
This command could seem pretty pointless especially when you can get the same result more easily using the rpm builtin queryformat, like: $ rpm -qa --qf "%{NAME} %{VERSION} %{RELEASE}.%{ARCH}\n" | sort | column -t but nonetheless I've learned that sometimes it can be quite interesting trying to explore alternative ways to accomplish the same task (as Perl folks like to say: There's more than one way to do it!)

Create a system overview dashboard on F12 key
Command binds a set of commands to the F12 key. Feel free to alter the dashboard according to your own needs. How to find the key codes? Type $ read Then press the desired key (example: F5) $ ^[[15~ Try $ bind '"\e[15~"':"\"ssh su@ip-address\C-m""" or $ bind '"\e[16~"':"\"apachectl -k restart\C-m"""

Convert CSV to JSON
Replace 'csv_file.csv' with your filename.

list files recursively by size

Kill all processes that listen to ports begin with 50 (50, 50x, 50xxx,...)
Run netstat as root (via sudo) to get the ID of the process listening on the desired socket. Use awk to 1) match the entry that is the listening socket, 2) matching the exact port (bounded by leading colon and end of column), 3) remove the trailing slash and process name from the last column, and finally 4) use the system(…) command to call kill to terminate the process. Two direct commands, netstat & awk, and one forked call to kill. This does kill the specific port instead of any port that starts with 50. I consider this to be safer.


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