Knock on ports to open a port to a service (ssh for example) and knock again to close the port. You have to install knockd.

See example config file below.

[options]

logfile = /var/log/knockd.log

[openSSH]

sequence = 3000,4000,5000

seq_timeout = 5

command = /sbin/iptables -A INPUT -i eth0 -s %IP% -p tcp --dport 22 -j ACCEPT

tcpflags = syn

[closeSSH]

sequence = 5000,4000,3000

seq_timeout = 5

command = /sbin/iptables -D INPUT -i eth0 -s %IP% -p tcp --dport 22 -j ACCEPT

tcpflags = syn

A common mistake in Bash is to write command-line where there's command a reading a file and whose result is redirected to that file.

It can be easily avoided because of :

1) warnings "-bash: file.txt: cannot overwrite existing file"

2) options (often "-i") that let the command directly modify the file

but I like to have that small function that does the trick by waiting for the first command to end before trying to write into the file.

Lots of things could probably done in a better way, if you know one...

This just combines multiple mp3's into one mp3 file. Basically it is a easy join for mp3's

That command bypass the entry limit specifing page results size, when the search arrive to the limit ldapsearch magically reiterate it from the last entry.

Output manpage as plaintext using cat as pager: man -P cat commandname

And redirect its stdout into a file: man -P cat commandname > textfile.txt

Example: man -P cat ls > man_ls.txt

This is better than doing a "for `find ...`; do ...; done", if any of the returned filenames have a space in them, it gets mangled. This should be able to handle any files.

Of course, this only works if you have rename installed on your system, so it's not a very portable command.

no grep, no perl, no pipe.

even better in zsh/bash4:

No find, no grep, no perl, no pipe

Great for sites like Gigapedia.org that give away great free rar'd books.

More similar commands here: http://www.howtogeek.com/howto/ubuntu/unzip-or-unrar-many-files-at-once-in-linux/

Just copy and paste the code in your terminal.

Note : sudo apt-get for debian versions , change as per your requirement .

Source : www.h3manth.com

Good for fixing web permissions. You might also want to do something like this and skip files or directories that begin with a period:

...or include a special case for scripts:

This should work anywhere perl and grep is available. :P

Stop tormenting the poor animal cat. See http://sial.org/howto/shell/useless-cat/.

Edit:

replaced

by

and, a lot uglier, with sed:

Edit:

Wanted to be shorter than the perl version. Still think that the perl version is the best..

In edit mode, toggle the case of a single word under the cursor in vim.

This command will generate "CHECK TABLE `db_name.table_name` ;" statements for all tables present in databases on a MySQL server, which can be piped into the mysql command. (Can also be altered to perform OPTIMIZE and REPAIR functions.)

Tested on MySQL 4.x and 5.x systems in a Linux environment under bash.

On Solaris 10 you used dtconfig -d to achieve this. The command will disable X and your system will now boot to a text console.

Get the IP address of all your network cards.

To change to $HOME in that manner you need to set a shell option. In zsh it is auto_cd, hence

in bash4 it is autocd, hence

What the option does is allow you to cd to a directory by just entering its name. This also works if the directory name is stored in a variable:

sends you to /var/www/lighttpd.

CAUTION: If a command or function name identical to the directory name exists it takes precedence.

Could use your ssh bash history if your known_hosts are hashed and you want to keep it hashed

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