***************
* Linux stuff *
***************


---------------
| chmod table |
---------------

value	read	write	execute
0	no	no	no
1	no	no	yes
2	no	yes	no
3	no	yes	yes
4	yes	no	no
5	yes	no	yes
6	yes	yes	no
7	yes	yes	yes

chmod a+x file - file executable to all
chmod u-w file - remove file write permission from user
chmod g+r file - file readable to all users in the same group

** practical **
---------------
Find [string] from unknown file:
	find . -name "*.*" | xargs -L1 grep -H [string]

Find [file], but don't print errors:
	find -name [file] 2>/dev/null

Run graphical [program] on (f.e. remote) computer's display:
	DISPLAY=:0 [program]

Sort du output:
	du -hs * | sort -h	    

** system  **
-------------
Set swappiness (default 60):
	echo [0-100] > /proc/sys/vm/swappiness
To make it permanent edit /etc/sysctl.conf and add:
	vm.swappiness = [0-100]
	
Remove CLI beeps. Edit /etc/inputrc and set:
	set bell-style none

Set [scheduler] for a [block device]:
	echo [scheduler] > /sys/block/[block device]/queue/scheduler
To make it permanent add kernel option:
	elevator=[scheduler]

Good generic fsck flags to fix filesystem problems:
(p=no questions f=force v=verbose D=optimize directories)
	fsck -pfvD /dev/[partition]


** rescue **
------------
Simplify HDD settings (useful to perform before trying to rescue data):
	hdparm -A0 -B255 -c0 -d0 -n0 -M128 -r1 -W0 /dev/[disk]

Try to rescue what is left on HDD (target could be f.e. sda6):
	myrescue -b1024 -B bitmap -S -r1 /dev/[disk] /dev/[target]
PS. Check also ddrescue.

** dd **
--------
Send USR1 signal to dd to print out progress:

	(dd if=/dev/random of=/dev/null bs=1K count=100 &); watch -n 1 killall -USR1 dd

** mutt **
----------
Send mail with attachement.

mutt -s "this is the post subject/title" user@doma.in -a "~/attachement.png" < mail.txt

*******************
* Debian specific *
*******************


** dpkg **
----------
Get status of package:
	dpkg --get-selections [package] 

Set [package] on hold:
	echo "[package] hold" | dpkg --set-selections

Show which packages are on hold:
	cat /var/lib/dpkg/status | grep -B1 Status | grep -B1 hold

List contents of deb file:
	dpkg -c [package.deb]

List all the files installed by [package]:
	dpkg -L [package]

Backing up package status in [file]:	
	dpkg --get-selections > [file]

Replicating status in [file] and installing packages as it instructs:
	cat [file] > dpkg --set-selections
	apt-get dselect-upgrade


** APT **
---------
Install from specified repository (-t flag):
	apt-get -t [repository] install [package]

Location of packages stored (cached) by apt:
	/var/cache/apt/archives/

Cleaning (removing) all stored packages from cache:
	apt-get clean

Cleaning (removing) not currently installed packages from cache:
	apt-get autoclean

Package extended states (auto-installed or manually installed) are stored in:
	/var/lib/apt/extended_states