rod.info: How-To: Linux

How-To: Linux

Documentation

OOM Killer (linux-mm.org)

Installing dictionaries and setting the default language for OpenOffice.org

Install a new dictionary

This step depends on your OS and distro. Under Gentoo Linux you can install one of the myspell dictionary packages. The following shows how to install the English package while logged in as root in Gentoo:

emerge app-dicts/myspell-en
eselect oodict set myspell-en

Set the default language

Then restart OpenOffice.org as a regular user, select the menu item 'tools/options' and then under the 'language settings/languages' dialog set the 'default languages for documents' field to your language of choice (in my case it is 'English (Canda)', in other words 'Canadian English').

Printing

Print 2 pages per sheet on a single sided printer

First print to a postscript file (say file.ps), then run:

psnup -2 -q -d1 -pletter file.ps > file2.ps
psselect -e file2.ps | lpr

Then rotate the printed pages around and insert printed face up into sheet feeder and run:

psselect -o file2.ps | lpr

Print an A4 sized document on a US-letter printer

First print to a postscript file (say file.ps), then run:

psresize -PA4 -pletter file.ps | lpr

Print a 2 page per sheet booklet on a single sided printer

First print to a postscript file (say file.ps), then run:

psbook -q file.ps test.ps
psnup -2 -q -pletter test.ps > book.ps
psselect -e book.ps | lpr

Then insert printed face up into sheet feeder and run (do not rotate):

psselect -o book.ps | lpr

Running windows under Linux

VMware

If you need to run windows (yes, even sometimes I do) I highly recommend VMware. I have used wine and win4lin, yet VMware is by far the most reliable and easy to use.

A side note: win4lin (the windows 98 version, not 'win4lin pro' which is used for windows 2000 and up) is still the best choice for windows 98 under Linux since it is the fastest and the cheapest. Yet how often do you find apps that will work under windows 98?

Up until the fall of 2005 VMware required the purchase of their full workstation product in order to run an emulated OS. However you can now simply create a 'virtual machine' (what they also refer to as a 'snapshot', which is simply the directory contents containing the emulated OS disk image and config files) using the regular VMware workstation tool (either pay for it, or 'try it out' using a demo license) and then run the FREE VMware Player product to 'play' (i.e. run) the OS on your computer. In other words, you can now run VMware effectively for free (sans creating the virtual machine using the full workstation tool, which can be done with a demo license).

Tips & tricks

Using full-screen

For full-screen hit CTRL-ALT-F7, hit F8 to switch back.

Links:

Encrypting a file-system with cryptsetup-luks

cryptsetup-luks uses the device-mapper to seamlessly encrypt a block device (either on the disk or with a file using a loop-back device). You will need a kernel with device mapper and crypto api support to use this.

Create and encrypt the file-system

Select a device and encrypt it. In this example I create a 1GB file-system that is backed by the file /crypt/test using the loop-back device /dev/loop0. You will be asked to 'Enter LUKS passphrase', this is your master passphrase that will be needed whenever you want to mount the file-system, so don't forget it!

dd if=/dev/zero of=/crypt/test bs=1M count=1 seek=1023
chmod 600 /crypt/test
losetup /dev/loop0 /crypt/test
cryptsetup -y -c aes-cbc-essiv:sha256 -s 256 luksFormat /dev/loop0
cryptsetup luksOpen /dev/loop0 testfs
mkfs.ext3 -m 0 /dev/mapper/testfs

Mount the file-system

Now you can mount the encrypted file-system. The following commands are all that is necessary to mount the file-system on reset (you can skip the first two lines if you just created it using the previous step).

losetup /dev/loop0 /crypt/test
cryptsetup luksOpen /dev/loop0 testfs
mount /dev/mapper/testfs /mnt/crypt

Unmount the file-system

Now you can unmount the encrypted file-system. These are all the commands that are needed to do a clean shutdown of the file-system.

umount /dev/mapper/testfs
cryptsetup luksClose testfs
losetup -d /dev/loop0

Check the device mapper table

Run the following command to ensure that the device mapper is correctly configured (after you have run cryptsetup luksOpen). You should see something starting with 'testfs: 0 2095096 crypt aes-cbc-plain'.

dmsetup table testfs

User management

Adding a user to a group

gpasswd can be used to add a user to a group. In the following example the user user1 is added to the group group1.

gpasswd -a user1 group1

Editing text

Using Vim

See my Vim How-To page for some useful information.

Spamassasin

Checking the configuration

spamassassin -D --lint

Mplayer

Using mplayer to extract a specific range of frames from a movie

mencoder dvd://1 -oac copy -ovc copy -ss START:TIME -endpos SCENESECONDS -o scene.avi

ack

ack -- better than grep, a power search tool for programmers

Honestly, this is *the* ultimate search tool. Faster than grep with intelligent behavior (such as automatically ignoring .svn, CVS and other VCS directories and binary files). Try it and you won't be disappointed!

Get it at the ack website. There is also a Gentoo ebuild. Read these nice blog entries here and here discussing some of the features.

BitTorrent

rTorrent

rTorrent is by far the best command line torrent client for Linux. Read the on-line manual here.

GNU Screen

Intro

GNU Screen is a full-screen window manager that multiplexes a physical terminal between several processes, typically interactive shells. It's the command line equivalent to a window manager, and is the best tool for running persistent interactive programs via the command line.

Links

GNU Screen (gnu.org)

GNU Screen (savannah.gnu.org)

GNU Screen (Wikipedia)

Screen (Gentoo Wiki)

Screen User's Manual (delorie.com)

Command usage

screen -ls lists your screen sessions

screen -S somename creates a new screen session named 'somename'

screen -r re-attaches to the first detached session found

screen -dr forces the first session found to detach then attaches to it

screen -dr somename forces the session named 'somename' to detach then re-attaches to it

Screen tips

Note: C-a means CTRL-A (the 'control' and 'a' keys pressed simultaneously).

C-a c create a new terminal

C-a A allows you to name the terminal

C-a d detaches from the screen session

C-a " lists the terminals

C-a p moves to the previous terminal

C-a n moves to the next terminal

C-A ESC enters scroll back mode, uses vim style movement/copy/paste keys

C-A q leaves scroll back mode

C-A :quit quits/kills the screen session

Gnome

Tweaks

Setting the wallpaper via the command line:

gconftool-2 -t str --set /desktop/gnome/background/picture_filename /path/to/some/file.png

Enabling wire-frame move and resize:

gconftool-2 -t bool --set /apps/metacity/general/reduced_resources true

Editing the menus:

alacarte

Useful commands

alt-f1 launch the applications menu
alt-f2 launch "run application" dialog prompt
ctrl-alt left-arrow move to the previous virtual desktop
ctrl-alt right-arrow move to the next virtual desktop
ctrl-alt-shift left-arrow move focused window to the previous virtual desktop
ctrl-alt-shift right-arrow move focused window to the next virtual desktop

Misc.

UUIDs

You can find good info in How To Manage Your Disk By UUID On Linux.

Find the UUIDs for all block devices:

blkid

Create a random UUID:

uuidgen