Linux Tips & Tricks here

Setup a Disk Drive

*Create a Partition:
o fdisk /dev/(device i.e. sdb)

File system types
o For ext2 use 'mke2fs'

For ext3 use 'mke2fs -j'

For reiserfs use 'mkreiserfs'

For xfs use 'mkfs.xfs'

For jfs use 'mkfs.jfs'

Create a file system (example)
o mke2fs /dev/(device i.e. sdb1)

Activate drive:
o Add entry to /etc/fstab
+ vi /etc/fstab

Mount all devices in fstab
+ mount -a

Note: If unfamiliar with vi, use pico to edit in non visual interface

Mount a Floppy Disk Drive

* mount -t msdos /dev/fd1 /mnt/floppy

(or use ufat instead of msdos)

Search for installed packages

* rpm -qa|grep package (redhat)
* dpkg -qa | grep (Debian Linux)

Remove Installed Package

* rpm -e package (Red Hat)
* dpkg -P package (Debian Linux)
else
apt-get remove package
Managing Most Services

* /etc/init.d

then use command stop i.e. ./Kasenna_Apache stop

Make a link

* ln -s destinationoflink linkname

Check kernel version

* uname -r

Make images of cd-roms or hdd

* dd if=/dev/hda of=/dev/hdc bs=4k block_size

Messages (to other users)

* Send to all
wall message

Send to one user (insert message after
write user

Send to one user on a specific terminal
write user tty1

Compare 2 Source Code Files

* diff -u file1 file2

+ means in #2 not in #1 - means in #1 not in #2

Make software tarball (compression methods)

*

tar -cvf hi.tar *

then

gzip hi.tar

Create md5 check sum

*

md5sum -b boot.gz

Find a file

*

find (dir) -name filename
o

eg. find ./ -name help.txt

find and execute a command on all found files:
o

find (dir) -name (expr) | xargs (command)

Search several text files in several directories

*

grep -r --with-filename 00:00:00:00:00: */mac_table

Get the size of all sub-directories

* du -s *

(use -sk for kilobytes or -sh for human readable)

Send e-mail from console

* echo "Message" | mail -s "subject" recipient1 recipient2 recipient3

Remove first character of line

* cut -c 2-

Remove password on sudo

* in ~/.bash_profile place the line:

export SUDO=sudo

as root run visudo uncomment

%wheel .... no passwords

add users who need passwrodless sudo to wheel group

vi /etc/group

Increase Priority of Process

* nice -n

(pri -20 to 20 where -20 is the fastest or highest priority)

To get files from a ramdisk

* Copy ramdisk to temp dir then:

gunzip ramdisk

mount -o loop -t ext2 ramdisk_img

Get the required files then:

umount

To print a test file from the cli

* lpr filename

To count the number of lines with sed

* sed -n '$=' filename

cat filename | sed -n '$='

Grab One Line out of a Text File

* cat textfile | sed -e 's#\t##g' | sed -n "Line_Number"

Replace one line in a textfile

* sed 10c\\"New_String = -mq${1}" textfile
o

-- Where 10 is the line number

Pull Out String From Line

* echo "inet addr:192.168.145.11 Bcast:192.168.145.255" |sed -e 's/[^i]*inet addr:\([0-9.]*\).*/\1/p'

Redirect Command output

* Redirect Standard to Null

* command > /dev/null
Redirect All Standard to Null

command &> /dev/null

Redirect Errors to Same Location as Standard

command > /dev/null 2>&1

Redirect Errors to Null

command 2> /dev/null

Redirect Standard to File

Just replace "/dev/null" with filename

-- use '>>' to append file instead of overwrite '>'

Use vi in split screen mode

* Enter split screen

* :split
o

Open new file

:e path/filename
o

Switch to Upper Window

ctnl+w k
o

Switch to Lower Window

ctnl+w j

Create a cron job entry

*

Run the crontab editor

crontab -e

Then add entry

Example crontab

*

A decent cron template. Remove commands or add commands as needed (was used for Gentoo so emerge commands will not be valid on a non-Gentoo rig)

#!/bin/sh
cdmailto=me
SHELL=/bin/bash
PATH=/sbin:/bin:/usr/sbin:/usr/bin:$HOME/bin
# minute (0-59),
# | hour (0-23),
# | | day of the month (1-31),
# | | | month of the year (1-12),
# | | | | day of the week (0-6 with 0=Sunday).
# | | | | | commands

# ------{ default cron crap }---------- #
0 * * * * rm -f /var/spool/cron/lastrun/cron.hourly
1 3 * * * rm -f /var/spool/cron/lastrun/cron.daily
15 4 * * 6 rm -f /var/spool/cron/lastrun/cron.weekly
30 5 1 * * rm -f /var/spool/cron/lastrun/cron.monthly
*/10 * * * * /usr/bin/test -x /usr/sbin/run-crons && /usr/sbin/run-crons
# ------{ daily cron jobs }------------ #
0 1 * * * emerge sync >/dev/null 2>&1
0 2 * * * /backup/backup.sh
40 1 * * * emerge -uDpv world >/home/ben/Reports/emerge.txt
0 3 * * * updatedb && eupdatedb >/dev/null 2>&1
0 4 * * * glsa-check -l | grep '\[N\]'
# ------{ weekly cron jobs }----------- #
15 7 * * 0 makewhatis
0 7 * * 1 fc-cache -fv
0 4 * * 2 tar -cvzf /backup/weekly-backup.tgz /backup/weekly/*
10 4 * * 3 rsync -v -a --delete /backup/weekly-backup.tgz /mnt/nfs/backup/weekly-backup.tgz
# ------{ bi-weekly & monthly jobs }--- #
"

Links

http://www.acck.edu/~jerod/spellbook.html
Boot into single user mode

1. On boot up get to the grub menu 2. press 'e' to edit your boot parameters 3. add "init=/bin/sh" to the list of kernel parameters 4. save and then boot off that modified selection 5. you will now have root access in singl user mode