vi is a powerful text editor found on practically every Unix based system. Consequently, it is quite beneficial to learn and master vi and its abundance of keyboard shortcuts. If you are not quite the guru you hoped to be, here is a handy reference page that will bring you up to speed quickly.

File Handling

vi
Open a  file to edit

:w
Save a file

:w
Save a file with a new filename

:q!
Quit without saving

:wq
Quit and save

Movement

h or (left arrow key)
Left one character

i or (right arrow key)
Right one character

k or (up arrow key)
Up one line

j or (down arrow key)
Down one line

^
Beginning of a line

$
End of  a line

1G
Beginning of a file

G
End of a file

:
move to line number

Editing

i
Insert text

A
Append text

r
Replace text

R
Replace a character

x
Cut/delete character

dd
Cut/delete line

D
Cut/delete to end of line

Y or yy
Copy line (yank)

p
Paste line

J
Join line below to this line

u
Undo last change

e
Undo all changes

Advanced Users

/ &/ (repeats last search)
Search for keyword

:set number & : set no number (turns off numbers)
Show line numbers

.
Repeat last command

:m//
Regular expression search

:s///
Regular expression replace

:,s///
Regular expression replace by lines

:
Repeat command x times

%
Find matching () or {}

:sh (type exit to return to vi)
Drop to shell

[tags]Unix, vi, Linux, vi shortcuts[/tags]

I recently migrated my network storage server, running Ubuntu Linux incidently, to a software RAID 5 configuration. RAID level 5 requires atleast 3 harddrives; giving you in total N-1 storage, where N is the number of disks in the array. For my deployment, I used 3 120GB drives (mixing IDE and SATA, Linux is indifferent here) giving me effectively 240GB. The missing 120GB is the parity information that allows transparent data recovery when 1 disk in the array fails. I’ve glossed over a lot of the details regarding RAID 5 but a quick google should fill in the blanks if need be.

Here is how I accomplished this under Ubuntu Dapper.

1. Install mdadm using apt-get, or your favorite package manager. mdadm is the tool used to administer Linux md device arrays (software RAID).
2. Partition your drives as appropriate using cfdisk /dev/hd<?>. Ensure that all partitions are of equal size and the partition type is set to Linux raid autodetect.
3. Using mdadm create your RAID-5 device:
   • mdadm --create /dev/md0 --chunk=64 --level=raid5 --raid-devices=3 /dev/hdc1 /dev/hde1 /dev/sda1; substituting for your own /dev/ devices.
4. Good Good.
   • # cat /proc/mdstat
     Personalities : [raid5]
     md0 : active raid5 sda1[0] hdc1[1] hde1[2]
     234371968 blocks level 5, 64k chunk, algorithm 2 [3/3] [UUU]
5. Format your newly created /dev/md0 device.
   • mkfs.ext3 /dev/md0
6. Create a mount point for your RAID-5 array and add it to /etc/fstab so it is mounted automagically on the next reboot.
   • /dev/md0 /storage ext3 defaults 0 1
7. Getting detailed info about your array.
   • # mdadm --detail /dev/md0
     /dev/md0:
     Version : 00.90.03
     Creation Time : Sat Apr 1 14:01:39 2006
     Raid Level : raid5
     Array Size : 234371968 (223.51 GiB 240.00 GB)
     Device Size : 117185984 (111.76 GiB 120.00 GB)
     Raid Devices : 3
     Total Devices : 3
     Preferred Minor : 0
     Persistence : Superblock is persistentUpdate Time : Tue Apr 18 07:39:21 2006
     State : clean
     Active Devices : 3
     Working Devices : 3
     Failed Devices : 0
     Spare Devices : 0Layout : left-symmetric
     Chunk Size : 64K

     UUID : 51dec40b:2d6fd4cc:a9e0addc:fe5303d4
     Events : 0.176640

     Number Major Minor RaidDevice State
     0 8 1 0 active sync /dev/sda1
     1 22 1 1 active sync /dev/hdc1
     2 33 1 2 active sync /dev/hde1

8. Managing the RAID device.
   • Setting a disk faulty/failed:
     # mdadm --fail /dev/md0 /dev/hdc1
   • Removing a faulty disk from an array:
     # mdadm --remove /dev/md0 /dev/hdc1
   • Clearing any previous raid info on a disk:
     # mdadm --zero-superblock /dev/hdc1
   • Adding a disk to an array:
     # mdadm --add /dev/md0 /dev/hdc1

RAID can be an intimadating piece of technology but it’s benefits are plainly obvious. Hopefully this framework howto is enough to ease your fears.

I’ve come across this problem in my profession and my solution is much simpler and easier to understand than the one proposed in this verbose write-up.

#!/bin/bash
if [ `date --date="+1 day" +%d` = 01 ]; then
execute desired task
fi

Have cron execute this bash script at the desired run-time each day to achieve the desired results.

Plug. Chug. Done.

read more | digg story

1) Get tiger-x86.tar.bz2

2) Unpack tiger-x86-flat.img to a separate NTFS hard drive

3) Load up the system with the Knoppix Live CD

4) If the drive from step 2 is external, attach it and let Knoppix automount it

5) Open up a terminal

• Use su to become root
• Switch to the directory Knoppix mounted from step 4 (look in /mnt/)
• Execute ls –all to verify that the .img file exists
• Execute dd bs=1048576 if=./tiger-x86-flat.img of=/dev/hda, where hda is the *drive* you wish to install to. hda=drive 1, hdb=drive 2, etc

6) When it has finished copying, reboot and select the drive you want as the startup from the BIOS or boot menu

7) With some luck, you should be staring at an Apple logon screen

• If the system hangs, Boot into safe mode by using the –x parameter at the Darwin boot screen

Log in as “deadmoo” password “bovinity”

9) Create your own account, Apple Menu->System Pref-> Users.

10) Relogin as yourself. It is safe to remove “deadmoo”

11) Finally, delete the file /System/Library/Extentions/AppleTPMACPI.ktext

• Hold down the Windows key and empty trash if the system complains the file is in use
• Reboot

12) Profit!

First off, I have to admit how amazed I was over the simple installation. That being said, realize what you are doing and what could happen if things go wrong. I merely claim that this “Worked for Me.”

• Connect your mini to your computer, ensuring that it is enabled for disk use.
• Download the iPod Linux Installer, the latest kernel.bin.gz, and the latest podzilla.gz.
• Unzip the three packages you’ve just downloaded.
• Rename file date-podzilla to podzilla and copy to the root of the mini.
• Rename file date-kernel.bin to linux.bin and replace the linux.bin inside the iPod Linux Installer folder.
• Run and install ipodlinux-installer. Choose to update the firmware, making sure to keep Apples firmware as the default boot order.
• Basically what you’ve just done is create a multi-boot option for your iPod, much the way you would dual boot Linux and Windows.
• Lastly, copy the file \4gipl\start to the root of the mini, replacing the existing file.

That’s it! Reboot your iPod mini (hold select and play buttons for 5-10sec). After reboot, hold the Rewind button; you should see the familiar linux text boot scroll.

Caio