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Thursday, March 29, 2001TABLE OF CONTENTS
1) Sean’s Notes
2) Linux News
2.2.18 Kernel Exploit (Local)
Tux in Space
How Perl Creates Orders for the Air Force
Red Hat Acquires Planning Technologies, Inc.3) Linux Resources
Install a Hard Drive in 5 Steps
Free Database Hosting
Solaris Jumpstart
Solaris 8 Essential Reference
RAID Upgrade4) App o’ the week
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1) Sean’s Notes
Last week I made a big goof when I wrote that RAID-0 was called mirroring. In fact, RAID-1 is mirroring (which stores data on two drives simultaneously), and RAID-0 is striping (in which data is stored over two drives in a non-redundant fashion). Take 2x9G drives. RAID-1 will give you a 9G drive set that can withstand the loss of one of the drives. RAID-0 will give you a 18G drive set that will break if one of the component drives goes to that big spindle in the sky, but should have better performance than just one 18G drive.
While I’m on the subject of RAID, I’ll show you how to set up software RAID on your Linux box. The first thing you’ll need is a couple of drives. You’ll probably want to partition them into just one partition, we’ll call them hdb1 and hdc1 for now. When you’re in partitioning them, set them as type “fd” (the ‘t’ option in fdisk).
http://www.ibiblio.org/pub/linux/docs/howto/mini/Partition has further information on partitioning hard drives.
By default, all RAID configuration goes in /etc/raidtab. The format is typical of most UNIX programs. Each RAID device starts with
raiddev /dev/mdX
where X is the device number. Start from 0 and go from there. After that, give some more information about the raid volume:
raid-level (0,1,5,linear)
raid-level 0
store RAID info on the drive too, so the kernel doesn’t
necessarily have to reference /etc/raidtab
persistent-superblock 1
chunk size specifies how many K are used per stripe
chunk-size 64
As you can see from above, we’re creating a RAID-0 device (striping). Now, we specify how many drives form the array, how many spares are available, and then assign drives to those jobs. Here, we’ve got two drives and no spares:
nr-raid-disks 2 nr-spare-disks 0
device and raid-disk must be paired, with device first
hdb1 is therefore the first drive in the array (zero indexed!)
device /dev/hdb1 raid-disk 0
hdc1 is the second drive in the array
device /dev/hdc1 raid-disk 1
If you had a spare disk hdd1 (not much use in raid-0) you would have changed nr-spare-disks to 1, and added
device /dev/hdd1 spare-disk 0
Now that raidtab is defined, it’s time to build the RAID set.
mkraid /dev/md0
Warning! You’ll lose everything on those drives! We’re creating a fresh drive here!
Check the status of the drive:
cat /proc/mdstat
Personalities : [raid0] read_ahead 1024 sectors md0 : active raid0 hdd1[1] hdc1[0] 3313088 blocks 32k chunks
unused devices: <none>
(That’s from my system, so some of the numbers are different)
At this point, you have a drive (/dev/md0) that’s like a real hard drive. May as well put a filesystem on it:
mke2fs /dev/md0
This week’s resource section also has a link on how to set up a new hard drive, the procedure there can be followed to make this volume a permanent addition to your system.
You stop the RAID volume via
raidstop /dev/md0
(the filesystem has to be unmounted)
and start it up again
raidstart /dev/md0
Most distributions auto detect the presence of RAID and will do the raidstart for you. If not, you’ll have to put it in your config files.
A couple of warnings. Don’t do this on your root partition without some extra research. Remember that this will destroy existing data, so don’t do this to an existing partition. I haven’t covered reconstruction, so if you plan to rely on this do some more reading to find out what to do when a drive does die!
http://www.linas.org/linux/Software-RAID/Software-RAID.html
Linux software RAID is very versatile. Changing this configuration to a mirror is pretty easy. You can also build RAID devices out of other RAID devices, such as mirroring two stripe sets (or striping two mirrors).
Long live the Penguin,
Sean mailto:swalberg@brainbuzz.com
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2) Linux News
-
18 Kernel Exploit (Local)
A bug has been found in kernels up to 2.2.18 involving a race condition in some system calls. The result is that a local user can get root if they can run a setuid program. Ouch. If you know a bit of C, the exploit itself is a worthwhile read.
http://www.securityfocus.com/archive/1/171708
Tux in Space
One of NASA’s divisions has funded a two year project to build a version of Linux suitable for use in space vehicles. It’s using part of RedHat’s embedded software toolkits. The article brings forward some interesting things about the restrictions, such as limited transmission windows.
http://www.newsforge.com/article.pl?sid/03/13/2112221
How Perl Creates Orders for the Air Force
By creating a web based order system, an Air Force group was able to save between 900-1500 man hours per year, and improve efficiency and service.
http://www.perl.com/pub/1998/07/rwperl.html
Red Hat Acquires Planning Technologies, Inc.
RedHat announced that it has acquired Planning Technologies, Inc., an Atlanta-based Professional Consulting Service company that specializes in infrastructure consulting for a wide array of clients, including enterprise, service providers and government.
http://www.redhat.com/about/presscenter/2001/press_planning.html
3) Linux Resources
Install a Hard Drive in 5 Steps
Installing a hard drive under Linux is a bit different than in Windows just due to the nature of the OS. Like all other things in Unix, there are some decisions to be made, commands to be run, and config files to edit. Read on to find out the details.
http://www.linuxnewbie.org/nhf/intel/hardware/hd_add.html
Free Database Hosting
Ever wanted to start learning SQL and databases like MySQL and PostgreSQL, but didn’t have the ability to get the server running? This site offers free database hosting (just MySQL for now, others to come)! Now you can have a database without the trouble of administering it.
http://superid.dyndns.org:8080/freesql/index.php
Solaris Jumpstart
Jumpstart is a Solaris tool that allows you to set up a lot of machines at once. If you thought Kickstart (RedHat’s version) was hard, Jumpstart will make your head spin. Having an example worked out for you will help out immensely, so here you go.
http://www.amorin.org/professional/jumpstart.php
Solaris 8 Essential Reference
This book is designed to be the ideal reference for Solaris users who know what they want to do, but just need to know how to do it. It’s a great reference book for people who work with SUN’s operating system on a daily basis.
http://itresources.brainbuzz.com/tutorials/tutorial.asp?t=S1TU1211
RAID Upgrade
As it turns out, many IDE controllers can be easily converted into hardware RAID controllers by some software upgrades and perhaps a touch of solder. Most chipsets are used in both the IDE controller and RAID version, so it makes sense that the manufacturer would just make one board and cripple the RAID functionality (ala 486SX FPU’s). If your controller or motherboard is listed here, you might just be able to go RAID.
http://www.tweakhardware.com/guide/
4) App o’ the week
Remember the old Sierra games like Leisure Suit Larry, King’s Quest, and Police Quest? You probably have them kicking around somewhere, just waiting to be played again. Rather than the traditional VMWare or WINE methods of playing DOS/Windows games, this group of people created FreeSCI, an emulator for Sierra games.
http://freesci.linuxgames.com/
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