Self-proclaimed genius, and ruler of the Internet. System admin the rest of the time

iSCSI is a protocol that allows you to use a disk in a remote machine, locally as a block device. It is a very popular SAN protocol, which allows the consolidation of storage into one large storage pool.

In iSCSI terminology, a target is a storage resource located on an iSCSI server and an initiator is a client which will be connecting to a target.

In this post I will demonstrate how to setup an iSCSI target and initiator on RedHat Enterprise Linux 5.

Target

RHEL5 has the stgt target daemon included with it. This is the server which allows initiators (clients) to connect to the disks using the iSCSI protocol. It is installable using yum:

yum install scsi-target-utils

To share a disk over iSCSI, you can either use a disk image, or a block device. I prefer to use LVM logical volumes as LVM allows easy management of free space.

Stgt’s configuration file lives in /etc/tgt/targets.conf, although most configuration can be done using the command line (although this is not persistant across reboots, so I prefer to use the configuration file).

To create a target, just add the following lines:

backing-store /dev/DiskArray/Archive1

Please note that you must replace iqn.2009-02.com.hamzahkhan:archive1 with your own domain name, and resource name. It must be in the iSCSI Qualified Name (IQN) format, iqn.yyyy-mm.{reversed domain name}:an_easy_to_remember_lablel.

The second line, backing-store /dev/DiskArray/Archive1 specifies the disk/disk image that is to become the target, I am using LVM logical volume although the procedure is exactly the same for disk images, and real physical disks.

By default, stgt will allow all IPs to connect to the target, which is highly insecure! To change this behaviour, it is possible to specify IP addresses which are allowed to use the targets. To do this, just place the following line under backing-store:

initiator-address 10.1.0.4

This will allow 10.1.0.4 to access the target.

Now, use chkconfig to make stgt start at boot, and start up the daemon.

/etc/init.d/tgtd start

chkconfig tgtd on

Thats all there is to it on the server side! All done

You can now connect to the target using any initiator, such as the one built into Windows Vista (although I have never tried using Windows).

Initiator

RedHat have included an iSCSI daemon which is also installable using yum:

yum install iscsi-initiator-utils

To connect to the target, edit /etc/iscsi/initiatorname.iscsi and change InitiatorName to something you prefer (Remember! it must be in the IQN format, iqn.yyyy-mm.{reversed domain name}:an_easy_to_remember_lablel. I usually use iqn.2009-02.com.hamzahkhan:hostname_of_box). Next start up iSCSId:

/etc/init.d/iscsid start

and use iSCSI target descovery to find the targets on the server:

iscsiadm -m discovery -t st -p $SERVERS_IP

If all is well, it should output the names of all the targets that the initiator is allowed to connect to!

Next, we need to create the disk nodes. To do this, RedHat have provided a nice start up script. This script will login to all the targets that the iSCSI daemon knows about. We have already used the iscsiadm command to tell the iSCSI daemon which targets exist on the server, so using the script is all that is left:

/etc/init.d/iscsi start

Thats all there is to it!

You should have a new disk node in /dev/. You can use lsscsi (yum install lsscsi) to find the exact name if you have a lot of USB/SATA/SCSI drives connected to the machine already.

Now all you have to do is partition the disk, and dump your files onto it

Please remember, you must NEVER mount a partition on two machines at the same time. Doing so will cause data loss!

It IS possible to mount the same disk on multiple machines, but this requires a special clustered filesystem such as GFS.

A few months ago, I bought a Western Digital 1TB Hard Drive (http://www.wdc.com/en/products/products.asp?DriveID=336) for my server.

Since every WD drive I have bought in the past has served me very well, I assumed this drive would do the same…. but VERY annoyingly, I just got an email from smartmon tools telling me that there are an increasing number of bad sectors on the drive!

eBuyer has agreed to replace the drive since it is still under warrenty, but the problem is that I have the drive in an LVM volume group, so backing up the data is a little difficult.

It would be easy if I had another 1TB Hard Drive to add to the volume group, the pvmove all the data off the broken one, but I do not have a spare 1TB drive, and eBuyer (naturally), didn’t agree to sending me the new drive before I give the old drive back to them.

I also have 1TB Seagate drive in the volume group, which is performing very well, so very reluctantly, I might just ask eBuyer if they would let me switch it for a Seagate one.

Oh well, I guess for now, my only option would be to buy another 1TB drive, move all the data onto that drive, remove the old drive from the VG, get it replaced, then if I feel brave enough, add the new one to the VG. I’ll have quite a large volume group if I do that (3TB!).

Speaking of which, if anyone has any tips for boosting LVM performance when using large volume groups, please tell me!

So after my last blog post, I decided to try out OS X inside a virtual machine ….. but after four tries, I gave up and just wiped my hard drive and installed natively.

Installation went surprisingly well, and most of my hardware is “liked” by the hacked versions of OS X (I used iATKOS 5i). Everything that should be working, is working except for my sound card… which is partially working. I hear sound, but the front audio ports for headphones and microphones does not work, and neither does the back microphone socket, but I’m still quite happy with that considering OS X wasn’t designed to be run on my hardware (and apparently with some hacking, I can make those things work too).

So far I’ve been using OS X for two days, and I must say, I like it much more than I had expected.

My first computer was a Mac, and I used a Mac till OS 8.something (in 1999 my dad bought me a my first PC because Macs were, and still are quite pricy). I was originally quite reluctant to leave Mac OS, but eventually had to BUT I soon discovered Linux, and started using and loving it.

For the last 5/6 years I’ve been using Linux, and I only really used OS X two or three times at my Dad’s work place. I originally thought I would LOVE to have a Mac (with OS X), but a few days ago I changed my mind because I thought I had become too used to Linux (which I have!) and would not be able to use OS X to do everything I want.

I thought there would be lots of things that I would not like about OS X, but it turns out the list is actually a lot smaller than I thought.

There are a few things I don’t like about OS X, and some things I miss from Linux. For example:

• I really hate the keyboard bindings. This is probably because I’m now used to Linux shortcuts etc. I managed to “fix” some of them (eg in the Terminal app I wanted page up/down to actually send the page up/down characters).
• I STILL dislike iTunes, although it is much better than in Windows. I really miss MPD with gmpc.
• I don’t really like the dock. This is probably one of the things that most people DO like, but I’m not really a fan of it.
• I can’t seem to find a decent IRC client on it. X-Chat Aqua isn’t really quite as nice as it is on Linux, and Linkinus isn’t too good either in my opinion.
• I don’t really like the fact that OS X doesn’t depend THAT much on log files. It does use them, but I don’t think the details it gives are always useful.
• I kinda miss the ability to configure things from the command line. I don’t know if you can configure things from the command line in OS X, but from what I understand you can’t really do much system configuration from the command line except small hacks.

Overall, I like OS X, and will probably continue using it on my machine till I get a real Mac (hopefully in September).

Some of the things I like about OS X:

• Undoubtably the thing I like most is how everything is so tightly integrated with each other. While this is also possible on Linux, it DOES need a lot of configuration to get it perfect. On OS X, it is all ready to go, out of the box. Linux is also heading that way, with things like d-bus interaction between apps has become more and more efficient, but not all apps take advantage of this yet.
• I like the fact that everything looks the same, and isn’t “odd”. By this I mean there is no “KDE” look, or Gnome Look. Everything fits in fine with the UI. I know you can use special tools etc to make KDE apps fit into Gnome, and vice-versa, but again that requires configuration. Personally I didn’t ever bother doing that, although I didn’t really like how KDE apps didn’t fit into my Gnome desktop.
• Close source applications work better on OS X than their Linux equivalents. For example Skype is on Linux and on Mac OS X, but the Mac version is MUCH more stable than the Linux version. I guess this is mainly due to all the sound systems that are available in Linux. Skype switched to ALSA recently from OSS, but now a lot of people want PulseAudio support too, or ESound support etc. There are too many choices I think, and I think that is causing a bit of chaos. This issue would probably be fixed a lot faster if Skype were open source, but I don’t think people should live in a dream world where everything is open source, sure it would be nice, but lets face it, thats never gonna happen. So in reality, the better choice will indeed be the one that works, and in my opinion, so far in OS X is the better choice.

On OS X, I’ve managed to actually have a pretty good quality conversation over Skype with my sister, which I haven’t been able to on Linux.

I don’t know if this makes me sound like I’m anti-Linux now, believe me I’m not! I LOVE Linux still (more than I like OS X!), in-fact I’m running it inside a VMware Fusion virtual machine right now and will wipe my machine and put Gentoo back on it as soon as I get a real Mac to sit beside my Gentoo machine.

I also thought I’d mention this: I know a lot of Linux users who say EVERYONE should use Linux, and there is no excuse for using Microsoft or Apple products. This goes to the people who think this way: You are all idiots .

Some people say Apple and Microsoft products should be avoided because they are buggy. Sure Windows IS buggy, and sure OS X probably has some bugs too (I haven’t found any yet!). BUT truthfully, can anyone say that Linux applications are bug free? The only difference is that you have the ability to fix the bugs yourself…. which is quite a useless ability if you are a normal user who doesn’t give a damn about how the internal works, and doesn’t have a clue what C++ is!

To be quite honest, A LOT of Linux applications have A LOT of bugs. NetworkManager is quite buggy, so I stopped using it and manually setup wpa_supplicant to connect to my wireless network, but I don’t think my Dad can do that! A normal user like my father needs GUIs to do everything, they are easier to use for someone who has no clue how to use a CLI (and doesn’t want to learn how to use it!). Naturally Linux IS becoming more and more user friendly, and I think there WILL be a point where I can safely install Linux on either of my parents computers, and not have to worry about them not knowing how to do something, but till that day comes I REALLY think it is pointless and ignorant for people to tell everyone to boycott Apple and Microsoft, and switch to Linux unless they are willing to understand the internals a little and figure out how to manually edit things from the CLI, which over 90% of the world’s population probably isn’t .

Besides… Apple products are really nice in my opinion, not very buggy and they work very well! (I love my iPhone <3!!!)

Lol like most of my posts, I wrote this while super sleepy so it probably makes no sense, oh well.

I finally moved my email server back home!

For quite a while now, I’ve been using Google Mail to host my email for all my domains, but I’ve always felt that it wasn’t as “nice” as running your own server.

Some reasons I moved away from Google are:

1. Although it might just be me, I’ve noticed that their IMAP server isn’t very stable. Quite often I haven’t been able to log in for quite a while.  (This was the main reason!)
2. I _REALLY_ dislike the labeling feature of Gmail. It makes IMAP messy, same email in multiple folders (even though I don’t use lables!)
3. I find the “Google Mail” folder annoying on IMAP, every time I get an email it shows up as a new email in my Inbox folder and Google Mail folder

Anyway, I setup Postfix with MySQL (I will be converting to LDAP soon) and noticed that I actually get quite a bit of spam.

From past experience, I knew that setting up a spam/antivirus filter requires quite a bit of maintinance, so I wanted a “lazy persons” solution.

After a bit of Googling, I came accross Astro Mail Gateway.

So I downloaded their VMware appliance and booted it up. It wasn’t as easy as I thought initially since the VMware image seems to have IPtables running which blocks access to the web interface, although I only had 4 hours sleep at that time so I could be wrong. So I had to log into the console, and disable IPtables temporarily, get into the web interface and configure the IP addresses to match my network (the default config uses 192.168.0.0/24, where as I use 10.1.0.0/16). After this it seems the UI added the various rules to IPtables to let me access everything properly.

After a bit more configuring I had a fully functional spam filtering proxy!

The only issue I’ve had with Astro so far is that it won’t accept my home user licence so in 28 days or so it will stop functioning , but hopefully the Astro support guys will reply to me and tell me how to fix that! .

What is really nice about Astro is that it makes nice graphs for you, and gives a lot of statistics such as Top Spamming countries, and Top malware reports (So far I’ve got 70% of my spam from the US!).

The only thing I wish Astaro Mail Gateway had is IPv6 support, but its not urgent I guess considering IPv6 isn’t used so widely yet.

Just to be clear, I don’t really hate the Wii. I just found the song funny