Wednesday, May 5, 2010

Crank up the throttle on DD transfers

This is a quick one but I want to write it down just because I always seem to forget it if I don't use DD for a while.

DD's default block size (bs) is 512 bytes!

That's fine for some small work but you'll be waiting around for hours if your trying to shovel large disk images around.

Kick DD into high gear by raising the bs value to 32k and be done in minutes.

dd if=/dev/loop0 of=/dev/sdb bs=32k

In the example above, I've mounted a KVM disk image locally and an iSCSI lun as /dev/sdb. With the default 512b, DD was only able capitalize my 1g network at 5Mb/s. Switching to a 32k block size it utilized 40Mb/s.

Monday, May 3, 2010

Use Clonezilla for physical disk to iSCSI volume transfer

For the last few nights, I've been playing around with open-iscsi on Debian, Ubuntu and Windows 2008. Getting things up and running was fairly straight forward thanks to all of the helpful blogs and howtos people have posted. What I found missing was how one moves a Linux installation from a physical or virtual disk to an iSCSI volume. The little I found about the subject involved physically mounting the source disk to the iSCSI host or performing some tricky PXE boot magic to run the Linux distribution's installer. I find both of these methods inelegant and limited.

Tonight I came at it again. This time with my favorite FOSS disk imaging tool, Clonezilla!. The wonderful team behind it didn't skimp out and included the open-iscsi packages.


Download and burn a copy of the latest Ubuntu version of Clonezilla.

Boot from the Clonezilla live CDROM. Select all of the regional configuration options you require.

Stop when you get the the ncurses prompt to begin using Clonezilla or use the console. Press +F2 to switch the second tty console. This will let you work with the tools and setup a connection to your iSCSI share.

Get some networking configured otherwise you aren't going to be able to connect to the LUN.
sudo dhclient eth0

Now edit the iscsid.conf file.
sudo vi /etc/iscsi/iscsid.conf

Look for the node.startup property and set it to automatic.

Now start the open-iscsi daemon.
sudo /etc/init.d/open-iscsi start

Use the following command to query the iSCSI target for LUNs.
iscsiadm -m discovery -t sendtargets -p IP_OF_YOUR_TARGET

Here's an example of what mine looked like:
user@karmic:~$ sudo iscsiadm -m discovery -t st -p localhost,1 iqn.2007-10.local.server-1:storage.lun0

Now I can connect using the following:
iscsiadm -m node -T iqn.2007-10.local.server-1:storage.lun0 -p -l

Now check the /var/log/messages for the newly created virtual SCSI device.
tail /var/log/messages

Now you can switch back to console #1 and continue with Clonezilla wizard. Select local disk to local disk when prompted for which mode to use.

Create Cisco VPN on Ubuntu Karmic/Lucid

It is very easy to setup a Cisco VPN on Ubuntu. I used the following instructions to get my corporate tunnels running. This tutorial assumes you have already acquired a .pcf file from your network IT staff.


Install the vpnc package and any required dependencies:
sudo apt-get install vpnc

Open your vpn pcf configuration file with your favorite text editor.
vim corporatenet.pcf

It will looking something like this:

Note the values for Host, GroupName and enc_GroupPwd. You'll need these to create your vpnc configuration file.

sudo vim /etc/vpnc/corpnet.conf

Make your configuration file look like this. Just make sure to change the fictional CorpNet values with your own.

IPSec gateway
IPSec ID CorpNet
IPSec obfuscated secret C555E3A4BE82FF0001601A38260A92D93FF5693A482367E117EF8697CBED681C5FDD7F2AE0DEEA4B37DBBB21434189A46D8955F11916040A
Xauth username YOURUSERNAME
Xauth password YOURPASSWORD

It's important to note the obfuscated option in the group password. Most of the examples and howtos I've seen on the Net leave this out because they were written several years ago before VPNC supported Cisco encrypted passwords. The older guides required you to de-crypt the Cisco string. This isn't necessary anymore with Karmic and Lucid releases.