Joe's Linux Blog Linux Admin tips and tricks

April 22, 2010

ALIX Centos Image

Filed under: ALIX,Centos,Installation — Tags: , , , , , — jfreivald @ 10:48 pm

UPDATE 12/31/2011: I have updated the Alix Centos 5 image to 5.7.  During the process, I removed the /etc/ssh/ssh_host* keys so that each host will generate its own keys on boot up.  Note that during the ‘yum upgrade’ process, I had boost the memory on the virtual image. Yum was unable to allocate enough ram with only 256 MB available. This means that it is unlikely that an update from 5.5 to 5.7 can be performed in a single step on a live board with only 256 MB of RAM.

As for the Centos 6 image, it is being troublesome because the up-line removed all of the non-pae kernel images for the 32-bit architecture.  I’ve attempted to custom package a few kernels to complete the image but none of the work to my satisfaction.

UPDATE 10/22/2010: Added a step in the ‘Using the Image’ section below. All active installations should ensure they replace their SSH System keys to prevent man-in-the-middle attacks. I will post an updated image that has the keys removed when I get around to it. Until then, just perform the commands in item 7 of the Using the Image section.

UPDATE: A new version of the image is available.  It had ‘yum upgrade’ executed on June 12th, 2010, which upgraded it to Centos Version 5.5.  The new image is located at  There is also an MD5 sum file at

I could not find my 2 GB card. I used the original image, copied it to a 4 GB card, performed the update, and then copied only the first 2 GB back into the new image. Please provide feedback if the image does not work on a 2GB card.

UPDATE: Hat-tip @Cris. In order to get the vga to work on the 3d3 board you must put the irqpoll as kernel boot parameter.  See his comment for more information.

INFO: For those who are unfamiliar with Centos, it is a distribution that is binary compatible with RedHat Enterprise Linux.

EDIT: We’ve been added to the ALIX web page. Thank you for the testing and support from the PC-Engines crew.

I’ve been working with one of PC Engine’s Alix 6e1 boards a bit lately.  It’s a 500 MHz i586 AMD Geode-based embedded board with 256 MB of RAM that sells for under $150. I was testing various distributions and found that Centos was pretty easy to adapt. It wasn’t listed as supported on the PC Engines Web Site, so I wanted to contribute an image back to the community.

The image I’ve created has the following changes from a base install:

1.  It has no swap.

2.  It has the noatime and nodiratime options for all mounted partitions, although it uses ext3 because of the wal-wart-no-backup-power-for-shutdown configuration.

3.  Grub is configured for a 2-second timeout, and uses the serial port as the console – both for grub and the kernel.  Hook up a terminal emulator set to 38000, 8N1 to view the boot sequence or access the console directly.

4.  /etc/inittab was modified to use the serial console.  xdm was also disabled.

5.  All console settings are set for 38400 because that is what the initial boot-up bios uses on the ALIX 6e1 that I have.

6.  /etc/securetty has been modified to allow login via /dev/ttyS0 (tty0 and vc/1 are also left open because I use VMWare to modify the image).

7.  Fortunately, due to the stock Centos LVM configuration, no changes were necessary to fstab or the initrd image.

8.  Only a base install was performed.  Several of the ‘default’ packages have been omitted (things like bluetooth, extra shells, smart card reader daemon, procmail, cups, NetworkManager, etc. )  Of course they are still available using YUM.

9.  Lots of the startup stuff is turned off (kudzu, gpm, netfs, iptables and others).  Use chkconfig to turn them back on if you want them.

10.  The root password is – yep, you guess it: password

11. The eth0 (next to the USB ports) is configured for DHCP. eth1 (next to the serial port) is configured for The hardware MAC lines have been commented out so that it will work with any box, but there is a slight chance that the order of the ports will get reversed. This has never happened to me, but YMMV. You can use either port to get the box up and running with ssh or putty if you don’t want to use or don’t have a serial interface.

12.  The CF card I used was A 2GB SanDisk Ultra 15MB/s.  Because it’s LVM based, you can use the LVM tools to shrink or grow the volumes.  Check out the LVM Howto for all the recipies you need.

13. I updated the packages using ‘yum update’ on the day it was created, so hopefully you won’t have as much downloading to do. I did not enable centosplus, extras, or any other repositories, which makes the image binary compatible with RHEL 5.4.

Using the Image

1.  Download the latest image from

2.  Unzip the image with bunzip2.  Please verify the uncompressed image with md5sum. Several users who had issues simply had bad downloads or uncompressed the file improperly.  An md5sum will catch these types of issues.  The md5sum file is in the same directory as the image.

3.  Copy it to your Compact Flash drive using ‘dd if=<inputfile> of=<outputdevice> bs=4096’.  <inputfile> is the uncompressed image that you verified in step 2.  <outputdevice> is your compact flash card.  You can find the correct one for your system with ‘sudo parted -l’.  You must use the disk device, not a partition i.e: /dev/sdc as opposed to /dev/sdc1.  This will install the boot loader and all necessary partitions to have a running system.  If your compact flash is larger than 2GB, see the comments section of this post for ways in which you can use the rest of the space.

4.  Install the Compact Flash into the ALIX.

5.  Attach your favorite terminal program to the ALIX platform.  I use putty.exe under Windows or minicom under linux.

6.  Apply power to the unit.  It should boot without any fuss. If you don’t have a serial port, use eth0 (next to the USB) to have your DHCP router assign and address, or use eth1 (next to the serial port) for a static configuration. eth1 is configured for and the connector auto-rolls the cable if it needs to, so configure your computer for something like and ping until the system is online. Then use ssh, or putty.exe if you are using Windows, to access the unit.

7.  I recommend some changes: Obviously, the root password.  Also, add an MD5 password to the grub configuration, since without one anyone with a serial cable can pass parameters to the kernel. You will also probably want to add more software using yum. You might also want to create some scratch space under /tmp, or some of the /var/cache directories using tmpfs. I didn’t do any of the these because they are simple, and different users will have different requirements, especially with the advancement of CF cards (wear leveling, 1000000+writes/block, etc.). You will probably want to customize /etc/securetty for your installation.

8. On images earlier than 5.7, change the SSH server keys with:
$ sudo rm /etc/ssh/ssh_host_*
$ sudo /etc/init.d/sshd restart
(Hat tip to @pmoor for catching this one!)

With this setup, the initial boot up takes 1:32 and has 193MB of free memory. Enjoy.


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