CT-PC89E Debian

From eLinux.org
Revision as of 21:48, 13 April 2011 by Peter Huewe (Talk | contribs)

(diff) ← Older revision | Latest revision (diff) | Newer revision → (diff)
Jump to: navigation, search

Debian/Lenny on the CT-PC89E

This page describes the process by which Debian/Lenny was installed onto the CT-PC89E, in case anyone wants to replicate it or install an alternative OS.

Caveats and Important Info

At this early stage, working with a factory full of people whose primary language is chinese not english, we have needed to repeat things several times. Also, we are prioritizing requests. Firmware first, GPL source code of kernel second, GPL source code of u-boot third, GPL and other free software licensed source code of the MOS mid-fun operating system fourth. We've received the firmware, which contains a binary-only compile of u-boot; a binary-only compile of the 2.6.24.2 kernel; various splash-screens needed to be loaded during the update phase for informational purposes; and the all-important replacement root filesystem, datang-epc.tar.gz

Also, the root filesystem partition is only 450mb, with about 64mb at the end of the NAND flash storing the kernel and u-boot, and the rest of the NAND flash allocated for user files. It is therefore, at the moment, to create a root filesystem that fits in under 450mb.

So, as of 27feb2010, the only option is to build a really quite small alternative root filesystem, and to use the existing binary u-boot and binary 2.6.24.2 kernel. Also, it is not clear as to why, but it would appear that the current kernel is somehow missing ext2 and ext3 drivers, making it impossible to mount the remaining 3rd 1.2gb partition!

The kernel is fortunately compiled with eabi, so despite evidence to the contrary on the MOS mid-linux operating system showing the debian architecture as "arm", this is in fact a mistake: the debian architecture recorded by MOS should be "armel". further evidence showing this mistake is in the form of the http://mid-linux/sdk which contains a gnueabi gcc compiler.

Also: thanks to lack of access to the GPL source code of the kernel and of u-boot, there is no video console access, period. both u-boot and the kernel have been compiled NOT to recognise the LCD framebuffer as console, and it is perhaps a wise choice, except for not compiling in any console fonts!

Creating a root filesystem with qemu

There are many ways to create a debian armel root filesystem: using qemu was chosen out of naivete, and an updated description compiled from following two other excellent HOWTOs can be found here: http://wiki.lkcl.net/ArmelQemu

The key thing to note is to NOT install too much. XFCE4 is too much. LXDE is too much. xserver-xorg is also too much, but the existence of kdrive was not known at the time of creation, and the primary focus was on getting it "working", fast, and adapting later.

Installing packages in the qemu environment

So, after getting qemu armel up-and-running, it was then necessary to take into account the fact that there will be no console access. Ordinarily it would be perfectly okay to just do a minimal debian install and then start logging in at the console and going from there... except there isn't one. Therefore, xdm, gpe and matchbox were installed and tested.

gpe was installed first, just to give some applications. xdm was installed second, so as to remove gpe meta-package and gpe-login. to get a window manager, matchbox was installed. Then, after creating a midfun user, /home/midfun/.xsessionrc was created with one line, "matchbox-session" in it. After logging in at xdm, this was sufficient to start up an xsession with the matchbox window manager.

Also, openssh server was installed, along with rsync and a few other essential goodies.

Then, /usr/share/doc/* entries were entirely deleted, as were some of the locales (not recommended unless you know what you're doing). The end result was a 350mb root filesystem once it ended up on the NAND flash of the CT-PC89E.

Retrospective modifications needed

Before describing how the filesystem was actually installed, it was discovered that there were problems at boot-up time which needed to be overcome. The first of these which was discovered was that LVM support is not compiled in to the mid-fun kernel, and because the root filesystem in qemu had been an LVM partition, bootup stalled with an (unreadable!) error message. By editing /etc/init.d/lvm and adding "exit 0" at the top, it was possible to bypass the error.

/etc/fstab on MOS is very weird: rootfs is not named by partition /dev/mmcblk0p1 but is named rootfs! so, that needed to be modified.

All console entries in /etc/inittab - tty1 through to tty6 - were commented out.

Copying the filesystem out of qemu

This was tricky: rather than mess about with a shutdown qemu image, local loopback etc. rsync was used to copy the files out of the running qemu session, with rsync --exclude=/proc/* --exclude=/sys/* --exclude=/selinux/* --delete / 192.168.1.220:/{somewhere}

Then, very simply, in the system to where the files had been copied, entering the directory, tar was used: tar -cvzf ../rootfs.tgz .

All that was then required was to copy that file, rootfs.tgz, as datang-epc.tar.gz, onto the FAT-formatted "firmware update" SDcard. Pressing and holding both mouse buttons as well as the power button during boot was sufficient to activate the u-boot "update" command sequence. Power-off was automatic; a reboot entered debian / lenny after the third attempt.