GuruPlug: misc stuff

Connecting to serial console


  1. Connect the JTAG board “UART” cable to the port on the GuruPlug
  2. Set the mode to UART (not RS232)
  3. Power up the plug
  4. Connect using screen /dev/ttyUSB0 115200

Accessing U-Boot console

Do as above, but connect to the serial port before powering up the plug. Then, as soon as you see serial output, press a key to interrupt normal boot and access the U-Boot console:

U-Boot 2009.11-rc1-00602-g28a9c08-dirty (Feb 09 2010 - 18:15:21)

SoC:   Kirkwood 88F6281_A0
DRAM:  512 MB
NAND:  512 MiB
In:    serial
Out:   serial
Err:   serial
Net:   egiga0, egiga1
88E1121 Initialized on egiga0
88E1121 Initialized on egiga1
Hit any key to stop autoboot:  0

Debian installation

As of 2012-04-13, I successfully followed these guides in order to get debian running on a usbkey

Upgrading uBoot

Follow the guide here: Upgrading SheevaPlug’s U-Boot

(mirrored here: GuruPlug: uBoot upgrade guide)

Installing debian on the usb stick, booting, etc.

Just follow the guide here: Installing Debian on Plug Computers

(mirrored here: GuruPlug: installing Debian)

Copy to flash

Step 1 Flash the kernel from the usb stick on the NAND:

usb start
ext2load usb 0:1 0x2000000 /uImage
nand erase 0x100000 0x400000
nand write 0x2000000 0x100000 0x400000

setenv mainlineLinux yes
setenv arcNumber 2097

Step 2 Boot from the usb stick:

setenv bootargs_console console=ttyS0,115200
setenv bootcmd_usb 'usb start; ext2load usb 0:1 0x00800000 /uImage; ext2load usb 0:1 0x01100000 /uInitrd'
setenv bootcmd 'setenv bootargs $(bootargs_console); run bootcmd_usb; bootm 0x00800000 0x01100000'
run bootcmd

Step 3 Clone USB rootfs to internal flash

When we make the copy, we don’t want mounted filesystems (dev, tmpfs and so on), though do want anything under any mount points (e.g. /dev/console is always handy), so bind-mount / somewhere, and copy that.

mkdir /tmp/rootfs
mount -o bind / /tmp/rootfs/
cd /tmp/rootfs
cp -av . /mnt/

Fix the fstab in /mnt/etc/fstab:

/dev/root  /               ubifs   defaults,noatime,rw                      0 0
tmpfs      /var/run        tmpfs   size=1M,rw,nosuid,mode=0755              0 0
tmpfs      /var/lock       tmpfs   size=1M,rw,noexec,nosuid,nodev,mode=1777 0 0
tmpfs      /tmp            tmpfs   defaults,nosuid,nodev                    0 0

After that, reboot and re-enter the uBoot console. Also, detach the USB stick to make sure we are booting from flash.

Step 4 Restore boot process from internal flash

To boot from the NAND again after copying the rootfs to NAND, I used these commands at the uBoot prompt:

setenv x_bootcmd_usb 'usb start'
setenv x_bootcmd_kernel 'nand read.e 0x6400000 0x100000 0x400000'
setenv x_bootargs_root 'ubi.mtd=2 root=ubi0:rootfs rootfstype=ubifs'
setenv x_bootargs 'console=ttyS0,115200'
setenv x_bootcmd '$(x_bootcmd_usb); $(x_bootcmd_kernel); setenv bootargs $(x_bootargs) $(x_bootargs_root) ;bootm 0x6400000;'
setenv bootcmd 'run x_bootcmd'

Kernel upgrade

I recently had an issue during a kernel upgrade (3.2.0-2-kirkwood): dpkg was getting stuck after this:

# dpkg --configure -a
Setting up linux-image-3.2.0-2-kirkwood (3.2.15-1) ...
Running depmod.
Examining /etc/kernel/postinst.d.
run-parts: executing /etc/kernel/postinst.d/initramfs-tools 3.2.0-2-kirkwood /boot/vmlinuz-3.2.0-2-kirkwood
update-initramfs: Generating /boot/initrd.img-3.2.0-2-kirkwood
Warning: root device /dev/root does not exist

Press Ctrl-C to abort build, or Enter to continue

I pressed Enter but nothing happened for a quite long time.

The process that got stuck is:

/usr/sbin/mkinitramfs -v -o /boot/ 3.2.0-2-kirkwood

but was running just fine when launched manually. To investigate further I tried this:

mv /usr/sbin/mkinitramfs /usr/sbin/mkinitramfs_orig
echo -e '#!/bin/sh\n/usr/sbin/mkinitramfs_orig -v "[email protected]"' > /usr/sbin/mkinitramfs
chmod +x /usr/sbin/mkinitramfs
dpkg --configure -a

but still, the process was getting stuck for no apparent reason.

At last, I solved by fixing the “/dev/root does not exist” thing using this:

ln -s /dev/ubi0_0  /dev/root

After that, the upgrade just went fine:

# dpkg --configure -a
Setting up linux-image-3.2.0-2-kirkwood (3.2.15-1) ...
Running depmod.
Examining /etc/kernel/postinst.d.
run-parts: executing /etc/kernel/postinst.d/initramfs-tools 3.2.0-2-kirkwood /boot/vmlinuz-3.2.0-2-kirkwood
update-initramfs: Generating /boot/initrd.img-3.2.0-2-kirkwood

... verbose output from mkinitramfs ...

Building cpio /boot/ initramfs
flash-kernel: deferring update (trigger activated)
run-parts: executing /etc/kernel/postinst.d/zz-flash-kernel 3.2.0-2-kirkwood /boot/vmlinuz-3.2.0-2-kirkwood
flash-kernel: deferring update (trigger activated)
Processing triggers for flash-kernel ...
flash-kernel: installing version 3.2.0-2-kirkwood
Generating kernel u-boot image... done.
Taking backup of uImage.
Installing new uImage.
Generating initramfs u-boot image... done.
Taking backup of uInitrd.
Installing new uInitrd.
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