相撲外：Running Universal Debian GNU/Linux in an emulator on a PC

This is useful for instance when you cannot use the Universal temporarily and want to update, or install software, etc. I've used it when my Universal was in service, to update the software.

All of the steps below, refer to actions you will take on a Debian GNU/Linux PC, not on the Universal.

1. Install QEMU

   # aptitude install qemu

2. Get an armel kernel, initrd, and root filesystem from the QEMU armel page, originally found here.

   $ wget -c http://sumoudou.org/uni/vmlinuz-2.6.24-1-versatile $ wget -c http://sumoudou.org/uni/initrd.img-2.6.24-1-versatile $ wget -c http://sumoudou.org/uni/debian_lenny_armel_small.qcow.gz

3. Gunzip the root filesystem.

   $ gunzip debian_lenny_armel_small.qcow.gz

4. Create a QEMU img file to contain the Universal root filesystem for PC manipulation.

   $ qemu-img create uni.img 6GB

   The 6GB refers to the image size, make it big enough, so that the whole Universal root filesystem fits inside it.
5. Create the emulator armel.sh launch file.

   $ echo 'qemu-system-arm -M versatilepb -hdb uni.img -kernel vmlinuz-2.6.24-1-versatile -initrd initrd.img-2.6.24-1-versatile -hda debian_lenny_armel_small.qcow -append "root=/dev/sda1" -m 256 -localtime' > armel.sh

6. Make the emulator launch file executable.

   $ chmod 755 armel.sh

7. Run the emulator for the first time to create a filesystem on the img file.

   $ ./armel.sh

   When the emulator boots, you can login as user with password user or as root with password root. Login as root.
8. Elementary networking now works, you can access the web, however ping doesn't work.
   Install dbus. Otherwise you will get the Can not write log, openpty() failed (/dev/pts not mounted?) error later on in chroot, when installing with apt-get or aptitude.

   # aptitude update # aptitude install dbus

9. Create one partition to span the whole img file mounted as /dev/sdb

   # cfdisk /dev/sdb

10. Create an ext2 filesystem on the partition.

    # mkfs.ext2 /dev/sdb1

11. Shutdown the QEMU emulated system.

    # halt

12. Back in the PC Debian GNU/Linux system, you need to figure out how to mount the img file so that you can write to it.

    # fdisk -ul uni.img

    You will get output similar to the following text:

    You must set cylinders. You can do this from the extra functions menu. Disk uni.img: 0 MB, 0 bytes 133 heads, 62 sectors/track, 0 cylinders, total 0 sectors Units = sectors of 1 * 512 = 512 bytes Disk identifier: 0x00000000 Device Boot Start End Blocks Id System uni.img1 62 8386181 4193060 83 Linux

    To figure out the offset, necessary to specify in the mount command to mount the img file multiply the start sector, in the above case 62, with the number of bytes in a sector, in the above case 512. Therefore in this example, the loop offset would be 31744.
13. Utilizing the offset number, figured out in the above step, mount the uni.img file on the PC.

    # mount -o loop,offset=31744 uni.img /mnt

14. Now the image file is mounted as /mnt/
    Copy the Universal root filesystem you wish to work on to /mnt/
15. When finished copying, copy /etc/resolv.conf file in the mounted /mnt/ system to /etc/resolv.conf.uni

    # cp -P /mnt/etc/resolv.conf /mnt/etc/resolv.conf.uni

16. Unmount the mounted img file.

    # umount /mnt

17. Start the QEMU emulator again.

    $ ./armel.sh

    Login as root.
18. In the armel emulated system create a Universal chroot launch file.

    # echo "mount /dev/sdb1 /mnt" > /usr/local/bin/uni # echo "mv /mnt/etc/resolv.conf /mnt/etc/resolv.conf.uni" >> /usr/local/bin/uni # echo "cp /etc/resolv.conf /mnt/etc/" >> /usr/local/bin/uni # echo "mount -o bind /dev /mnt/dev" >> /usr/local/bin/uni # echo "mount -o bind /dev/pts /mnt/dev/pts" >> /usr/local/bin/uni # echo "mount -o bind /proc /mnt/proc" >> /usr/local/bin/uni # echo "mount -o bind /dev/shm /mnt/dev/shm" >> /usr/local/bin/uni # echo "mount -t tmpfs none /mnt/tmp" >> /usr/local/bin/uni # echo "mount -t tmpfs none /mnt/var/run" >> /usr/local/bin/uni # echo "mount -t tmpfs none /mnt/var/lock" >> /usr/local/bin/uni # echo "mount -t tmpfs none /mnt/var/tmp" >> /usr/local/bin/uni # echo "chroot /mnt/" >> /usr/local/bin/uni # echo "rm /mnt/etc/resolv.conf" >> /usr/local/bin/uni # echo "mv /mnt/etc/resolv.conf.uni /mnt/etc/resolv.conf" >> /usr/local/bin/uni # echo "umount /mnt/var/tmp" >> /usr/local/bin/uni # echo "umount /mnt/var/lock" >> /usr/local/bin/uni # echo "umount /mnt/var/run" >> /usr/local/bin/uni # echo "umount /mnt/tmp" >> /usr/local/bin/uni # echo "umount /mnt/dev/shm" >> /usr/local/bin/uni # echo "umount /mnt/proc" >> /usr/local/bin/uni # echo "umount /mnt/dev/pts" >> /usr/local/bin/uni # echo "umount /mnt/dev" >> /usr/local/bin/uni # echo "umount /mnt" >> /usr/local/bin/uni

19. Make the chroot launch file executable.

    # chmod 755 /usr/local/bin/uni

20. Now you can launch the Universal chroot, which will put you in the Universal environment.

    # uni

    Here you can install software, run aptitude update and aptitude full-upgrade, etc. Elementary networking will work, allowing you to access the internet. ping will not work, as it needs root privileges on the host system side, but apt-get and aptitude will work.
21. When finished, exit the chroot.

    # exit

    This will have unmounted the Universal image file and brought you back to the QEMU armel emulated environment.
22. Exit the QEMU armel emulated environment.

    # halt

    After the QEMU armel emulated environment is halted you can close the QEMU window.
23. Now you can mount the uni.img file in the same way as described above and copy the root filesystem off of it to the SD card you use in the Universal.

© sumoudou.org 2008