[DEV] Reworked process for running Ubuntu on Nexus One (Device busy error eliminated) - Nexus One Android Development

Few months ago, there was a post on XDA:
http://forum.xda-developers.com/showthread.php?t=718952
and a link to:
http://nexusonehacks.net/nexus-one-hacks/how-to-install-ubuntu-on-your-nexus-oneandroid/
They explain how to install and run Ubuntu on Nexus One.
But a lot of people got problems when running script bootubuntu and ubuntu.sh, and I was one of them.
After Cyanogen Mod 6.0 was released, I could successfully run Ubuntu according to given instructions, but later I discovered the two scripts (ubuntu.sh and bootubuntu) don't always work, and I found them very complex and unnecessary statements can be removed.
Since few months ago I've been refining the two scripts to make them able to boot Ubuntu with less likelihood to get error. I thought I would like to share my findings to everyone interested.
Here are some reasons why it's useful to have Ubuntu on Nexus One
1. Fully functional web browser Firefox
2. Fully functional office suite OpenOffice
3. Fully functional Linux terminal with lots of ultilities
4. Fully functional image manipulation tool Gimp
5. Ability to run lots of useful native Linux programs
6. Python, gcc, g++..
I'll talk about my findings in next few posts.
Post #2: simplify ubuntu.sh, remove unnecessary script files
Post #3: simplify bootubuntu, forcibly umount
Post #4: how to shutdown Ubuntu properly if terminal application was closed by Android
Post #5: a little script which should be run before exiting from Ubuntu
Post #6: how to start GNOME desktop (instead of LXDE) and get correct keyboard mapping
Post #7: a possible solution to loop device's "resource or device busy" error
About my Nexus One:
bought on 2nd March
Cyanogen Mod 6.0
IntersectRaven HAVS CM CFS 1020 kernel
Busybox 1.17
Radio 5.0.8
Gapps hdpi 20101020.1
Please don't hesitate to tell me if I made any mistake, I'm a Linux beginner because I taught myself Linux, my University will teach Unix next semester.
Attachment: ubuntu_scripts.zip
contains all modified scripts.

---

Finding #1:
In original Zip package, there are five scripts, but only two of them are actually used to install and boot up Ubuntu.
fsrw, mountonly, unionfs are not necessary to install and boot ubuntu, thus their reference can be removed from ubuntu.sh
Here is my simplified version of ubuntu.sh
#-------------------------------
mount -o rw,remount -t yaffs2 /dev/block/mtdblock3 /system
rm -f /system/bin/bootubuntu
rm -r -f /data/local/ubuntu
cp -f bootubuntu /system/bin
cd /
echo "Type 'bootubuntu' to boot Ubuntu"
#-------------------------------
Simplified ubuntu.sh removed unnecessary statements to reduce risk of error.
Also I discovered:
Files in /sdcard/ubuntu can not be chmod, and it's unnecessary to chmod 4777 to them.
chmod 4777 /system/bin/* will cause some Android softwares to malfunction (e.g. Orbot), also it *possibly* cause some roms to fail to boot up next time (CM6.0)

---

Finding #2:
Here's my simplified bootubuntu script, there are minor changes to script flow and removed all unnecessary statements:
#-------------------------------
mount -o remount,rw -t yaffs2 /dev/block/mtdblock3 /system
echo "SETTING VARIABLES"
export bin=/system/bin
export mnt=/data/local/ubuntu
export PATH=$bin:/usr/bin:/usr/sbin:/bin:$PATH
export TERM=linux
export HOME=/root
if [ ! -d /data/local/ubuntu ]
then
mkdir /data/local/ubuntu
fi
echo "SETTING UP LOOP DEVICE"
losetup /dev/block/loop1 /sdcard/ubuntu/ubuntu.img
echo "MOUNTING"
mount -t ext2 /dev/block/loop1 /data/local/ubuntu
mount -t devpts devpts $mnt/dev/pts
mount -t proc proc $mnt/proc
mount -t sysfs sysfs $mnt/sys
echo "SETTING UP NETWORK"
sysctl -w net.ipv4.ip_forward=1
echo "nameserver 208.67.222.222" > $mnt/etc/resolv.conf
echo "nameserver 208.67.220.220" >> $mnt/etc/resolv.conf
echo "127.0.0.1 localhost" > $mnt/etc/hosts
echo "Brought to you by NexusOneHacks.net and the open source community! "
chroot $mnt /bin/bash
echo "UMOUNTING"
umount -lfr $mnt/dev/pts
umount -lfr $mnt/proc
umount -lfr $mnt/sys
umount -lfr $mnt
losetup -d /dev/block/loop1
#-------------------------------
and it forcibly,lazily,read-only-if-failed umount $mnt, thus losetup -d will less likely to fail and eliminate the problem when booting ubuntu second time.

---

Finding #3:
If terminal application is terminated automatically by Android system, in this situation, the Ubuntu is not properly umounted.
Thus we change ubuntu.sh into:
#------------------------------
mount -o rw,remount -t yaffs2 /dev/block/mtdblock3 /system
rm -f /system/bin/bootubuntu
rm -f /system/bin/exitu
rm -r -f /data/local/ubuntu
cp -f bootubuntu /system/bin
cp -f exitu /system/bin
cd /
echo "Type 'bootubuntu' to boot Ubuntu"
#------------------------------
and we create a new script named "exitu" in sdcard/ubuntu directory:
#------------------------------
export mnt=/data/local/ubuntu
echo "UMOUNTING"
umount -lfr $mnt/dev/pts
umount -lfr $mnt/proc
umount -lfr $mnt/sys
umount -lfr $mnt
losetup -d /dev/block/loop1
#------------------------------
remember to run "sh ./ubuntu.sh" to copy new exitu script into /system/bin.
Then whenever you went back to terminal, found Ubuntu terminal is gone, simply type exitu (remember to be su first) to exit ubuntu, then bootubuntu again to enter ubuntu terminal. It's harmless to execute exitu multiple times to ensure $mnt is umounted successfully.
Sometimes exitu still can not successfully remove loop1 assignment with /sdcard/ubuntu/ubuntu.img, but seems like it doesn't really matter, ubuntu still can boot up successful even loop1 was not unassigned successfully

---

Finding #4:
To reduce likelihood of getting "device or resource busy" error when removing loop device assignment, it's good to have this script in your Ubuntu, and run the script before exiting from Ubuntu:
#-------------------
export USER=root
vncserver -kill :1
vncserver -kill :2
sudo reboot
sudo halt
#-------------------
(remember, the script should be in your Ubuntu's file system, not your android's file system!)
run the script before you exiting from Ubuntu, this will greatly reduce likelihood of getting device or resource busy error when exiting.

---

Finding #5:
For those of you who prefer to enter GNOME desktop manually (no automatically start-up), this script may help, also this script should be able to fix androidVNC keyboard mapping problem:
(this script should be in Ubuntu)
#--------------------
cd /
rm -r -f tmp
mkdir tmp
cd /
export USER=root
export XKL_XMODMAP_DISABLE=1
vncserver -geometry 800x600
#--------------------
regarding the guide:
http://nexusonehacks.net/nexus-one-hacks/how-to-install-ubuntu-on-your-nexus-oneandroid/
if you would like to enter gnome and not to autostart desktop environment, please don't follow its instruction on making change to /root/.vnc/xstartup and /root/.bashrc
instead, create a script as I mentioned above, and run the script to bring up VNC server, and you will get GNOME desktop in VNC with correct keyboard mapping

---

Finding #6
If you're constantly getting "device or resource busy" error when mounting loop1 to /data/local/ubuntu, the reason might be caused by Android App2SD (Froyo version), if you have any software installed on SD card, it may cause all loop devices to be busy all the time (even newly created loop device!) And busy loop device can not be mounted, thus generates "device or resource busy" error message.
Most people had the same problem few months ago, when they execute bootubuntu, they get an error saying loop device is busy, and even changing loop device wouldn't help.
Now I think the reason is determined. After uninstalled all applications which are on SD card (or move all of them from SD card to internal storage), the Ubuntu can boot successfully without getting "device or resource busy" error when mounting loop device.
Edit 2010-11-04:
If bootubuntu gets executed before Android loads all app2sd applications, it is possible solves the loop device busy error even with App2SD applications installed. It requires a very perfect timing, today after few experiments on my phone, I worked out a process which can always boot up Ubuntu on my phone:
1. Reboot phone
2. as soon as you enter lock screen, unlock screen
3. quickly go to terminal emulator
4. become su by typing su and enter
5. type bootubuntu and wait (type it fast... practice )
-------------
1-5 must be done before SD "Checking for errors" notification disappears, if you fail to do so.. reboot and try again
------------
6. as soon as SD "Checking for errors" notification disappears, hit enter IMMEDIATELY
Now you should be able to enter Ubuntu terminal.
Do NOT exit from your Android terminal (don't press back or home button), wait 1-2 minutes for Android to load applications on SD card.
Once you reboot your phone, you'll need to repeat the above procedure again to enter Ubuntu successfully.

---

Also chmod 4777 is horrible from a security point of view. It makes all the system bin files writable by anyone and run with root privileges (setuid root).
Sent from my Nexus One using XDA App

---

houzuoguo said:
Finding #6
If you're constantly getting "device or resource busy" error when mounting loop1 to /data/local/ubuntu, the reason might be caused by Android App2SD (Froyo version), if you have any software installed on SD card, it may cause all loop devices to be busy all the time, thus loop device can not be mounted to /data/local/ubuntu anymore.
Most people had the same problem few months ago, when they execute bootubuntu, they get an error saying loop device is busy, and even changing loop device wouldn't help.
Now I think the reason is determined. After uninstalled all applications which are on SD card (or move all of them from SD card to internal storage), the Ubuntu can boot successfully without getting "device or resource busy" error when mounting loop device.
Click to expand...
Click to collapse
This is because with Froyo apps to SD android creates an encrypted loopback device for each app on the SD card, so depending on the number of apps on your SD card loop0-7 may be in use. I solve this by using a high loop number with losetup - loop99.
Sent from my Nexus One using XDA App

---

Use a higher loop device, the best option
It worked for me on loop7, but to be on the safe side, decided to use a higher loop number as suggested, but it requires to create the loop device as it doesn't exists, use mknod:
Code:
echo "SETTING UP LOOP DEVICE"
mknod /dev/block/loop99 b 7 99
losetup /dev/block/loop99 /sdcard/ubuntu/ubuntu.img
Now is working on loop99 too!. The clean up section for both bootubuntu and exitu scripts:
Code:
echo "UMOUNTING"
umount -f $mnt/dev/pts
umount -f $mnt/proc
umount -f $mnt/sys
umount -f $mnt
losetup -d /dev/block/loop99
rm /dev/block/loop99
I'm not sure about how I am cleaning up the new node, rm erases it... but is this the best method? rebooting the phone will erase the node anyway so maybe an if clause to test for the node loop99 before creating it will be better.

---

fralacos said:
It worked for me on loop7, but to be on the safe side, decided to use a higher loop number as suggested, but it requires to create the loop device as it doesn't exists, use mknod:
Code:
echo "SETTING UP LOOP DEVICE"
mknod /dev/block/loop99 b 7 99
losetup /dev/block/loop99 /sdcard/ubuntu/ubuntu.img
Now is working on loop99 too!. The clean up section for both bootubuntu and exitu scripts:
Code:
echo "UMOUNTING"
umount -f $mnt/dev/pts
umount -f $mnt/proc
umount -f $mnt/sys
umount -f $mnt
losetup -d /dev/block/loop99
rm /dev/block/loop99
I'm not sure about how I am cleaning up the new node, rm erases it... but is this the best method? rebooting the phone will erase the node anyway so maybe an if clause to test for the node loop99 before creating it will be better.
Click to expand...
Click to collapse
thanks a lot
I tried this idea already but it seems doesn't work under CM6.0...
and the problem was, every newly created loop device will always be busy, if app2sd is used. (Don't know why)
I'm going to try a different approach, I try to mount loop device to /data/local/ubuntu before Android mounts all app2sd applications

---

mathrock said:
This is because with Froyo apps to SD android creates an encrypted loopback device for each app on the SD card, so depending on the number of apps on your SD card loop0-7 may be in use. I solve this by using a high loop number with losetup - loop99.
Sent from my Nexus One using XDA App
Click to expand...
Click to collapse
thanks.
my finding is, Android froyo app2sd uses dm-xx loop devices for sd applications, for example, now I have three games on sd card, by entering mount in terminal, i read that
/dev/block/dm-0,dm-1,dm-2 are used.
After I removed all SD applications and reboot system, all of those dm-xxx devices are not mounted anymore.
Also the only difference between mount result with app2sd and mount result without app2sd is usage of dm-xx devices.

---

Finally I've found solution to the "device or resource busy" error
but it seems like people are now less interested in running Ubuntu on Nexus One
the original post got more than 35k hits and more than 200 replies

---

Hi houzuoguo!!
I'm trying to type bootubuntu when enter in system, but i think i'm not fast enough or that not work for me. Everytime i get:
# bootubuntu
SETTING VARIABLES
SETTING UP LOOP DEVICE
losetup: /dev/block/loop1
MOUNTING
mount: mounting /dev/block/loop1 on /data/local/ubuntu failed: Device or resource busy
mount: mounting devpts on /data/local/ubuntu/dev/pts failed: No such file or directory
mount: mounting proc on /data/local/ubuntu/proc failed: No such file or directory
mount: mounting sysfs on /data/local/ubuntu/sys failed: No such file or directory
SETTING UP NETWORK
net.ipv4.ip_forward = 1
bootubuntu: cannot create /data/local/ubuntu/etc/resolv.conf: directory nonexistent
bootubuntu: cannot create /data/local/ubuntu/etc/resolv.conf: directory nonexistent
bootubuntu: cannot create /data/local/ubuntu/etc/hosts: directory nonexistent
Brought to you by NexusOneHacks.net and the open source community!
chroot: can't execute '/bin/bash': No such file or directory
UMOUNTING
umount: can't forcibly umount /data/local/ubuntu/dev/pts: No such file or directory
umount: can't forcibly umount /data/local/ubuntu/proc: No such file or directory
umount: can't forcibly umount /data/local/ubuntu/sys: No such file or directory
umount: can't forcibly umount /data/local/ubuntu: Invalid argument
losetup: /dev/block/loop1: Device or resource busy
#
Whats the problem then?¿?
Thanks in advance.

---

devex said:
Hi houzuoguo!!
I'm trying to type bootubuntu when enter in system, but i think i'm not fast enough or that not work for me. Everytime i get:
# bootubuntu
SETTING VARIABLES
SETTING UP LOOP DEVICE
losetup: /dev/block/loop1
MOUNTING
mount: mounting /dev/block/loop1 on /data/local/ubuntu failed: Device or resource busy
mount: mounting devpts on /data/local/ubuntu/dev/pts failed: No such file or directory
mount: mounting proc on /data/local/ubuntu/proc failed: No such file or directory
mount: mounting sysfs on /data/local/ubuntu/sys failed: No such file or directory
SETTING UP NETWORK
net.ipv4.ip_forward = 1
bootubuntu: cannot create /data/local/ubuntu/etc/resolv.conf: directory nonexistent
bootubuntu: cannot create /data/local/ubuntu/etc/resolv.conf: directory nonexistent
bootubuntu: cannot create /data/local/ubuntu/etc/hosts: directory nonexistent
Brought to you by NexusOneHacks.net and the open source community!
chroot: can't execute '/bin/bash': No such file or directory
UMOUNTING
umount: can't forcibly umount /data/local/ubuntu/dev/pts: No such file or directory
umount: can't forcibly umount /data/local/ubuntu/proc: No such file or directory
umount: can't forcibly umount /data/local/ubuntu/sys: No such file or directory
umount: can't forcibly umount /data/local/ubuntu: Invalid argument
losetup: /dev/block/loop1: Device or resource busy
#
Whats the problem then?¿?
Thanks in advance.
Click to expand...
Click to collapse
I worked on that problem for few weeks and finally I discovered, once I moved all SD applications back to Internal storage, loop1 no longer be busy.
Are you using Froyo app2sd?

---

houzuoguo said:
thanks a lot
I tried this idea already but it seems doesn't work under CM6.0...
and the problem was, every newly created loop device will always be busy, if app2sd is used. (Don't know why)
I'm going to try a different approach, I try to mount loop device to /data/local/ubuntu before Android mounts all app2sd applications
Click to expand...
Click to collapse
Some of us are still interested in this info but ubuntu runs pretty slow on the nexus. I say it would be nice to have the newest ubuntu (10.10) installed on the nexus one. Possibly the netbook remix version.

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Lou2serious said:
Some of us are still interested in this info but ubuntu runs pretty slow on the nexus. I say it would be nice to have the newest ubuntu (10.10) installed on the nexus one. Possibly the netbook remix version.
Click to expand...
Click to collapse
thanks haha, good to hear that I'm not the only one still interested in running Ubuntu on Nexus One.
I'm thinking, if Nexus Two can be overclocked to 1.4Ghz, together with top class SD card, the speed will be enough to run Ubuntu fluently.

---

Hi! Thanx for ur work! It helped me.....
Now i´m having another issue....i´m triying either to resize the ubuntu.img to make it bigger so i can install the stuff i want ( clean install has 100 mb left) or (preffered option) mounting my sdcard so i can install the native programs from there...any ideas?¿

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I think the simple way is just to create another file bigger.

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funkatiko said:
Hi! Thanx for ur work! It helped me.....
Now i´m having another issue....i´m triying either to resize the ubuntu.img to make it bigger so i can install the stuff i want ( clean install has 100 mb left) or (preffered option) mounting my sdcard so i can install the native programs from there...any ideas?¿
Click to expand...
Click to collapse
You might want to build your own rootfs - check this site out - it worked great for me.
https://wiki.ubuntu.com/ARM/RootfsFromScratch