Tutorials Linux opt on loopback
Background & Purpose
The Palm Pre's 8GB HD is configured with three partitions:
1) /dev/mmcblk0p1 defined as a Linux/PA-RISC boot partition is only 4MB 2) /dev/mmcblk0p2 defined as a Linux partition and is 32MB mounted as /boot 3) /dev/mmcblk0p3 defined as a Linux LVM partition is 7.62GB
The /dev/mmcblk0p3 partition is a Linux Volume Group that is sliced into six Logical Volumes:
/dev/store/root mounted on / (root) 456 MB /dev/store/var mounted on /var 256MB /dev/store/update mounts on /var/lib/update 56MB (not mounted) /dev/store/log/ mounted on /var/log 40MB /dev/store/media mounted /media/internal 6.69GB /dev/store/swap Linux swap 128MB
It has been observed that if /var or / (root) usage is greater than or equal to 90% than the FAILED_NOT_ENOUGH_INSTALL_SPACE error is generated. "Builtin" applications reside on the root file system in /usr/palm/applications. Downloaded apps and those installed with palm-install reside on the /var file system in /var/usr/palm/applications. Also for so-called "rooted" Pre's the Optware Linux-based apps are stored in /var/opt.
One fix for a rooted Pre is to create a virtual Linux file system using a portion of the space allocated to /media/internal using a procedure similar to this one:
Linux Online - Using a file instead of a partition
Then mount the virtual file system on /opt vs binding /var/opt to /opt. Then relocating the files/directories under /var/opt to the new virtual file system.
NOTE: The /dev/store/update is mounted when you run the Update process. It would seem that the updates are stored here (at least some of them) prior to installation.
Requirements
You must have access to the Linux shell to perform this process. It is assumed that you followed the procedure to install Optware apps in /var/opt and linked /var/opt to /opt with the "mount -o bind /var/opt /opt" command and there is an equivalent entry in the /etc/fstab file.
Procedure for Creating a Linux Virtual File System
Do NOT do this if you want to connect your Pre to your computer in the USB Drive or Media Sync modes.
The following commands will move all of your Optware packages to an ext3 1GB loopback image that resides on /media/internal. <source lang="bash">
- Create a directory on the USB drive portion to hold the virtual file system
mkdir /media/internal/vfs
- Create a 1GB file (adjust size (bs*count) as needed, the minimum size should be 256MB)
dd if=/dev/zero of=/media/internal/vfs/optware.img bs=1024 count=1024k
- Create linux ext3 file system
mkfs.ext3 -F /media/internal/vfs/optware.img
- Create a temporary mount point
mkdir /tmp/opt
- Mount newly created virtual file system
mount -o loop /media/internal/vfs/optware.img /tmp/opt
- Populate new virtual file system.
- Must be in the source directory.
cd /opt tar cvf - . | (cd /tmp/opt; tar xf -) cd /
- Unmount virtual file system
umount /tmp/opt
- Unbind /var/opt from /opt
umount /opt
- If no errors, mount virtual file system on /opt
- otherwise skip
mount -o loop /media/internal/vfs/optware.img /opt
- Add the following line to /etc/fstab to automount (without the #).
- /media/internal/vfs/optware.img /opt ext3 loop,noatime 1 2
- Comment out the /var/opt entry, should be similar to next line
- /var/opt /opt bind defaults,bind 0 0
- reboot your phone, if error noted when attempting to unmount /opt
reboot
- If no errors noted with the Optware apps,
- remove files/directories from /var/opt
rm -r /var/opt </source>
Caveats
Currently this procedure will disable USB Drive and Media Sync modes.
A method to safely unmount Virtual file system when selecting USB Drive and Media Sync modes is under development.
See the start/stop script below for now. The script needs to be run from a non-ssh terminal (ie novaproxy or novaterm). In the future this should be wrapped inside a homebrew GUI.
Workaround for USB Drive/Media Sync: Start/Stop and Mount/Unmount Script
This script will start/stop (mount/unmount) the virtual file system, thus functioning as a work-a-round to allow using the Palm Pre's USB Drive and Media Sync modes. It is a work in progress and needs to be bullet-proofed. Ideally it should be wrapped around a WebOS GUI app—we are working on this. This script should be saved to a file (i.e. /home/root/vfs), made executable (i.e. chmod 750 /home/root/vfs and then run (i.e. with /home/root/vfs on or /home/root/vfs off). Do not save the script to an /opt path. Make sure you're running the script to toggle the virtual file system on or off when /media/internal is not mounted as a USB drive and the Media Sync mode is not enabled, otherwise the script will fail.
Note: We need this put in a Java service, which means we need to translate it to Java that the Pre can understand! This will be for the app that is used as a front-end GUI to toggle the the VFS. Please look into this if you have the knowledge, on Gitorious. The source is there.
<source lang="bash">
- !/bin/sh
- List of Optware applications to start/stop
- in conjunction with mounting/unmounting VFS.
- Check to make sure /media/internal is
- mounted
FSINT=`/bin/df|/bin/grep "/dev/mapper/store-media"` if [ "$FSINT" = "" ] then
echo "USB Drive not mounted. Exiting" exit 1
fi
- OpenSSH and Dropbear are most common.
- Edit to suit environment.
APPS="optware-openssh optware-dropbear"
- An entry in /etc/fstab must exist for the VFS
- Grab and parse entry
FSVFS=`/bin/grep "/opt" /etc/fstab|grep loop` if [ "$FSVFS" != "" ] then
# Complete FileName of VFS to mount/unmount LVFSFN=`echo $FSVFS|/usr/bin/awk '{print $1}'` # VFS Mount Point (ie /opt) LVFSMP=`echo $FSVFS|/usr/bin/awk '{print $2}'` # VFS file system Type (ie ext3) LVFSTP=`echo $FSVFS|/usr/bin/awk '{print $3}'`
else
echo "**** No /etc/fstab entry" exit 1
fi
- Determine if VFS is mounted
VFSMTD=`/bin/df|/bin/grep "$LVFSMP"|/bin/grep "^/dev/loop"` if [ "$VFSMTD" != "" ] then
# Loopback device associated with VFS (ie /dev/loop0) LVFSDV=`echo $VFSMTD|/usr/bin/awk '{print $1}'`
fi
case $1 in
"on" ) if [ -e "$LVFSFN" -a -d "$LVFSMP" -a "$VFSMTD" = "" ] then echo '**** Mounting Linux VFS' /bin/mount "$LVFSFN" echo '**** Starting Applications' for x in $APPS do if [ -f /etc/event.d/"$x" ] then /sbin/initctl start "$x" fi done echo '**** Linux VFS Enabled' else echo '**** Error mounting VFS' exit 1 fi ;; "off" ) if [ "$VFSMTD" != "" -a "$LVFSDV" != "" ] then echo '**** Stopping Applications' for x in $APPS do if [ -f /etc/event.d/"$x" ] then /sbin/initctl stop "$x" fi done echo '**** Unmounting Linux VFS' /bin/umount "$LVFSMP" # Work-a-round to disassociate VFS from loopback device /sbin/losetup -d $LVFSDV echo '**** Linux VFS Disabled' else echo '**** Error unmounting VFS' exit 1 fi ;; * ) echo "Usage: `/usr/bin/basename $0` on|off" ;;
esac </source>
Credits
PuffTheMagic - Devised the initial process 1lnxraider - Expanded, modified, & published tutorial - Helped ultraBlack troubleshoot toggle script - Confirmed caveat ultraBlack - Found & had confirmed the major caveat which disables Media Sync & USB modes - Devised plan for front-end 'Toggle VFS' GUI, envisioning it as a way to also easily create it rwhitby - Provided skeleton & basic methods for front-end GUI's Opt Loop Service NetWhiz - Gave additional warning that this process disables Media Sync and USB modes