Customized LiveUSB setup cannot handle persistence

Bug #1279106 reported by LVU on 2014-02-11
14
This bug affects 2 people
Affects Status Importance Assigned to Milestone
casper (Ubuntu)
Undecided
Unassigned

Bug Description

I'm making a LiveUSB with xubuntu-13.10-desktop-i386 as one of the OSes. It happens that specifying live-media kernel parameter with UUID breaks the find_cow_device() function in casper-helpers script.

Here are my syslinux params ("break=casper-bottom vga=normal nomodeset" are there for debugging, of course):

    KERNEL /os/xubuntu/casper/vmlinuz
    APPEND file=/os/xubuntu/preseed/xubuntu.seed boot=casper initrd=/os/xubuntu/casper/initrd.lz live-media=/dev/disk/by-uuid/DD9D-5941 live-media-path=os/xubuntu/casper persistent persistent-path=os/xubuntu/casper break=casper-bottom vga=normal nomodeset --

What we get after break:

casper.log:
        Begin: Running /scripts/casper-premount ... done.
        done.
        mount: mounting /dev/sda1 on /casper-rw-backing failed: Device or resource busy
        Warning: Unable to find the persistent medium
        mount: mounting /dev/sda1 on /home-rw-backing failed: Device or resource busy
        Warning: Unable to find the persistent home medium
        /init: line 7: can't open /dev/fd0: No such device or address
        mount: mounting /dev/sda1 on /casper-sn-backing failed: Device or resource busy
        Warning: Impossible to include the casper-sn Snapshot
        /init: line 7: can't open /dev/fd0: No such device or address
        mount: mounting /dev/sda1 on /home-sn-backing failed: Device or resource busy
        Warning: Impossible to include the home-sn Snapshot
        done.
        Begin: Creating debconf-communicate fifo mechanism ... done.
        Spawning shell within the initramfs

/proc/mounts:
        rootfs / rootfs rw 0 0
        sysfs /sys sysfs rw,nosuid,nodev,noexec,relatime 0 0
        proc /proc proc rw,nosuid,nodev,noexec,relatime 0 0
        udev /dev devtmpfs rw,relatime,size=503316k,nr_inodes=125829,mode=755 0 0
        devpts /dev/pts devpts rw,nosuid,noexec,relatime,gid=5,mode=620,ptmxmode=000 0 0
        tmpfs /run tmpfs rw,nosuid,noexec,relatime,size=102640k,mode=755 0 0
        /dev/disk/by-uuid/DD9D-5941 /cdrom vfat ro,noatime,fmask=0022,dmask=0022,codepage=437,iocharset=iso8859-1,shortname=mixed,errors=remount-ro 0 0
        /dev/loop0 /root/rofs squashfs ro,noatime 0 0
        tmpfs /cow tmpfs rw,noatime,mode=755 0 0
        /cow /root overlayfs rw,relatime,lowerdir=//filesystem.squashfs,upperdir=/cow 0 0

I've investigated the issue; the source of the problem is that the where_is_mounted() function in casper-helpers doesn't recognize that /dev/disk/by-uuid/DD9D-5941 is a symlink to /dev/sda1, and thus the try_mount() function attempts to do an actual mount instead of bind, which, of course, fails.

The solution to this should be replacing the live-media argument with uuid, like this:

       APPEND file=/os/xubuntu/preseed/xubuntu.seed boot=casper initrd=/os/xubuntu/casper/initrd.lz uuid=DD9D-5941 live-media-path=os/xubuntu/casper persistent persistent-path=os/xubuntu/casper break=casper-bottom vga=normal nomodeset --

so that casper looks for the proper block device by itself. But this doesn't work either. In this case we repeatedly get the following lines in the console:

        calling: test-builtin
        error reading /lib/udev/hwdb.bin: No such file or directory
        load module index
        unload module index

After lots of repetitions, we finally get the "Unable to find a medium containing a live file system" message.

This happens in the is_nice_device() function of casper script, when executing "udevadm test-builtin path_id". Adding the hwdb.bin file from squashfs to the initrd.lz doesn't help either. Looks like casper isn't compatible with the current udevadm.

The provided patch addresses both these issues, although I'm not sure if the second one is solved correctly. Please take a look.

LVU (valentin-lavrinenko) wrote :
LVU (valentin-lavrinenko) wrote :

Sorry, wrong patch :( Here is the correct one.

The attachment "casper-initrd.patch" seems to be a patch. If it isn't, please remove the "patch" flag from the attachment, remove the "patch" tag, and if you are a member of the ~ubuntu-reviewers, unsubscribe the team.

[This is an automated message performed by a Launchpad user owned by ~brian-murray, for any issues please contact him.]

tags: added: patch
Launchpad Janitor (janitor) wrote :

Status changed to 'Confirmed' because the bug affects multiple users.

Changed in casper (Ubuntu):
status: New → Confirmed
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