[lxc-users] LXC not starting with already mounted LV as read-only mount
Claudio Kuenzler
ck at claudiokuenzler.com
Wed Nov 26 12:29:35 UTC 2014
I made a couple of mistakes in my modified patch - so please ignore
that.But the basic idea of it was to handle special mount flags (in this
case RDONLY) before it hits
if (mount(fsname, target, fstype, mountflags & ~MS_REMOUNT, data))
Will be glad to test additional patches for you.
On Wed, Nov 26, 2014 at 11:19 AM, Claudio Kuenzler <ck at claudiokuenzler.com>
wrote:
> I applied the patch but it does not work for the read only mount.
>
> lxc-start 1416993491.172 INFO lxc_conf -
> conf.c:check_autodev:3821 - Autodev not required.
> lxc-start 1416993491.172 ERROR lxc_conf - conf.c:mount_entry:1916
> - Device or resource busy - failed to mount '/dev/vglxc/apps' on
> '/usr/local/lib/lxc/rootfs/mnt/apps'
>
> I have modified the patch order a bit. Please note that I'm not a
> developer so this might be plain wrong:
>
> 1901 static int mount_entry(const char *fsname, const char *target,
> 1902 const char *fstype, unsigned long mountflags,
> 1903 const char *data, int optional)
> 1904 {
> 1905 #ifdef HAVE_STATVFS
> 1906 struct statvfs sb;
> 1907 #endif
> 1908
> 1909 if ((mountflags & MS_REMOUNT) || (mountflags & MS_BIND)) {
> 1910 DEBUG("remounting %s on %s to respect bind or remount
> options",
> 1911 fsname ? fsname : "(none)", target ? target :
> "(none)");
> 1912 unsigned long rqd_flags = 0;
> 1913 if (mountflags & MS_RDONLY)
> 1914 rqd_flags |= MS_RDONLY;
> 1915
> 1916
> 1917 else if (mount(fsname, target, fstype, mountflags &
> ~MS_REMOUNT, data)) {
> 1918 if (optional) {
> 1919 INFO("failed to mount '%s' on '%s'
> (optional): %s", fsname,
> 1920 target, strerror(errno));
> 1921 return 0;
> 1922 }
> 1923 else {
> 1924 SYSERROR("failed to mount '%s' on '%s'",
> fsname, target);
> 1925 return -1;
> 1926 }
> 1927 }
> 1928
> 1929 #ifdef HAVE_STATVFS
>
> This time the LV was mounted:
>
> lxc-start 1416996121.708 INFO lxc_conf -
> conf.c:check_autodev:3823 - Autodev not required.
> lxc-start 1416996121.708 DEBUG lxc_conf - conf.c:mount_entry:1975
> - mounted '/dev/vglxc/apps' on '/usr/local/lib/lxc/rootfs/mnt/apps', type
> 'ext4'
> lxc-start 1416996121.708 INFO lxc_conf -
> conf.c:mount_file_entries:2224 - mount points have been setup
>
> But I got different errors - which could be because of the modified code
> or because of something else:
>
> lxc-start 1416996121.730 DEBUG lxc_conf -
> conf.c:setup_rootfs_pivot_root:1082 - pivot_root syscall to
> '/usr/local/lib/lxc/rootfs' successful
> lxc-start 1416996121.731 INFO lxc_conf - conf.c:setup_pts:1641 -
> created new pts instance
> lxc-start 1416996121.731 INFO lxc_conf -
> conf.c:setup_personality:1658 - set personality to '0x0'
> lxc-start 1416996121.731 ERROR lxc_conf - conf.c:setup_caps:2339
> - unknown capability mac_admin
> lxc-start 1416996121.731 ERROR lxc_conf - conf.c:lxc_setup:4174 -
> failed to drop capabilities
> lxc-start 1416996121.731 ERROR lxc_start - start.c:do_start:688 -
> failed to setup the container
> lxc-start 1416996121.731 ERROR lxc_sync - sync.c:__sync_wait:51 -
> invalid sequence number 1. expected 2
> lxc-start 1416996121.731 WARN lxc_conf -
> conf.c:lxc_delete_network:3175 - failed to remove interface '(null)'
> lxc-start 1416996121.758 ERROR lxc_start -
> start.c:__lxc_start:1088 - failed to spawn 'mycontainer'
> lxc-start 1416996121.759 WARN lxc_commands -
> commands.c:lxc_cmd_rsp_recv:172 - command get_init_pid failed to receive
> response
> lxc-start 1416996121.759 WARN lxc_cgmanager -
> cgmanager.c:cgm_get:963 - do_cgm_get exited with error
> lxc-start 1416996126.764 ERROR lxc_start_ui -
> lxc_start.c:main:342 - The container failed to start.
> lxc-start 1416996126.765 ERROR lxc_start_ui -
> lxc_start.c:main:344 - To get more details, run the container in foreground
> mode.
> lxc-start 1416996126.765 ERROR lxc_start_ui -
> lxc_start.c:main:346 - Additional information can be obtained by setting
> the --logfile and --logpriority options.
>
> Will try to redo this in a clean installation.
>
> On Wed, Nov 26, 2014 at 7:31 AM, Claudio Kuenzler <ck at claudiokuenzler.com>
> wrote:
>
>> I've read that mailing list post yesterday, too and was actually hoping
>> this could solve the mount issue. When I looked at it, it seems that this
>> patch hasnt been merged into the github repo yet, correct?
>>
>> Will try it and let you know.
>> On Nov 26, 2014 6:35 AM, "Serge Hallyn" <serge.hallyn at ubuntu.com> wrote:
>>
>>> Quoting Claudio Kuenzler (ck at claudiokuenzler.com):
>>> > Hello all,
>>> >
>>> > OS: Ubuntu 14.04.1 LTS
>>> > LXC Version: 1.0.6-0ubuntu0.1
>>> >
>>> > Experienced a weird issue when I tried to launch a container which
>>> mounts
>>> > an additional logical volume (ext4 formatted) through the container's
>>> fstab
>>> > file:
>>> >
>>> > # cat /var/lib/lxc/mycontainer/fstab
>>> > /dev/vglxc/apps mnt/apps ext4 ro 0 0
>>> >
>>> > This LV is already mounted on the physical host:
>>> >
>>> > # mount /dev/vglxc/apps /mnt
>>> >
>>> > Now when I try to launch the container, I get the following error:
>>> >
>>> > # lxc-start -n mycontainer -l trace -o mycontainer.out
>>> > lxc-start: Device or resource busy - failed to mount '/dev/vglxc/apps'
>>> on
>>> > '/usr/lib/x86_64-linux-gnu/lxc/mnt/apps'
>>> > lxc-start: failed to setup the mounts for 'mycontainer'
>>> > lxc-start: failed to setup the container
>>> > lxc-start: invalid sequence number 1. expected 2
>>> > lxc-start: failed to spawn 'mycontainer'
>>> > lxc-start: The container failed to start.
>>> > lxc-start: Additional information can be obtained by setting the
>>> --logfile
>>> > and --logpriority options.
>>> >
>>> > In the output file the following information is shown:
>>> >
>>> > lxc-start 1416921918.699 INFO lxc_conf - Autodev not
>>> required.
>>> > lxc-start 1416921918.699 ERROR lxc_conf - Device or resource
>>> busy
>>> > - failed to mount '/dev/vglxc/apps' on
>>> > '/usr/lib/x86_64-linux-gnu/lxc/mnt/apps'
>>> > lxc-start 1416921918.699 ERROR lxc_conf - failed to setup the
>>> > mounts for 'mycontainer'
>>> >
>>> > When I change the mount option in the container's fstab file from "ro"
>>> to
>>> > "defaults" (or basically "rw"), the container starts up:
>>> >
>>> > # cat /var/lib/lxc/mycontainer/fstab
>>> > /dev/vglxc/apps mnt/apps ext4 defaults 0 0
>>> >
>>> > # lxc-start -n mycontainer -l trace -o mycontainer.out
>>> >
>>> > lxc-start 1416921799.912 INFO lxc_conf - Autodev not
>>> required.
>>> > lxc-start 1416921799.912 DEBUG lxc_conf - mounted
>>> > '/dev/vglxc/apps' on '/usr/lib/x86_64-linux-gnu/lxc/mnt/apps', type
>>> 'ext4'
>>> >
>>> > If the LV /dev/vglxc/apps is nowhere mounted yet, the container starts
>>> up -
>>> > with the read only mount option, too.
>>> >
>>> > Is this a (known) bug I ran into?
>>>
>>> I think it is. Can you please try with this patch:
>>>
>>>
>>> https://lists.linuxcontainers.org/pipermail/lxc-devel/2014-November/010876.html
>>>
>>> applied?
>>> _______________________________________________
>>> lxc-users mailing list
>>> lxc-users at lists.linuxcontainers.org
>>> http://lists.linuxcontainers.org/listinfo/lxc-users
>>
>>
>
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