Bug#857743: reason for kernel-panic

[Martin Pitt]

Hello Andreas,

Andreas Glaeser [2017-03-17  8:31 +0100]:
> I am not convinced, that what you claim is true, since the 
> hybrid-filesystem-concept
> worked on pure debian-stable

For some value of "works" -- the change between stable and testing (and perhaps
some backports) is that some libraries in /usr are now required during boot.
The initramfs has mounted /usr since before Jessie, which helped a lot with
the countless big and small bugs that occur from the / vs. /usr split. (The
/usr merge, once it lands, will fix this once and for all.)

> You can have /usr in a separate partition, the symlink-workaroud to 
> BTRFS-constraints
> should also be workable.

As Felipe explained, this will only work if your initrd then also mounts the
file system that /usr points to.

> Please don't try to shine your communication-problems by giving me incorrect 
> facts.

This is a totally inappropriate ad-hominem attack. Once more and we will ignore
further bug reports from you.

> > In this configuration /usr is a regular dir on the root filesystem.
> > What caused the earlier problem was having /usr being a symlink to
> > something that was not mounted by the initramfs. Debian does not
> > support such configurations[1]. While you are using an initramfs, your
> > configuration is such that the initramfs does not mount the filesystem
> > that will end up being seen in /usr.
> > 
> > I'm now closing this bug, as it appears the root cause is an
> > unsupported configuration.

This is totally correct information, not a "communication problem".

Martin

Bug#857743: reason for kernel-panic

[Andreas Glaeser]

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I am not convinced, that what you claim is true, since the 
hybrid-filesystem-concept
worked on pure debian-stable, it should be workable with backports included and 
on current
testing, too.
You can have /usr in a separate partition, the symlink-workaroud to 
BTRFS-constraints
should also be workable.
I will make a KVM-image with an hybrid filesystem in order to prove, that this 
is not an
unsupported concept, but Debian is currently suffering from some severe 
regressions in
the field of md-raid. md-raid has never been workable very well in asymmetric
configurations at least from my own experience.
Please don't try to shine your communication-problems by giving me incorrect 
facts.

 


On Thu, 16 Mar 2017 10:07:05 -0300
Felipe Sateler  wrote:

> On Thu, Mar 16, 2017 at 5:09 AM, Andreas Glaeser
>  wrote:
> > Now I was sitting down again to install without md-raid and without 
> > XFS-root.
> > I can reconfirm, that the described problem does not appear with BTRFS-raid 
> > only:
> >  
> >> /dev/sda5  btrfs 46872576 2298224  44044944   5% /
> >> udev   devtmpfs 10240   0 10240   0% /dev
> >> tmpfs  tmpfs   7694288936760492   2% /run
> >> tmpfs  tmpfs  1923568   0   1923568   0% /dev/shm
> >> tmpfs  tmpfs 5120   0  5120   0% /run/lock
> >> tmpfs  tmpfs  1923568   0   1923568   0% /sys/fs/cgroup
> >> /dev/sda6  btrfs 742174721280  72051712   1% /home
> >> /dev/sda1  xfs 972460   88268884192  10% /boot
> >> /dev/sdb1  xfs   30712168 3630772  27081396  12% /mnt/usb  
> 
> In this configuration /usr is a regular dir on the root filesystem.
> What caused the earlier problem was having /usr being a symlink to
> something that was not mounted by the initramfs. Debian does not
> support such configurations[1]. While you are using an initramfs, your
> configuration is such that the initramfs does not mount the filesystem
> that will end up being seen in /usr.
> 
> I'm now closing this bug, as it appears the root cause is an
> unsupported configuration. Please reopen if you can reproduce the
> issue with other configuration that does not involve /usr as a
> symlink.
> 
> 
> [1]
> https://www.debian.org/releases/stretch/amd64/release-notes/ch-information.en.html#late-mounting-usr
> 

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Bug#857743: reason for kernel-panic

[Andreas Glaeser]

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Now I was sitting down again to install without md-raid and without XFS-root.
I can reconfirm, that the described problem does not appear with BTRFS-raid 
only:

> /dev/sda5  btrfs 46872576 2298224  44044944   5% /
> udev   devtmpfs 10240   0 10240   0% /dev
> tmpfs  tmpfs   7694288936760492   2% /run
> tmpfs  tmpfs  1923568   0   1923568   0% /dev/shm
> tmpfs  tmpfs 5120   0  5120   0% /run/lock
> tmpfs  tmpfs  1923568   0   1923568   0% /sys/fs/cgroup
> /dev/sda6  btrfs 742174721280  72051712   1% /home
> /dev/sda1  xfs 972460   88268884192  10% /boot
> /dev/sdb1  xfs   30712168 3630772  27081396  12% /mnt/usb

> Disk /dev/mmcblk0: 59.5 GiB, 63864569856 bytes, 124735488 sectors
> Units: sectors of 1 * 512 = 512 bytes
> Sector size (logical/physical): 512 bytes / 512 bytes
> I/O size (minimum/optimal): 512 bytes / 512 bytes
> Disklabel type: dos
> Disk identifier: 0xe2290299
> 
> Device BootStart   End  Sectors  Size Id Type
> /dev/mmcblk0p1  2048  46874623 46872576 22.4G 83 Linux
> /dev/mmcblk0p2  46876670 121094143 74217474 35.4G  5 Extended
> /dev/mmcblk0p5  46876672 121094143 74217472 35.4G 83 Linux
> 
> Disk /dev/sda: 232.9 GiB, 250059350016 bytes, 488397168 sectors
> Units: sectors of 1 * 512 = 512 bytes
> Sector size (logical/physical): 512 bytes / 512 bytes
> I/O size (minimum/optimal): 512 bytes / 512 bytes
> Disklabel type: dos
> Disk identifier: 0x40bc4016
> 
> Device Boot Start   End   Sectors  Size Id Type
> /dev/sda1  * 2048   1953791   1951744  953M 83 Linux
> /dev/sda2 1955838 130861055 128905218 61.5G  5 Extended
> /dev/sda5 1955840  48828415  46872576 22.4G 83 Linux
> /dev/sda648830464 123047935  74217472 35.4G 83 Linux
> /dev/sda7   123049984 130861055   7811072  3.7G 82 Linux swap / Solaris

The setup-history was as follows:

#  btrfs device add -f /dev/mmcblk0p1 /
#  btrfs balance start -v -mconvert=raid1 -dconvert=raid1 /
#  btrfs device add -f /dev/mmcblk0p5 /home
#  btrfs balance start -v -mconvert=raid1 -dconvert=raid1 /home
  (init 6)
#  echo "deb http://ftp2.debian.org/debian jessie-backports main contrib 
non-free"
#  >> /etc/apt/sources.list
#  echo "Package: *" >> /etc/apt/preferences
#  echo "Pin: release a=jessie-backports" >> etc/apt/preferences
#  echo "Pin: release a=jessie-backports" >> /etc/apt/preferences
#  echo "Pin-Priority: 520" >> /etc/apt/preferences
#  echo "alias ate='aptitude'" >> .profile 
#  source .profile 
#  ate update
#  ate upgrade

It is workable now, so the problem may be located in the vicinity of systemd, 
but it
actually does not show without XFS on md-RAID and hybrid filesystem-/.

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