[Bug 1615021] Comment bridged from LTC Bugzilla
bugproxy
bugproxy at us.ibm.com
Thu Sep 15 21:20:38 UTC 2016
------- Comment From gpiccoli at br.ibm.com 2016-09-15 17:13 EDT-------
> On Tue, Sep 13, 2016 at 06:20:49PM -0000, bugproxy wrote:
[...]
> Based on the feedback from gpiccoli at br.ibm.com, it does not appear that the
> buggy udev rule is blocking progress on this bug.
>
[...]
> > I should also ammend my previous comment by saying, if Canonical has some
> > suggestions of how to gather more information in order to help debug this,
> > they should let us know and we can make test runs for them.
>
> My previous suggestion to gpiccoli on IRC was to modify the initrd to dump
> the state of the udev database at a point after the hang. I haven't seen
> such output attached here; does that mean it's not possible to produce such
> results because the kernel hard locks? Currently the only debugging
> information I've seen is that the /lib/debian-installer/start-udev script
> never returns, but that does not mean the kernel has locked up - it only
> shows that udev believes it has not finished processing. I would still like
> to see a dump of the udev database at the point of the hang, not just a udev
> debug log showing processing up to that point.
>
> Is this problem only reproducible with the X710 ethernet adapter? Is this a
> removable ethernet adapter, and have you tested what happens if it's
> removed? If it's not removable, have you tested what happens if you
> blacklist the i40e driver? The ethernet driver may be a complete red
> herring, and the problem may be with something that normally happens after
> ethernet driver initialization rather than with the ethernet driver itself.
>
> I would also have asked whether this could be an issue with the console
> output being redirected to some different device, but since Guilherme
> indicated that the problem appeared to be racy, with boot to the installer
> sometimes succeeding, that seems unlikely to be the problem.
>
> If you can reproduce this problem with the cloud image from
> <http://cloud-images.ubuntu.com/xenial/current/xenial-server-cloudimg-
> ppc64el-disk1.img>,
> that would present additional debugging opportunities since that uses a
> standard Ubuntu initramfs instead of the installer initramfs and will
> support various 'break=' options to interrupt the boot and introspect the
> system state.
Vorlon, thanks very much for your assistance. In fact, your ideas were
useful and we tried many of them. And finally we seem to have figured
what's going on hehehe
Firstly, our bad trials:
i) "udev info -e" was impossible to accomplish in a bad boot, because
even if I try to run it as one of the first things in init, the system
seems still hangs.
ii) Adding modprobe blacklist to any driver makes things work. In fact,
I added the command-line "vorlon" and it worked too hehehe
iii) I wasn't able to test this Cloud image - never installed this
before, is it a complete functional image? I wondered if it needs to be
write directly on the disk, perhaps...
Anyway, after all the analysis we finally observed something important: by putting any command-line we ended up overwriting the default cmdline, and that was the reason of _any_ command-line worked.
Now, the default cmdline was: "console=hvc0 console=tty1", so I guess the installer was booting normally, but with the output redirected to tty1!
It was that simple mistake that makes things show as hanged. We were reading that default command-line from Petitboot, the ppc64 bootloader.
By the way, you already suggested that might be a console output redirection vorlon, so unfortunately I was unable to figure it until today.
Thanks very much for the help!
Now, let me ask: is it expected that Ubuntu redirects output preferably
to tty1, or to the last "console" presented in cmdline?
Cheers,
Guilherme
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https://bugs.launchpad.net/bugs/1615021
Title:
Unable to network boot Ubuntu 16.04 installer normally on Briggs
Status in busybox package in Ubuntu:
Fix Released
Status in debian-installer package in Ubuntu:
Triaged
Status in systemd package in Ubuntu:
Fix Released
Status in busybox source package in Xenial:
Won't Fix
Status in debian-installer source package in Xenial:
Triaged
Status in systemd source package in Xenial:
Fix Released
Status in busybox source package in Yakkety:
Fix Released
Status in debian-installer source package in Yakkety:
Triaged
Status in systemd source package in Yakkety:
Fix Released
Bug description:
== Comment: #7 - Guilherme Guaglianoni Piccoli <gpiccoli at br.ibm.com> - 2016-08-19 10:08:07 ==
The normal procedure to perform a Netboot installation of Ubuntu 16.04 is to download the latest vmlinux and initrd.gz files available, and kexec them with no parameters (at least in ppc64el).
We're experiencing a strange issue in which the installer freezes
before menus are showed. The system hangs in the point specified
below, right after the i40e driver initialization:
[ 11.052832] i40e 0002:01:00.0 enP2p1s0f0: renamed from eth0
[ 11.073976] i40e 0002:01:00.1 enP2p1s0f1: renamed from eth1
[ 11.117799] i40e 0002:01:00.2 enP2p1s0f2: renamed from eth2
[ 11.225745] i40e 0002:01:00.3 enP2p1s0f3: renamed from eth3
***HANG***
The most difficult part in this issue is that it seems to be a timing
issue/race condition, and many debug trials end up by avoiding the
issue reproduction (heisenbug).
We were successful though in getting logs by booting the kernel with
the command-line "BOOT_DEBUG=2" and by changing the initrd in order to
enable systemd debug; only the files "init" and "start-udev" were
changed in initrd, both attached here.
We've attached here a saved screen session that shows the entire boot
process until it gets flooded with lots of messages like:
"starting '/bin/readlink /etc/udev/rules.d/80-net-setup-link.rules'
'/bin/readlink /etc/udev/rules.d/80-net-setup-link.rules'(err) 'failed to execute '/bin/readlink' '/bin/readlink /etc/
udev/rules.d/80-net-setup-link.rules': No such file or directory'
seq 3244 queued, 'add' 'pci_bus'
starting '/bin/readlink /etc/udev/rules.d/80-net-setup-link.rules'
passed 408 byte device to netlink monitor 0x1003cfe8020seq 3236 running'/bin/readlink /etc/udev/rules.d/80-net-setup-l
ink.rules'(err) 'failed to execute '/bin/readlink' '/bin/readlink /etc/udev/rules.d/80-net-setup-link.rules': No such
file or directory'
'/bin/readlink /etc/udev/rules.d/80-net-setup-link.rules'(err) 'failed to execute '/bin/readlink' '/bin/readlink /etc/
udev/rules.d/80-net-setup-link.rules': No such file or directory'
Process '/bin/readlink /etc/udev/rules.d/80-net-setup-link.rules' failed with exit code 2.
PROGRAM '/bin/readlink /etc/udev/rules.d/80-net-setup-link.rules' /lib/udev/rules.d/73-usb-net-by-mac.rules:6
passed device to netlink monitor 0x1003d01f730
"
Then it keeps hanged in this stage. We re-tested it by changing the
file 73-usb-net-by-mac.rules in initrd, replacing "
/etc/udev/rules.d/80-net-setup-link.rules" to "/lib/udev/rules.d/80
-net-setup-link.rules", since the former does not exist whereas the
latter does. Same issue were observed!
Notice that if we boot the installer with command-line "net.ifnames=0"
or "net.ifnames=1", the problem does not reproduces anymore.
We want to ask Canonical's help in investigating this issue.
Thanks,
Guilherme
SRU INFORMATION for systemd
===========================
Test case:
* Check what happens for uevents on devices which are not USB network interfaces:
udevadm test /sys/devices/virtual/mem/null
udevadm test /sys/class/net/lo
With the current version these will run
PROGRAM '/bin/readlink /etc/udev/rules.d/80-net-setup-link.rules'
/lib/udev/rules.d/73-usb-net-by-mac.rules:6
which is pointless. With the proposed version these should be gone.
* Ensure that the rule still works as intended by connecting an USB
network device that has a permanent MAC address (e. g. Android
tethering uses a temporary MAC): You should get a MAC-based name like
"enx12345678" for it. Now disconnect it again, disable ifnames with
sudo ln -s /dev/null /etc/udev/rules.d/80-net-setup-link.rules
and reconnect the device. You should now get a kernel name like "usb0"
for it.
* Regression potential: Errors in the rule could break persistent
naming - or its disabling - of USB network interfaces. Running the
above test carefully is important to ensure this keeps working. This
has little to no actual effect on anything else on the system (aside
from a performance impact and spamming logs), so overall the
regression potential is low.
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