[Bug 1594658] Re: diskless setup with nfs mounted home hangs on shutdown/reboot

[ben thielsen]

it appears that my symptoms also relate to this bug report.  however,
i'd like to add that the feedback provided by the system, at least in my
particular case, is extremely unhelpful.  i think it can be better.

i have a very minimal virtual guest, running 16.04.  it has a "physical"
wired connection, and an nfs mount in fstab:

>cat /etc/fstab 
# /etc/fstab: static file system information.
#
# Use 'blkid' to print the universally unique identifier for a
# device; this may be used with UUID= as a more robust way to name devices
# that works even if disks are added and removed. See fstab(5).
#

# <file system>							<mount point>					<type>		<options>							<dump>  <pass>
proc									/proc							proc		nodev,noexec,nosuid					0		0
LABEL=root								/								ext4		errors=remount-ro					0		1
LABEL=var								/var							ext4		defaults							0		2
LABEL=swap								none							swap		sw									0		0
10.128.35.251:/foo_example_com		/home/foo.example.com			nfs			rw,hard,intr						0		0

>cat /etc/network/interfaces
# This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).

# The loopback network interface
auto lo
iface lo inet loopback

# The primary network interface
auto eth0
iface eth0 inet static
	address		10.101.27.31/24
	gateway		10.101.27.1

in this case, there is no [perceptible] delay during shutdown, but a
lengthy delay at boot, while system waits for mounting to
succeed/timeout.

when there are network problems, the nfs mount attempt cannot succeed,
and this is when the system says "a start job is running for raise
network interfaces", while it sits for five minutes, yet ultimately
proceeds, with a perfectly operational network interface.

this sucks.  while the root cause here, in terms of the actual problem,
is that 1] the nfs mount obviously fails, and 2] the timeout for this
failure is [imho] too long, the troubleshooting process to determine
this was made much longer than it should have been due to the poor
feedback about what was actually happening.

in this particular case, the system should, at the minimum, at least
tell the operator that there is a mount attempt waiting, and ideally,
provide some actual detail about what mount attempt in particular.
saying "a start job is running for raise network interfaces" is woefully
inadequate.

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https://bugs.launchpad.net/bugs/1594658

Title:
  diskless setup with nfs mounted home hangs on shutdown/reboot

Status in nfs-utils package in Ubuntu:
  Confirmed
Status in systemd package in Ubuntu:
  Confirmed

Bug description:
  Ubuntu 16.04 fresh install hangs when shutting down.
  The system is diskless PXE-booted with a couple of nfs mounted directories including homedir.

  As I have no persistent storage whatsoever, I don't have any logs, but
  in debug-shell, running journalctl -f I can see that it hangs at

  [   *] (1 of 2) A stop job running for Raise Network Interfaces (10s / 1min 30s)Jun 20 20:23:05 $hostname kernel: nfs: server $nfs-ip-address not responding, still trying
  Jun 20 20:23:05 $hostname kernel: nfs: server $nfs-ip-address not responding, still trying
  Jun 20 20:23:14 $hostname kernel: nfs: server $nfs-ip-address not responding, still trying
  Jun 20 20:24:08 $hostname kernel: nfs: server $nfs-ip-address not responding, still trying

  Second job in "(1 of 2)" is thermald, turning it off does not fix the problem.
  Also, this counter "(10s / 1min 30s)" stops visually updating.

  server $nfs-ip-address is not responding, because, all network
  interfaces are already down at this point.

  I am not exactly sure why this happens. Looks like there is a wrong
  ordering of shutdown of systemd services, which bring down interfaces
  before something nfs-related, but I am not sure if that's the reason
  of hanging.

  
  Workaround that fixes the problem:
  In /lib/systemd/system/networking.service
  comment following line:
  ExecStop=/sbin/ifdown -a --read-environment

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