[Bug 1731211] [NEW] systemd breaks interface configuration due to late resolv.conf

Hadmut Danisch hadmut at danisch.de
Thu Nov 9 11:03:20 UTC 2017 

Public bug reported:

Hi,

I have configured a linux bridge (vlan0) for virtual machines in
/etc/network/interfaces.d/vlan0. The usual configuration including to
start dnasmasq as a dhcp and dns server for that network.

With 17.10 that fails, systemd can't start networking.service

# systemctl |fgrep networking.service                          
● networking.service                                                                        loaded failed failed    Raise network interfaces           


systemctl status networking.service 
● networking.service - Raise network interfaces
   Loaded: loaded (/lib/systemd/system/networking.service; enabled; vendor preset: enabled)
   Active: failed (Result: exit-code) since Thu 2017-11-09 10:16:02 CET; 1h 35min ago
     Docs: man:interfaces(5)
 Main PID: 1938 (code=exited, status=1/FAILURE)
      CPU: 257ms

Nov 09 10:15:59 pcdanisch systemd[1]: Starting Raise network interfaces...
Nov 09 10:16:01 pcdanisch ifup[1938]: Waiting for vlan0 to get ready (MAXWAIT is 2 seconds).
Nov 09 10:16:01 pcdanisch ifup[1938]: Set name-type for VLAN subsystem. Should be visible in /proc/net/vlan/config
Nov 09 10:16:01 pcdanisch ifup[1938]: dnsmasq: directory /etc/resolv.conf for resolv-file is missing, cannot poll
Nov 09 10:16:01 pcdanisch ifup[1938]: Failed to bring up vlan0.
Nov 09 10:16:02 pcdanisch systemd[1]: networking.service: Main process exited, code=exited, status=1/FAILURE
Nov 09 10:16:02 pcdanisch systemd[1]: Failed to start Raise network interfaces.
Nov 09 10:16:02 pcdanisch systemd[1]: networking.service: Unit entered failed state.
Nov 09 10:16:02 pcdanisch systemd[1]: networking.service: Failed with result 'exit-code'.


# ls -lF /etc/resolv.conf 
lrwxrwxrwx 1 root root 39 Okt 24 11:58 /etc/resolv.conf -> ../run/systemd/resolve/stub-resolv.conf


As far as I can see at that time of booting, the /etc/resolv.conf shows into a a directory which is not yet created (/run is a tmpfs, thus empty at boot time), and I have seen more trouble caused by this, that there is a certain amount of time in the boot process, where /etc/resolv.conf is neither absent nor readable, but a dangling symlink, causing lots of trouble. 

This construction to have a permanent symlink pointing to nowhere while
booting is broken by design.

Furthermore, it's really difficult to get rid of that filthy systemd
dns. That's really odd stuff.

ProblemType: Bug
DistroRelease: Ubuntu 17.10
Package: systemd 234-2ubuntu12.1
ProcVersionSignature: Ubuntu 4.13.0-16.19-generic 4.13.4
Uname: Linux 4.13.0-16-generic x86_64
NonfreeKernelModules: zfs zunicode zavl zcommon znvpair
ApportVersion: 2.20.7-0ubuntu3.1
Architecture: amd64
CurrentDesktop: XFCE
Date: Thu Nov  9 11:53:46 2017
InstallationDate: Installed on 2017-10-24 (16 days ago)
InstallationMedia: Lubuntu 17.10 "Artful Aardvark" - Release amd64 (20171017.1)
MachineType: To Be Filled By O.E.M. To Be Filled By O.E.M.
ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-4.13.0-16-generic root=UUID=c100cc19-4ea7-4c2c-a2ee-10d8ed40c2e7 ro rootflags=subvol=@ nomodeset quiet splash
SourcePackage: systemd
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 03/16/2016
dmi.bios.vendor: American Megatrends Inc.
dmi.bios.version: P1.50
dmi.board.name: N3150-NUC
dmi.board.vendor: ASRock
dmi.chassis.asset.tag: To Be Filled By O.E.M.
dmi.chassis.type: 3
dmi.chassis.vendor: To Be Filled By O.E.M.
dmi.chassis.version: To Be Filled By O.E.M.
dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvrP1.50:bd03/16/2016:svnToBeFilledByO.E.M.:pnToBeFilledByO.E.M.:pvrToBeFilledByO.E.M.:rvnASRock:rnN3150-NUC:rvr:cvnToBeFilledByO.E.M.:ct3:cvrToBeFilledByO.E.M.:
dmi.product.family: To Be Filled By O.E.M.
dmi.product.name: To Be Filled By O.E.M.
dmi.product.version: To Be Filled By O.E.M.
dmi.sys.vendor: To Be Filled By O.E.M.

** Affects: systemd (Ubuntu)
     Importance: Undecided
         Status: New


** Tags: amd64 apport-bug artful

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https://bugs.launchpad.net/bugs/1731211

Title:
  systemd breaks interface configuration due to late resolv.conf

Status in systemd package in Ubuntu:
  New

Bug description:
  Hi,

  I have configured a linux bridge (vlan0) for virtual machines in
  /etc/network/interfaces.d/vlan0. The usual configuration including to
  start dnasmasq as a dhcp and dns server for that network.

  With 17.10 that fails, systemd can't start networking.service

  # systemctl |fgrep networking.service                          
  ● networking.service                                                                        loaded failed failed    Raise network interfaces           


  systemctl status networking.service 
  ● networking.service - Raise network interfaces
     Loaded: loaded (/lib/systemd/system/networking.service; enabled; vendor preset: enabled)
     Active: failed (Result: exit-code) since Thu 2017-11-09 10:16:02 CET; 1h 35min ago
       Docs: man:interfaces(5)
   Main PID: 1938 (code=exited, status=1/FAILURE)
        CPU: 257ms

  Nov 09 10:15:59 pcdanisch systemd[1]: Starting Raise network interfaces...
  Nov 09 10:16:01 pcdanisch ifup[1938]: Waiting for vlan0 to get ready (MAXWAIT is 2 seconds).
  Nov 09 10:16:01 pcdanisch ifup[1938]: Set name-type for VLAN subsystem. Should be visible in /proc/net/vlan/config
  Nov 09 10:16:01 pcdanisch ifup[1938]: dnsmasq: directory /etc/resolv.conf for resolv-file is missing, cannot poll
  Nov 09 10:16:01 pcdanisch ifup[1938]: Failed to bring up vlan0.
  Nov 09 10:16:02 pcdanisch systemd[1]: networking.service: Main process exited, code=exited, status=1/FAILURE
  Nov 09 10:16:02 pcdanisch systemd[1]: Failed to start Raise network interfaces.
  Nov 09 10:16:02 pcdanisch systemd[1]: networking.service: Unit entered failed state.
  Nov 09 10:16:02 pcdanisch systemd[1]: networking.service: Failed with result 'exit-code'.

  
  # ls -lF /etc/resolv.conf 
  lrwxrwxrwx 1 root root 39 Okt 24 11:58 /etc/resolv.conf -> ../run/systemd/resolve/stub-resolv.conf

  
  As far as I can see at that time of booting, the /etc/resolv.conf shows into a a directory which is not yet created (/run is a tmpfs, thus empty at boot time), and I have seen more trouble caused by this, that there is a certain amount of time in the boot process, where /etc/resolv.conf is neither absent nor readable, but a dangling symlink, causing lots of trouble. 

  This construction to have a permanent symlink pointing to nowhere
  while booting is broken by design.

  Furthermore, it's really difficult to get rid of that filthy systemd
  dns. That's really odd stuff.

  ProblemType: Bug
  DistroRelease: Ubuntu 17.10
  Package: systemd 234-2ubuntu12.1
  ProcVersionSignature: Ubuntu 4.13.0-16.19-generic 4.13.4
  Uname: Linux 4.13.0-16-generic x86_64
  NonfreeKernelModules: zfs zunicode zavl zcommon znvpair
  ApportVersion: 2.20.7-0ubuntu3.1
  Architecture: amd64
  CurrentDesktop: XFCE
  Date: Thu Nov  9 11:53:46 2017
  InstallationDate: Installed on 2017-10-24 (16 days ago)
  InstallationMedia: Lubuntu 17.10 "Artful Aardvark" - Release amd64 (20171017.1)
  MachineType: To Be Filled By O.E.M. To Be Filled By O.E.M.
  ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-4.13.0-16-generic root=UUID=c100cc19-4ea7-4c2c-a2ee-10d8ed40c2e7 ro rootflags=subvol=@ nomodeset quiet splash
  SourcePackage: systemd
  UpgradeStatus: No upgrade log present (probably fresh install)
  dmi.bios.date: 03/16/2016
  dmi.bios.vendor: American Megatrends Inc.
  dmi.bios.version: P1.50
  dmi.board.name: N3150-NUC
  dmi.board.vendor: ASRock
  dmi.chassis.asset.tag: To Be Filled By O.E.M.
  dmi.chassis.type: 3
  dmi.chassis.vendor: To Be Filled By O.E.M.
  dmi.chassis.version: To Be Filled By O.E.M.
  dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvrP1.50:bd03/16/2016:svnToBeFilledByO.E.M.:pnToBeFilledByO.E.M.:pvrToBeFilledByO.E.M.:rvnASRock:rnN3150-NUC:rvr:cvnToBeFilledByO.E.M.:ct3:cvrToBeFilledByO.E.M.:
  dmi.product.family: To Be Filled By O.E.M.
  dmi.product.name: To Be Filled By O.E.M.
  dmi.product.version: To Be Filled By O.E.M.
  dmi.sys.vendor: To Be Filled By O.E.M.

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