CUPS Web UI stops responding after a while

[Iiro Laiho]

CUPS Web administration UI available at localhost:631 stops responding after a while. Initially it works fine, but after it has been running for a moment it just shows the "Connection refused" message of the browser. The printing system keeps running otherwise. This is a clean install of Ubuntu. I have installed Seafile from PPA but I don't think it has anything to do with this.

I am unable to find anything relevant from journalctl nor CUPS logs.

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: cups 2.1.3-4
ProcVersionSignature: Ubuntu 4.4.0-36.55-generic 4.4.16
Uname: Linux 4.4.0-36-generic x86_64
ApportVersion: 2.20.1-0ubuntu2.1
Architecture: amd64
CupsErrorLog:

CurrentDesktop: Unity
Date: Mon Sep 12 21:10:33 2016
EcryptfsInUse: Yes
InstallationDate: Installed on 2016-09-12 (0 days ago)
InstallationMedia: Ubuntu 16.04.1 LTS "Xenial Xerus" - Release amd64 (20160719)
Lpstat: Error: command ['lpstat', '-v'] failed with exit code 1: lpstat: No destinations added.
MachineType: Dell Inc. Latitude E6320
Papersize: a4
ProcEnviron:
 LANGUAGE=fi
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=fi_FI.UTF-8
 SHELL=/bin/bash
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-4.4.0-36-generic.efi.signed root=UUID=0b75be02-897e-4a0b-9ff6-441512bb7493 ro quiet splash vt.handoff=7
SourcePackage: cups
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 11/14/2013
dmi.bios.vendor: Dell Inc.
dmi.bios.version: A19
dmi.board.name: 05VMY6
dmi.board.vendor: Dell Inc.
dmi.board.version: A00
dmi.chassis.type: 9
dmi.chassis.vendor: Dell Inc.
dmi.modalias: dmi:bvnDellInc.:bvrA19:bd11/14/2013:svnDellInc.:pnLatitudeE6320:pvr01:rvnDellInc.:rn05VMY6:rvrA00:cvnDellInc.:ct9:cvr:
dmi.product.name: Latitude E6320
dmi.product.version: 01
dmi.sys.vendor: Dell Inc.

[Iiro Laiho (iiro)]

It seems to start responding again if I restart the CUPS service but it seems to clear out after a while anyway. Now I proceed to test if it is CUPS or the networking of the operating system by installing lighttpd and trying if it has the same problem.

[Iiro Laiho (iiro)]

It does not seem to affect lighttpd.

Journalctl did output following when it happened last time:

syys 12 22:03:41 sipuli dhclient[3111]: PRC: Renewing lease on wlp2s0b1.
syys 12 22:03:41 sipuli dhclient[3111]: XMT: Renew on wlp2s0b1, interval 9430ms.
syys 12 22:03:41 sipuli dhclient[3111]: RCV: Reply message on wlp2s0b1 from fe80::924e:2bff:fe5b:9c6e.
syys 12 22:03:41 sipuli NetworkManager[2495]: <info> [1473707021.3234] valid_lft 7200
syys 12 22:03:41 sipuli NetworkManager[2495]: <info> [1473707021.3235] preferred_lft 3600
syys 12 22:03:41 sipuli NetworkManager[2495]: <info> [1473707021.3236] address 2001:14bb:170:83bf::6
syys 12 22:03:41 sipuli NetworkManager[2495]: <info> [1473707021.3236] nameserver 'fe80::924e:2bff:fe5b:9c6e'
syys 12 22:03:41 sipuli NetworkManager[2495]: <info> [1473707021.3237] dhcp6 (wlp2s0b1): state changed bound -> boun
syys 12 22:03:41 sipuli dbus[2491]: [system] Activating via systemd: service name='org.freedesktop.nm_dispatcher' uni
syys 12 22:03:41 sipuli systemd[1]: Starting Network Manager Script Dispatcher Service...
syys 12 22:03:41 sipuli dbus[2491]: [system] Successfully activated service 'org.freedesktop.nm_dispatcher'
syys 12 22:03:41 sipuli systemd[1]: Started Network Manager Script Dispatcher Service.
syys 12 22:03:41 sipuli nm-dispatcher[23149]: req:1 'dhcp6-change' [wlp2s0b1]: new request (1 scripts)
syys 12 22:03:41 sipuli nm-dispatcher[23149]: req:1 'dhcp6-change' [wlp2s0b1]: start running ordered scripts...
syys 12 22:17:01 sipuli CRON[23324]: pam_unix(cron:session): session opened for user root by (uid=0)
syys 12 22:17:01 sipuli CRON[23325]: (root) CMD ( cd / && run-parts --report /etc/cron.hourly)
syys 12 22:17:01 sipuli CRON[23324]: pam_unix(cron:session): session closed for user root
syys 12 22:17:33 sipuli unix_chkpwd[23333]: password check failed for user (il)
syys 12 22:17:33 sipuli compiz[3410]: pam_unix(unity:auth): authentication failure; logname= uid=1000 euid=1000 tty=
syys 12 22:17:39 sipuli compiz[3410]: pam_ecryptfs: seteuid error
syys 12 22:17:39 sipuli compiz[3410]: gkr-pam: unlocked login keyring
syys 12 22:18:59 sipuli systemd[1]: Started CUPS Scheduler.
syys 12 22:19:12 sipuli dbus[2491]: [system] Activating via systemd: service name='org.freedesktop.hostname1' unit='d
syys 12 22:19:12 sipuli systemd[1]: Starting Hostname Service...
syys 12 22:19:13 sipuli dbus[2491]: [system] Successfully activated service 'org.freedesktop.hostname1'
syys 12 22:19:13 sipuli systemd[1]: Started Hostname Service.

[Iiro Laiho (iiro)]

Sorry for this comment flood.

Now I think I have finally solved it out:

If I run cupsd -l in console, it just quits with exit status 0 after a while. If I run it as a service, it exits but goes back on-line immediately after I do something that needs printing service.

It almost looks like there is some kind of resource-saving feature here that does not take the Web UI into account.

This seems to be a duplicate of #1598300 (https://bugs.launchpad.net/ubuntu/+source/cups/+bug/1598300).