This happened to me yesterday on a 16.04 desktop system using update- manager. Apparently failed during setup of package unattended-upgrades.
Below is apt/history.log, apt/term.log, ps and debconf version taken while the GUI has been hanging (greyed out and unresponsive) for ~15 hours. GUI screenshot as shown in attachment. $ tail -4 /var/log/apt/history.log Start-Date: 2017-05-20 21:12:22 Commandline: aptdaemon role='role-commit-packages' sender=':1.438' Upgrade: iproute:amd64 (1:4.3.0-1ubuntu3, 1:4.3.0-1ubuntu3.16.04.1), iproute2:amd64 (4.3.0-1ubuntu3, 4.3.0-1ubuntu3.16.04.1), unattended-upgrades:amd64 (0.90ubuntu0.5, 0.90ubuntu0.6), libjasper1:amd64 (1.900.1-debian1-2.4ubuntu1, 1.900.1-debian1-2.4ubuntu1.1) End-Date: 2017-05-20 21:12:29 $ tail -23 /var/log/apt/term.log Log started: 2017-05-20 21:12:22 (Reading database ... 359114 files and directories currently installed.) Preparing to unpack .../iproute2_4.3.0-1ubuntu3.16.04.1_amd64.deb ... Unpacking iproute2 (4.3.0-1ubuntu3.16.04.1) over (4.3.0-1ubuntu3) ... Preparing to unpack .../iproute_1%3a4.3.0-1ubuntu3.16.04.1_all.deb ... Unpacking iproute (1:4.3.0-1ubuntu3.16.04.1) over (1:4.3.0-1ubuntu3) ... Preparing to unpack .../libjasper1_1.900.1-debian1-2.4ubuntu1.1_amd64.deb ... Unpacking libjasper1:amd64 (1.900.1-debian1-2.4ubuntu1.1) over (1.900.1-debian1-2.4ubuntu1) ... Preparing to unpack .../unattended-upgrades_0.90ubuntu0.6_all.deb ... Unpacking unattended-upgrades (0.90ubuntu0.6) over (0.90ubuntu0.5) ... Processing triggers for man-db (2.7.5-1) ... Processing triggers for libc-bin (2.23-0ubuntu7) ... Processing triggers for systemd (229-4ubuntu17) ... Processing triggers for ureadahead (0.100.0-19) ... Setting up iproute2 (4.3.0-1ubuntu3.16.04.1) ... Setting up iproute (1:4.3.0-1ubuntu3.16.04.1) ... Setting up libjasper1:amd64 (1.900.1-debian1-2.4ubuntu1.1) ... Setting up unattended-upgrades (0.90ubuntu0.6) ... Use of uninitialized value $_[1] in join or string at /usr/share/perl5/Debconf/DbDriver/Stack.pm line 111, <GEN0> line 12. Use of uninitialized value $val in substitution (s///) at /usr/share/perl5/Debconf/Format/822.pm line 83, <GEN7> line 11. Use of uninitialized value $val in concatenation (.) or string at /usr/share/perl5/Debconf/Format/822.pm line 84, <GEN7> line 11. Processing triggers for libc-bin (2.23-0ubuntu7) ... Log ended: 2017-05-20 21:12:29 $ ps aux |grep update miki 5027 0.0 1.2 730908 95960 ? Sl May20 0:20 /usr/bin/python3 /usr/bin/update-manager miki 10100 0.0 0.2 591036 22164 ? Sl May20 0:01 update-notifier $ dpkg -l|grep debconf |head -1 ii debconf 1.5.58ubuntu1 all Debian configuration management system $ lsb_release -a No LSB modules are available. Distributor ID: Ubuntu Description: Ubuntu 16.04.2 LTS Release: 16.04 Codename: xenial ** Attachment added: "Hanging GUI of update-manager" https://bugs.launchpad.net/ubuntu/+source/php7.0/+bug/1646739/+attachment/4880641/+files/Screenshot%20from%202017-05-21%2011-40-19.png -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1646739 Title: "Use of uninitialized value" in debconf via update-manager To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/debconf/+bug/1646739/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs