There's more complexity of course because I only talk about the first of the two solvers apt runs. The first solver marks the changes based on following the graph from the user-initiated actions downward to dependencies, marking Depends for install, Conflicts for remove, and so on.
If that produces any broken packages, the second solver tries to heuristically solve them. It's code has grown over 20 years and we can't reason much about it. Installing chrony manually is somewhat stronger than automatically installing it in the scoring for the solver, shifting the fates a bit. I plan to eventually return to work on a state of the art solver, which will solve all issues (you know what I mean), but so far am lacking time. I've written a bunch of solvers, or problem converters, using z3 and clasp as backends, but I'm struggling a bit with solver runtime, explaining why solving failed, and handling order expectations - more research is needed. Usually those happen in my free time during the christmas break. -- You received this bug notification because you are a member of Ubuntu Touch seeded packages, which is subscribed to apt in Ubuntu. https://bugs.launchpad.net/bugs/2016141 Title: [focal] cannot resolve dependency when installing a package depending on 'chrony' since 245.4-4ubuntu3.21 Status in apt package in Ubuntu: Won't Fix Status in systemd package in Ubuntu: Invalid Status in apt source package in Focal: Won't Fix Status in systemd source package in Focal: Invalid Bug description: Hello, Since the publishing of version 245.4-4ubuntu3.21 on focal-updates, we cannot install our product. Our product depends on specifically chrony for the time-daemon, but apt cannot resolve the dependency anymore when systemd 245.4-4ubuntu3.20 is installed. It might be specific to systemd-timesyncd, or an issue with apt itself but I am not sure. Reproduced using the "hello" package by modifying its dependencies: > root@ubuntu2004:~# apt download hello > Get:1 http://mirrors.ubuntu.com/mirrors.txt Mirrorlist [71 B] > Get:2 http://archive.ubuntu.com/ubuntu focal/main amd64 hello amd64 2.10-2ubuntu2 [28.2 kB] > Fetched 28.3 kB in 0s (95.6 kB/s) > W: Download is performed unsandboxed as root as file '/root/hello_2.10-2ubuntu2_amd64.deb' couldn't be accessed by user '_apt'. - pkgAcquire::Run (13: Permission denied) > root@ubuntu2004:~# dpkg-deb -R hello_2.10-2ubuntu2_amd64.deb hello > root@ubuntu2004:~# sed -i -e '/Depends/s/$/, chrony/' hello/DEBIAN/control > root@ubuntu2004:~# dpkg -b hello/ > dpkg-deb: building package 'hello' in 'hello.deb'. > root@ubuntu2004:~# apt -y install ./hello.deb > Reading package lists... Done > Building dependency tree > Reading state information... Done > Note, selecting 'hello' instead of './hello.deb' > Some packages could not be installed. This may mean that you have > requested an impossible situation or if you are using the unstable > distribution that some required packages have not yet been created > or been moved out of Incoming. > The following information may help to resolve the situation: > > The following packages have unmet dependencies: > hello : Depends: chrony > E: Unable to correct problems, you have held broken packages. The issue can be fixed by upgrading systemd to 245.4-4ubuntu3.21: > root@ubuntu2004:~# apt -y install systemd [...] > Setting up systemd (245.4-4ubuntu3.21) ... > Setting up systemd-timesyncd (245.4-4ubuntu3.21) ... [...] > root@ubuntu2004:~# apt -y install ./hello.deb [...] > The following packages will be REMOVED: > systemd-timesyncd > The following NEW packages will be installed: > chrony hello [...] But that solution is a bit annoying as our customers might not want to upgrade systemd for some reason. OR by manually installing chrony: > root@ubuntu2004:~# apt -y install chrony [...] > The following packages will be REMOVED: > systemd-timesyncd > The following NEW packages will be installed: > chrony [...] > root@ubuntu2004:~# apt -y install ./hello.deb [...] > The following NEW packages will be installed: > hello [...] Conflict with enabled debug logs: > root@ubuntu2004:~# apt -o Debug::pkgProblemResolver=1 install ./hello.deb > Reading package lists... Done > Building dependency tree > Reading state information... Done > Note, selecting 'hello' instead of './hello.deb' > Starting pkgProblemResolver with broken count: 1 > Starting 2 pkgProblemResolver with broken count: 1 > Investigating (0) hello:amd64 < none -> 2.10-2ubuntu2 @un puN Ib > > Broken hello:amd64 Depends on chrony:amd64 < none | 3.5-6ubuntu6.2 @un uH > > Considering chrony:amd64 1 as a solution to hello:amd64 9999 > Re-Instated chrony:amd64 > Investigating (0) systemd-timesyncd:amd64 < 245.4-4ubuntu3.20 -> 245.4-4ubuntu3.21 @ii umU Ib > > Broken systemd-timesyncd:amd64 Conflicts on time-daemon:amd64 < none @un H > > Conflicts//Breaks against version 1:4.2.8p12+dfsg-3ubuntu4.20.04.1 for ntp but that is not InstVer, ignoring > Considering chrony:amd64 1 as a solution to systemd-timesyncd:amd64 14 > Added chrony:amd64 to the remove list > Conflicts//Breaks against version 1:6.2p3-4 for openntpd but that is not InstVer, ignoring > Conflicts//Breaks against version 1.1.8+dfsg1-4build1 for ntpsec but that is not InstVer, ignoring > Conflicts//Breaks against version 1:4.2.8p12+dfsg-3ubuntu4 for ntp but that is not InstVer, ignoring > Conflicts//Breaks against version 3.5-6ubuntu6 for chrony but that is not InstVer, ignoring > Fixing systemd-timesyncd:amd64 via keep of chrony:amd64 > Investigating (1) hello:amd64 < none -> 2.10-2ubuntu2 @un puN Ib > > Broken hello:amd64 Depends on chrony:amd64 < none | 3.5-6ubuntu6.2 @un uH > > Considering chrony:amd64 1 as a solution to hello:amd64 9999 > Considering chrony:amd64 1 as a solution to hello:amd64 9999 > Considering maas:amd64 0 as a solution to hello:amd64 9999 > Re-Instated apparmor:amd64 > Re-Instated liblzo2-2:amd64 > Re-Instated squashfs-tools:amd64 > Re-Instated dbus-user-session:amd64 > Re-Instated snapd:amd64 > Re-Instated maas:amd64 > Investigating (1) maas:amd64 < none -> 1:0.7 @un uN Ib > > Broken maas:amd64 Conflicts on isc-dhcp-server:amd64 < 4.4.1-2.1ubuntu5.20.04.5 @ii mK > > Considering isc-dhcp-server:amd64 0 as a solution to maas:amd64 0 > Holding Back maas:amd64 rather than change isc-dhcp-server:amd64 > Investigating (2) hello:amd64 < none -> 2.10-2ubuntu2 @un puN Ib > > Broken hello:amd64 Depends on chrony:amd64 < none | 3.5-6ubuntu6.2 @un uH > > Considering chrony:amd64 1 as a solution to hello:amd64 9999 > Considering chrony:amd64 1 as a solution to hello:amd64 9999 > Considering maas:amd64 0 as a solution to hello:amd64 9999 > Considering maas:amd64 0 as a solution to hello:amd64 9999 > Done > Some packages could not be installed. This may mean that you have > requested an impossible situation or if you are using the unstable > distribution that some required packages have not yet been created > or been moved out of Incoming. > The following information may help to resolve the situation: > > The following packages have unmet dependencies: > hello : Depends: chrony > E: Unable to correct problems, you have held broken packages. Thank you for any help you can provide on that matter! To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/apt/+bug/2016141/+subscriptions -- Mailing list: https://launchpad.net/~touch-packages Post to : touch-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~touch-packages More help : https://help.launchpad.net/ListHelp
