Am 27.03.2014 09:41, schrieb Gesh: > Basically, if I understood what happens correctly, the units under /etc/systemd/system/*.wants/ - or their targets, if they're symlinks - replace their corresponding units in the dependency graph. Not exactly. When you place a unit in foo.wants, then foo gets an additional Wants= dependency. Basically, this is a way to extend units with new Wants= and Requires= statements without modifying unit files. You don't *replace* the dependency graph, but *extend* it. > In addition, all unit files are installed to /usr/lib/systemd/system/, Unit files can also be installed to /etc/systemd/system/, for example if you want to use a modified version of a system-supplied unit file. When you run start or enable on a unit name, system looks into those directories, taking the first one it finds. /run/systemd/generator.early /etc/systemd/system /run/systemd/system (*) /run/systemd/generator (*) /usr/lib/systemd/system /run/systemd/generator.late I am not 100% sure if I got the order of the ones marked with (*) right. As you can see here, there are units installed by the package manager (/usr/lib), units installed by the admin (/etc), temporary units installed either by automatic tools or by the admin (/run/systemd/system) and units installed by generators during systemd startup or reload (/run/systemd/generator*). Again, backing up the ones in /usr/lib does not make sense since those are contained in packages and can be reinstalled. Backing up the ones in /run makes no sense either since they only live until you reboot (or reload the configuration, in the case of generator units). However, backing up /etc/systemd/system entirely (not just the symlinks) make lots of sense, since the admin is likely to have custom units in there. > and the symlinks must have the same name as their targets, so only the symlinks' names need to be backed up. Not necessarily. For example, /etc/systemd/system/display-manager.service points to /usr/lib/systemd/system/kdm.service. Most symlinks have the same name, but that's only convention, not necesity. > Therefore, only what's under /etc/systemd/system/ needs to be backed up, ignoring symlinks' targets. I'd back up the symlinks including their targets. This makes it easier to restore configuration. > Besides that, the .wants directories in /usr/lib/systemd/system/ are managed by pacman, and represent upstream decisions to automatically start their units. Indeed.
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