On Sat, Sep 17, 2022 at 8:35 PM Yuri Kanivetsky <yuri.kanivet...@gmail.com> wrote:
> Hi, > > I've noticed that an Arch Linux package (gnupg) seemingly > automatically enables a socket: > > ln -s "../dirmngr.socket" > "/usr/lib/systemd/user/sockets.target.wants/dirmngr.socket" > > > https://github.com/archlinux/svntogit-packages/commit/e74444a6851881e2cfea37b76cfb16ba97af2fcc > > Before the change they were symlinked to > /etc/systemd/user/sockets.target.wants. > > Later I was told that there's such a thing as preset units (an > undocumented feature?): > > https://bbs.archlinux.org/viewtopic.php?pid=2057758#p2057758 > > The way I understood it, if I put dirmngr.socket at > /usr/lib/systemd/user/sockets.target.wants, it's like adding "enable > dirmngr.service" to the preset policy. In other words, it won't be > enabled by default, and won't be activated on boot unless I do > `systemctl --user preset dirmngr`. > No, everything linked to a <unit>.wants/ directory immediately becomes a Wants= dep of <unit> and is therefore "enabled", it doesn't matter whether that .wants/ is in /etc or /usr/lib or /run. In fact, units linked into /usr/.../*.wants/ are enabled *permanently, *as the sysadmin can no longer `systemctl` disable them at all – they can only be masked. So the Arch change is moving into the opposite direction than what you thought. > Can you clarify this? Are there preset units? Is my understanding of > how they work correct? > It's not entirely correct. Systemd indeed has presets, but they work differently – there are separate config files in /usr/lib/systemd/{user,system}-preset/ that would be read by a `systemctl preset <unit>`. See systemd.preset(5) for details. (For example, https://aur.archlinux.org/cgit/aur.git/tree/?h=softu2f uses presets to enable sockets by default.) So the reason systemctl says "preset: enabled" is *not *because of any existing .wants/ symlinks (those still correspond to the main "enabled" status) – instead it's because the unit doesn't match any .preset files that would disable it (i.e. it only matches the compiled-in default "enable *" preset), and therefore systemctl *would create *a .wants/ symlink from the preset. -- Mantas Mikulėnas
