How do we determine that a specific instance of a filesystem mount is "remote", or even requires a "network"? Consider that the network endpoint might be localhost, a netlink/unix/other socket, or, say, an IP address of the virtual host (practically guaranteed to be there and not truly "remote").
systemd has .mount units which are way more configurable than /etc/fstab lines, so they'd let you, as the administrator, describe the network dependency for that specific instance.
But what if all we have is the filesystem type (e.g. if someone used mount or /etc/fstab)?
Linux doesn't tell us that the filesystem type is a network filesystem. Linux doesn't tell us that the specific mount request for that filesystem type will depend on the "network". Linux doesn't tell us that the specific mount request for that filesystem type will require true network connectivity beyond the machine itself.
So, before/without investing in a long-winded and potentially controversial improvement to Linux, we're stuck with heuristics. And systemd's chosen heuristic is pretty reasonable - match against a list of filesystem types that probably require network connectivity.
If you think that's stupid, how would you solve it?
> How do we determine that a specific instance of a filesystem mount is "remote", or even requires a "network"?
Like systemd authors do! Hard-code the list of them in the kernel, including support for fuse and sshfs. Everything else is pure blasphemy and should be avoided.
Me? I'd have an explicit setting in the mount unit file, with defaults inferred from the device type. I would also make sure to not just randomly add landmines, like systemd-update-done.service. It has an unusual dependency requirements, it runs before the network filesystems but after the local filesystems.
I bet you didn't know about it? It's a service that runs _once_ after a system update. So the effect is that your system _sometimes_ fails to boot.
> systemd has .mount units which are way more configurable than /etc/fstab lines
It's literally the inverse. As in, /etc/fstab has _more_ options than native mount units. No, I'm not joking.
Sounds like your admin, distro, or the systemd team could pay some attention to systemd-update-done.service
The "can only be used in /etc/fstab" systemd settings are essentially workarounds to do those things via fstab (and workaround fstab related issues) rather than depend on other systemd facilities (c.f. systemd-gpt-auto-generator). From a "what can you do in /etc/fstab without knowing systemd is working behind the scenes" point of view, then yes, systemd units are vastly more configurable.
> How do we determine that a specific instance of a filesystem mount is "remote", or even requires a "network"?
The '_netdev' option works a treat on sane systems. From mount(8):
_netdev
The filesystem resides on a device that requires network access
(used to prevent the system from attempting to mount these
filesystems until the network has been enabled on the system).
It should work on SystemD and is documented to in systemd.mount
Mount units referring to local and network file systems are distinguished by their file system type specification. In some cases this is not sufficient (for example network block device based mounts, such as iSCSI), in which case _netdev may be added to the mount option string of the unit, which forces systemd to consider the mount unit a network mount.
but -surprise surprise- it doesn't reliably work as documented because SystemD is full of accidental complexity.
Sure, and systemd would translate that directly into a dependency on network startup, which is precisely equivalent to the approach I mentioned that depends on operator knowledge. It's configuration, not "just works" inference.
> Sure, and systemd would translate that directly into a dependency on network startup...
You'd think so, but the Github Issue linked by GP shows that the machinery is unreliable:
In practice, adding `_netdev` does not always force systemd to [consider the mount unit a network mount], in some instances even showing *both* local and remote ordering. ... This can ultimately result in dependency cycles during shutdown which should not have been there - and were not there - when the units were first loaded.
> ...not "just works" inference.
Given that SystemD can't reliably handle explicit use of _netdev, I'd say it has no hope of reliably doing any sort of "just works" inference.
LFS never had academic, educational, or pedagogical merit. It was always sheer faith that by doing enough busywork (except the truly difficult stuff), something might rub off. Maybe you learn some names of component parts. Components change.
Why do people even begin to believe that a large language model can usefully understand and interpret health data?
Sure, LLM companies and proponents bear responsibility for the positioning of LLM tools, and particularly their presentation as chat bots.
But from a systems point of view, it's hard to ignore the inequity and inconvenience of the US health system driving people to unrealistic alternatives.
(I wonder if anyone's gathering comparable stats on "Doctor LLM" interactions in different countries... there were some interesting ones that showed how "Doctor Google" was more of a problem in the US than elsewhere.)
oh god
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