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calid

Member

Registered: 2013-10-18

Posts: 5

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How are virtual filesystems mounted under systemd?

Hey guys,

I'm trying to understand the systemd boot process, but one thing that has me stumped is where the virtual and boot filesystems (/proc, /run, /sys, /dev, etc) get mounted?

I'm not seeing a systemd .mount unit file for these filesystems anywhere, nor did I see any in systemctl list-unit-files.  I grepped for 'Where=<mountpoint>' recursively on /usr/lib and /etc for each of the mount points, but that didn't bring up anything either.

So it looks like these just opaquely get mounted as part of systemd bootstrapping?  Is that right?

Thanks!

Pse

Member

Registered: 2008-03-15

Posts: 413

Re: How are virtual filesystems mounted under systemd?

AFAIK, systemd takes care of common special filesystems. In fact, when running a systemd container, it takes care of redirecting the host virtual filesystems to the guest, and setting them as read only inside the container. I haven't really checked the source code, but it should be easy to find, I guess.