Hi,
Currently systemd is using cgroups kernel interface for process containment.
Cgroups is a very easy solution on linux to handle the double fork used by
daemons, and it can help respawning services in case of self-crash. However
cgroups seems to be the major stopper for systemd to be cross platform.
I'm thinking about an alternative approach for process containment, utilizing
the widely accepted FUSE interface in all major unix systems. Below is a brief
description:
a). A fuse daemon will providing a special file system, let's say /run/initfs
b). For every daemon which needs to be contained, we can start a helper process
first, and open a file in the special file system. For instance, to start
apache daemon, we start the helper and create/open a file "/run/initfs/apache".
Make sure close-on-exit is NOT set on this file descriptor.
c). Fork-exec to start the daemon. Now we can identify all process with
reference to "/run/initfs/apache" as a part of the apache daemon.
Aside from being cross platform, the FUSE interface also gives very powerful
api for many advanced functionalities. This initfs file server is basically an
user space extension of the kernel, just like some normal server in the
microkernels. You could even have multiple instance of such initfs server
running on the same box(using separate vfs/pid namespace to hide them from each
other), thus making init on linux containers much easier.
Any thoughts?
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