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by cyphar 3780 days ago
> I'm talking about systemd inside a container (as pid 1). I think that's the part that's not working.

Ah sorry, I misunderstood. I'm not sure why you'd want to use systemd as your process manager in a container. systemd has a very "monolithic" view of the system and I'm not sure you gain much by using systemd over supervisord (I'd argue you lose simplicity for useless complexity).

> Overlayfs is still causing some problems though.

I've been looking into overlayfs and I really encourage you to not use it. There have been an endless stream of bugs that the Docker community has discovered in overlayfs, and as far as I can see the maintainer is not particularly responsive. There's also some other issues (not being POSIX complete) which are pretty much unresolvable without redesigning it.
1 comments
sandGorgon 3780 days ago
Whoa... Thank you so much for pointing out the issue with overlays. There seems to be no real consensus on what should be used. Could you talk about what should be used?

Just FYI - we use Debian on Linode.

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cyphar 3780 days ago
Devicemapper works (make sure you don't use loop devices) okay. Unfortunately it's slow to warm up, but it's probably the most tested storage driver (it's the default on a bunch of systems).

btrfs works pretty well and is quite a bit faster. It's the default for SLE and openSUSE (as well as other distros which use btrfs by default). I'd recommend it (but I can't remember if it requires you to use btrfs on your / partition, which might be an issue for you).

ZFS, while being an awesome filesystem, I doubt has had much testing under Docker, so I'd be wary about using it.

And I've already told you what I thought about overlay. I'd like to point out that it's a good filesystem for what it was designed for (persistent or transient livecds) but the hacks in Docker in order to use it for their layering keeps me up at night.

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sandGorgon 3780 days ago
Yeah - all of which mean that I have to move away from Linode. They can't backup anything other than a vanilla ext4 volume. I setup a direct lvm docker vm on Linode (was surprisingly easy) - but Linode is refusing to back it up.

Oh well, should have done this long ago.

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cyphar 3780 days ago
If Linode supports ZFS, you could use ZFS send-recieve to make backups to your local machine. But like I said, the ZFS storage driver probably hasn't been well tested.
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sandGorgon 3780 days ago
nope. no backup for anything other than EXT4. Its really weird and limiting. I mean LVM volumes have to be pretty standard right ? (I would argue more standard than ZFS).
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