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Docker applies similar concepts (change management at the file and directory level, a chrootable filesystem as the unit of delivery, atomic and revertable deplo

by shykes 13y ago

Docker applies similar concepts (change management at the file and directory level, a chrootable filesystem as the unit of delivery, atomic and revertable deployments), except it applies them 1 level higher in the stack. Instead of rebooting machines into a new filesystem, docker spawns processes directly into them, using the sandboxing capabilities of the linux kernel. So you get a much more powerful and flexible deployment mechanism. But of course, you need a machine to exist in the first place, which docker isn't designed to do. So OSTree is a good companion for Docker, because you need a machine to run docker. A good workflow is probably: pack the bare minimum on a physical machine, using ostree. Then put everything else into docker containers. That's the approach of new "just enough" distros like CoreOS.

colinwalters 13y ago
Right, this is a pretty good summary (that docker is 1 level above). One fundamental difference is that OSTree has a custom serialization format for trees (inspired by git), whereas from what I can tell from the code, docker is just tar (I assume whatever the host /usr/bin/tar serializes to). For example, OSTree explicitly supports extended attributes, so it can support SELinux (and SMACK). Fedora ships a patched tar but...the tar format is a really serious mess. I would further add though that OSTree does, providing the OS is compatible with it, allow booting a separate "deployment" as a container. So for example if you have Debian in /ostree/deploy/debian/90cd266 while you're booted into /ostree/deploy/fedora/562d0a, you can easily just systemd-nspawn /ostree/deploy/debian/90cd266 and boot the same OS as a container. But the emphasis right now of OSTree is indeed on bare metal deployments, and I'd like to push hard to integrate with package systems.
- shykes 13y ago
  > you can easily just systemd-nspawn /ostree/deploy/debian/90cd266 and boot the same OS as a container Perhaps we should be looking at integrating ostree and docker then? :) > I'd like to push hard to integrate with package systems. How would that integration work exactly?
  - colinwalters 13y ago
    > Perhaps we should be looking at integrating ostree and docker then? :) It might make sense for docker to be able to store containers as OSTree commits in addition to tarfiles. But I haven't used it myself. On the HTTP side, OSTree may be less efficient or more efficient than what docker does on the wire for updates; I don't know. Static deltas will help significantly. > How would that integration work exactly? This section describes it very briefly: https://people.gnome.org/~walters/ostree/doc/adapting-package-manager.html https://people.gnome.org/~walters/ostree/doc/adapting-packag... Basically this is something you can do on a build server or on a client.

by shykes 13y ago

colinwalters 13y ago

Right, this is a pretty good summary (that docker is 1 level above). One fundamental difference is that OSTree has a custom serialization format for trees (inspired by git), whereas from what I can tell from the code, docker is just tar (I assume whatever the host /usr/bin/tar serializes to). For example, OSTree explicitly supports extended attributes, so it can support SELinux (and SMACK). Fedora ships a patched tar but...the tar format is a really serious mess. I would further add though that OSTree does, providing the OS is compatible with it, allow booting a separate "deployment" as a container. So for example if you have Debian in /ostree/deploy/debian/90cd266 while you're booted into /ostree/deploy/fedora/562d0a, you can easily just systemd-nspawn /ostree/deploy/debian/90cd266 and boot the same OS as a container. But the emphasis right now of OSTree is indeed on bare metal deployments, and I'd like to push hard to integrate with package systems.

shykes 13y ago
> you can easily just systemd-nspawn /ostree/deploy/debian/90cd266 and boot the same OS as a container Perhaps we should be looking at integrating ostree and docker then? :) > I'd like to push hard to integrate with package systems. How would that integration work exactly?
- colinwalters 13y ago
  > Perhaps we should be looking at integrating ostree and docker then? :) It might make sense for docker to be able to store containers as OSTree commits in addition to tarfiles. But I haven't used it myself. On the HTTP side, OSTree may be less efficient or more efficient than what docker does on the wire for updates; I don't know. Static deltas will help significantly. > How would that integration work exactly? This section describes it very briefly: https://people.gnome.org/~walters/ostree/doc/adapting-package-manager.html https://people.gnome.org/~walters/ostree/doc/adapting-packag... Basically this is something you can do on a build server or on a client.