"Hacktree" is now known as "OSTree"
It just sounds better.
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Colin Walters committed
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@@ -1,4 +1,4 @@
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Hacktree
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OSTree
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========
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Problem statement
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@@ -48,7 +48,7 @@ Comparison with existing tools
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the old package.
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This is most realistic option for people hacking on system
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components currently, but hacktree will be better.
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components currently, but ostree will be better.
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- LXC / containers
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@@ -66,7 +66,7 @@ Comparison with existing tools
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this means you can't build NetworkManager, and thus are permanently
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stuck on whatever the distro provides.
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Who is hacktree for?
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Who is ostree for?
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------------------------------
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First - operating system developers and testers. I specifically keep
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@@ -103,22 +103,19 @@ Debian). It has a root filesystem like this:
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Now, what we can do is have a system that installs chroots as a subdirectory
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of the root, like:
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/usr
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/etc
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/home
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/gnomeos/root-3.0-opt/{usr,etc,var,...}
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/gnomeos/root-3.2-opt/{usr,etc,var,...}
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/ostree/gnomeos-3.0-opt-393a4555/{usr,etc,sbin,...}
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/ostree/gnomeos-3.2-opt-7e9788a2/{usr,etc,sbin,...}
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These live in the same root filesystem as your regular distribution
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(Note though, the root partition should be reasonably sized, or
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hopefully you've used just one big partition).
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You should be able to boot into one of these roots. Since hacktree
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You should be able to boot into one of these roots. Since ostree
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lives inside a distro created partition, a tricky part here is that we
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need to know how to interact with the installed distribution's grub.
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This is an annoying but tractable problem.
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Hacktree will allow efficiently parallel installing and downloading OS
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OSTree will allow efficiently parallel installing and downloading OS
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builds.
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An important note here is that we explicitly link /home in each root
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@@ -126,6 +123,40 @@ to the real /home. This means you have your data. This also implies
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we share uid/gid, so /etc/passwd will have to be in sync. Probably
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what we'll do is have a script to pull the data from the "host" OS.
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Other shared directories are /var and /root. Note that /etc is
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explicitly NOT shared!
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On a pure OSTree system, the filesystem layout will look like this:
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.
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|-- boot
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|-- home
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|-- ostree
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| |-- current -> gnomeos-3.2-opt-7e9788a2
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| |-- gnomeos-3.0-opt-393a4555
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| | |-- etc
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| | |-- lib
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| | |-- mnt
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| | |-- proc
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| | |-- run
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| | |-- sbin
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| | |-- srv
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| | |-- sys
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| | `-- usr
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| `-- gnomeos-3.2-opt-7e9788a2
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| |-- etc
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| |-- lib
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| |-- mnt
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| |-- proc
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| |-- run
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| |-- sbin
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| |-- srv
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| |-- sys
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| `-- usr
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|-- root
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`-- var
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Making this efficient
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---------------------
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@@ -142,14 +173,14 @@ that point to it. This mutability means that we have to either:
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This is probably tractable over a long period of time, but if anything
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has a bug, then it corrupts the file effectively.
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2. Make the core OS read-only, with a well-defined mechanism for mutating
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under the control of hacktree.
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under the control of ostree.
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I chose 2.
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A userspace content-addressed versioning filesystem
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---------------------------------------------------
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At its very core, that's what hacktree is. Just like git. If you
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At its very core, that's what ostree is. Just like git. If you
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understand git, you know it's not like other revision control systems.
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git is effectively a specialized, userspace filesystem, and that is a
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very powerful idea.
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@@ -162,16 +193,16 @@ source trees - it goes to effort to be sure it's compressing text for
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example, under the assumption that you have a lot of text. Its
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handling of binaries is very generic and unoptimized.
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In contrast, hacktree is explicitly designed for binaries, and in
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In contrast, ostree is explicitly designed for binaries, and in
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particular one type of binary - ELF executables (or it will be once we
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start using bsdiff).
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Another big difference versus git is that hacktree uses hard links
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Another big difference versus git is that ostree uses hard links
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between "checkouts" and the repository. This means each checkout uses
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almost no additional space, and is *extremely* fast to check out. We
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can do this because again each checkout is designed to be read-only.
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So we mentioned above the
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So we mentioned above there are:
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/gnomeos/root-3.0-opt
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/gnomeos/root-3.2-opt
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@@ -206,7 +237,7 @@ change =)
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Atomic upgrades, rollback
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-------------------------
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Hacktree is designed to atomically swap operating systems - such that
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OSTree is designed to atomically swap operating systems - such that
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during an upgrade and reboot process, you either get the full new
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system, or the old one. There is no "Please don't turn off your
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computer". We do this by simply using a symbolic link like:
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@@ -272,13 +303,13 @@ What about "packages"?
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Basically I think they're a broken idea. There are several different
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classes of things that demand targeted solutions:
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1. Managing and upgrading the core OS (hacktree)
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1. Managing and upgrading the core OS (ostree)
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2. Managing and upgrading desktop applications (gnome-shell, glick?)
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3. System extensions - these are arbitrary RPMs like say the nVidia driver.
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We apply them after constructing each root. Media codecs also fall
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into this category.
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How one might install say Apache on top of hacktree is an open
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How one might install say Apache on top of ostree is an open
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question - I think it probably makes sense honestly to ship services
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like this with no configuration - just the binaries. Then admins can
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do whatever they want.
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@@ -286,7 +317,7 @@ do whatever they want.
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Downloads
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---------
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I'm pretty sure hacktree should be significantly better than RPM with
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I'm pretty sure ostree should be significantly better than RPM with
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deltarpms. Note we only download changed objects. If say just one
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translation changes, we only download that new translation! One
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problem we will have to hunt down is programs that inject
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@@ -350,7 +381,7 @@ approach is it doesn't solve the race conditions that happen when
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unpacking packages into the live system. This problem is really
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important to me.
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Note though hacktree can definitely take advantage of BTRFS features!
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Note though ostree can definitely take advantage of BTRFS features!
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In particular, we could use "reflink"
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<http://lwn.net/Articles/331808/> instead of hard links, and avoid
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having the object store corrupted if somehow the files are modified
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@@ -383,7 +414,7 @@ didn't use them:
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- Conary: <http://wiki.rpath.com/wiki/Conary:Updates_and_Rollbacks>
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If rpm/dpkg are like CVS, Conary is closer to Subversion. It's not
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bad, but hacktree is better than it for the exact same reasons git
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bad, but ostree is better than it for the exact same reasons git
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is better than Subversion.
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- BTRFS: <http://en.wikipedia.org/wiki/Btrfs>
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@@ -393,4 +424,4 @@ didn't use them:
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- Jhbuild: <https://live.gnome.org/Jhbuild>
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What we've been using in GNOME, and has the essential property of allowing you
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to "fall back" to a stable system. But hacktree will blow it out of the water.
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to "fall back" to a stable system. But ostree will blow it out of the water.
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