Provided by: fsvs_1.2.6-3_amd64 
NAME
HOWTO: Master/Local repositories -
This HOWTO describes how to use a single working copy with multiple repositories. This HOWTO describes
how to use a single working copy with multiple repositories.
Please read the HOWTO: Backup first, to know about basic steps using FSVS.
Rationale
If you manage a lot of machines with similar or identical software, you might notice that it's a bit of
work keeping them all up-to-date. Sure, automating distribution via rsync or similar is easy; but then
you get identical machines, or you have to play with lots of exclude patterns to keep the needed
differences.
Here another way is presented; and even if you don't want to use FSVS for distributing your files, the
ideas presented here might help you keep your machines under control.
Preparation, repository layout
In this document the basic assumption is that there is a group of (more or less identical) machines, that
share most of their filesystems.
Some planning should be done beforehand; while the ideas presented here might suffice for simple
versioning, your setup can require a bit of thinking ahead.
This example uses some distinct repositories, to achieve a bit more clarity; of course these can simply
be different paths in a single repository (see Using a single repository for an example configuration).
Repository in URL base:
trunk/
bin/
ls
true
lib/
libc6.so
modules/
sbin/
mkfs
usr/
local/
bin/
sbin/
tags/
branches/
Repository in URL machine1 (similar for machine2):
trunk/
etc/
HOSTNAME
adjtime
network/
interfaces
passwd
resolv.conf
shadow
var/
log/
auth.log
messages
tags/
branches/
User data versioning
If you want to keep the user data versioned, too, a idea might be to start a new working copy in every
home directory; this way
• the system- and (several) user-commits can be run in parallel,
• the intermediate home directory in the repository is not needed, and
• you get a bit more isolation (against FSVS failures, out-of-space errors and similar).
• Furthermore FSVS can work with smaller file sets, which helps performance a bit (less dentries to cache
at once, less memory used, etc.).
A/
Andrew/
.bashrc
.ssh/
.kde/
Alexander/
.bashrc
.ssh/
.kde/
B/
Bertram/
A cronjob could simply loop over the directories in /home, and call fsvs for each one; giving a target
URL name is not necessary if every home-directory is its own working copy.
Note:
URL names can include a forward slash / in their name, so you might give the URLs names like
home/Andrew - although that should not be needed, if every home directory is a distinct working copy.
Using master/local repositories
Imagine having 10 similar machines with the same base-installation.
Then you install one machine, commit that into the repository as base/trunk, and make a copy as
base/released.
The other machines get base/released as checkout source, and another (overlaid) from eg. machine1/trunk.
Per-machine changes are always committed into the machineX/trunk of the per-machine repository; this
would be the host name, IP address, and similar things.
On the development machine all changes are stored into base/trunk; if you're satisfied with your changes,
you merge them (see Branching, tagging, merging) into base/released, whereupon all other machines can
update to this latest version.
So by looking at machine1/trunk you can see the history of the machine-specific changes; and in
base/released you can check out every old version to verify problems and bugs.
Note:
You can take this system a bit further: optional software packages could be stored in other subtrees.
They should be of lower priority than the base tree, so that in case of conflicts the base should
always be preferred (but see 1).
Here is a small example; machine1 is the development machine, machine2 is a client.
machine1$ fsvs urls name:local,P:200,svn+ssh://lserver/per-machine/machine1/trunk
machine1$ fsvs urls name:base,P:100,http://bserver/base-install1/trunk
# Determine differences, and commit them
machine1$ fsvs ci -o commit_to=local /etc/HOSTNAME /etc/network/interfaces /var/log
machine1$ fsvs ci -o commit_to=base /
Now you've got a base-install in your repository, and can use that on the other machine:
machine2$ fsvs urls name:local,P:200,svn+ssh://lserver/per-machine/machine2/trunk
machine2$ fsvs urls name:base,P:100,http://bserver/base-install1/trunk
machine2$ fsvs sync-repos
# Now you see differences of this machines' installation against the other:
machine2$ fsvs st
# You can see what is different:
machine2$ fsvs diff /etc/X11/xorg.conf
# You can take the base installations files:
machine2$ fsvs revert /bin/ls
# And put the files specific to this machine into its repository:
machine2$ fsvs ci -o commit_to=local /etc/HOSTNAME /etc/network/interfaces /var/log
Now, if this machine has a harddisk failure or needs setup for any other reason, you boot it (eg. via
PXE, Knoppix or whatever), and do (3)
# Re-partition and create filesystems (if necessary)
machine2-knoppix$ fdisk ...
machine2-knoppix$ mkfs ...
# Mount everything below /mnt
machine2-knoppix$ mount <partition[s]> /mnt/[...]
machine2-knoppix$ cd /mnt
# Do a checkout below /mnt
machine2-knoppix$ fsvs co -o softroot=/mnt <urls>
Branching, tagging, merging
Other names for your branches (instead of trunk, tags and branches) could be unstable, testing, and
stable; your production machines would use stable, your testing environment testing, and in unstable
you'd commit all your daily changes.
Note:
Please note that there's no merging mechanism in FSVS; and as far as I'm concerned, there won't be.
Subversion just gets automated merging mechanisms, and these should be fine for this usage too. (4)
Thoughts about tagging
Tagging works just like normally; although you need to remember to tag more than a single branch. Maybe
FSVS should get some knowledge about the subversion repository layout, so a fsvs tag would tag all
repositories at once? It would have to check for duplicate tag-names (eg. on the base -branch), and just
keep it if it had the same copyfrom-source.
But how would tags be used? Define them as source URL, and checkout? Would be a possible case.
Or should fsvs tag do a merge into the repository, so that a single URL contains all files currently
checked out, with copyfrom-pointers to the original locations? Would require using a single repository,
as such pointers cannot be across different repositories. If the committed data includes the
$FSVS_CONF/.../Urls file, the original layout would be known, too - although to use it a sync-repos would
be necessary.
Using a single repository
A single repository would have to be partitioned in the various branches that are needed for bookkeeping;
see these examples.
Depending on the number of machines it might make sense to put them in a 1- or 2 level deep hierarchy;
named by the first character, like
machines/
A/
Axel/
Andreas/
B/
Berta/
G/
Gandalf/
Simple layout
Here only the base system gets branched and tagged; the machines simply backup their specific/localized
data into the repository.
# For the base-system:
trunk/
bin/
usr/
sbin/
tags/
tag-1/
branches/
branch-1/
# For the machines:
machines/
machine1/
etc/
passwd
HOSTNAME
machine2/
etc/
passwd
HOSTNAME
Per-area
Here every part gets its trunk, branches and tags:
base/
trunk/
bin/
sbin/
usr/
tags/
tag-1/
branches/
branch-1/
machine1/
trunk/
etc/
passwd
HOSTNAME
tags/
tag-1/
branches/
machine2/
trunk/
etc/
passwd
HOSTNAME
tags/
branches/
Common trunk, tags, and branches
Here the base-paths trunk, tags and branches are shared:
trunk/
base/
bin/
sbin/
usr/
machine2/
etc/
passwd
HOSTNAME
machine1/
etc/
passwd
HOSTNAME
tags/
tag-1/
branches/
branch-1/
Other notes
1
Conflicts should not be automatically merged. If two or more trees bring the same file, the file from the
highest tree wins - this way you always know the file data on your machines. It's better if a single
software doesn't work, compared to a machine that no longer boots or is no longer accessible (eg. by
SSH)).
So keep your base installation at highest priority, and you've got good chances that you won't loose
control in case of conflicting files.
2
If you don't know which files are different in your installs,
• install two machines,
• commit the first into fsvs,
• do a sync-repos on the second,
• and look at the status output.
3
As debian includes FSVS in the near future, it could be included on the next KNOPPIX, too!
Until then you'd need a custom boot CD, or copy the absolute minimum of files to the harddisk before
recovery.
There's a utility svntar available; it allows you to take a snapshot of a subversion repository directly
into a .tar -file, which you can easily export to destination machine. (Yes, it knows about the meta-data
properties FSVS uses, and stores them into the archive.)
4
Why no file merging? Because all real differences are in the per-machine files -- the files that are in
the base repository are changed only on a single machine, and so there's an unidirectional flow.
BTW, how would you merge your binaries, eg. /bin/ls?
Feedback
If you've got any questions, ideas, wishes or other feedback, please tell us in the mailing list users
[at] fsvs.tigris.org.
Thank you!
Author
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Version trunk:2424 11 Mar 2010 FSVS - Master/Local HOWTO(5)