Using mercurial for configuration files version control

[Jouni Airaksinen]

In one project I had setup for application specific cronjob configurations 
and the jobs were different for each server in the cluster (not equally 
balanced system and some services were fixed to certain servers). It was 
solved so that in the repository had separate files for each server and 
each server was just configured to use those certain files (either 
directly or through symlinks). Then each server cloned/pulled changes from 
one main repository. Whole thing was orchestrated with Capistrano.



From:   FELD Boris <lothiraldan at gmail.com>
To:     Vadym Chepkov <vchepkov at gmail.com>
Cc:     mercurial at selenic.com
Date:   25.11.2010 16.19
Subject:        Re: Using mercurial for configuration files version 
control
Sent by:        mercurial-bounces at selenic.com



Hi,

I am not sure to understand all of your problem, but i can give you my 
point of view.

The situation you describe is a common problem with dcvs where every 
developer must adapt configuration files to his system.

The solution is quite simple, you just track a template version of your 
configuration file.
In your case, the  template version could be very short :
hostname=""
ifconfig_bce0="inet 192.168.17. netmask 255.255.255.0"

You named this file /etc/rc.conf.tpl and track this file into mercurial. 
Then for each node, you create a local file based on this template file.

For the second problem you describe, it's normal. If i resume your 
process, on each node :
- You pull from "master" (rev 1)
- You modify /etc/rc.conf and commit locally (rev 2)
- After a modification on "master" repository, you pull from "master" (rev 
3)

The problem is when you commit locally your changes on /etc/rc.conf, 
master repository not contains this changeset and when you try to update, 
mercurial does not know to which repository to update.
To visualise this situation, go to your local repository, type this 
command "hg serve -v". Then launch your webbrowser and go to this adress : 
 "ht tp://You r_node_adress:8000/graph"

I'm not sure i was clear, i hope it help you 

-- 
FELD Boris
Sent with Sparrow

On jeudi 25 novembre 2010 at 14:54, Vadym Chepkov wrote:
Hi,

I am trying to use mercurial for tracking / populating configuration files 
and I am facing some obstacles I need help to overcome.
The technique works quite well with a standalone host. I usually do this:

cd /etc
hg init 
cat > .hgignore <<EOF
syntax: glob
*
EOF
hg add .hgignore
hg commit -m "Starting with empty set"

Then I add all files I modify to the repository and track changes that 
were made.

Now I want to use this repository to populate configuration among members 
of a cluster, because all changes that are made almost always absolutely 
the same on all nodes.

First challenge - I am not able to clone remote repository into an 
existing /etc directory on a second node - there is no such thing as 
"force", at least I wasn't able to find it.
So, instead, I did hg init on the second node and did hg pull 
ssh://master//etc/ . This concerns me a bit, because the repositories 
don't have a common "parent", don't know how essential this is.
Anyway, all works well until I added /etc/rc.conf into repository. This is 
one of those seldom cases where some lines in the file are different on 
every node.
for example, on master node

hostname="master"
ifconfig_bce0="inet 192.168.17.254 netmask 255.255.255.0"

on slave:
hostname="slave"
ifconfig_bce0="inet 192.168.17.253 netmask 255.255.255.0"

After I pulled form master's mercurial, as expected, overwrote local 
rc.conf, so I modified those few lines in it and committed these changes 
locally, without any future intents to push any local changes back to 
master.

And now I have a second challenge. Now every time I pull from the master 
it creates a new head I have to merge and commit, even changes that has 
nothing to do with rc.conf, but even then, if I just add one single line 
to the end of master's rc.conf, I would expect mercurial to be able to 
duplicate this simple delta without do ing any manual merges.

I realize not many use mercurial this way, so I had to describe the task 
in details, but I don't think I am trying to do something unreasonable and 
would appreciate your advice to how to do it properly.

Thank you,
Vadym Chepkov

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