Configuration File Version Control

Bazaar Overview

We are using Bazaar to track files in /etc on python.org machines. Bazaar, also known as BZR, is a version-control system written in Python.

The home page for Bazaar is at http://bazaar-vcs.org/.

Bazaar cheatsheet

The command-line interface resembles that of CVS, but the executable is named bzr.

A more detailed introduction to Bazaar's basic features is part of the docs: http://doc.bazaar-vcs.org/bzr.dev/tutorial.htm

To get a list of available subcommands, run bzr help.

To get more details about one particular subcommand, run bzr help <command-name>.

Setting your ID

Bazaar remembers your ID and uses this ID when committing changes. If you're doing stuff as root, this means we won't know who made a particular change.

/usr/bin/bzr is a wrapper script that checks that the ID has been set, reporting an error and stopping when it hasn't been.

To set your ID, set the BZREMAIL environment variable:

export BZREMAIL=admin-person@python.org

Making changes

To commit a change: bzr commit -m "Add new virtual host" /etc

If you omit the path name, committing takes the current working directory as its starting point, so you don't need to supply the path if you're currently in /etc. It's OK to commit only a portion of the tree; if you're in /etc/apache2 and do a commit without specifying the path, you'll only commit changes in /etc/apache2 and its subdirectories.

To back out a change: bzr revert /etc/database.conf restores the last committed version of the file.

The revert` subcommand works recursively on directories, so bzr revert /etc will undo all the changes you've made to the configuration files.

What have I changed?

bzr status lists the names of files that are different from the last committed version:

root@matterhorn:/etc# bzr status
removed:
  nanorc
added:
  vnc.conf
modified:
  syslog.conf
root@matterhorn:/etc#

To get a diff-style display of changes, use bzr diff:

root@matterhorn:/etc# bzr diff |less
=== removed file 'nanorc'
--- nanorc
+++ /dev/null
@@ -1,314 +0,0 @@
-## Sample initialization file for GNU nano
 ...
=== modified file 'syslog.conf'
--- syslog.conf
+++ syslog.conf
@@ -56,16 +56,3 @@
 #      *.=debug;*.=info;\
 #      *.=notice;*.=warn       /dev/tty8

-# The named pipe /dev/xconsole is for the `xconsole' utility.  To use it,
-# you must invoke `xconsole' with the `-file' option:
-#
-#    $ xconsole -file /dev/xconsole [...]
-#
-#
-daemon.*;mail.*;\
-       news.crit;news.err;news.notice;\
-       *.=debug;*.=info;\
-       *.=notice;*.=warn       |/dev/xconsole
-

The --diff-options switch can be used to change the output of the underlying diff program.

Adding/removing files

To begin tracking a new configuration file, it must be added to the repository and then committed:

bzr add /etc/database.conf
bzr commit -m "Add database config" /etc/

If you delete a tracked file using rm, Bazaar will notice it's gone and remove it from the repository when you commit:

root@matterhorn:/etc# rm database.conf
root@matterhorn:/etc# bzr status
removed:
  database.conf
root@matterhorn:/etc# bzr commit -m "Remove file"
missing database.conf
deleted database.conf
Committed revision 9.
root@matterhorn:/etc#

The bzr rm subcommand stops tracking a file, but does **not** remove the working copy in /etc.

Viewing history

bzr log displays all changes that have been made to the tracked files:

root@bag:/etc# bzr log |less
------------------------------------------------------------                   
revno: 3
committer: XXX@python.org
branch nick: etc
timestamp: Sat 2007-03-03 04:14:44 +0100
message:
  Add Apache files
------------------------------------------------------------
revno: 2
committer: XXX@python.org
branch nick: etc
timestamp: Sat 2007-03-03 00:16:43 +0100
message:
  Add a bunch of postfix config files.

...

Initializing a new machine

Here's how to set up the version control on a new system.

1. Initialize the /etc directory as a Bazaar repository.

bzr init /etc

This will create a directory called /etc/.bzr/ that stores the history of changes.

2. Make the 'add' and 'status' subcommands ignore all files by default.

bzr ignore '*'

This prevents a stray bzr add lacking arguments from adding lots and lots of files.

3. Manually add the files you want to track:

bzr add /etc/network/interfaces
bzr add /etc/apache2/httpd.conf
 ...

4. Commit for the first time:

cd /etc
bzr commit -m "Record configuration files"