If you're at all like me, you probably have made customizations to your system from following other HOWTOs and then completely forgotten about what you changed. I find that this can be really inconvenient. Sometimes I follow a HOWTO and it turns out that it doesn't do what I want and I have to change things back, but I don't always remember what I did. Other times I modify configuration files and then forget what I changed in them.
To help deal with this I've written a program called apt-diff that prints out the things that you have modified on your system.
Installation
I have a PPA with packages for Ubuntu 10.04 and later. To install, just run:
Code:
sudo add-apt-repository ppa:tschmelcher/apt-diff
sudo apt-get update
sudo apt-get install apt-diff
Usage
apt-diff can be used in two main ways. You can show all the customizations made to a certain directory, or you can show all the customizations made to a certain package. In both cases you just need to give the name of the directory/package on the command-line.
Here's an example. Recently I customized the CUPS configuration file on my computer to enable printer sharing, but I don't remember what the name of the file is or what I changed in it. All I remember is that the file was in /etc/cups. To see what I changed, I can run:
Which prints:
Code:
Skipping obsolete conffile /etc/cups/acroread.conf owned by cups
Skipping obsolete conffile /etc/cups/mime.convs owned by cups
Skipping obsolete conffile /etc/cups/mime.types owned by cups
Skipping obsolete conffile /etc/cups/oopstops.convs owned by cups
Skipping obsolete conffile /etc/cups/oopstops.types owned by cups
Skipping obsolete conffile /etc/cups/pdftops.conf owned by cups
Skipping obsolete conffile /etc/cups/pstopdf.convs owned by cups
--- /tmp/apt-diff_1000/extracted/cups/etc/cups/cupsd.conf 2011-05-29 23:01:35.000000000 -0700
+++ /etc/cups/cupsd.conf 2011-05-12 21:03:34.000000000 -0700
@@ -1,128 +1,81 @@
-#
-#
-# Sample configuration file for the CUPS scheduler. See "man cupsd.conf" for a
-# complete description of this file.
-#
-
-# Log general information in error_log - change "warn" to "debug"
-# for troubleshooting...
LogLevel warn
-
-# Deactivate CUPS' internal logrotating, as we provide a better one, especially
-# LogLevel debug2 gets usable now
MaxLogSize 0
-
-# Administrator user group...
SystemGroup lpadmin
-
-
-# Only listen for connections from the local machine.
-Listen localhost:631
+# Allow remote access
+Port 631
Listen /var/run/cups/cups.sock
-
-# Show shared printers on the local network.
-Browsing Off
+# Share local printers on the local network.
+Browsing On
BrowseOrder allow,deny
-BrowseAllow all
-BrowseLocalProtocols CUPS dnssd
+BrowseRemoteProtocols
BrowseAddress @LOCAL
-
-# Default authentication type, when authentication is required...
+BrowseLocalProtocols CUPS dnssd
DefaultAuthType Basic
... snip ...
-#
-#
--------------------------------
Found 1 differences between filesystem state and package state
Ignored 10 extra paths not owned by any package
Skipped 2 unverifiable directories
Finished in 1.74972 seconds
The apt-diff output tells me several things:
- There are a bunch of obsolete configuration files. Obsolete configuration files are ones that were used by previous versions of a package but aren't used anymore. These can be ignored, and I could even delete them if I wanted to.
- The /etc/cups/cupsd.conf file has been modified, and apt-diff shows me what the changes are. The changes are displayed in the common "unified diff" format, which is explained on Wikipedia here. It shows me that I replaced Listen localhost:631 with Port 631, I changed some of the browsing options, and (for some crazy reason) I removed all the comments.
(There are some other changes but I've left them out.) - At the end, apt-diff gives me a summary where it tells me how many differences it reported (1) and also certain other things that it ignored or skipped:
- It ignored 10 "extra" paths not owned by any package. Typically this means a configuration file that was manually created from scratch, or perhaps one that was autogenerated. If you want to see the list, you can re-run with the option --no-ignore-extras.
- It skipped 2 unverifiable directories. This simply means a directory where apt-diff can't figure out what is supposed to be inside it, if anything. Usually this means a directory that contains autogenerated or user-created content. If you want to see the list, you can re-run with the option --report-unverifiable.
Of course, the only information I cared about in this case was the change to /etc/cups/cupsd.conf, but apt-diff couldn't have known that so it told me everything about the /etc/cups directory that might be relevant.
Here's another example. I have a web server where I have customized the configuration of Apache, and I don't remember what I did. Let's suppose that I don't even remember where the Apache configuration file was located, but I do at least remember that it was an Apache file. I can give package names to apt-diff instead of a path!
First, I find the list of all Apache packages that are installed, which can be done with dpkg and grep like so:
Code:
dpkg -l | grep apache
Which prints:
Code:
ii apache2 2.2.17-1ubuntu1 Apache HTTP Server metapackage
ii apache2-mpm-prefork 2.2.17-1ubuntu1 Apache HTTP Server - traditional non-threaded model
ii apache2-utils 2.2.17-1ubuntu1 utility programs for webservers
ii apache2.2-bin 2.2.17-1ubuntu1 Apache HTTP Server common binary files
ii apache2.2-common 2.2.17-1ubuntu1 Apache HTTP Server common files
ii libapache2-mod-php5 5.3.5-1ubuntu7.2 server-side, HTML-embedded scripting language (Apache 2 module)
ii libapache2-mod-python 3.3.1-9build2 Python-embedding module for Apache 2
Then I take that list of packages and give it to apt-diff:
Code:
apt-diff apache2 apache2-mpm-prefork apache2-utils apache2.2-bin apache2.2-common libapache2-mod-php5 libapache2-mod-python
Which prints:
Code:
--- /tmp/apt-diff_1000/extracted/apache2.2-common/etc/apache2/envvars 2011-02-22 10:34:51.000000000 -0800
+++ /etc/apache2/envvars 2011-05-07 21:53:36.000000000 -0700
@@ -13,8 +13,8 @@
# Since there is no sane way to get the parsed apache2 config in scripts, some
# settings are defined via environment variables and then used in apache2ctl,
# /etc/init.d/apache2, /etc/logrotate.d/apache2, etc.
-export APACHE_RUN_USER=www-data
-export APACHE_RUN_GROUP=www-data
+export APACHE_RUN_USER=nebula
+export APACHE_RUN_GROUP=nebula
export APACHE_PID_FILE=/var/run/apache2$SUFFIX.pid
export APACHE_RUN_DIR=/var/run/apache2$SUFFIX
export APACHE_LOCK_DIR=/var/lock/apache2$SUFFIX
--------------------------------
Found 1 differences between filesystem state and package state
Skipped 8 unverifiable directories
Skipped 14 unverifiable symbolic links
Finished in 1.31191 seconds
It shows me that I modified /etc/apache2/envvars and changed the user and group. I can also see which of the packages it's in from looking at the first line of the output: the /tmp/apt-diff_1000/extracted/apache2.2-common/etc/apache2/envvars path has the apache2.2-common package name inside it, right after "extracted".
Again, I also get a summary, and this time apt-diff reports 14 unverifiable symbolic links. apt-diff doesn't have a way to check for changes to a symbolic link, so it skips them. Again, the --report-unverifiable option would print the list if I needed to know.
That's all for this HOWTO! I hope apt-diff will be as useful to you as it has been to me. 
You can also read about it at http://randomtristan.blogspot.com/20...-help-you.html.
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Originally Posted by Tristan Schmelcher
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