pkgwatch -- A Package Management Wrapper

Introduction

In the past I was trying many different linux distros. Each has its own package management systems: debian has apt, mandrake has urpmi, yellowdog has an apt front-end for rpm, suse has yast... While they all are quite similar and not difficult to use, I found that I often made mistakes because I often forgot which system I was using and the exact commands on that system. Another issue is that I wish I could keep track how I installed/removed those packages. So I wrote a simple wrapper for various package management systems. It serves two purposes:

to free me from remembering the exact commands for different systems
to help me keep track of what packages I installed

For example, when I need to install e.g. vim, I always say pkg-install vim, and the wrapper would invoke aptitude, apt-get or yum depending on the current system.

Installation

download from http://download.river-valley.com/pkgwatch/pkgwatch-1.0.tgz
unpack and run installer (as root):
```
bash INSTALL.sh
```

edit /etc/pkgwatchrc to fit your system. You must set PWTOOL and PWDIR:
- PWTOOL is the name of the package management system on your system. It must be one of the following:
```
aptitude-deb
apt-deb
urpm
yast-rpm
yum-rpm
fink-deb
macports-port
```

PWDIR is a directory to keep track of package installation/removal.

since I use mostly debian-based systems, I set default as follows:
```
PWTOOL=aptitude-deb
PWDIR=/root/config/pkgwatch
```

Usage examples

Instead of listing all the details, I describe the commands I use most frequently and the effect of each command.

pkg-update

Update the package management:

on an apt-based system this is similar to apt-get update
on an yum system this is similar to yum update
on macports (macosx) this is similar to port selfupdate

pkg-install vim

Install package vim. The details of this command will be explained later.

pkg-remove vim

Remove package vim.

pkg-list

List all installed packages on my system:

on deb-based system this is similar to dpkg --get-selections
on rpm-based system this is similar to rpm -qa

pkg-file vim

List all files belonging to package vim.

on deb-based system this is similar to dpkg -L vim
on rpm-based system this is similar to rpm -ql vim

pkg-own /usr/bin/vim

Find which package owns file /usr/bin/vim:

on deb-based system this is similar to dpkg -S /usr/bin/vim
on rpm-based system this is similar to rpm -qf /usr/bin/vim

pkg-info vim

Display info about package vim:

on deb-based system this is similar to dpkg -p vim
on rpm-based system this is similar to rpm -qi vim

pkg-check vim

Check whether package vim is already installed on my system:

on deb-based system this is similar to dpkg -s vim
on rpm-based system this is similar to rpm -q vim

pkg-search vim

Search for all packages containing vim in their name:

on apt-based system this is similar to apt-cache pkgnames vim
on yum-based system this is similar to yum list vim

The above commands don't cover everything, however I find them enough for regular use. If I need something more specific, then I had no choice but use the exact command of the underlying system, for example apt.

Keep track of installed packages

Let's again use examples to illustrate things. Assume we have a fresh debian-based system.In our /etc/pkgwatchrc we have:

PWTOOL=aptitude-deb
PWDIR=/root/config/pkgwatch

Let's install vim:
```
pkg-install vim
```
. This will invoke aptitude install vim to install vim, then create the following files:
- /root/config/pkgwatch/pkglist.0: list of installed packages on the system before installing vim. This happens only when we run pkg-install for the first time.
- /root/config/pkgwatch/pkglist.1: list of packages installed by aptitude:
```
+ vim
+ vim-runtime
```

/root/config/pkgwatch/pkglist.vim: symlink to pkglist.0

Let's try remove vim:
```
pkg-remove vim
```
. This will invoke aptitude purge vim, plus:
- create a file /root/config/pkgwatch/pkglist.2: list of packages removed by aptitude:
```
- vim
- vim-runtime
```

remove the symlink /root/config/pkgwatch/pkglist.vim

While it might looks a bit confusing at the first sight, the concept of this is really simple: anytime we run pkg-install or pkg-remove, a new file pkglist.<number> will be created, with the number increased after each run. The contents of this file is the list of package being installed or removed during that run. Packages marked with + are those that have been installed, and packages marked with - are those that have been removed. Apart from that, during installation a symlink pkglist.<package-name> is created, and during removal that symlink is removed.

So the wrapper works a bit like a poor-man version control on the list of packages installed/removed. By examination of the pkglist.* files, it's easy to find out what I did.

Further notes

The wrapper is rather trivial, there are too many things to be improved and bugs to be fixed. However I find it good enough for my need. If you want to improve the scripts, please go ahead.
It's also easy to add support for a new system. I tried this with fink and macports on macosx, and it took very little effort to get pkgwatch working on macosx.
Some back-ends are out-of-date, since I don't use the underlying system anymore: urpmi, yast, or yum.

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