How to install dependencies while creating a .deb installer?

Question

I have created a deb package say abc.deb. Now there are few dependencies like python-dev, python-mysql etc., which are needed to be installed as a part of deb installation itself.

(i.e. when user runs dpkg -i abc.deb, the dependencies should also get installed automatically).

I am using a control file which contains few parameters like preinst, postinst etc. I tried to add Depends to the control file, but I guess, Depends only stops package installation if dependencies mentioned are not present. How could I install the dependencies as a part of deb package installation itself? I am looking for a solution that will work on Ubuntu 12.04.

P.S. When I try to install dependencies in my postinst script as

sudo apt-get install python-dev -y

I gives me an error:

E: Could not get lock /var/lib/dpkg/lock - open (11: Resource temporarily unavailable) 
E: Unable to lock the administration directory (/var/lib/dpkg/), is another process using it?`

Answer 1

dpkg can only install single packages.

You should declare all your package's dependencies in the Depends field of the control file.

If your user then installs the package with dpkg -i package.deb, they will get a message that dependencies are missing. The user can then invoke apt-get -f install to fix missing dependencies from the package repository (this assumes that your dependencies actually are in the official repositories).

An alternative is to use a tool such as gdebi to install your package; gdebi knows how to fetch missing dependencies, making the apt-get -f install step unnecessary.

My advice is to ship your package.deb file (with proper dependency declaration) to your users, and advise them to install it with gdebi.