Why can't I use two package managers at the same time?

When you try to start another package manager like ap-get on the console and synaptic at the same time you can get this error:

E: Unable to lock the administration directory (/var/lib/dpkg/), is another process using it?

The reason, cause there are only one package manager on ubuntu, Synaptic, Aptitude, Apt-get, Gnome-App-Install, Adept, etc, all are like front-ends, so there are using the same package manager "dpkg". For these reason you can only use one at the time. If you want, you can install packages with dpkg, but it's a long and tedius process. :-)

I hope it is now clear for you

Regards from Bolivia.

That did help a lot; but still cannot you open two instances of dpkg?

Thanks Mario César Señoranis, that solved my question.

Be welcome, Keep asking this was an Interesting question.

Regards from Bolivia.