I am having a weird problem with mongodb after installation it is ending with a message
invoke-rc.d: unknown initscript, /etc/init.d/mongodb not found.
dpkg
The issue is that you are trying to install a version packaged for Upstart init services, but Debian Squeeze still uses SysV init by default.
There is a note on this in the install docs: http://docs.mongodb.org/manual/tutorial/install-mongodb-on-debian-or-ubuntu-linux/#installing-mongodb
If you are using Debian or Ubuntu that uses SysV style init process, use the following line:
deb http://downloads-distro.mongodb.org/repo/debian-sysvinit dist 10gen