I have a package that previously only targeted RPM based distros for which I am now building .deb packages for Debian based distros.

The aim is to simulate a test installation from user-space that is isolated from the system you are building on. It may be multi-user and you do not want to require root access just to build the software. Many of our tests simulate the installation directory structure already. This is for the next step up to simulate an actual installation using packages built.

For the RPM packages I was able to create test installations using:

```
WSDIR=/where/I/want/my/tests/to/run
rpmdb --initdb --dbpath "$WSDIR"/rpmdb
rpm --relocate /opt="$WSDIR"/opt --dbpath $WSDIR/rpmdb -i <package>.rpm 

```

The equivalent in the Debian world is something like:

```
dpkg --force-not-root --admindir=$WSDIR/dpkg --root=$WSDIR/install --install "$DEB" 

```

However, I am stuck over the equivalent to the `rpmdb --initdb` step.

Note that I can just unpack the archive using:

```
dpkg-deb -x "$DEB" $WSDIR/install

```

But I would prefer to be closer to how a real package is installed.
Also I don't think this will run `preinstall` and `postinstall` scripts.

Similar questions have suggested using `deboostrap` to create a `chroot` environment but this creates a complete new installation. As well as being overkill it is too slow for an automated test. I intend to use this for quick tests of the installation package prior to further testing in actual test environments.

My experiments so far:

```
(cd $WSDIR/dpkg && mkdir alternatives info parts triggers updates)
cp /var/lib/dpkg/status $WSDIR/dpkg/status

```

have at best resulted in:

```
dpkg: error: unable to access dpkg status area: No such file or directory

```

which does not indicate clear what is wrong.

So how **do** you create a dpkg admin directory?

Cross posted as <https://superuser.com/questions/1271145/how-do-you-create-a-dpkg-admin-directory>

---

Update 24/11/2017

I've tried copying using the dpkg dir from an environment created by [cowdancer][1] (which uses deboostrap under the hood) or copying the real one from /var/lib/dpkg but I still get the same error message so perhaps the error (and/or the --admindir option) doesn't mean quite what I think it means.

Note that: 

```
sudo dpkg --force-not-root --root=$WSDIR/install  --admindir=/var/lib/dpkg --install "$DEB"

```

does work. So it is something to do with the admin dir.
I've also retitled the question as "How do you create a dpkg admin directory" is interesting question but the answer is not necessarily the solution to my problem.