Update wsgi doc with alternative self-made venv

web/wsgi.markdown

@@ -38,17 +38,29 @@ which contains any custom python packages and is activated by our webserver conf
 
 If your app needs custom python packages, please specify them in the
 [requirements file](https://pip.pypa.io/en/stable/reference/requirements-file-format/).
-We will have to generate a new venv should there be any changes,
+Our deployment will install the venv from the requirements.txt and automatically
+generate the freeze.txt file, which contains all package versions installed in the venv.
+The freeze.txt file is needed to reproducibly re-generate the exact state of the venv later,
+please do not modify this file.
+
+Should there be any changes in the requirements.txt file, we will have to generate a new venv,
 so please [[contact us|services/contact]] in that case.
 
-In the future we might provide a way for you to re-generate the venv yourself.
+Alternatively you can use [[SSH access|/web/webshares/#ssh-access]] to generate the venv yourself.
+After logging in via SSH, follow the exact steps below:
+
+```sh
+rm -r private/venv
+python3 -m venv private/venv
+private/venv/bin/pip --no-cache-dir install --upgrade pip setuptools wheel
+private/venv/bin/pip --no-cache-dir install -r private/requirements.txt
+private/venv/bin/pip --no-cache-dir freeze --local > private/freeze.txt
+touch public/*.wsgi
+```
+
 But this should not be needed often, since development should happen on your local machine
 and your app should only be deployed to our server once it is stable.
 
-The freeze file will be automatically generated and contains all package versions installed
-in the venv. It is needed to reproducibly re-generate the exact state of the venv later,
-please do not modify this file.
-
 ## Database
 
 If your app needs a database connection, please directly include the generated YAML settings from your app: