Update instructions for using a proxy

Update-recommendations-and-troubleshooting.md

@@ -60,8 +60,32 @@ done
 
 # If your Linux server needs to use a proxy to access the internet
 
-* I take you already configured your Linux system so it can install and update packages via your proxy.
+a) company proxy on an other host or
-* [Docker needs to have the proxy configured](https://docs.docker.com/network/proxy/) to be able to pull images
+
+b) a proxy tunneled in via ssh: ```ssh -R 9090:localhost:9090 egw.example.org```
+
+> Following config assumes the proxy is running under ```localhost:9090```, replace that with your host, port and - if necessary credentials (```user:pass@host:port```)
+
+* Configured your Linux system so it can install and update packages via your proxy:
+```
+# /etc/apt/apt.conf.d/proxy.conf
+Acquire::http::Proxy "http://localhost:9090";
+```
+* set environment variables eg. in ```~/.bashrc``` to get eg. curl working:
+```
+export http_proxy=http://localhost:9090
+export https_proxy=http://localhost:9090
+# to import in your running shell use: . ~/.bashrc
+```
+* [Docker needs to have the proxy configured](https://docs.docker.com/config/daemon/systemd/#httphttps-proxy) to be able to pull images:
+```
+# /etc/systemd/system/docker.service.d/http-proxy.conf
+[Service]
+Environment="HTTP_PROXY=http://localhost:9090"
+Environment="HTTPS_PROXY=http://localhost:9090"
+#Environment="NO_PROXY=localhost,127.0.0.1,docker-registry.example.com,.corp"
+# the following will refresh your running docker daemon: systemctl daemon-reload && systemctl restart docker
+```
 * EGroupware can also use a proxy to eg. check for an update. Proxy settings are in Setup (https://example.com/egroupware/setup/) upper login under: Edit current configuration > Host information
 
 # Trouble-shooting a not working installation after the update