11.1. Lesson: Installa QGIS Server

The goal for this lesson: To learn how to install QGIS Server on Debian Stretch. With negligible variations you can also follow it for any Debian based distribution like Ubuntu and its derivatives.

Nota

In Ubuntu you can use your regular user, prepending sudo to commands requiring admin permissions. In Debian you can work as admin (root), without using sudo.

11.1.1. moderate Follow Along: Installa da pacchetti

In this lesson we’re going to do only the install from packages as shown here .

Installa QGIS Server con:

apt install qgis-server
# if you want to install server plugins, also:
apt install python-qgis

QGIS Server should be used in production without QGIS Desktop (with the accompanying X Server) installed on the same machine.

11.1.2. moderate Follow Along: QGIS Server eseguibile

L’eseguibile di QGIS Server è qgis_mapserv.fcgi. Puoi verificare dove è stato installato con find / -name 'qgis_mapserv.fcgi' che dovrebbe rispondere qualcosa di simile /usr/lib/cgi-bin/qgis_mapserv.fcgi.

Se vuoi fare una prova da terminale puoi eseguire /usr/lib/cgi-bin/qgis_mapserv.fcgi` che dovrebbe rispondere qualcosa come:

QFSFileEngine::open: No file name specified
Warning 1: Unable to find driver ECW to unload from GDAL_SKIP environment variable.
Warning 1: Unable to find driver ECW to unload from GDAL_SKIP environment variable.
Warning 1: Unable to find driver JP2ECW to unload from GDAL_SKIP environment variable.
Warning 1: Unable to find driver ECW to unload from GDAL_SKIP environment variable.
Warning 1: Unable to find driver JP2ECW to unload from GDAL_SKIP environment variable.
Content-Length: 206
Content-Type: text/xml; charset=utf-8

<ServiceExceptionReport version="1.3.0" xmlns="https://www.opengis.net/ogc">
 <ServiceException code="Service configuration error">Service unknown or unsupported</ServiceException>
</ServiceExceptionReport>

Questa è una buona cosa, ti dice che sei sulla strada giusta mentre il server sta dicendo che non hai chiesto un servizio supportato. Vedrai in seguito come fare richieste WMS.

11.1.3. Follow Along: Configura il server HTTP

Per accedere da un navigatore internet al server QGIS installato devi utilizzare un server HTTP.

In this lesson we’re going to use the Apache HTTP server, colloquially called Apache.

First we need to install Apache by running the following command in a terminal:

apt install apache2 libapache2-mod-fcgid

You can run QGIS server on your default website, or configure a virtualhost specifically for this, as follows.

Nella cartella /etc/apache2/sites-available crea un file chiamato qgis.demo.conf, con questo contenuto:

<VirtualHost *:80>
  ServerAdmin webmaster@localhost
  ServerName qgis.demo

  DocumentRoot /var/www/html

  # Apache logs (different than QGIS Server log)
  ErrorLog ${APACHE_LOG_DIR}/qgis.demo.error.log
  CustomLog ${APACHE_LOG_DIR}/qgis.demo.access.log combined

  # Longer timeout for WPS... default = 40
  FcgidIOTimeout 120

  FcgidInitialEnv LC_ALL "en_US.UTF-8"
  FcgidInitialEnv PYTHONIOENCODING UTF-8
  FcgidInitialEnv LANG "en_US.UTF-8"

  # QGIS log (different from apache logs) see https://docs.qgis.org/testing/en/docs/user_manual/working_with_ogc/ogc_server_support.html#qgis-server-logging
  FcgidInitialEnv QGIS_SERVER_LOG_FILE /var/log/qgis/qgisserver.log
  FcgidInitialEnv QGIS_SERVER_LOG_LEVEL 0

  FcgidInitialEnv QGIS_DEBUG 1

  # default QGIS project
  SetEnv QGIS_PROJECT_FILE /home/qgis/projects/world.qgs

  # QGIS_AUTH_DB_DIR_PATH must lead to a directory writeable by the Server's FCGI process user
  FcgidInitialEnv QGIS_AUTH_DB_DIR_PATH "/home/qgis/qgisserverdb/"
  FcgidInitialEnv QGIS_AUTH_PASSWORD_FILE "/home/qgis/qgisserverdb/qgis-auth.db"

  # See https://docs.qgis.org/testing/en/docs/user_manual/working_with_vector/supported_data.html#pg-service-file
  SetEnv PGSERVICEFILE /home/qgis/.pg_service.conf
  FcgidInitialEnv PGPASSFILE "/home/qgis/.pgpass"

  # Tell QGIS Server instances to use a specific display number
  FcgidInitialEnv DISPLAY ":99"

  # if qgis-server is installed from packages in debian based distros this is usually /usr/lib/cgi-bin/
  # run "locate qgis_mapserv.fcgi" if you don't know where qgis_mapserv.fcgi is
  ScriptAlias /cgi-bin/ /usr/lib/cgi-bin/
  <Directory "/usr/lib/cgi-bin/">
    AllowOverride None
    Options +ExecCGI -MultiViews -SymLinksIfOwnerMatch
    Order allow,deny
    Allow from all
    Require all granted
  </Directory>

 <IfModule mod_fcgid.c>
 FcgidMaxRequestLen 26214400
 FcgidConnectTimeout 60
 </IfModule>

</VirtualHost>

You can do the above in a linux Desktop system by pasting and saving the above configuration after doing nano /etc/apache2/sites-available/qgis.demo.conf.

Nota

Alcune delle opzioni di configurazione sono spiegate nella sezione server Advanced configuration.

Crea ora la cartella che archivierà i registri di QGIS Server e il database di autenticazione.

mkdir /var/log/qgis/
chown www-data:www-data /var/log/qgis

mkdir /home/qgis/qgisserverdb
chown www-data:www-data /home/qgis/qgisserverdb

Nota

www-data è l’utente Apache su sistemi basati su Debian e Apache deve accedre a queste posizioni o file. I comandi chown www-data ... `` cambiano il proprietario delle rispettive cartelle e file in ``www-data.

Ora puoi abilitare il servizio di rete virtuale, abilitare il modulo fcgid mod se non è già abilitato e riavviare il servizio apache2:

a2enmod fcgid
a2ensite qgis.demo
systemctl restart apache2

Nota

Se hai installato QGIS Server senza eseguire un X server (incluso in Linux Desktop) e se vuoi anche usare il comando `` GetPrint``, allora dovresti installare un server X falso e dire a QGIS Server di usarlo. Puoi farlo eseguendo i seguenti comandi.

Installa xvfb:

apt install xvfb

Cea il file di servizio:

sh -c \
"echo \
'[Unit]
Description=X Virtual Frame Buffer Service
After=network.target

[Service]
ExecStart=/usr/bin/Xvfb :99 -screen 0 1024x768x24 -ac +extension GLX +render -noreset

[Install]
WantedBy=multi-user.target' \
> /etc/systemd/system/xvfb.service"

Abilita, avvia e verifica lo stato di xvfb.service:

systemctl enable xvfb.service
systemctl start xvfb.service
systemctl status xvfb.service

In the above configuration file there’s a FcgidInitialEnv DISPLAY ":99" that tells QGIS Server instances to use display no. 99. If you’re running the Server in Desktop then there’s no need to install xvfb and you should simply comment with # this specific setting in the configuration file. More info at https://www.itopen.it/qgis-server-setup-notes/.

Now that Apache knows that he should answer requests to http://qgis.demo we also need to setup the client system so that it knows who qgis.demo is. We do that by adding 127.0.0.1 qgis.demo in the hosts file. We can do it with sh -c "echo '127.0.0.1 qgis.demo' >> /etc/hosts". Replace 127.0.0.1 with the IP of your server.

Nota

Remember that both the myhost.conf and /etc/hosts files should be configured for our setup to work. You can also test the access to your QGIS Server from other clients on the network (e.g. Windows or macOS machines) by going to their /etc/hosts file and point the myhost name to whatever IP the server machine has on the network. You can be sure that that specific IP is not 127.0.0.1 as that’s the local IP, only accessible from the local machine. On *nix machines the hosts file is located in /etc, while on Windows it’s under the C:\Windows\System32\drivers\etc directory. Under Windows you need to start your text editor with administrator privileges before opening the hosts file.

Puoi testare uno dei server qgis installati con una richiesta http dalla riga di comando curl http://qgis.demo/cgi-bin/qgis_mapserv.fcgi che dovrebbe produrre:

<ServiceExceptionReport version="1.3.0" xmlns="https://www.opengis.net/ogc">
<ServiceException code="Service configuration error">Service unknown or unsupported</ServiceException>
</ServiceExceptionReport>

Nota

curl can be installed with apt install curl.

Apache è ora configurato.

Also, from your web browser you can check the capabilities of the server:

http://qgis.demo/cgi-bin/qgis_mapserv.fcgi?SERVICE=WMS&VERSION=1.3.0&REQUEST=GetCapabilities

11.1.4. moderate Follow Along: Crea un altro virtual host

Crea un altro host virtuale Apache che punta a QGIS Server. Puoi scegliere il nome che preferisci (coco.bango, super.duper.training, example.com, etc.) ma per semplicità userai myhost.

  • Let’s set up the myhost name to point to the localhost IP by adding 127.0.0.1 x to the /etc/hosts with the following command: sh -c "echo '127.0.0.1 myhost' >> /etc/hosts" or by manually editing the file with gedit /etc/hosts.

  • Puoi controllare che myhost punti a localhosteseguendo nel terminale ping myhost che dovrebbe produrre:

qgis@qgis:~$ ping myhost
PING myhost (127.0.0.1) 56(84) bytes of data.
64 bytes from localhost (127.0.0.1): icmp_seq=1 ttl=64 time=0.024 ms
64 bytes from localhost (127.0.0.1): icmp_seq=2 ttl=64 time=0.029 ms

  • Puoi accedere a QGIS Server dal sito myhost eseguendo: curl http://myhost/cgi-bin/qgis_mapserv.fcgi accedendo all’URL dal tuo browser di Debian. Probabilmente otterrai:

<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN">
<html><head>
<title>404 Not Found</title>
</head><body>
<h1>Not Found</h1>
<p>The requested URL /cgi-bin/qgis_mapserv.fcgi was not found on this server.</p>
<hr>
<address>Apache/2.4.25 (Debian) Server at myhost Port 80</address>
</body></html>

  • Apache doesn’t know that he’s supposed to answer requests pointing to the server named myhost. In order to setup the virtual host the simplest way would be to make a myhost.conf file in the /etc/apache2/sites-available directory that has the same content as qgis.demo.conf except for the ServerName line that should be ServerName myhost. You could also change where the logs go as otherwise the logs for the two virtual hosts would be shared but this is optional.

  • Let’s now enable the virtual host with a2ensite myhost.conf and then reload the Apache service with service apache2 reload.

  • Se provi di nuovo ad accedere all’URL http: //myhost/cgi-bin/qgis_mapserv.fcgi noterai che tutto sta funzionando!

11.1.5. In Conclusion

Hai imparato come installare diverse versioni di QGIS Server dai pacchetti, come configurare Apache con QGIS Server, su distribuzioni Linux basate su Debian.

11.1.6. What’s Next?

Now that you’ve installed QGIS Server and it’s accessible through the HTTP protocol, we need to learn how to access some of the services it can offer. The topic of the next lesson is to learn how to access QGIS Server WMS services.