The rpi-timeset utility is a simple PHP script which allows quick update of a remote system clock via the web browser. The system time is synchronized to the remote client system time obtained using Javascript. Originally intended for use on the Raspberry Pi, this script could be easily adapted to other hardware platforms as desired.
The mostly likely use case would be an RPi which has been configured to failover to a hotspot/ad hoc network connection if wireless LAN association fails at boot. In this instance an Internet connection would be unavailable so the RPi could not sync via ntp. However, a user could utilize this utility to adjust the system clock to match that of a tablet, smartphone, laptop, or other device on the ad hoc network which may have a better idea of the current time.
This documentation assumes the Raspbian Stretch operating system. Commands and prerequisites should be similar on other platforms.
The only dependencies are a web server and PHP, which can be obtained with:
sudo apt-get update
sudo apt-get install apache2 php
To install this script, simply copy it to a folder accessible from your web browser. Creation of a unique folder for this utility is recommended. For Raspbian Stretch:
sudo mkdir /var/www/html/rpi-timeset
sudo chown www-data:www-data /var/www/html/rpi-timeset
Place the index.php file in the desired folder. If necessary, this file can be renamed and the script should still function normally.
Then, grant your web server sudo permissions for /bin/date. On Raspbian Stretch, use sudo visudo to add a line like this:
www-data ALL=NOPASSWD: /bin/date *
Change www-data to your web server process owner name.
To run this script simply access the file on the web browser. The URL will vary depending on the path chosen during installation and the method used to connect (direct vs. SSH tunnel). Using the paths in this documentation, the URL might be:
http://raspberrypi.local/rpi-timeset/
http://192.168.1.100/rpi-timeset/
http://127.0.0.1:8000/rpi-timeset/
The script will display the before-and-after time stamps and a success/fail message.
The amount of security that needs to be applied is up to the discretion of the administrator of the target system. At a minimum, the installation should be password protected. Assuming Apache web server was selected:
cd /var/www/html/rpi-timeset # or other install location
htpasswd -c .htpasswd username
and then create an .htaccess file in the installation folder:
AuthType Basic
AuthName "rpi-timeset access"
AuthUserFile /var/www/html/rpi-timeset/.htpasswd
Require valid-user
You may also wish to configure the web server to connect only via the loopback interface, which will require client connections over an SSH tunnel. To configure Apache for this, modify /etc/apache2/ports.conf:
Listen 127.0.0.1:80
<IfModule ssl_module>
Listen 127.0.0.1:443
</IfModule>
<IfModule mod_gnutls.c>
Listen 127.0.0.1:443
</IfModule>
From the client end, you would ssh username@domain.com -L 8000:127.0.0.1:80 and use your web browser to connect to http://127.0.0.1:8000.
If additional commands should be run after updating the time, place those commands in a script called postrun.sh in the same folder and do a chmod +x postrun.sh to make it executable.
Comments, questions, and bug reports can be directed to the GitHub project page. The author may be contacted directly at mailto:steve@stevecrow.net.
Copyright (c) 2017 Steve Crow. Licensed under the BSD 2-clause “Simplified” License.
For license information, see the LICENSE.md file or visit http://github.com/scrow/rpi-timeset.