Raspberry Pi - Synchronize time in an environment where the Internet is not available
Single Board Computer (SBC), such as Raspberry Pi, does not have a Real Time Clock (RTC) that maintains the current time. At the time of system boot, they connect to the Internet's time server and synchronize the current time. If the Internet is not connected, the last time the system was used remains the same. In most cases, there is no problem because it is an environment where Internet connectivity is possible. However, there are times when Internet access is blocked due to security issues such as well. Recently I had to build an environment like the following picture. One Raspberry Pi connected WiFi and LAN to two different networks (192.168.11.0/24 and 192.168.10.0/24). And the rest of the Raspberry Pi connected to the LAN network (192.168.10.0/24). Therefore, Raspberry Pi connected to LAN is blocked from internet access. The Raspberry Pi connected to the 192.168.10.0/24 network has no Internet access and only needs to communicate with Raspberry Pi using the 192.1...