the state of clock synchronization and setting in debian
In the PC "architecture", there are two main clocks in the sense of what's the time. The hardware clock lives on the motherboard, and can be spotted by its button-shaped CR2032 battery, which maintains the time even when no power supply is connected. The OS clock exists in volatile state, somehow between the memory and the CPU, meaning it is lost when the OS is shut down. From the perspective of a POSIX user, the OS time is accessed thru functions like time(2), or the date(1) utility. On boot, the OS clock gets its time initialised from the hardware clock. Shortly after, depending on the system's ntp configuration, and the right network access, this may get replaced straight away with an ntp server's notion of the time. Therefore, the sysadmin may not notice if the hardware clock is wrong, if the system gets its time from ntp shortly after each boot. This creates a situation where, if the system has to be brought up without network (or internet,...