On Sun, Dec 28, 2025 at 07:31:12PM +0100, Sylvain Saboua wrote: > The same "error" message often appears on my device, especially during > updates. To confirm with more experienced people, but I think it can be > ignored, especially when it doesn't display otherwise.
When the kernel boots, it checks the RTC time with a timestamp stored in the root filesystem. If those two timestamps differ significantly, the warning is displayed, along with another qualifier, the one you will most commonly see is: WARNING: clock gained FOO days. When booting the ramdisk kernel, the filesystem timestamp is obviously stale, because it comes from the disk image embedded in the kernel. In that case, the warning can be ignored. In any other case, it's worth investigating the actual cause. The other common case is a failed CMOS battery, causing your RTC to be wrong, (or indeed no RTC battery at all as is the case on some SBCs).
