Comment 0 for bug 1743027

(originally asked over at askubuntu.com, but is still unresolved: https://askubuntu.com/questions/971349/problem-with-real-time-clock-since-upgrading-to-ubuntu-17-10)

I recently upgraded from Ubuntu 17.04 to Ubuntu 17.10 using the software update process. The update completed without any errors, and Ubuntu 17.10 is now running without any major issues.

However, I was running a script previously that uses rtcwake which has since stopped working. The script automatically hibernates my laptop after a set period of time in sleep mode, and was working perfectly in Ubuntu 17.04.

In the process of troubleshooting, I discovered that the problem was with rtcwake which is complaining about /dev/rtc0 missing.

Here is output from a sample rtcwake command:

peter@haven:~$ rtcwake -m no -s 1300
rtcwake: assuming RTC uses UTC ...
rtcwake: /dev/rtc0: unable to find device: No such file or directory

I verified that in fact, that directory is missing. Since this was working prior to the upgrade, I have to assume that it was there previously, but I don't know for sure.

In researching the error, I found some suggestions to get further information with timedatectl and hwclock, so here are the results from those commands as well.

Output of timedatectl:

peter@haven:~$ timedatectl
      Local time: Fri 2017-10-27 19:06:26 EDT
  Universal time: Fri 2017-10-27 23:06:26 UTC
        RTC time: n/a
       Time zone: America/New_York (EDT, -0400)
 Network time on: yes
NTP synchronized: yes
 RTC in local TZ: no

Output of hwclock --debug:

peter@haven:~$ sudo hwclock --debug
[sudo] password for peter:
hwclock from util-linux 2.30.1
Trying to open: /dev/rtc0
Trying to open: /dev/rtc
Trying to open: /dev/misc/rtc
No usable clock interface found.
hwclock: Cannot access the Hardware Clock via any known method.

UPDATE

When I boot with my old kernel, 4.10.0-37-generic the real-time clock works fine.

I get the following RTC messages in dmesg when I boot the 4.13.0-16-generic kernel:

peter@haven:~$ dmesg | grep -i rtc
[ 0.089393] RTC time: 17:03:55, date: 11/01/17
[ 1.238784] rtc_cmos 00:01: RTC can wake from S4
[ 1.238794] rtc_cmos: probe of 00:01 failed with error -16
[ 1.295459] hctosys: unable to open rtc device (rtc0)

UPDATE #2

Well, I was starting to believe that I had a hardware issue, since discovering I was unable to save changes to my BIOS and could not boot from USB. As it turns out, my laptop was bitten by this bug: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1734147 causing my BIOS to be locked in a read-only state.

Once I resolved the BIOS issue, and fixed the USB boot problem, I did a live boot of Ubuntu 17.10. The issue with my real time clock still exists under this clean boot scenario, yet when I boot other distros, like Linux Mint 18.3 and the real time clock works fine. I feel this definitely has something to do with the Ubuntu install, perhaps even a kernel bug.

UPDATE #3

More evidence to suggest this is a kernel bug: I live-booted a copy of Antergos Linux, which was using the Arch kernel 4.14.12-1-ARCH and it exhibited the same problem with the real time clock as Ubuntu 17.10. In addition, I confirmed that the Linux Mint version I booted earlier (see Update #2) was on the Ubuntu kernel 4.10.0-38-generic.

So, I suspect that sometime between kernels 4.10 and 4.13 this bug was introduced.