SEE UPDATES BELOW
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
Here is output from a sample
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
hwclock, so here are the results from those commands as well.
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
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.
Has anyone else experienced any similar issues since upgrading? If not, please offer any suggestions how best to proceed with my troubleshooting.
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
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)
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.
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
So, I suspect that sometime between kernels 4.10 and 4.13 this bug was introduced. Can anyone provide me with information for filing a kernel bug?
UPDATE Jan. 30, 2018
Kernel bug reported on Launchpad (https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1743027) and with upstream kernel developers.