Can you do a kernel bisection?
First, find the last good -rc kernel and the first bad -rc kernel from
$ sudo apt build-dep linux
$ git clone git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
$ cd linux
$ git bisect start
$ git bisect good $(the good version you found)
$ git bisect bad $(the bad version found)
$ make localmodconfig
$ make -j`nproc` deb-pkg
Install the newly built kernel.
If the issue still happens,
$ git bisect bad
$ git bisect good
Repeat to "make -j`nproc` deb-pkg" until you find the commit that causes the
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error loading realtime clock since upgrading to 17.10
Status in linux package in Ubuntu:
(originally asked over at askubuntu.com, but is still unresolved:
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
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:
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.
When I boot with my old kernel, 4.10.0-37-generic the real-time clock
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:
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
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
USER PID ACCESS COMMAND
/dev/snd/controlC0: peter 1832 F.... pulseaudio
/dev/snd/controlC1: peter 1832 F.... pulseaudio
DistroRelease: Ubuntu 17.10
InstallationDate: Installed on 2017-04-05 (292 days ago)
InstallationMedia: Ubuntu 16.10 "Yakkety Yak" - Release amd64 (20161012.2)
MachineType: LENOVO 20354
Package: linux (not installed)
PATH=(custom, no user)
ProcFB: 0 inteldrmfb
root=UUID=fa5454aa-9072-475d-b515-acd51a6166cc ro quiet splash vt.handoff=7
ProcVersionSignature: Ubuntu 4.13.0-25.29-generic 4.13.13
Tags: wayland-session artful
Uname: Linux 4.13.0-25-generic x86_64
UpgradeStatus: Upgraded to artful on 2017-10-24 (90 days ago)
UserGroups: adm cdrom dip kismet lpadmin plugdev sambashare sudo
dmi.board.asset.tag: No Asset Tag
dmi.board.name: Lancer 5A5
dmi.chassis.asset.tag: No Asset Tag
dmi.chassis.version: Lenovo Z50-70
dmi.product.version: Lenovo Z50-70
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