[Bug 1880839] Re: Clock skew on testbeds

[Balint Reczey]

My suspect is systemd-timesyncd:

See src/timesync/timesyncd-manager.c:

/*                                                                                                                                                                            
 * Maximum delta in seconds which the system clock is gradually adjusted                                                                                                      
 * (slewed) to approach the network time. Deltas larger that this are set by                                                                                                  
 * letting the system time jump. The kernel's limit for adjtime is 0.5s.                                                                                                      
 */
#define NTP_MAX_ADJUST                  0.4

I suspect the boost compilation's load made the internal clock diverge
enough for systemd to jump the time.

The default PollIntervalMaxSec is 2048 seconds in systemd.

I can reduce it in systemd, but there is a jump as high as 0.85 in
https://objectstorage.prodstack4-5.canonical.com/v1/AUTH_77e2ada1e7a84929a74ba3b87153c0ac/autopkgtest-focal/focal/amd64/b/boost1.71/20200317_211804_626ff@/log.gz
which could not have been prevented by just halving the default.

How about changing the autopkgtest setup to either change a default or
disable systemd-timesyncd or install chrony instead?


** Also affects: systemd (Ubuntu)
   Importance: Undecided
       Status: New

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https://bugs.launchpad.net/bugs/1880839

Title:
  Clock skew on testbeds

Status in Auto Package Testing:
  New
Status in systemd package in Ubuntu:
  New

Bug description:
  Clock stepped backward on a testbed:

  https://objectstorage.prodstack4-5.canonical.com/v1/AUTH_77e2ada1e7a84929a74ba3b87153c0ac
  /autopkgtest-
  groovy/groovy/amd64/b/boost1.71/20200501_151103_1e387@/log.gz

  ...
  context              FAIL stderr: make[2]: Warning: File '/tmp/tmp.qPfGPM84a1/src/demo2.cpp' has modification time 0.52 s in the future
  autopkgtest [13:55:37]: test context:  - - - - - - - - - - stderr - - - - - - - - - -
  make[2]: Warning: File '/tmp/tmp.qPfGPM84a1/src/demo2.cpp' has modification time 0.52 s in the future
  make[2]: warning:  Clock skew detected.  Your build may be incomplete.
  ..

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