[cinder] add --single-child to dumb-init for backup pods - #12685
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Without --single-child, dumb-init sends SIGTERM to the entire process group. The ProcessLauncher parent exits before backup children finish draining in-flight operations (e.g., backup restore), and the kernel SIGKILLs the remaining processes. With --single-child, dumb-init forwards SIGTERM only to the ProcessLauncher parent, which then forwards to each child and waits for all children to exit. This matches the cinder-volume VMware deployment (added in #11680) and is required for the graceful shutdown feature (sapcc/cinder#358). See also: sapcc/cinder#314 (Antelope testing)
hemna
requested review from
Scsabiii,
fwiesel,
jagoleni,
joker-at-work and
sumitarora2786
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August 27, 2026 14:40
Scsabiii
approved these changes
Aug 27, 2026
hemna
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Without
--single-child,dumb-initsends SIGTERM to the entire process group. The ProcessLauncher parent exits before backup children finish draining in-flight operations (e.g., backup restore), and the kernel SIGKILLs the remaining processes.With
--single-child,dumb-initforwards SIGTERM only to the ProcessLauncher parent, which then forwards to each child and waits for all children to exit.This matches the cinder-volume VMware deployment (added in #11680) and is required for the graceful shutdown feature (sapcc/cinder#358).
What changed
One line added to
backup_deployment.yaml:Background
During Antelope testing of the graceful shutdown feature, we discovered that
dumb-initwithout--single-childbroadcasts SIGTERM to the entire process group, causing premature container exit. PR #11680 fixed this for cinder-volume VMware pods but the backup deployment was missed. This PR closes that gap.Risk
None —
--single-childonly changes signal forwarding behavior (SIGTERM to direct child only instead of process group). No functional change to backup operations. Safe to deploy without the graceful shutdown cinder code change.Supersedes the backup portion of #10305 (which proposed dropping dumb-init entirely but is stale/conflicts with master).