Time Machine has stopped working on my iMac running Mojave. The symptom is that it will be in “Preparing Backup…” for a long time, then the backup just quits with no errors shown.
I can see in the logs that what’s happening is the kernel is killing backupd because it is using too much memory:
21-10-16 14:06:23.436 kernel low swap: killing largest compressed process with pid 1366 (backupd) and size 260 MB
(com.apple.backupd): Service exited due to SIGKILL | sent by kernel_task
iStat menus shows that each time it attempts a backup, the swap memory grows to just short of 50 GB, then backupd gets killed.
I’m thinking that when Time Machine is comparing the last backup to the current state of the iMac, there’s too many changes found.
Or, maybe there’s something wrong in the Spotlight database – SuperDuper was getting stuck yesterday trying to clone those folders in /private, before I updated it to the 3.5 beta which ignores the Spotlight metadata.
The question is, how to get past this and get Time Machine working again?