Back to the Future

Ed: the first in a likely series, this is one of the posts I drafted but never published during my seven years in the blogging wilderness

I have been having persistent issues on MacOS with Time Machine backups interacting badly with several configuration elements and other services. This is exacerbated by my use of maildirs to backup emails, with my Gmail account leading to a directory with some millions of files. (Yeah, ok, maybe not wise but hey, we are where we are.)

So in the course of trying to get backups to work reliably, I found the following commands useful to at least some degree:

• mdutil -sav to get info about spotlight indexing status
• sudo mdutil -Ea -i [off|on] to turn off|on spotlight indexing where possible
• sudo fs_usage -w mdworker mds_stores backupd obtain the current filesystem usage for those services
• sudo fs_usage -w -e iTerm2 to obtain current filesystem usage for services excluding those listed
• sudo sysctl debug.lowpri_throttle_enabled=[0|1] stop|start throttling to go faster|be nice!
• to obtain the various different hostnames that MacOS seems to want to give; note that renaming ComputerName (also possible via SysPrefs>Sharing>>name) caused the Time Machine directory to be renamed when the backup started

for n in  ComputerName LocalHostName HostName ; do 
  scutil --get $n
done

• tmutil listbackups to list backups
• tmutil listlocalsnapshotdates / to list local snapshots
• tmutil destinationinfo to list the Time Machine destination volumes
• to stream Time Machine log entries live

log stream --style syslog --debug --info \
  --predicate 'senderImagePath contains[cd] "TimeMachine"'

• to show Time Machine log entries from YYYY-MM-DD

log show --style syslog --debug --info --start YYYY-MM-DD \
  --predicate 'senderImagePath contains[cd] "TimeMachine"'\