My laptop was filling up on space. I couldn't track it down for a long time.
jh1:~ ytjohn$ df -h
Filesystem Size Used Avail Use% Mounted on
/dev/disk1s1 932G 797G 134G 86% /
jh1:.vol ytjohn$ tmutil listlocalsnapshots /
com.apple.TimeMachine.2018-05-28-104940
com.apple.TimeMachine.2018-08-14-194329
com.apple.TimeMachine.2018-08-15-014525
com.apple.TimeMachine.2018-08-15-075247
com.apple.TimeMachine.2018-08-15-084935
com.apple.TimeMachine.2018-08-15-113300
jh1:.vol ytjohn$ tmutil deletelocalsnapshots 2018-05-28-104940
Deleted local snapshot '2018-05-28-104940'
jh1:.vol ytjohn$ tmutil deletelocalsnapshots 2018-08-14
Error parsing argument 2018-08-14
jh1:.vol ytjohn$ tmutil deletelocalsnapshots 2018-08-14-194329
Deleted local snapshot '2018-08-14-194329'
jh1:.vol ytjohn$ tmutil deletelocalsnapshots 2018-08-15-014525
Deleted local snapshot '2018-08-15-014525'
jh1:.vol ytjohn$ df -h
Filesystem Size Used Avail Use% Mounted on
/dev/disk1s1 932G 650G 281G 70% /
About an hour later, it was showing used at 405G.