The solution to disabling the "almost full" and "full" notification is to disable the daemon responsible for it:
launchctl unload -w /System/Library/LaunchAgents/com.apple.diskspaced.plist
Alternatively, if you only want to prevent the "almost full" from appearing so often then you can lower the GB threshold via:
minFreeSpace (int) - minimal free size in GB. Default: 20
The default 20GB is too high for small SSDs and a possible bug causes the alert to be shown every day rather than just once, so as a workaround you can lower the free space before the alert appears, e.g. to 10GB:
defaults write com.apple.diskspaced minFreeSpace 10
The daemon only reads its prefs on startup so you need to restart it if you have system integrity turned off:
launchctl unload -w /System/Library/LaunchAgents/com.apple.diskspaced.plist launchctl load -w /System/Library/LaunchAgents/com.apple.diskspaced.plist
Otherwise kill it:
killall diskspaced
In case you are interested in the other preferences for these disk alerts you can view some of them using the help param:
/System/Library/PrivateFrameworks/StorageManagement.framework/Versions/A/Resources/diskspaced help --- Domain: com.apple.diskspaced Supported keys: debugLog (BOOL) - log additional debug information. Default: NO checkAllVolumes (BOOL) - check all volumes. Default: NO minDiskSize (int) - minimal disk size in GB. Default: 128 minFreeSpace (int) - minimal free size in GB. Default: 20 minPurgeableSpace (int) - minimal purgeabe space size in GB. Default: 20 --- Commands: removeAllNotifications - Removes all scheduled and delivered user notificiations.
And here are a couple of hidden ones:
warningInterval (integer default 0) lastWarningDate (string e.g. 2018-05-05 16:48:29 +0000)
