obfuscurity.
hidden in plain sight

I've discovered that restoring a user account from a Snow Leopard (10.6) Time Machine backup to a new system running Lion (10.7) fails to preserve membership in gid 20(staff). I don't know if this only affects users in this particular scenario or might affect other upgrades/fresh instsalls, but it certainly bit me in the ass. I first encountered problems when trying to brew update, only to discover that it wouldn't let me write anything to /usr/local even though the directory had group-write permissions. Lo and behold, I finally realized that my membership had been revoked.

$ id
uid=501(jdixon) 
gid=501(jdixon) 
groups=501(jdixon),401(com.apple.access_screensharing),12(everyone),33(_appstore),
61(localaccounts),80(admin),98(_lpadmin),100(_lpoperator),204(_developer),
101(com.apple.access_ssh),402(com.apple.sharepoint.group.1)

The fix is simple enough. Use dscl to add yourself back to the staff group membership.

$ sudo dscl . append /Groups/staff GroupMembership `whoami`