Removing Time Machine backup directories and other stubborn files

(Try in this order: chmod -R +nw . ; find . -type d -print0 | xargs -0 chmod +x ; find . -type l -print0 | xargs -0 chmod -N ; chmod -R -N . ; chflags -R nouchg . ; then remove all.)

Here’s the approximate incantation:

First, remove all user-immutable flags:

chflags -R nouchg .

Second, make everything readable and writeable:

chmod -R +rw .

Next, make sure all the directories are listable (using the execute bit):

find . -type d -print0 | xargs -0 chmod +x

Remove any access control lists (ACLs):

chmod -R -a# 0 .

For some reason the above doesn’t remove ACLs on symbolic links; remove these ACLs:

find . -type l -print0 | xargs -0 chmod -h -a# 0

Now the subdirectories should be removable.

Note: The chmod -a commands will report lots of files without ACLs; consider piping their output through a grep:

chmod -R -a# 0 . 2>&1 | grep -v ‘No ACL present’

NB: The success of all this seems to depend on having the filesystem mounted with the noowners option (i.e. mount -o noowners…). This can be accomplished with mount(8) or by clicking the box at the very bottom of the volume's ‘Get Info’ box - though note that some volumes don’t offer this switch, even if they can be mounted noowners.

Boot into recovery mode (⌘+R at boot). Use disk utility to ensure proper disk is mounted.

umount disk99
mkdir /Volumes/Name
mount -o noowners /dev/disk99 /Volumes/Name

(From Evernote)