How to make a Time Machine drive writable?

Inherit a Backup

Inherit a Backup (2)

Time Machine doesn't make a drive non-writable.

Can you explain what happens when you attempt to delete or write to the drive?

Time Machine deals with something called "snapshots" - and you can delete these snapshots if you are trying to find room on the Time Machine backup disk or make the space of what it consumes smaller.

But not sure what you're trying to do - so just to make it more clear, are you trying to get the size of all the Time Machine backups small enough so that you can do a restore to your new MacBook Pro or are you trying to make room on the Time Machine disk in order to backup the MacBook Pro to the Time Machine disk you now have?

So which scenario are you trying to accomplish?

In any event I would not start removing files on your own from the Time Machine backups - you risk corrupting the whole Time Machine backup database.

You shouldn't delete stuff from a Time Machine backup using the Finder. Do it in Time Machine.

If you've been changing permissions and deleting stuff, it will likely not work as a Time Machine backup anymore.

Don't delete it directly. DO NOT.

Note that Time Machine backups are not what they appear to be from the Finder. If you *could* delete stuff from the Finder, it might not get deleted, because you would be deleting a 'hard link' to the file. A file is actually only deleted when ALL 'hard links' that point to it are deleted. Time Machine does this to save space, and to do incremental backups.

Generally, you cannot delete stuff from the Finder because there is an extra security layer in OS X to prohibit you from doing so. People must sometimes be protected from themselves 😉

The way to free up space is to go into the Time Machine interface, find something you want to delete, control click on it, and select "delete all instances of this." It will then be deleted. Note this can take some time, so let the drive grind for a while.