How do I copy a Mac volume using cp?

I have researched this for hours. In Single User Mode, I used:

cp -Rpvn /* /Volumes/MyBackup

My external USB is mounted on /Volumes/MyBackup

The issue however is that after 24hrs it still has not stopped copying 300GB of data to an external USB drive. I think it is having issues with symbolic links such as the /Volumes/MacHD volume also having a /Volumes/MacHD and /Volumes/MyBackup I am not sure about this however.

How do I copy a Mac volume using cp? Is cp -Rpvn /* /Volumes/MyBackup correct?

Solution 1:

Use rsync for this purpose since cp cannot faithfully reproduce all the files that exist on OS X. The benefits of rsync over ditto and cp are:

• interrupted transfers can restart easily with very little cost.
• restarts even resume part way through a large file.
• file exclusion and --dry-run allow easy testing and iterative thinning.

The simplest way to use rsync and preserve most things (permissions, symlinks, edit dates, etc) is to use the -a or --archive flag to archive. To see your progress use -P or --progress

Rsync works as:

rsync options source destination

In your case I would recommend the following:

rsync --archive --verbose --one-file-system --human-readable --progress /from/ /to

Or in short:

rsync -avxhP /from/ /to

Mind the lack of trailing slash in the /to location.

see comments for more useful flags

Solution 2:

If you want to make a faithful copy of the filesystem contents, avoid using cp. Instead, use the ditto(1) command, which preserves hard links, file permissions, resource forks, and HFS metadata. Unlike cp, ditto is meant to preserve as much of that information as possible by default.

It's just a matter of running sudo ditto src dest.