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For more information, take a look at:
OS X: How to migrate data from another Mac using Mavericks
The amount of time that it takes for migration to complete depends on the amount of data being copied, and the speed of the connection.
Command q will quit the migration.
Have a nice day,
That's an oversimplistic answer.
There is a chance you could be left with a partially migrated system, making your destination system unbootable. So hopefully you backed up both systems before you began the migration process. If you do find things are unbootable, and you have no backup these solutions exist: