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I have two users on my MBP, and IIRC, both are Admin accounts. I want to upgrade to Lion GM, and have the dmg to do that. However, to be safe, I want to have a backup. I am not familiar with Time-machine, being new to this ecosystem and all.

Will running a backup from an Admin account backup all the user accoiunts on the machine? Is it a 1:1 backup?

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up vote 5 down vote accepted

Time Machine backs up an entire drive/partition/volume unless you specifically remove files and folders under "Options". All User accounts are included unless you uncheck them in Options.

All of this info is available in your Finder Help menu.

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This is not the case. Time Machine is a file-level backup, and does not back up many files by design. See: /System/Library/CoreServices/backupd.bundle/Contents/Resources/StdExclusions.pli‌​st – zzz Aug 17 '11 at 12:49
You are absolutely correct. There are caches and a number of others omitted by TM in backing up, but TM by default backs up everything you need for recovery purposes. The OP needs to know what is backed up by default, and how to customize TM backups for his needs. – modelamac Aug 17 '11 at 17:21
One another thing excluded from backups is trash. – user63918 Dec 3 '13 at 3:16

In essense, it's not a true one to one backup, but it's like 99.9% there. It will backup all your files, users, user documents, settings, applications etc, but not quite every file. Pagefiles, certain cache files, logs areas etc can be ommitted as they are recreatable and as such don't need to be recoverable. I don't believe you need to be an admin user to do a backup, as the backup daemon is always running as a priveleged process anyway and you just pass it the message to go and do it's stuff, therefore you do not need access to all the files under your own accounts permissions.

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