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I just formatted a brand-new USB external hard drive with a single ext4 partition using GParted. I want to back up my files so I can do a fresh install of Oneric on my only machine. Natty mounted the new partition and I can see the "lost+found" directory, but I cannot copy files to the drive - I get "Permission denied".

If I ll /media, I see:

drwxr-xr-x  3 root root 4096 2011-12-31 10:00 MyDisk/

I have a very limited understanding of permissions, but is the lack of 'w' permission on the "others" class what's preventing me from copying my files? I'm tempted to try chmod o+w MyDisk, but would that apply to others on a different system, or just my current one (I need to copy files from the disk after installing Oneric)? Same question with root ownership - is that "root" on my current system only, or root on any system I connect the drive to?

Even if my thinking is way off, why doesn't GParted make the drive writable to my user account by default?

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up vote 5 down vote accepted

What it says there is that the owner of the disk is root. So you will need to change the permissions. Since it's ext4 the permissions are stored on the disk. It's not odd GParted made it read-only except for root because ext4 is not commonly used for USB drives. It seems GParted assumed it is most likely you would use ext4 for an operating system, for which it would be best to only have root access to the root of the partition.

It will always be possible to mount the drive and use the root user from a different computer to change the permissions.

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I was able to change permissions by mounting it with root nautilus and transferring permissions to 'guest'. – Vadi Dec 31 '11 at 22:18

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