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I have a quick question about how the read permission works. Does read permission mean I can open the file?

The situation is this: FTP server where I have an account that is not Root. There, files are owned by Root inside a 777 folder that have 604 permission -- so where "public" can "read".

Why can't I open those 604 files?

Does read mean only that you can see if the files exist?

Just curious if also there's a way to not showing the files at all to non-root users.

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1 Answer

up vote 3 down vote accepted

604 gives no permission to members of the file's group. If your account is a member of that group, it doesn't matter that the last digit is more permissive; you don't have these permissions.


To prevent users from accessing a file's contents, remove the read permission from the file. To hide a file, you can remove a directory's read permission. It can be entered, and files can be accessed and modified (given the correct permissions), but the directory contents will not be available.

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but I tried to make a test on my server. I created a file with 604 permission owned by root:root. The user user1:users can read the 604 file because "public" have read permission –  Sandro Antonucci Jan 22 '12 at 18:12
    
@SandroAntonucci You didn't mention the file group in your question, so I had to assume. What's the error message when you try to open? –  Daniel Beck Jan 22 '12 at 18:14
    
you are right sorry, I didn't get your answer right and I didn't notice the group. I'm in the same group as the 604 files so that makes sense now. Isn't "stupid" giving access to public but not to an user in the same group? –  Sandro Antonucci Jan 22 '12 at 18:24
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@SandroAntonucci On some Unixes, users are not able to change their group membership (i.e. leave a group). That makes it easy to create e.g. a quarantine group. There's a reason the octal digits in a file permission are usually descending. Also, it's easier if you think of owner/group/other, instead of owner/group/public. –  Daniel Beck Jan 22 '12 at 18:35
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