在 chown 和 chmod 之后，用户在文件夹中的权限被拒绝

Question

I have a directory at

/home/ec2-user/vertica1

and I'm trying to get user dbadmin all privilages in that folder.

I've done chown to dbadmin and chmod 777 on that folder but dbadmin still gets a permission denied error.

If I put sudo in front of the command(I put dbadmi in sudoers), then it works. Why can't I get it to work without sudo?

Answer 1

Can dbadmin traverse /home/ec2-user ? Try doing chmod a+x /home/ec2-user

There could be more reasons for being denied, like a specific acl or a LSM but this is the most likely cause.

UNIX permissions on directories

The UNIX permissions rwx¹ work on directories as follows:

• r: You can view the contents of the directory (the names of the files or folders inside)
• w: You can create new files, delete or rename existing files.
• x: You can traverse the folder.

The traverse permission means that you can access the folder children (assuming you know its name -which you can obtain if you also have read permission-).

In this case dbadmin could read and traverse / as well as /home, but /home/ec2-user probably had a mode like drwx------ 2 ec2-user in order to protect its contents. Thus, even if you had an important file readable by anyone deep inside your home folder, other users can't get into it, since they wouldn't be able to go pass /home/ec2-user (which is exactly what you wanted to do, in this case).

¹ Note that I am skipping over the more exotic ones.

Answer 2

what is the result of ls -la for this dir and also parent dir? Maybe the directory doesn't have read permissions for your user.

sudo chmod ug+r vertica1

Also ec2-user directory should be writable by the user dbadmin.