Reading/Accessing a file owned by user account which is under a directory that is owned by root

Question

I have a ssh only user account called pgbackrest with disabled password . I have created a directory /etc/pgbackrest/ as root (sudo mkdir -p /etc/pgbackrest). Then I create a config file under the above directory and changed the ownership to the account pgbackrest and sudo chmod 640 /etc/pgbackrest/pgbackrest.conf When I try to edit it with

1. Switch to pgbackrest user sudo su - pgbackrest and vim /etc/pgbackrest/pgbackrest.conf, I get /etc/pgbackrest/pgbackrest.conf" [Permission Denied] in the vim editor.
2. sudo -u pgbackrest vim /etc/pgbackrest/pgbackrest.conf, I get /etc/pgbackrest/pgbackrest.conf" [Permission Denied] in the vim editor.

does the permissions on the upper level directory prohibit the edit ? 640 means the owner and the group members can read, write. I am accessing the file as the owner, why am I getting access denied ?

Answer 1

In order for a user to be able to access a file, they also need permissions on all the directories in the path leading to the file.

At a bare minimum they need x permissions on the directory.

In your case (from comments) you have

drwxr-x---   3 root root       4096 Aug 10 22:56 pgbackrest

And the file itself:

-rw-r-----   1 pgbackrest pgbackrest    0 Aug 10 01:12 pgbackrest.conf

This means the pgbackrest user can not get to the file to read it.

A simple solution would be to add x permissions:

chmod a+x /etc/pgbackrest

Now anyone who knows the name of the file in that directory could try to access the file but the file permissions also take effect. So only the pgbackrest user or anyone in the pgbackrest group will be able to open the file; everyone else will be blocked.