Force new files to inherit specified ownership and permissions

Question

There is a directory I have

/var/new_share/KRA2017/Prateek

with these contents

-rwx------  1 superadmin   superadmin    0 Feb 16 15:14 file1.txt*
-rwx------  1 superadmin   superadmin    0 Feb 16 15:14 file2.txt*
-rwx------  1 superadmin   superadmin    0 Feb 16 15:15 file3.txt*
-rwx------  1 superadmin   superadmin    0 Feb 16 15:15 file4.txt*

in

/var/new_share/KRA2017/

The permission and ownership of directory /var/new_share/KRA2017/Prateek is

dr-xrwx--- 2 prateekkaien superadmin 4096 Feb 16 15:15 Prateek/

i.e the group owner can only write and user can only read and execute.

Whenever a file is being written by user superadminthe user and group owner of the files becomes superadmin as shown here. file1.txt file2.txt file3.txt file4.txt are written by user superadmin.

I want the user owner of the files to stick to prateekkaien with the same permissions r-x and the group owner to be superadmin with rwx permission like its parent directory.

How is this possible?

Basically all I want is for the files to inherit the owner, group, and permissions of the parent directory.

Answer 1

You are trying to enforce r-x access to owner user prateekkaien, and rwx access to owner group superadmin. This won't work because prateekkaien, as file owner, has full permission over it and it can simply do a chmod u+r to gain write access to the file.

What you could do is set the SGID bit on the directory, as @dirkt and @Murphy commented, so all newly created files will have superadmin as owner group.

Answer 2

On Unix the owner of a file is the user, who created it.

There are several questions, which already answer this and explain why:

• Why can't a normal user `chown` a file?
• Setting default username and group for files in directory
• How do you set the default user in Linux for file creation?