chmod to change permissions of specific user

Question

I have two users, user1 and user2. I also have a file in /path/to/file. user1 should be able to have read-write access, while user2 should only have read access.

I know that I can change permissions with chmod u=r /path/to/file to read-only, however this changes the permissions for everyone? When executing the command as user1 the access changes for user1 and user2 as well. I haven't found a option to specify a user. Is this something where I'd have to use the groups? Or chown? How would I go about doing this?

Is this also possible to do for a whole directory full of files? If there is a dir /path/to/dir that contains n files and m subdirs, to change the permissions of every file and every file in the subdirs?

Solution

You can use next solution:

• change the ownership of the file: chown user1 /path/to/file
• change permission for the owner, group and other: chmod 644 /path/to/file

This will give rw to user1 and r to user2

For directories you must add x to give the option to the user to change in this directory:

chmod 755 /path/to/directory

Be careful with -R because this will change also the subdirectories

To automate the work you can use something like. Be very carefull for the start directory because those commands can change permissions of files you do not want to touch

find /path/to/file -type f -exec chmod 644 {} \;

for files

find /path/to/dir -type d -exec chmod 755 {} \; 

for directories

Comments

[Legatio]

I just edited the question: is this possible for whole dirs as well? I just did chown user1 ./ and chmod -R 644 ./ and now I don't have any access to the dir, even as user1.

[Atul Vekariya]

@Legatio, please check my edited answer

[Legatio]

thanks now I can access the dir again. Is it possible to add x to the dir and subdirs but not the files in those dirs? I would want user2 to only read the files and not execute them.

[Atul Vekariya]

@Legatio, yes, thats possible, see my edited answer

[Legatio]

how would I use the 2 find commands for the concrete example I added to my question?

[Atul Vekariya]

@Legatio, answer edited