How do you set the default user in Linux for file creation?

Question

I want to create a directory, for example:

/public/all

But I want it so that if you create a file in all, the owner is root, but anyone with access to the /public/all folder can delete/edit/etc the file, just not change the permissions. (I will use a self-created "setx" application to change the execute value if needed.)

Reason for this, I don't want you to be able to deny other users write/read access to files in /public/all. I heard setuid on directories doesn't work for that.

Answer 1

You cannot do this; the initial owner is always the object's creator.

What you can do is set the default ACLs to automatically allow read/write to everyone:

setfacl -m default:u::rwx,default:g::rwx,default:o::rwx /public/all

Also optionally set a default group:

chown :nobody /public/all
chmod g+s /public/all

However, none of these will prevent the owner from changing the permissions later.

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An alternative solution is to monitor the directory with inotify (using incron) and automatically run chown on creation. Put this to incrontab:

/public/all IN_CREATE chown nobody:nobody $@/$#; chmod 0666 $@/$#