How to prevent users from deleting a directory?

Create a file ".protected" and do as root

chattr +i .protected

You can then delete all files except .protected within this directory, thus the directory can't be deleted by any other user.

chattr +a

should do the job. You can create files inside but you won't be able to delete them.

So what is wrong with a simple chown/chmod?:

cd /tmp
mkdir question
sudo chown root:root question
[sudo] password for user: 
chmod 777 ./question
touch sth
rm sth
cd ..
rm question -rf
rm: cannot remove `question': Operation not permitted

OK, let me tell you what is wrong with this: every user has all access to every file in the question directory due to the 777 permissions. It is better to

• create a new group groupadd question
• mkdir question
• chown root:question ./question
• chmod 770 ./question
• add the users that must have access to the files to the new group: usermod -G group user

The important trick here is that the directory has a different owner than any of the users that will try to delete it.