Symbolic link and hard link

1 Create a link

So this is how you create a symbolic link:

ln -s real_file_or_dir linked_file_or_dir

and to create a hard link:

ln original_file_or_dir linked_file_or_directory

2 Symbolic link vs. hard link

• Symbolic links have a different inode, whereas for hard links they share the same inode.

• Symbolic links are system-portable, but hard links aren't.

• You can delete any of the hard links or the original file. If you keep one of the linked files, the data remains intact. However, if you delete the real file (not the linked one) in a symbolic link, you get a broken link and you lose the data.

To check the inode and properties of a file or directory:

ls -il real_file_or_directory linked_file_or_directory

3 The danger of recursive deletion (rm -rf)

If you run rm -rf linked_directory/ in a symbolic link, you are deleting the contents of the original directory. If you want to delete just the linked_directory, remove the trailing slash /.

you aren't just deleting the "shortcut." Because of that trailing slash /, some shells and versions of rm interpret that as "go inside the folder and delete everything."

4 The permission "trap"

Permissions on a symbolic link are always lrwxrwxrwx, it looks like there is full access for everyone. However, these permissions are ignored.

When you try to access a file through a symlink, Linux looks at the permissions of the target (the original file/directory), not the link itself.

You can try changing permissions to a file/directory with more restricted permissions and try to access through the symlink. If you get a permission denied trying to access the original file, you will also get a permission denied when trying to access the same file through the symlink.

5 Ownership Changes (chown)

If you try to change the owner of a symlink, you will accidentally change the owner of the original file instead.

If you run:

chown user:group linked_file_or_directory

6 Where I am

It can be difficult to know if you accessed through a symlink or if you are under the real directory because the files inside look exactly the same. To know the if you are under a symlink, try running and comparing both outputs:

pwd

pwd -P

If the output is different, it means that you may be accessing the files through a symlink.