Working With Links

# Create working directory and move into it
student@control:~$ mkdir -p links-demo
student@control:~$ cd links-demo

# Create a file with content
student@control:~/links-demo$ printf "Hello World, link me\n" > file1.txt

# Show file listing and link count (initially 1)
student@control:~/links-demo$ ls -l
total 4
-rw-r--r-- 1 student student 21 Apr 15 16:11 file1.txt

# Create a hard link to file1.txt
student@control:~/links-demo$ ln file1.txt hard_link_file1

# Now the link count increases to 2 because there are two directory entries to the same inode
student@control:~/links-demo$ ls -l
total 8
-rw-r--r-- 2 student student 21 Apr 15 16:11 file1.txt
-rw-r--r-- 2 student student 21 Apr 15 16:11 hard_link_file1

# Verify both names share the same inode number
student@control:~/links-demo$ ls -i
123456 file1.txt
123456 hard_link_file1

# Both files show identical content
student@control:~/links-demo$ cat hard_link_file1
Hello World, link me

# Modify the original file; the hard link reflects the change because they share the same inode
student@control:~/links-demo$ echo "Appended line" >> file1.txt
student@control:~/links-demo$ cat hard_link_file1
Hello World, link me
Appended line

# Create a symbolic (soft) link to file1.txt
student@control:~/links-demo$ ln -s file1.txt soft_link_file1

# Listing shows the symlink pointing to file1.txt (symlink is a separate inode and stores the target path)
student@control:~/links-demo$ ls -l
total 12
-rw-r--r-- 2 student student 35 Apr 15 16:11 file1.txt
-rw-r--r-- 2 student student 35 Apr 15 16:11 hard_link_file1
lrwxrwxrwx 1 student student  9 Apr 15 16:12 soft_link_file1 -> file1.txt

# Remove the original file name
student@control:~/links-demo$ rm -f file1.txt

# The hard link remains (it still references the inode that contains the data).
# The link count is decremented to 1.
student@control:~/links-demo$ ls -l
total 8
-rw-r--r-- 1 student student 35 Apr 15 16:11 hard_link_file1
lrwxrwxrwx 1 student student  9 Apr 15 16:12 soft_link_file1 -> file1.txt

# The hard link still provides access to the data
student@control:~/links-demo$ cat hard_link_file1
Hello World, link me
Appended line

# The symbolic link is now dangling because its target path no longer exists
student@control:~/links-demo$ cat soft_link_file1
cat: soft_link_file1: No such file or directory

# Create a directory
student@control:~/links-demo$ mkdir linkme

# Attempt to create a hard link to a directory (usually not permitted)
student@control:~/links-demo$ ln linkme hardlinkme
ln: failed to create hard link 'hardlinkme' => 'linkme': Operation not permitted

# Create a symbolic link to the directory (this works)
student@control:~/links-demo$ ln -s linkme softlink_dir
student@control:~/links-demo$ ls -l
total 8
drwxr-xr-x 2 student student 4096 Apr 15 16:20 linkme
lrwxrwxrwx 1 student student    6 Apr 15 16:20 softlink_dir -> linkme
-rw-r--r-- 1 student student   35 Apr 15 16:11 hard_link_file1
lrwxrwxrwx 1 student student    9 Apr 15 16:12 soft_link_file1 -> file1.txt