Linux Hardlink and Softlink/Symlink explained.

What is Inode? it’s the metadata about a regular file and directory in Linux.

Let’s create a file with some contents.

# vim myfile.txt

How to find Inode information of a file?

# stat myfile.txt
  File: myfile.txt
  Size: 2023      	Blocks: 8          IO Block: 4096   regular file
Device: fd03h/64771d	Inode: 15997895    Links: 1
Access: (0644/-rw-r--r--)  Uid: ( 1000/   antop)   Gid: ( 1000/   antop)
Context: unconfined_u:object_r:user_home_t:s0
Access: 2019-08-30 08:29:16.974661276 +0530
Modify: 2019-08-30 08:29:16.974661276 +0530
Change: 2019-08-30 08:29:16.974661276 +0530
Birth: 2019-08-30 08:29:16.974661276 +0530

In above inode information it is showing Links : 1.

Create a Hard Link to myfile.txt:

# ln myfile.txt myfile_hardlink.txt

Again check the value of Links:

# stat myfile.txt
  File: myfile.txt
  Size: 2023      	Blocks: 8          IO Block: 4096   regular file
Device: fd03h/64771d	Inode: 15997895    Links: 2
Access: (0644/-rw-r--r--)  Uid: ( 1000/   antop)   Gid: ( 1000/   antop)
Context: unconfined_u:object_r:user_home_t:s0
Access: 2019-08-30 08:29:16.974661276 +0530
Modify: 2019-08-30 08:29:16.974661276 +0530
Change: 2019-08-30 08:29:44.868059994 +0530
 Birth: 2019-08-30 08:29:16.974661276 +0530

Now Value changed: “Links = 2”.

Check the inode information of hardlink we have created (myfile_hardlink.txt):

# stat myfile_hardlink.txt
  File: myfile_hardlink.txt
  Size: 2023      	Blocks: 8          IO Block: 4096   regular file
Device: fd03h/64771d	Inode: 15997895    Links: 2
Access: (0644/-rw-r--r--)  Uid: ( 1000/   antop)   Gid: ( 1000/   antop)
Context: unconfined_u:object_r:user_home_t:s0
Access: 2019-08-30 08:29:16.974661276 +0530
Modify: 2019-08-30 08:29:16.974661276 +0530
Change: 2019-08-30 08:29:44.868059994 +0530
 Birth: 2019-08-30 08:29:16.974661276 +0530

Create Soft Link/Symlink:

# ln -s myfile.txt myfile_softlink.txt

Check and compare inode and size of myfile.txt and it’s links.

# ls -il                              
total 8
15997895 -rw-r--r--. 2 antop antop 2023 Aug 30 08:29 myfile_hardlink.txt
16025624 lrwxrwxrwx. 1 antop antop   10 Aug 30 08:30 myfile_softlink.txt -> myfile.txt
15997895 -rw-r--r--. 2 antop antop 2023 Aug 30 08:29 myfile.txt                           # Here 3rd column showing `2` means `Links: 2`

Now we could see that inode of myfile.txt and myfile_hardlink.txt are same.

Let’s continue. Create a copy of hardlink we have created before:

# cp myfile_hardlink.txt myfile_hardlink_copy.txt

# ls -il
total 12
16026660 -rw-r--r--. 1 antop antop 2023 Aug 30 08:31 myfile_hardlink_copy.txt
15997895 -rw-r--r--. 2 antop antop 2023 Aug 30 08:29 myfile_hardlink.txt
16025624 lrwxrwxrwx. 1 antop antop   10 Aug 30 08:30 myfile_softlink.txt -> myfile.txt
15997895 -rw-r--r--. 2 antop antop 2023 Aug 30 08:29 myfile.txt

So copy mean’s, both files don’t have any relation. It’s a COPY.

Create a copy of softlink:

# cp myfile_softlink.txt myfile_softlink_copy.txt

# ls -il
total 16
16026660 -rw-r--r--. 1 antop antop 2023 Aug 30 08:31 myfile_hardlink_copy.txt
15997895 -rw-r--r--. 2 antop antop 2023 Aug 30 08:29 myfile_hardlink.txt
16023584 -rw-r--r--. 1 antop antop 2023 Aug 30 08:31 myfile_softlink_copy.txt
16025624 lrwxrwxrwx. 1 antop antop   10 Aug 30 08:30 myfile_softlink.txt -> myfile.txt
15997895 -rw-r--r--. 2 antop antop 2023 Aug 30 08:29 myfile.txt

And check size of both links and their copies.

# du -sch *

4.0K	myfile_hardlink_copy.txt
4.0K	myfile_hardlink.txt
4.0K	myfile_softlink_copy.txt
0	myfile_softlink.txt
12K	total

Copy will create a copy of entire contents. It’s a COPY.

Upon creating a hardlink, Links =2 in inode of the myfile.txt

# stat myfile.txt|grep Links:
Device: fd03h/64771d	Inode: 15997895    Links: 2

Let’s remove hardlink and check the value of “Links”:

# rm myfile_hardlink.txt

# stat myfile.txt|grep Links:
Device: fd03h/64771d	Inode: 15997895    Links: 1

Links value become 1 again. So the actual content/file info gets deleted/removed only if there are no HARDLINKS present.

See the video demonstration from below: