Symbolic links:
-> A symbolic link (also known as a symlink) is a file that points to another file within the system.
-> These links are analogous to shortcuts in Windows.
-> Symlinks can be created for any regular files, special files, or directories.
-> A symlink can span across different filesystems.
-> The original file and the symlink file have distinct inode numbers.
NOTE: If you happen to delete the original file, the symlink file will no longer function and its existence will become meaningless.
A common use case where symlinks can be beneficial is when one of your filesystems (e.g., /) is approaching full capacity, and you want to relocate some files or directories to a larger filesystem (e.g., /mnt/data). However, directly moving the files or directories is not feasible because certain applications (e.g., Docker) are linked to specific locations under / (e.g., /var/lib/docker).
In this scenario, you have two options:
Option 1:
Directly copy the files and directories from the original location (/var/lib/docker) to the new location (/mnt/data/var-lib-docker) using the command:mv /var/lib/docker/* /mnt/data/var-lib-docker
Once the files and directories have been copied, modify the application’s configuration to point to the new location (/mnt/data/var-lib-docker) instead of the original location (/var/lib/docker).
Option 2:
Utilize symbolic links to maintain the application’s existing location (/var/lib/docker) while actually storing the files and directories in the new location (/mnt/data/var-lib-docker).
1) mv /var/lib/docker/* /mnt/data/var-lib-docker2) ln -s /mnt/data/var-lib-docker /var/lib/docker
Now when you run the below command,
ls -ltrh /var/lib/ | grep docker
You should see the Symlink as follows,
lrwxrwxrwx 1 root root 22 Nov 6 08:46 docker -> /mnt/data/var-lib-docker
NOTE:
For both options described above, it is crucial to temporarily halt any applications, such as the Docker application in our case, that are accessing or modifying the directory in question (/var/lib/docker).
Hard Links:
-> Hard links can only be created for regular files, not directories or special files.
-> A hard link cannot exist across multiple filesystems.
-> The original file and the hard link file share the same inode number.
NOTE: Even if the original file is deleted, the hard link file remains functional, and its contents remain accessible.
Syntax:ln actual_file_name hard_link_file_name
