LPIC-1 104.6: Hard and symbolic links

Hard links and symlinks side by side, the limits of hard links, directory link counts, switching a current symlink, and following a chain of links.

Before you start

The lab creates an empty /root/links/. Work as root (sudo -i) and in that directory, and write answers to the files in /root/lab-answers/.

Create original.txt with some text, make a hard link hard.txt and a symlink soft.txt to it, and look at all three with ls -li. Delete the original, then cat both links.
Try to hard-link a file onto another filesystem (df shows which directories are on separate ones; /dev/shm is a tmpfs everywhere, while /tmp is only on some systems), and to hard-link a directory. Write both error messages to /root/lab-answers/2.
Make a directory parent, check its link count, add two subdirectories, and check again. Write the first count on line 1 of /root/lab-answers/3 and the second on line 2.
Set up releases/1.0, releases/1.1 and a current symlink in releases/ pointing to 1.0. Switch current to 1.1 with ln -sf, and then with ln -sfn, and look at what each did.
On Debian or Ubuntu, follow /usr/bin/editor to the real program with readlink -f, and with ls -l one link at a time. Write every name in the chain, from /usr/bin/editor to the real program, one per line, to /root/lab-answers/5.

ln, ln -s, ls -li; a symlink stores a name, a hard link is another name for the same inode.
ln FILE /dev/shm/; ln DIR NEWNAME.
ls -ld parent (the second column), stat -c %h parent.
Without -n, ln -sf 1.1 current follows current into 1.0 and makes the link there.
readlink -f, ls -l /usr/bin/editor, then ls -l on what it points to.