Symbolic and Hard Links Explained

Linux has two ways to make a file appear in multiple places without copying the data: symbolic links (symlinks) and hard links. They look identical when you use them, but they work differently — and choosing the wrong one will bite you.

The mental model: inodes

Every file on disk has an inode — a metadata record holding permissions, size, timestamps, and the location of the actual data. The filename is just a pointer to an inode.

ls -i myfile.txt
# 1234567 myfile.txt   ← the number is the inode

This is why renaming a file is instant — only the directory entry changes, not the inode.

Hard links

A hard link creates a NEW filename that points to the SAME inode as an existing file. Both filenames are equally “real” — the file isn’t deleted until ALL hard links to it are removed.

echo "hello" > original.txt
ln original.txt twin.txt        # create hard link

ls -li original.txt twin.txt
# 1234567 -rw-r--r-- 2 alice ... original.txt
# 1234567 -rw-r--r-- 2 alice ... twin.txt
#                    ^ link count is now 2

# Edit through one — both reflect the change
echo "modified" > original.txt
cat twin.txt          # modified

# Delete one — the other still works
rm original.txt
cat twin.txt          # still "modified" — file lives on

Limitations of hard links

• Cannot link across different filesystems (different inodes namespaces).
• Cannot link to directories (would create infinite loops).
• If both filenames are in the same place, this is mostly invisible.

Symbolic links (symlinks)

A symlink is a small file that contains a path to another file. It’s a pointer at the filesystem-name level, not the data level.

echo "hello" > target.txt
ln -s target.txt shortcut       # the -s makes it a symlink

ls -li target.txt shortcut
# 1234567 -rw-r--r-- 1 alice ... target.txt
# 1234568 lrwxrwxrwx 1 alice ... shortcut -> target.txt
#         ^ different inode; the 'l' marks it as a symlink

# Read through symlink — works
cat shortcut          # hello

# Delete the target — symlink becomes broken (dangling)
rm target.txt
cat shortcut          # cat: shortcut: No such file or directory

Why symlinks are more useful

• Can cross filesystems and disks.
• Can link to directories.
• You can SEE what they point to (ls -l shows the target).
• Editing/replacing the target updates the symlink’s contents automatically.

Real-world uses

Symlinks: latest version of a config or app

# Versioned releases, with 'current' always pointing to live one
/opt/myapp/releases/v1.0
/opt/myapp/releases/v1.1
/opt/myapp/current -> releases/v1.1

# Switch versions atomically
ln -snf /opt/myapp/releases/v1.2 /opt/myapp/current

Symlinks: dotfiles management

# Keep your dotfiles in a git repo, symlink them home
ln -s ~/dotfiles/.vimrc ~/.vimrc
ln -s ~/dotfiles/.bashrc ~/.bashrc
ln -s ~/dotfiles/.config/nvim ~/.config/nvim

Hard links: backups with deduplication

Tools like rsync --link-dest or rsnapshot create incremental backups where unchanged files are hard-linked to the previous snapshot — same data on disk, but appears in every snapshot folder.

Useful commands

ln -s target linkname            # create symlink
ln -sf target linkname           # force overwrite if linkname exists
ln -snf target linkname          # don't follow if linkname is a symlink to dir
ln target linkname               # create hard link

readlink linkname                # show what symlink points to
readlink -f linkname             # resolve all symlinks to absolute path
realpath linkname                # same idea

ls -l                            # symlinks shown with -> target
ls -li                           # also show inodes

find / -lname "/old/path"        # find symlinks pointing to old/path
find / -inum 1234567             # find all hard links to inode 1234567

When to use which

Need	Use
Pointer to a file in a different folder	Symlink
Versioned releases with “current” pointer	Symlink
Linking to a directory	Symlink (only option)
Cross-filesystem linking	Symlink
Backup deduplication	Hard link
Multiple “real” names for the same file	Hard link

Common mistakes

• Broken symlinks when you delete or move the target. Use ls -lL to spot them, or find / -xtype l.
• Relative vs absolute paths in symlinks: ln -s ../foo bar only works if you don’t move bar. Use absolute paths for stability.
• Hard linking before editing: writing to one hard link affects all of them. Sometimes that’s what you want; sometimes it’s a surprise.

What to learn next

Now that the basics of files and structure are covered, the next chunk of the roadmap is text processing — grep, sed, awk — the tools that make the shell a data processing environment.