Unshare

The Podman container technology relies on namespaces. New Linux Namespaces are typically spawned by using either the clone or unshare system calls. These exist as C functions that have wrapper in many languages. For using in a shell, unshare is more straight forward.

unshare --help

The mnt_ns is what responsible for storing the mount table in Linux kernel. When a sandboxed environment like a container runs in a new Mount Namespace, it can mount filesystems not present on the host.

sudo unshare -m /bin/bash

[sudo] password for localhost:
root@localhost:/var/home/localhost/# whoami
root

depending on where you are using, you may need sudo.

• Unshare wraps the unshare kernel sys call.
• -m requests a mount new Namespace.
• /bin/bash tells what program to run after the mount. We ran bash thus, it gave a bash terminal

mount -t tmpfs tmpfs /mnt
mount | grep mnt

It creates a tem fs in ram and covers up the existing up one.

Now lets add something to the new /mnt

date > /mnt/date
cat /mnt/date

Fri Sep 11 10:49:31 AM +0530 2026

Seems date added to /mnt ?

We can exit the name space either by closing the terminal tab or using the exit command.

exit

exit

Now let's try reading from /mnt/date

cat /mnt/date

cat: /mnt/date: No such file or directory

As it was created in a temporary mount namespace, it is gone after exit.