Run Docker Container in Privileged Mode

When working with Docker, containers are designed to be isolated and restricted from performing sensitive host operations like mounting filesystems, managing devices, or manipulating the kernel. This security model is great for safety - but sometimes, it gets in the way when you need low-level system access. This tutorial explains how to run Docker container in privileged mode.

Try running a standard Ubuntu container:

docker run -it --rm ubuntu

Inside the container, run the following commands to mount a temporary file system (tmpfs) to /mnt/test:

mkdir -p /mnt/test

mount -t tmpfs none /mnt/test

You'll get an error:

mount: /mnt/test: permission denied.
       dmesg(1) may have more information after failed mount system call.

This happens because mounting filesystems requires elevated capabilities (CAP_SYS_ADMIN), which are not available in standard containers for security reasons.

Privileged mode gives the container almost full access to the host system, including capabilities and devices that are normally blocked.

Here's how to run the same container with --privileged:

docker run -it --rm --privileged ubuntu

Now inside the container, repeat the same commands to mount tmpfs.

Check the disk space usage in a human-readable format using the following command:

df -h

Output example:

Filesystem                         Size  Used Avail Use% Mounted on
overlay                             39G   11G   26G  30% /
tmpfs                               64M     0   64M   0% /dev
shm                                 64M     0   64M   0% /dev/shm
/dev/mapper/ubuntu--vg-ubuntu--lv   39G   11G   26G  30% /etc/hosts
none                                12G     0   12G   0% /mnt/test

You can now see that the tmpfs mount at /mnt/test succeeded.

Using --privileged is powerful - and dangerous:

• The container gets access to all devices.
• It can mount filesystems, modify host networking, and more.
• It effectively runs as root on the host.

Avoid using --privileged in production unless you absolutely need to, and only with trusted images.