A new breed of distros for sure but how immutable is it, really? What I'm interested in knowing is the mechanisms and techniques in place for making sure no one can change any core components of the system. It's just like randomness. At first, it sounds super secure but we all know nothing is truly random
Around 2000 I made a firewall-oriented Linux distro that made use of immutable bits and SELinux and various other security hardening. The bulk of the filesystem was immutable, and the system was then put into multi-user mode, where the kernel enforced that the filesystem couldn't go back to mutable.
During boot time, a directory was checked for update packages, and if the public key signature of the package matched, the updates would be applied before the filesystem went into immutable mode. This update directory was one of the few mutable directories on the system.
Back around that time I remember running such a firewall OS on a floppy disk. You would set the floppy readonly, and you could update the floppy by taking it out. It ran entirely in RAM. I forgot the name, it was either Linux 2.0.x or 2.2.x. I don't even remember if settings were kept after reboot. I installed it for a friend of a friend in his student apartment.
Years later, I gave a daughter of a friend of my mother my old PC. It would boot up a Linux live CD. That, too, is immutable, and you'd update it by burning a new live CD.
But where did we arrive to this? Well, computers had all services enabled for some reason (not with big bad internet in mind, but LAN). And updates were distributed via CDs or different media. Some airgapped environments are still going to work akin to that. Now, if the devices are connected to internet, they have to be updated because security vulnerabilities are going to have been discovered.
I don't think most immutable distros are designed to prevent users from mounting the root filesystem as read write. They're instead designed around delivering a core system that's guaranteed to work
> I don't think most immutable distros are designed to prevent users from mounting the root filesystem as read write.
Someone mentioned running Puppy Linux from a CD/DVD (write once).
I do wonder: it'd probably be possible for me to boot a Linux distro from a DVD and then launch Promox and my VMs/containers automatically. I take it I'd have to burn a new DVD every time a security patch affecting programs installed on the bare system comes out.
The "main" OS would be hard to compromise in a persistent way as you cannot remount a write-only DVD read-write.
