Comment on What's the deal with Docker?
uzay@infosec.pub 8 months agoTo put it in simpler terms, I’d say that containers virtualise only the operating system rather than the whole underlying machine.
The operating system is explicitly not virtualised with containers.
What you’ve described is closer to paravirtualisation where it’s still a separate operating system in the guest but the hardware doesn’t pretend to be physical anymore and is explicitly a software interface.
Not exactly IMO, as containers themselves can simultaneously access devices and filesystems from the host system natively (such as VAAPI devices used for hardware encoding & decoding) or even the docker socket to control the host system’s Docker daemon.
They also can launch directly into a program you specify, bypassing any kind of init system requirement.
OC’s suggestion of a chroot jail is the closest explanation I can think of too, if things were to be simplified
pztrn@bin.pztrn.name 8 months ago
It virtualises only parts of operating system (namely processes and network namespaces with ability to passthru devices and mount points). It is still using host kernel, for example.
loudwhisper@infosec.pub 8 months ago
I wouldn’t say that namespaces are virtualization either. Container don’t virtualize anything, namespaces are all inherited from the root namespaces and therefore completely visible from the host (with the right privileges). It’s just a completely different technology.
steakmeoutt@sh.itjust.works 8 months ago
The word you’re all looking for is sandboxing. That’s what containers are - sandboxes. And while they a different approach to VMs they do rely on some similar principals.
pztrn@bin.pztrn.name 8 months ago
I never said that it is a virtualization. Yet for easy understanding I named created namespaces “virtualized”. Here I mean “virtualized” = “isolated”. Systemd able to do that with every process btw.
Also, some “smart individuals” called comtainerization as type 3 hypervisors, that makes me laugh so hard :)