Comment on What's the deal with Docker?
slazer2au@lemmy.world 6 months ago
IMHO with docker and containerization in general you are trading drive space for consistency and relative simplicity.
a hypothetical:
You set up your mumble server and it requires the leftpad 3.7 package to run. you install it and everything is fine.
Now you install your ftp server but it needs leftpad 5.5. what do you do? hope the function that mumble uses in 3.7 still exists in 5.5? run each app in its own venv?
Docker and containerization resolve this by running each app in its own mini virtual machine. A container running mumble and leftpad 3.7 can coexist on host that also has a container running a ftp server with leftpad 5.5.
Here is a good video on what hole docker and containerization looks to fill
www.youtube.com/watch?v=Nm1tfmZDqo8
I would also add security, or at least accessible security. Containers provide a number of isolation features out-of-the-box or extremely easy to configure which other systems require way more effort to achieve, or can’t achieve.
Ironically, after some conversation on the topic here on Lemmy I compiled a blog post about it.
Tbf, systemd also makes it relatively easy to sandbox processes. But it’s opt-in, while for containers it’s opt-out.
Yeah, and it also requires quite many options, some with harder-to-predict outcomes. For example RootDirectory can be used to effectively chroot the process, but that carries implications such as the application not having access to CA certificates anymore, which in general in containers is a solved problem.
Docker and containerization resolve this by running each app in its own mini virtual machine
While you’re wrong, I get why you did the comparison, however there are tons of other containerization solutions that can exactly what you’re describing without the dark side of Docker.
riskable@programming.dev 6 months ago
Docker containers aren’t running in a virtual machine. They’re running what amounts to a fancy chroot jail… It’s just an isolated environment that takes advantage of several kernel security features to make software running inside the environment think everything is normal despite being locked down.
This is a very important distinction because it means that docker containers are very light weight compared to a VM. They use but a fraction of the resources a VM would and can be brought up and down in milliseconds since there’s no hardware to emulate.
notfromhere@lemmy.ml 6 months ago
FYI docker engine can use different runtimes and there is are lightweight vm runtimes like kata or firecracker. I hope one day docker will default with that technology as it would be better for the overall security of containers.
uzay@infosec.pub 6 months ago
To put it in simpler terms, I’d say that containers virtualise only the operating system rather than the whole underlying machine.
pztrn@bin.pztrn.name 6 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 6 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.
Atemu@lemmy.ml 6 months ago
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.
lemann@lemmy.dbzer0.com 6 months ago
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