Linux

47373 readers

795 users here now

From Wikipedia, the free encyclopedia

Linux is a family of open source Unix-like operating systems based on the Linux kernel, an operating system kernel first released on September 17, 1991 by Linus Torvalds. Linux is typically packaged in a Linux distribution (or distro for short).

Distributions include the Linux kernel and supporting system software and libraries, many of which are provided by the GNU Project. Many Linux distributions use the word "Linux" in their name, but the Free Software Foundation uses the name GNU/Linux to emphasize the importance of GNU software, causing some controversy.

Rules

Posts must be relevant to operating systems running the Linux kernel. GNU/Linux or otherwise.
No misinformation
No NSFW content
No hate speech, bigotry, etc

Related Communities

Community icon by Alpár-Etele Méder, licensed under CC BY 3.0

founded 5 years ago

MODERATORS

[email protected]

104

Is there an advantage of using doas over sudo (self.linux)

submitted 6 months ago by whyisthesheep to c/[email protected]

72 comments fedilink hide all child comments

I see people talking about doas saying it's just like sudo but with less features. I'm just wondering if there is any situation where you should use doas or if it's just personal preference.

you are viewing a single comment's thread
view the rest of the comments

[–] [email protected] 2 points 6 months ago (1 children)

The short answer is that my distro did not let me do this easily. But that was for good reason.

A system update would require too many privileges that it would be almost indistinguishable from root.

Currently, every user I have is restricted in what files it has access to. A system update user would need access to so many files, including install locations of all binaries, and non-binary installation paths of all current and future programs I install (some package installs modify /var, many modify /etc, and so on).

This user will also have access to all these programs, down to system applications. It can trivially break a permission system I come up with.

It may be possible to restrict system updates to a user, but it would be such a powerful user that its not really worth it.

[–] [email protected] 1 points 6 months ago (1 children)

Does the user have that access? In my case with rpm-ostree they can just execute 2 commands rpm-ostree refresh-md (get updates) and rpm-ostree update. rpm-ostree rebase is used for system upgrades afaik, that one needs a password.

[–] [email protected] 1 points 6 months ago (1 children)

Only the root user has access to system updates on my system currently.

What does rpm-ostree update do exactly? Does it execute the update? Or is that the rebase command only?

[–] [email protected] 1 points 6 months ago (2 children)

No rpm-ostree downloads the diffs, applies existing changes (added or removed packages) and builds a new image that gets staged as first boot target. After reboot you are on an updated system.

[–] [email protected] 3 points 6 months ago (1 children)

If it builds a new image that replaces the entire system it could be compromised to give full access to the entire system just as easily as sudo, possibly more easily.

[–] [email protected] 1 points 6 months ago (1 children)

No it just pulls the ostree / OCI image from the fedora image registry and applies changes that need sudo privileges to change, remove etc.

Deploying a different image is not allowed.

See this issue for details

[–] [email protected] 2 points 6 months ago (1 children)

The component that is like sudo in this case is polkit. Of course an unprivileged user can be used to run sudo commands as well, limited by the rules in the sudo config file, just as these polkit rules limit what the user can do...as long as there is no security issue in sudo and polkit respectively but the actual work is done by a privileged process that is merely controlled by the commands given by the unprivileged user.

[–] [email protected] 1 points 6 months ago

Yes thats the point, the specific actions are a good way to act like a firewall for the access to the privileged process, invoked by anyone.

This is brilliant, as unprivileged users over ssh, or not even logged in, can invoke the updates in that case, making a "grandma pc" that is immutable and autoupdating possible.

See this discussion on how it would eventually be implemented

[–] [email protected] 2 points 6 months ago (1 children)

I see. I have little knowledge, but I bet that the "root privileges" part of this process is the reboot. Upon rebooting, system updates are applied from the new image via some privileged process.

That's pretty neat. Unfortunately I haven't ventured deeply enough into that type of system yet (was it called immutable distro or something?). I use gentoo, which doesn't support this out of the box.

Thanks for showing me something new!

[–] [email protected] 1 points 6 months ago

Rebooting does not need root privileges either, on no system. There really is nothing privileged about updating already existing software. Android is completely rootless and updates are automatic, but can be done manually too.

You can read a bit into OSTree, its very cool. But seems to be very complex and somehow they want to switch to OCI images now, idk.

But the way ublue builds their systems is astonishing, elegant, simple, structured and fully automated.