GNU Coreutils are what they sound like; a GNU version of a bunch of basic, core Unix programs such as 'mkdir', 'head', 'chmod', 'cp', 'mv', and so on. For a long time, talking about 'GNU Coreutils' was unnecessary and you could just talk about 'Coreutils'. Then some people decided to rewrite Coreutils in Rust, the uutils coreutils , which still wouldn't be very important for most people except that Canonical decided to make the Rust versions the default in Ubuntu 25.10 and then 26.04.

In theory the Rust coreutils aim for 100% compatibility with GNU Coreutils and anything to the contrary is a bug. In practice, I found an incompatibility almost immediately when testing 26.04 pre-release, Ubuntu bug reports are useless , and I was pretty certain that other people on our systems would run into other issues, so I decided that we would sit out this round of Canonical making 26.04 LTS people mandatory beta-testers of their current passion project.

Canonical doesn't make it easy to switch from Rust uutils to GNU Coreutils, but they do at least make it possible. The magic apt-get command you need is:

apt-get install coreutils-from-gnu coreutils-from-uutils- --allow-remove-essential

(Taken from here .)

If you do this, I suggest that you immediately do ' apt-mark hold coreutils-from-uutils ' (you may not want to hold 'coreutils-from-gnu', since there might be bugfix updates to it for some reason, although the real programs are in the ' gnu-coreutils ' package).

The reason you might want to do this is, well, let me quote a Fediverse post of mine :

Ubuntu: you can totally continue to use GNU Coreutils in 26.04 LTS.
Also Ubuntu: build-essential depends on the new Rust coreutils.

Yeah, that's not "you can totally continue to use GNU Coreutils", although it sure is tempting to build my own build-essential package with a different dependency.

What this means in practice is that if you install coreutils-from-gnu, the build-essential package is uninstalled if you have it installed, and if you install build-essential later, coreutils-from-gnu is uninstalled and coreutils-from-uutils (the Rust version) is reinstalled. If you're not paying close attention to all of the messages that an 'apt-get' is printing out, you might miss this (especially if the apt-get is happening in the middle of your general install framework). Then you will be surprised, as I was, when it turns out that your 26.04 systems have Rust coreutils despite you theoretically having switched.

Build-essential itself doesn't do much, although installing it is a convenient way to get some core software building tools (especially if you want to build Ubuntu packages, perhaps to make local changes). What really matters is that 'apt-get build-dep' will insist on installing build-essential, and you may want to do 'apt-get build-dep <some package>' for all sorts of reasons. For example, if you're going to build your own Emacs , 'apt-get build-dep emacs' is a convenient way to get most or all of the development packages it's going to want, rather than looking them up and getting each one yourself.

The build-essential dependency is explicit:

$ apt-cache show build-essential
[...]
Depends: libc6-dev | libc-dev, gcc (>= 4:14.2), g++ (>= 4:14.2), make, dpkg-dev (>= 1.22.11), coreutils-from-uutils

Not 'coreutils' (a meta-package that depends on either), not explicitly 'coreutils-from-uutils | coreutils-from-gnu', a direct, specific dependency on the Rust coreutils. This turns out to be a Canonical bodge from September 2025 that's not in the upstream package ( via ). Since this is an explicit dependency, dealing with it requires things like building your own version of build-essential that has a fixed dependency ( perhaps with dgit ).

There may be other packages with specific dependencies on 'coreutils-from-uutils', which is why I suggested you explicitly 'apt-mark hold' it. With the package held (or both coreutils-from-* packages held), 'apt-get install <some package>' will abort rather than flip your Coreutils setup around. Then at least you can find out which new package will make you unhappy with Canonical.

("apt-cache rdepends coreutils-from-uutils' doesn't show me anything on our Ubuntu 26.04 LTS machines, but I don't know if that's complete across the entire Ubuntu package set for 26.04.)