This is emphatically NOT true.

If you absolutely could not write to /etc, then you would never be able to change your password.

The passwd, chsh, chfn, and other utilities allow a non-privileged user to make controlled changes to privileged files via the setuid/gid system calls.

A user can trigger controlled writes to files in /etc.

> If you absolutely could not write to /etc, then you would never be able to change your password.

Since we're talking about Linux, I would refrain from using absolute clauses like "never".

systemd-homed allows you to create "portable" user profiles which contain everything pertaining to a particular user, including his password. So user profiles (including your files, etc) can be moved between computers simply by rsync'ing that directory, or putting it on a network share.

`homectl passwd` (which changes a portable user's password) does not require writable /etc.

I think I've seen a few other solutions like that.

https://wiki.archlinux.org/title/Systemd-homed

https://systemd.io/HOME_DIRECTORY/

Users can not write to /etc, those programs like passwd can because they have the suid bit on and run as root regardless of which user initiated the process.

It's more so that users can ask the administrator to write to `/etc/` for them.

The administrator in this case has an automated tool that handles this requæst but the actual user the writing occurs under is the root user.

That's like saying you've broken RSA because you can cause controlled reads. All you have to do is send the encrypted message to the intended recipient and wait for them to decrypt it.

That's being a bit pedantic innit?

Maybe in OPs opinion, using `passwd` to write to `/etc/passwd` is not the same thing as using the registry API to write to the registry?

Personally, I feel it is the same thing.