xsetuser 'root': Function not implemented

[imycroft]

I am building a minimal Linux system, I was trying with busybox and everything worked fine, I decided to try toybox, so I used its init file and included getty as well. When I tried to login I got the error message :
xsetuser 'root': Function not implemented
so, I searched that function, I found it in login.c, I searched its implementation and it is in xwrap.c
xwrap.c

void xsetuser(struct passwd *pwd) { if (initgroups(pwd->pw_name, pwd->pw_gid) || setgid(pwd->pw_gid) || setuid(pwd->pw_uid)) perror_exit("xsetuser '%s'", pwd->pw_name); }

I think it fails when trying to initgroups, even though I do have an /etc/group, so what I did is changing the code to :
xwrap.c modified

void xsetuser(struct passwd *pwd)
{
    int res;

    res = initgroups(pwd->pw_name, pwd->pw_gid);

    // tolerate ENOSYS if UID matches current UID
    if (res != 0) {
        if (errno == ENOSYS && pwd->pw_uid == getuid()) {
            // skip, assume single-user system
        } else {
            perror_exit("xsetuser '%s'", pwd->pw_name);
        }
    }

    if (setgid(pwd->pw_gid) < 0 || setuid(pwd->pw_uid) < 0)
        perror_exit("xsetuser '%s'", pwd->pw_name);
}

almost similar to busybox's and it is working fine.
NB: I enabled the multiuser on my kernel, so the problem does not come from there
So I don't know where the failure is coming from.

[landley]

On 1/30/26 11:40, HAFID Walid wrote: imycroft created an issue (landley/toybox#595) I am building a minimal Linux system, I was trying with busybox and everything worked fine, I decided to try toybox, so I used its **init** file and included getty as well.

You mean toys/pending/getty.c next to https://github.com/landley/toybox/blob/master/toys/pending/README that says commands in this directory may not work at all? The toybox init script doesn't use getty, it uses setsid -c: https://github.com/landley/toybox/blob/master/mkroot/mkroot.sh#L139

When I tried to login I got the error message : xsetuser 'root': Function not implemented

That's a kernel message, it means either initgroups(), setgid(), or setuid() returned... I'd guess ENOSYS, which the kernel's asm-generic/errno-base.h labels "Invalid system call number" but your libc seems to have renamed... Yup, that's what musl-libc uses for ENOSYS in src/errno/__strerror.h The busybox code you pasted added a special case to ignore that error with a comment that someone could remove it in their kernel config, which seems to be what you've done here (and then want me to add support for). And then ran getty whose job is (and I quote the --help output): "Wait for a modem to dial into serial port, adjust baud rate, call login." What is login supposed to do in this case?

[imycroft]

I would say that ToyBox's login isn't tolerant about single user Systems or minimalistic ones.