Cannot add/modify/delete users and groups, cannot su to them, nor set their password

[Deleted user]

useradd, usermod, userdel, groupadd, groupmod, groupdel all result in Permission denied.
su root results in System Error.
passwd results in

passwd: System error
passwd: password unchanged

The strange thing is that I am able to do all these in the arch linux proot.

I've attempted replacing /etc, /bin, /lib` with arch linux's (yes I really did that :p) to sadly, no prevail.

[al20ov]

Same here, but I managed to execute passwd to change my user's password. But still, I can't add that user to the sudoers file.