I accidentally changed my root shell to use a nonexistent shell, and now the root user crashes when I attempt to log in. Since I do not have sudo installed, I can't manually change the shell in etc/passwd. Are there any options in rescue mode that might help me?
Posting this as the answer to further help those in need.
Use a Live disc in this case any live disc will work.
Mount the Drive and use chroot like
@Christoper Simon stated.
And modify any settings you made that made the Distro Unusable.
/etc/shells to include a line that matches the shell you have defined for root, such as
Just having this present seems to be enough to ignore it.
su -s '/bin/bash' -c 'vi /etc/passwd'
This should hang for a bit while it looks for zsh, then carry on and run bash and execute the command.