Seu comando está errado.
passwd -d Madhu G
passwd
aceita isso:
passwd [options] [LOGIN]
Seu comando se desvia desse requisito e, portanto, uma lista de possíveis parâmetros será exibida:
$ passwd -d Madhu G
Usage: passwd [options] [LOGIN]
Options:
-a, --all report password status on all accounts
-d, --delete delete the password for the named account
-e, --expire force expire the password for the named account
-h, --help display this help message and exit
-k, --keep-tokens change password only if expired
-i, --inactive INACTIVE set password inactive after expiration
to INACTIVE
-l, --lock lock the password of the named account
-n, --mindays MIN_DAYS set minimum number of days before password
change to MIN_DAYS
-q, --quiet quiet mode
-r, --repository REPOSITORY change password in REPOSITORY repository
-R, --root CHROOT_DIR directory to chroot into
-S, --status report password status on the named account
-u, --unlock unlock the password of the named account
-w, --warndays WARN_DAYS set expiration warning days to WARN_DAYS
-x, --maxdays MAX_DAYS set maximum number of days before password
change to MAX_DAYS
Corrija a sintaxe, mas ainda errada, porque com espaço e sem minúsculas:
sudo passwd -d "Madhu G"
Para sua conta (má ideia)
sudo passwd -d "$USER"
ou para outro nome de login (sem espaços e com letras minúsculas):
sudo passwd -d <username>