Admin-CLI can create realms but cannot configure them due to unauthorized errors

Getting advice
1

I’m totally new to keycloak and trying to create a new realm via the admin cli. I can authenticate to the master realm, configure it, and create other realms. But I can’t configure those other realms, I just get a 401 unauthorised error. And since the other realms have no users I can’t authenticate to them directly. Here is an example trying to add a user to a newly created realm. Everything works except that last command. How could this be solved?

KCADM=/path-to/bin/kcadm.sh
KCADM_SERVER=http://localhost:80
ADMIN_USERNAME=theAdmin
ADMIN_PASSWORD=adminKey
# Authenticate
$KCADM config credentials \
    --server $KCADM_SERVER \
    --user $ADMIN_USERNAME \
    --password $ADMIN_PASSWORD \
    --realm master \
    --client admin-cli
REALM_NAME=second_realm
$KCADM create realms \
    --server $KCADM_SERVER \
    -s realm=${REALM_NAME} \
    -s enabled=true
$KCADM create users \
    --server $KCADM_SERVER \
    --realm $REALM_NAME \
    -s username="aNewUsername" \
    -s enabled=true \
    -s firstName="New" \
    -s lastName="User" \
    -s email="new.user@example.com"