Kubelet service not starting up - KUBELET_EXTRA_ARGS (code=exited, status=255) - kubernetes

Question

I am trying to start up the kubelet service on a worker node (the 3rd worker node)... at the moment, I can't quite tell what the error is here.. I do however, see F0716 16:42:20.047413 556 server.go:155] unknown command: $KUBELET_EXTRA_ARGS in the output given by sudo systemctl status kubelet -l:
[svc.jenkins#node6 ~]$ sudo systemctl status kubelet -l
● kubelet.service - kubelet: The Kubernetes Node Agent
Loaded: loaded (/etc/systemd/system/kubelet.service; enabled; vendor preset: disabled)
Drop-In: /etc/systemd/system/kubelet.service.d
└─10-kubeadm.conf
Active: activating (auto-restart) (Result: exit-code) since Mon 2018-07-16 16:42:20 CDT; 4s ago
Docs: http://kubernetes.io/docs/
Process: 556 ExecStart=/usr/bin/kubelet $KUBELET_KUBECONFIG_ARGS $KUBELET_SYSTEM_PODS_ARGS $KUBELET_NETWORK_ARGS $KUBELET_DNS_ARGS $KUBELET_AUTHZ_ARGS $KUBELET_CADVISOR_ARGS $KUBELET_CGROUP_ARGS $KUBELET_CERTIFICATE_ARGS $KUBELET_EXTRA_ARGS (code=exited, status=255)
Main PID: 556 (code=exited, status=255)
Jul 16 16:42:20 node6 kubelet[556]: --tls-cert-file string File containing x509 Certificate used for serving HTTPS (with intermediate certs, if any, concatenated after server cert). If --tls-cert-file and --tls-private-key-file are not provided, a self-signed certificate and key are generated for the public address and saved to the directory passed to --cert-dir. (DEPRECATED: This parameter should be set via the config file specified by the Kubelet's --config flag. See https://kubernetes.io/docs/tasks/administer-cluster/kubelet-config-file/ for more information.)
Jul 16 16:42:20 node6 kubelet[556]: --tls-cipher-suites strings Comma-separated list of cipher suites for the server. If omitted, the default Go cipher suites will be used. Possible values: TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA,TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256,TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256,TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA,TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384,TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305,TLS_ECDHE_ECDSA_WITH_RC4_128_SHA,TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA,TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA,TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256,TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256,TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA,TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384,TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305,TLS_ECDHE_RSA_WITH_RC4_128_SHA,TLS_RSA_WITH_3DES_EDE_CBC_SHA,TLS_RSA_WITH_AES_128_CBC_SHA,TLS_RSA_WITH_AES_128_CBC_SHA256,TLS_RSA_WITH_AES_128_GCM_SHA256,TLS_RSA_WITH_AES_256_CBC_SHA,TLS_RSA_WITH_AES_256_GCM_SHA384,TLS_RSA_WITH_RC4_128_SHA (DEPRECATED: This parameter should be set via the config file specified by the Kubelet's --config flag. See https://kubernetes.io/docs/tasks/administer-cluster/kubelet-config-file/ for more information.)
Jul 16 16:42:20 node6 kubelet[556]: --tls-min-version string Minimum TLS version supported. Possible values: VersionTLS10, VersionTLS11, VersionTLS12 (DEPRECATED: This parameter should be set via the config file specified by the Kubelet's --config flag. See https://kubernetes.io/docs/tasks/administer-cluster/kubelet-config-file/ for more information.)
Jul 16 16:42:20 node6 kubelet[556]: --tls-private-key-file string File containing x509 private key matching --tls-cert-file. (DEPRECATED: This parameter should be set via the config file specified by the Kubelet's --config flag. See https://kubernetes.io/docs/tasks/administer-cluster/kubelet-config-file/ for more information.)
Jul 16 16:42:20 node6 kubelet[556]: -v, --v Level log level for V logs
Jul 16 16:42:20 node6 kubelet[556]: --version version[=true] Print version information and quit
Jul 16 16:42:20 node6 kubelet[556]: --vmodule moduleSpec comma-separated list of pattern=N settings for file-filtered logging
Jul 16 16:42:20 node6 kubelet[556]: --volume-plugin-dir string The full path of the directory in which to search for additional third party volume plugins (default "/usr/libexec/kubernetes/kubelet-plugins/volume/exec/")
Jul 16 16:42:20 node6 kubelet[556]: --volume-stats-agg-period duration Specifies interval for kubelet to calculate and cache the volume disk usage for all pods and volumes. To disable volume calculations, set to 0. (default 1m0s) (DEPRECATED: This parameter should be set via the config file specified by the Kubelet's --config flag. See https://kubernetes.io/docs/tasks/administer-cluster/kubelet-config-file/ for more information.)
Jul 16 16:42:20 node6 kubelet[556]: F0716 16:42:20.047413 556 server.go:155] unknown command: $KUBELET_EXTRA_ARGS
Here is the configuration for my dropin loacated at /etc/systemd/system/kubelet.service.d/10-kubeadm.conf (it is the same on the other nodes that are in a working state):
[Service]
Environment="KUBELET_KUBECONFIG_ARGS=--bootstrap-kubeconfig=/etc/kubernetes/bootstrap-kubelet.conf --kubeconfig=/etc/kubernetes/kubelet.conf"
Environment="KUBELET_SYSTEM_PODS_ARGS=--pod-manifest-path=/etc/kubernetes/manifests --allow-privileged=true"
Environment="KUBELET_NETWORK_ARGS=--network-plugin=cni --cni-conf-dir=/etc/cni/net.d --cni-bin-dir=/opt/cni/bin"
Environment="KUBELET_DNS_ARGS=--cluster-dns=10.96.0.10 --cluster-domain=cluster.local"
Environment="KUBELET_AUTHZ_ARGS=--authorization-mode=Webhook --client-ca-file=/etc/kubernetes/pki/ca.crt"
Environment="KUBELET_CADVISOR_ARGS=--cadvisor-port=0"
Environment="KUBELET_CGROUP_ARGS=--cgroup-driver=cgroupfs"
Environment="KUBELET_CERTIFICATE_ARGS=--rotate-certificates=true --cert-dir=/data01/kubelet/pki"
Environment="KUBELET_EXTRA_ARGS=$KUBELET_EXTRA_ARGS --root-dir=/data01/kubelet"
ExecStart=
ExecStart=/usr/bin/kubelet $KUBELET_KUBECONFIG_ARGS $KUBELET_SYSTEM_PODS_ARGS $KUBELET_NETWORK_ARGS $KUBELET_DNS_ARGS $KUBELET_AUTHZ_ARGS $KUBELET_CADVISOR_ARGS $KUBELET_CGROUP_ARGS $KUBELET_CERTIFICATE_ARGS $KUBELET_EXTRA_ARGS
Just need help diagnosing what the issue preventing it from starting so that it can be resolved.. Thank in advanced :)
EDIT:
[svc.jenkins#node6 ~]$ kubelet --version
Kubernetes v1.10.4

Answer 1

Currently, in systemd a bit different approach is used. All options are put to separate file and systemd config script refers to that file.
In your case, it would be something like this:
/etc/sysconfig/kubelet
----------------------
KUBELET_KUBECONFIG_ARGS=--bootstrap-kubeconfig=/etc/kubernetes/bootstrap-kubelet.conf --kubeconfig=/etc/kubernetes/kubelet.conf
KUBELET_SYSTEM_PODS_ARGS=--pod-manifest-path=/etc/kubernetes/manifests --allow-privileged=true
KUBELET_NETWORK_ARGS=--network-plugin=cni --cni-conf-dir=/etc/cni/net.d --cni-bin-dir=/opt/cni/bin
KUBELET_DNS_ARGS=--cluster-dns=10.96.0.10 --cluster-domain=cluster.local
KUBELET_AUTHZ_ARGS=--authorization-mode=Webhook --client-ca-file=/etc/kubernetes/pki/ca.crt
KUBELET_CADVISOR_ARGS=--cadvisor-port=0
KUBELET_CGROUP_ARGS=--cgroup-driver=cgroupfs
KUBELET_CERTIFICATE_ARGS=--rotate-certificates=true --cert-dir=/data01/kubelet/pki
KUBELET_EXTRA_ARGS=$KUBELET_EXTRA_ARGS --root-dir=/data01/kubelet
/etc/systemd/system/kubelet.service.d/10-kubeadm.conf
-----------------------------------------------------
...
[Service]
EnvironmentFile=/etc/sysconfig/kubelet
ExecStart=/usr/bin/kubelet $KUBELET_KUBECONFIG_ARGS $KUBELET_SYSTEM_PODS_ARGS $KUBELET_NETWORK_ARGS $KUBELET_DNS_ARGS $KUBELET_AUTHZ_ARGS $KUBELET_CADVISOR_ARGS $KUBELET_CGROUP_ARGS $KUBELET_CERTIFICATE_ARGS $KUBELET_EXTRA_ARGS
The variables in systemd config file could look like ${VARIABLE} or $VARIABLE. Both cases should work fine.