問題1: k3s-agent啟動成功但是提示錯誤信息
錯誤信息示例：
[root@host122 ~]# k3s agent --server ${K3S_URL} --token ${K3S_TOKEN}
INFO[0000] Preparing data dir /var/lib/rancher/k3s/data/2492a28b74abfbdbd3f943c8109a93e979669647bbbe95eadae43b60c667df69
INFO[2019-11-27T00:37:00.465328558-05:00] Starting k3s agent v1.0.0 (18bd921c)
INFO[2019-11-27T00:37:00.466031302-05:00] module overlay was already loaded
INFO[2019-11-27T00:37:00.466065090-05:00] module nf_conntrack was already loaded
INFO[2019-11-27T00:37:00.466082470-05:00] module br_netfilter was already loaded
INFO[2019-11-27T00:37:00.468531171-05:00] Running load balancer 127.0.0.1:36065 -> [192.168.163.121:6443]
ERRO[2019-11-27T00:37:00.472709375-05:00] failed to get CA certs at https://127.0.0.1:36065/cacerts: Get https://127.0.0.1:3606
錯誤原因：k3s的server端iptables設定不正確。
問題2: 缺省安裝是否需要設定防火牆、iptables和SELINUX
在最小化的CentOS 7.6下缺省安裝，firewalld服務啟動狀態，SELINUX缺省狀態，並未特意做任何設定。使用離線安裝方式，k3s可以正常啟動和使用。SELINUX缺省狀態下只需要保證semanage所在的包policycoreutils-python安裝了即可。
問題3: kubectl cluster-info僅顯示127.0.0.1下能夠連接節點成功么
服務器端缺省安裝，使用kubectl cluster-info命令中返回的機器信息均為127.0.0.1，這是因為server的bind_address缺省設定的原因，在服務器端設定此項即可解決問題。但是如下狀態之下，並不影響agent的連接和kubectl get node的節點顯示。
[root@host121 ~]# kubectl cluster-info
Kubernetes master is running at https://127.0.0.1:6443
CoreDNS is running at https://127.0.0.1:6443/api/v1/namespaces/kube-system/services/kube-dns:dns/proxy
Metrics-server is running at https://127.0.0.1:6443/api/v1/namespaces/kube-system/services/https:metrics-server:/proxy
To further debug and diagnose cluster problems, use 'kubectl cluster-info dump'.
[root@host121 ~]#