本文使用的istio版本：
1.4.2
查看默认sidecar配置
kubectl get mutatingwebhookconfiguration istio-sidecar-injector -o yaml | grep "namespaceSelector:" -A5
namespaceSelector:
matchLabels:
istio-injection: enabled
objectSelector: {}
reinvocationPolicy: Never
rules:
可以看出，istio默认sidecar注入规则是，namespace带有标签istio-injection: enabled才会注入sidecar。
查看哪些namespace已经配置注入：
[root@k8s-master istio-1.4.2]# kubectl get namespace -L istio-injection
NAME STATUS AGE ISTIO-INJECTION
default Active 70d
ingress-nginx Active 69d
istio-system Active 19h
kube-node-lease Active 70d
kube-public Active 70d
kube-system Active 70d
naftis Active 19h
test-deri Active 47d
为namespace打上注入sidecar标签：
kubectl label namespace default istio-injection=enabled --overwrite
默认情况，是没有设置。
为namespace设置不注入sidecar
有些k8s系统组件namespace不应该注入sidecar，如kube-system等，参考如下设置
kubectl get mutatingwebhookconfiguration istio-sidecar-injector -o yaml | grep "namespaceSelector:" -A5
namespaceSelector:
matchExpressions:
- key: istio-injection
operator: NotIn
values:
- disabled
rules:
- apiGroups:
- ""
为namespace打上不注入sidecar标签:
kubectl label namespace istio-system istio-injection=disabled --overwrite
kubectl get namespace -L istio-injection
NAME STATUS AGE ISTIO-INJECTION
default Active 18d
istio-system Active 3d disabled
kube-public Active 18d disabled
kube-system Active 18d disabled
查看sidecar配置策略
sidecar配置保存在configmap-istio-sidecar-injector中，更多配置可以在install/kubernetes/helm/istio/charts/sidecarInjectorWebhook/values.yaml中查看。
主要配置，默认策略：
kubectl -n istio-system get configmap istio-sidecar-injector -o jsonpath='{.data.config}' | grep policy:
允许的值为disabled和enabled。仅当Webhook namespaceSelector匹配目标名称空间时，才应用默认策略。无法识别的策略导致注入被完全禁用。
注意：①策略为
disabled，但是想要为POD注入sidecar，增加annotation sidecar.istio.io/inject: "true"即可
②策略为enabled，但是不想要为POD注入sidecar，增加annotation sidecar.istio.io/inject: "false"即可
apiVersion: apps/v1
kind: Deployment
metadata:
name: ignored
spec:
template:
metadata:
annotations:
sidecar.istio.io/inject: "false"
spec:
containers:
- name: ignored
image: tutum/curl
command: ["/bin/sleep","infinity"]
手动注入sidecar
为一个写好的yaml文件手动注入sidecar，我们可以使用istioctl kube-inject:
istioctl kube-inject -f samples/sleep/sleep.yaml | kubectl apply -f -
默认情况下，这将使用集群内配置。或者，可以使用配置的本地副本来完成注入。下面命令可以将默认配置导出到文件：
kubectl -n istio-system get configmap istio-sidecar-injector -o=jsonpath='{.data.config}' > inject-config.yaml
kubectl -n istio-system get configmap istio-sidecar-injector -o=jsonpath='{.data.values}' > inject-values.yaml
kubectl -n istio-system get configmap istio -o=jsonpath='{.data.mesh}' > mesh-config.yaml
然后再将文件中配置注入到已建好的YAML中并运行：
istioctl kube-inject \
--injectConfigFile inject-config.yaml \
--meshConfigFile mesh-config.yaml \
--valuesFile inject-values.yaml \
--filename samples/sleep/sleep.yaml \
| kubectl apply -f -
这和第一条命令效果一样。验证sidecar已经注入：
kubectl get pod -l app=sleep
NAME READY STATUS RESTARTS AGE
sleep-64c6f57bc8-f5n4x 2/2 Running 0 24s
其它配置：neverInjectSelector/alwaysInjectSelector
参考官网
示例：
apiVersion: v1
kind: ConfigMap
metadata:
name: istio-sidecar-injector
data:
config: |-
policy: enabled
neverInjectSelector:
- matchExpressions:
- {key: openshift.io/build.name, operator: Exists}
- matchExpressions:
- {key: openshift.io/deployer-pod-for.name, operator: Exists}
template: |-
initContainers:
...
配置优先级
如果POD配置了注解、neverInjectSelector/alwaysInjectSelector也都配置了，默认策略也配置了，那么他们之间的优先级参考如下：
Pod Annotations → NeverInjectSelector → AlwaysInjectSelector → Default Policy
卸载自动注入sidecar
卸载istio中sidecar组件
kubectl delete mutatingwebhookconfiguration istio-sidecar-injector
kubectl -n istio-system delete service istio-sidecar-injector
kubectl -n istio-system delete deployment istio-sidecar-injector
kubectl -n istio-system delete serviceaccount istio-sidecar-injector-service-account
kubectl delete clusterrole istio-sidecar-injector-istio-system
kubectl delete clusterrolebinding istio-sidecar-injector-admin-role-binding-istio-system
删除某个namespace自动注入
kubectl label namespace default istio-injection-
sidecar注入问题
更多可以参考官网.