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Reviewed-by: Eotvos, Oliver <oliver.eotvos@t-systems.com> Co-authored-by: qiujiandong1 <qiujiandong1@huawei.com> Co-committed-by: qiujiandong1 <qiujiandong1@huawei.com>
108 lines
9.5 KiB
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108 lines
9.5 KiB
HTML
<a name="ucs_01_0150"></a><a name="ucs_01_0150"></a>
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<h1 class="topictitle1">Setting Environment Variables</h1>
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<div id="body8662426"><div class="section" id="ucs_01_0150__en-us_topic_0000001199341154_section91908379912"><h4 class="sectiontitle">Scenario</h4><p id="ucs_01_0150__en-us_topic_0000001199341154_p1566654220910">An environment variable is a variable whose value can affect the way a running container will behave. You can modify environment variables even after workloads are deployed, increasing flexibility in workload configuration.</p>
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<p id="ucs_01_0150__en-us_topic_0000001199341154_p33421347172917">The function of setting environment variables on UCS is the same as that of specifying <span class="parmname" id="ucs_01_0150__en-us_topic_0000001199341154_parmname1630339175319"><b>ENV</b></span> in a Dockerfile.</p>
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<div class="notice" id="ucs_01_0150__en-us_topic_0000001199341154_note1262611218201"><span class="noticetitle"><img src="public_sys-resources/notice_3.0-en-us.png"> </span><div class="noticebody"><p id="ucs_01_0150__en-us_topic_0000001199341154_p103084565278">After a container is started, do not modify configurations in the container. If configurations in the container are modified (for example, passwords, certificates, and environment variables of a containerized application are added to the container), the configurations will be lost after the container restarts and container services will become abnormal. An example scenario of container restart is pod rescheduling due to node anomalies.</p>
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<p id="ucs_01_0150__en-us_topic_0000001199341154_p26271321192016">Configurations must be imported to a container as arguments. Otherwise, configurations will be lost after the container restarts.</p>
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</div></div>
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<p id="ucs_01_0150__en-us_topic_0000001199341154_p78261119155911">Environment variables can be set in the following modes:</p>
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<ul id="ucs_01_0150__en-us_topic_0000001199341154_ul1669104610598"><li id="ucs_01_0150__en-us_topic_0000001199341154_li266913468594"><strong id="ucs_01_0150__b1539395315590">Custom</strong>: Enter a variable name and value.</li><li id="ucs_01_0150__en-us_topic_0000001199341154_li13148164912599"><strong id="ucs_01_0150__en-us_topic_0000001199341154_b151552136536">Added from ConfigMap</strong>: Import all keys in a ConfigMap as environment variables.</li><li id="ucs_01_0150__en-us_topic_0000001199341154_li1855315291026"><strong id="ucs_01_0150__en-us_topic_0000001199341154_b5398577535">Added from ConfigMap key</strong>: Import a key in a ConfigMap as the value of an environment variable. For example, if you import <strong id="ucs_01_0150__b47601957162410">configmap_value</strong> of <strong id="ucs_01_0150__b1476015717240">configmap_key</strong> in ConfigMap <strong id="ucs_01_0150__b47611557192417">configmap-example</strong> as the value of environment variable <strong id="ucs_01_0150__b07619573246">key1</strong>, an environment variable named <strong id="ucs_01_0150__b137613571242">key1</strong> with its value <strong id="ucs_01_0150__b18761657162414">is configmap_value</strong> exists in the container.</li><li id="ucs_01_0150__en-us_topic_0000001199341154_li1727795616592"><strong id="ucs_01_0150__en-us_topic_0000001199341154_b675162614437">Added from secret</strong>: Import all keys in a secret as environment variables.</li><li id="ucs_01_0150__en-us_topic_0000001199341154_li93353201773"><strong id="ucs_01_0150__en-us_topic_0000001199341154_b0483141614480">Added from secret key</strong>: Import the value of a key in a secret as the value of an environment variable. For example, if you import <strong id="ucs_01_0150__en-us_topic_0000001199341154_b20412138105018">secret_value</strong> of <strong id="ucs_01_0150__en-us_topic_0000001199341154_b1248714112506">secret_key</strong> in secret <strong id="ucs_01_0150__en-us_topic_0000001199341154_b2010675411500">secret-example</strong> as the value of environment variable <strong id="ucs_01_0150__en-us_topic_0000001199341154_b1260612005113">key2</strong>, an environment variable named <strong id="ucs_01_0150__en-us_topic_0000001199341154_b2906162410511">key2</strong> with its value <strong id="ucs_01_0150__en-us_topic_0000001199341154_b26293438519">secret_value</strong> exists in the container.</li><li id="ucs_01_0150__en-us_topic_0000001199341154_li1749760535"><strong id="ucs_01_0150__en-us_topic_0000001199341154_b44091721105314">Variable Value/Reference</strong>: Use the field defined by a pod as the value of the environment variable, for example, the pod name.</li><li id="ucs_01_0150__en-us_topic_0000001199341154_li16129071317"><strong id="ucs_01_0150__en-us_topic_0000001199341154_b11429919184010">Resource Reference</strong>: Use the field defined by a container as the value of the environment variable, for example, the CPU limit of the container.</li></ul>
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</div>
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<div class="section" id="ucs_01_0150__en-us_topic_0000001199341154_section13829152011595"><h4 class="sectiontitle">Adding Environment Variables</h4><ol id="ucs_01_0150__en-us_topic_0000001199341154_ol4904646935"><li id="ucs_01_0150__en-us_topic_0000001199341154_li190412461831"><span>When creating a workload, select <strong id="ucs_01_0150__en-us_topic_0000001199341154_b23218253516">Environment Variables</strong> under <strong id="ucs_01_0150__en-us_topic_0000001199341154_b1763818524318">Container Settings</strong>.</span></li><li id="ucs_01_0150__en-us_topic_0000001199341154_li468251942720"><span>Set environment variables.</span></li></ol>
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</div>
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<div class="section" id="ucs_01_0150__en-us_topic_0000001199341154_section19591158201313"><h4 class="sectiontitle">YAML Example</h4><pre class="screen" id="ucs_01_0150__en-us_topic_0000001199341154_screen1034117614147">apiVersion: apps/v1
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kind: Deployment
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metadata:
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name: env-example
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namespace: default
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spec:
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replicas: 1
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selector:
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matchLabels:
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app: env-example
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template:
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metadata:
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labels:
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app: env-example
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spec:
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containers:
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- name: container-1
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image: nginx:alpine
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imagePullPolicy: Always
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resources:
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requests:
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cpu: 250m
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memory: 512Mi
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limits:
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cpu: 250m
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memory: 512Mi
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env:
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- name: key # Custom
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value: value
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- name: key1 # Added from ConfigMap key
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valueFrom:
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configMapKeyRef:
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name: configmap-example
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key: key1
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- name: key2 # Added from secret key
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valueFrom:
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secretKeyRef:
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name: secret-example
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key: key2
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- name: key3 # Variable reference, which uses the field defined by a pod as the value of the environment variable.
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valueFrom:
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fieldRef:
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apiVersion: v1
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fieldPath: metadata.name
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- name: key4 # Resource reference, which uses the field defined by a container as the value of the environment variable.
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valueFrom:
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resourceFieldRef:
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containerName: container1
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resource: limits.cpu
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divisor: 1
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envFrom:
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- configMapRef: # Added from ConfigMap
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name: configmap-example
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- secretRef: # Added from secret
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name: secret-example
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imagePullSecrets:
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- name: default-secret</pre>
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</div>
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<div class="section" id="ucs_01_0150__en-us_topic_0000001199341154_section74514162911"><h4 class="sectiontitle">Viewing Environment Variables</h4><p id="ucs_01_0150__en-us_topic_0000001199341154_p67543412911">If the contents of <strong id="ucs_01_0150__en-us_topic_0000001199341154_b173111319716">configmap-example</strong> and <strong id="ucs_01_0150__en-us_topic_0000001199341154_b1469452310710">secret-example</strong> are as follows:</p>
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<pre class="screen" id="ucs_01_0150__en-us_topic_0000001199341154_screen11127515162414">$ kubectl get configmap configmap-example -oyaml
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apiVersion: v1
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data:
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configmap_key: configmap_value
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kind: ConfigMap
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...
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$ kubectl get secret secret-example -oyaml
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apiVersion: v1
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data:
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secret_key: c2VjcmV0X3ZhbHVl # <strong id="ucs_01_0150__en-us_topic_0000001199341154_b197355321293">c2VjcmV0X3ZhbHVl</strong> is the value of secret_value in Base64 mode.
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kind: Secret
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...</pre>
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<p id="ucs_01_0150__en-us_topic_0000001199341154_p1573082017305">The environment variables in the pod are as follows:</p>
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<pre class="screen" id="ucs_01_0150__en-us_topic_0000001199341154_screen21636141912">$ kubectl get pod
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NAME READY STATUS RESTARTS AGE
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env-example-695b759569-lx9jp 1/1 Running 0 17m
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$ kubectl exec env-example-695b759569-lx9jp -- printenv
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/ # env
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key=value # Custom environment variable
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key1=configmap_value # Added from ConfigMap key
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key2=secret_value # Added from secret key
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key3=env-example-695b759569-lx9jp # metadata.name defined by the pod
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key4=1 # limits.cpu defined by container1. The value is rounded up, in unit of cores.
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configmap_key=configmap_value # Added from ConfigMap. The key value in the original ConfigMap key is directly imported.
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secret_key=secret_value # Added from key. The key value in the original secret is directly imported.</pre>
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</div>
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</div>
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<div>
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<div class="familylinks">
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<div class="parentlink"><strong>Parent topic:</strong> <a href="ucs_01_0105.html">Workload Management</a></div>
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</div>
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</div>
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