K8S中的mountPath和subPath使用詳解
1 mountPath
mountPath是容器內(nèi)部文件系統(tǒng)的掛載點(diǎn),它定義了容器內(nèi)部將外部存儲卷(如 PersistentVolume、ConfigMap、Secret 等)掛載到哪個路徑下。通過 mountPath,容器可以訪問這些掛載的數(shù)據(jù)或配置。
2 subPath
subPath 是 mountPath 下的子路徑,它允許容器將掛載的數(shù)據(jù)卷中的特定文件或目錄掛載到容器中的指定路徑下。這樣可以實(shí)現(xiàn)更加精細(xì)的文件系統(tǒng)級別的訪問控制。
3 mountPath使用場景
比如我需要創(chuàng)建一個nginx deployment,需要將自定義的nginx.conf配置文件獨(dú)立出來,作為一個configmap來掛載到pod中。
apiVersion: v1 kind: ConfigMap metadata: name: nginx-config data: my-nginx.conf: | server { listen 80; server_name localhost; location / { root /usr/share/nginx/html; index index.html index.htm; } error_page 500 502 503 504 /50x.html; location = /50x.html { root /usr/share/nginx/html; } } --- apiVersion: apps/v1 kind: Deployment metadata: name: nginx-deployment spec: replicas: 1 selector: matchLabels: app: nginx template: metadata: labels: app: nginx spec: containers: - name: nginx image: nginx volumeMounts: - name: nginx-config-volume mountPath: /etc/nginx/conf.d volumes: - name: nginx-config-volume configMap: name: nginx-config
部署完成后,你可以進(jìn)入pod,可以看到如下文件,這就是通過configmap掛載到容器中。
kubectl exec -it nginx-deployment-5b4699b7dd-fh4qc -- /bin/sh # cd /etc/nginx/conf.d # ls my-nginx.conf
4 subPath使用場景
如果我想直接通過configmap定義/etc/nginx/nginx.conf,這時候如果還是只使用mountPath,就會有問題了。
apiVersion: v1 kind: ConfigMap metadata: name: nginx-config data: nginx.conf: | user nginx; worker_processes auto; error_log /var/log/nginx/error.log notice; pid /var/run/nginx.pid; events { worker_connections 1024; } http { include /etc/nginx/mime.types; default_type application/octet-stream; log_format main '$remote_addr - $remote_user [$time_local] "$request" ' '$status $body_bytes_sent "$http_referer" ' '"$http_user_agent" "$http_x_forwarded_for"'; access_log /var/log/nginx/access.log main; sendfile on; #tcp_nopush on; keepalive_timeout 65; #gzip on; include /etc/nginx/conf.d/*.conf; } --- apiVersion: apps/v1 kind: Deployment metadata: name: nginx-deployment spec: replicas: 1 selector: matchLabels: app: nginx template: metadata: labels: app: nginx spec: containers: - name: nginx image: nginx volumeMounts: - name: nginx-config-volume mountPath: /etc/nginx volumes: - name: nginx-config-volume configMap: name: nginx-config
創(chuàng)建容器后,服務(wù)無法起來,會報(bào)錯,因?yàn)榇藭r容器中的/etc/nginx/目錄會被我們掛載的configmap給覆蓋,所以原先/etc/nginx/目錄下的文件都無法被pod訪問,也就報(bào)錯了。
2024/03/25 06:56:58 [emerg] 1#1: open() "/etc/nginx/mime.types" failed (2: No such file or directory) in /etc/nginx/nginx.conf:14 nginx: [emerg] open() "/etc/nginx/mime.types" failed (2: No such file or directory) in /etc/nginx/nginx.conf:14
那如果我將volumeMount改為如下配置呢,
- name: nginx image: nginx volumeMounts: - name: nginx-config-volume mountPath: /etc/nginx/nginx.conf
此時原來/etc/nginx/目錄下的文件都不會受影響,但是依舊會報(bào)錯,連容器都無法創(chuàng)建,
Error: failed to create containerd task: failed to create shim task: OCI runtime create failed: runc create failed: unable to start container process: error during container init: error mounting "/var/lib/kubelet/pods/6755a0be-2f05-4edb-813b-ece2dcc2e8f1/volumes/kubernetes.io~configmap/nginx-config-volume" to rootfs at "/etc/nginx/nginx.conf": mount /var/lib/kubelet/pods/6755a0be-2f05-4edb-813b-ece2dcc2e8f1/volumes/kubernetes.io~configmap/nginx-config-volume:/etc/nginx/nginx.conf (via /proc/self/fd/6), flags: 0x5001: not a directory: unknown
這是因?yàn)榇藭r容器中/etc/nginx/nginx.conf這個路徑已經(jīng)是存在的,鏡像中默認(rèn)的文件,沒法作為mountpath使用。
當(dāng)然,你可以將nginx.conf換成其他名字,比如mynginx.conf,
- name: nginx image: nginx volumeMounts: - name: nginx-config-volume mountPath: /etc/nginx/mynginx.conf
這樣就不會報(bào)錯,但是這樣的效果是,容器中會創(chuàng)建一個目錄/etc/nginx/mynginx.conf/,這個目錄下有個文件nginx.conf,與最開始我們在/etc/nginx/conf.d/定義my-nginx.conf一樣,但這并不是我們所要的。
kubectl exec -it nginx-deployment-6bf5f55df8-f452d -- /bin/sh # cd /etc/nginx/mynginx.conf/ # ls nginx.conf
這個時候,我們就需要使用subPath了,將volumeMount做如下修改,
- name: nginx image: nginx volumeMounts: - name: nginx-config-volume mountPath: /etc/nginx/nginx.conf subPath: nginx.conf
這時服務(wù)就按照我們預(yù)期啟動了,容器內(nèi)文件如下,而且nginx.conf的內(nèi)容就是我們configmap中定義的配置,
kubectl exec -it nginx-deployment-bb7d454c6-75bwz -- /bin/sh # cd /etc/nginx/ # ls conf.d fastcgi_params mime.types modules nginx.conf scgi_params uwsgi_params
類似的場景,比如需要在/etc/nginx/conf.d/為不同的host定義不同的配置,我們就可以創(chuàng)建多個configmap,配合使用subPath來掛載到同一個目錄下,
- name: nginx image: nginx volumeMounts: - name: nginx-config-volume mountPath: /etc/nginx/conf.d/nginx.conf subPath: nginx.conf - name: my-nginx-config-volume mountPath: /etc/nginx/conf.d/my-nginx.conf subPath: my-nginx.conf
參考文檔:
- https://stackoverflow.com/questions/65399714/what-is-the-difference-between-subpath-and-mountpath-in-kubernetes
總結(jié)
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