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Q

Question

mounting a path override the existing content

4/11/2020

I am facing issues when mounting a path.My objective is to make the data persistent even when the pod restarts.But its creating a new directory which doesnt have any of my config files. How to mount a entire directory without overriding it? I should have all my database data inside the path eventhough the pod restarts.In my scenario,its creating a new path.

my dockerfile

FROM centos:7
ENV DIR /binaries
ENV PASS admin
WORKDIR ${DIR}
COPY libstdc++-4.8.5-39.el7.x86_64.rpm ${DIR} 
COPY numactl-libs-2.0.12-3.el7.x86_64.rpm ${DIR}
COPY mysqlmonitor-8.0.18.1217-linux-x86_64-installer.bin ${DIR}
RUN yum install -y libaio && yum -y install gcc && yum -y install gcc-c++ && yum -y install compat-libstdc++-33 && yum -y install libstdc++-devel && yum -y install elfutils-libelf-devel && yum -y install glibc-devel && yum -y install libaio-devel && yum -y install sysstat
RUN yum install -y gcc && yum install -y make && yum install -y apr-devel && yum install -y openssl-devel && yum install -y java
RUN rpm -ivh numactl-libs-2.0.12-3.el7.x86_64.rpm
RUN useradd sql
RUN chown sql ${DIR}
RUN chmod 777 ${DIR}
RUN chmod 755 /home/sql
USER sql
WORKDIR ${DIR}
RUN ./mysqlmonitor-8.0.18.1217-linux-x86_64-installer.bin --installdir /home/sql/mysql/enterprise/monitor --mode unattended --tomcatport 18080 --tomcatsslport 18443 --adminpassword ### --dbport 13306
RUN rm -rf /binaries/*
VOLUME /home/mysql/mysql/enterprise/monitor/mysql/data
ENTRYPOINT ["/bin/bash", "-c", "/home/sql/mysql/enterprise/monitor/mysqlmonitorctl.sh start && tail -f /home/sql/mysql/enterprise/monitor/apache-tomcat/logs/mysql-monitor.log"]

my deployment file

apiVersion: apps/v1
kind: Deployment
metadata:
  name: mypod
spec:
  replicas: 1
  selector:
    matchLabels:
      app: mem     
  template:
    metadata:
      labels:
        app: mem
    spec:
      containers:
      - name: mem
        image: 22071997/mem
        command: 
        volumeMounts:
        - mountPath: /home/sql/mysql/enterprise/mysql/data
          name: volume
      volumes:
      - name: volume
        persistentVolumeClaim:
          claimName: mem-pvc2

output:

[sql@mypod-67cb4f85b8-9km26 data]$ pwd
/home/sql/mysql/enterprise/mysql/data
[sql@mypod-67cb4f85b8-9km26 data]$ ls
[sql@mypod-67cb4f85b8-9km26 data]$

-- Sowmiya

docker

kubernetes

1 Answer

4/14/2020

By default when you mount some volume over a existent path, the content of this existent path will be hidded.

If you want to keep both there is an option called subPath, in this way you are able to mount each file individually using the same volume:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: echo
spec:
  selector:
    matchLabels:
      app: echo
  template:
    metadata:
      labels:
        app: echo
    spec:
      volumes:
        - name: task-pv-storage
          persistentVolumeClaim:
            claimName: task-pv-claim
      containers:
      - name: echo
        image: nginx
        ports:
        - name: http
          containerPort: 80
        volumeMounts:
          - name: task-pv-storage
            mountPath: "/usr/share/nginx/html/index.htm"
            subPath: "index.htm"
          - name: task-pv-storage
            mountPath: "/usr/share/nginx/html/teste.html"
            subPath: "teste.html"

In this example I have only one volume called task-pv-storage, is a hostPath volume and in the folder there are only 2 files: teste.yaml and index.html, and when I apply this config, both files will be placed beside the original files in the container:

$ kubectl exec echo-5955898b58-gvgh9 -- ls /usr/share/nginx/html
50x.html  index.htm  index.html  teste.html

As you can see it is possible, but will cost an addional configuration, maybe you could keep all file only in the volume instead directly in the container.

References

Configure volume storage/

Multiple kubernetes volumes directory

-- KoopaKiller

Source: StackOverflow

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mounting a path override the existing content

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