Mounting the external volumes to jenkins docker container

Creating a docker volume

To use the external volume for our future container, we need to format a filesystem on the volume.
We use the ext4 filesystem to format our block device, we will demonstrate that as follows:

vamshi@node03:~$ sudo mkfs.ext4 /dev/sdb
mke2fs 1.43.4 (31-Jan-2017)
Discarding device blocks: done
Creating filesystem with 524288 4k blocks and 131072 inodes
Filesystem UUID: bc335e44-d8e9-4926-aa0a-fc7b954c28d1
Superblock backups stored on blocks:
32768, 98304, 163840, 229376, 294912

Allocating group tables: done
Writing inode tables: done
Creating journal (16384 blocks): done
Writing superblocks and filesystem accounting information: done

Here is the command to create a volume by mentioning the path to the block device and using it in the local scope

docker volume create jenkins_vol1 --driver local --opt device=/dev/sdb
jenkins_vol1

We have successfully creates a docker volume using a block device.

Inspecting the docker volume that is created:

vagrant@node03:~$ docker volume inspect jenkins_vol1
[
    {
        "CreatedAt": "2020-05-12T17:22:11Z",
        "Driver": "local",
        "Labels": {},
        "Mountpoint": "/var/lib/docker/volumes/jenkins_vol1/_data",
        "Name": "jenkins_vol1",
        "Options": {
            "device": "/dev/sdb",
            "type": "ext4"
        },
        "Scope": "local"
    }
]

Creating my jenkins container which will use the docker volume jenkins_vol1 and mount it to /var/jenkins_home/.m2

docker run -d -p 8080:8080 --name jenkins --mount 'type=volume,src=temp_vol,dst=/var/jenkins_home/.m2,
volume-driver=local' jenkins:latest

We have successfully started our container and now lots login to the container and check our volume.

jenkins@fc2c49313ddb:/$ df -hT
Filesystem     Type     Size  Used Avail Use% Mounted on
overlay        overlay   29G  4.9G   23G  18% /
tmpfs          tmpfs     64M     0   64M   0% /dev
tmpfs          tmpfs    970M     0  970M   0% /sys/fs/cgroup
shm            tmpfs     64M     0   64M   0% /dev/shm
/dev/sda3      ext4      29G  4.9G   23G  18% /var/jenkins_home
/dev/sdb       ext4     2.0G  6.0M  1.8G   1% /var/jenkins_home/.m2
tmpfs          tmpfs    970M     0  970M   0% /proc/acpi
tmpfs          tmpfs    970M     0  970M   0% /sys/firmware

As we can see from the output the mount point /var/jenkins_home/.m2 is mounted with block device /dev/sdb using a ext4 filesystem

/dev/sdb ext4 2.0G 6.0M 1.8G 1% /var/jenkins_home/.m2

Creating a 200MB temp filesystem volume.

docker volume create --name temp_vol --driver local --opt type=tmpfs --opt device=tmpfs --opt o=size=200m

The inspect of the temp_vol we created is as follows:

vamshi@node03:~$ docker volume inspect temp_vol
[
    {
        "CreatedAt": "2020-05-02T17:31:01Z",
        "Driver": "local",
        "Labels": {},
        "Mountpoint": "/var/lib/docker/volumes/temp_vol/_data",
        "Name": "temp_vol",
        "Options": {
            "device": "tmpfs",
            "o": "size=100m,uid=1000",
            "type": "tmpfs"
        },
        "Scope": "local"
    }
]
docker run -d -p 8080:8080 --name jenkins --mount 'type=volume,src=jenkins_vol1,dst=/var/jenkins_home/.m2,volume-driver=local' jenkins:latest
vamshi@node03:~$ docker exec -it jenkins bash
jenkins@2267ba462aa2:/$ df -hT
Filesystem     Type     Size  Used Avail Use% Mounted on
overlay        overlay   29G  4.9G   23G  18% /
tmpfs          tmpfs     64M     0   64M   0% /dev
tmpfs          tmpfs    970M     0  970M   0% /sys/fs/cgroup
shm            tmpfs     64M     0   64M   0% /dev/shm
/dev/sda3      ext4      29G  4.9G   23G  18% /var/jenkins_home
tmpfs          tmpfs    100M     0  100M   0% /var/jenkins_home/.m2
tmpfs          tmpfs    970M     0  970M   0% /proc/acpi
tmpfs          tmpfs    970M     0  970M   0% /sys/firmware
jenkins@2267ba462aa2:/$ exit

Here is shows the mount point details:

tmpfs tmpfs 200M 0 200M 0% /var/jenkins_home/.m2

Please note the mount point /var/jenkins_home/.m2 which has 200MB space as defined.

Thus we can make use of the docker volumes and use the persistent fileystems and attach the block disks to a running container.

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