This volume driver plug-in implements the docker volume driver api. It provides volumes to docker images based on LVM logical volumes.
There is one deviation from the API description at https://docs.docker.com/engine/extend/plugins_volume/: a volume may not be used by several containers and the attempt to do so may fail. The volume API demands that the number of mount operations is kept and the volume is only unmounted after the last matching unmount operation. This would require that the plug-in would have to keep some state persistently.
The goal is to make this list disappear. The getting started may refer to these features that have not been implemented yet.
- rename main to lvmvd
- check that the given volume group exists on startup
- ensure that process runs as root on startup (otherwiese nothing will work)
- check that the mount root directory exists (otherwiese create it)
- create socket /json files for docker on startup
- implement socket listener (this should actually be used)
- make sure everything is single threaded
- rework usage text
- pass size for volume via volume name
- catch ctrl-c and remove the json/spec file
- better parameter validation for incoming requests (avoid denial of service)
- fix socket-file vs. socket dir issue
Will not do
- do some initial size management on the volume (not sure what that would look like)
You should have Golang installed to run this project.
Also, Docker needs to be installed if you want to use it locally. Follow this to install Docker.
First, sync the repository and cd into the src path. Then run the go build to build the code.
git clone https://github.com/SAP/service-fabrik-lvm-volume-driver.git
cd service-fabrik-lvm-volume-driver
export GOPATH=`pwd`/..
go build lvmvd.go
The lvm volume driver expects that the lvm volume group has been created prior to running the volume driver. Follow these instructions for setting up the volume group:
- Make sure lvm2 is installed
sudo apt-get install lvm2
- Create sparse file
truncate -s 50g docker-lvm-volume.img
- Set up loopback device with image
sudo losetup /dev/loop0 docker-lvm-volume.img
- Create physical volume:
sudo pvcreate /dev/loop0
- Create volume group with name
services-vg:
sudo vgcreate services-vg /dev/loop0
- Start the plug-in
sudo lvmvd --default-size=1 --volume-group-name=services-vg --mount-root=/var/volume/mnt-services-vg
This will start the lvm volume driver daemon serving volumnes from the services-vg volume group and mounting them to /var/volume/mnt-services-vg directory
- Start Docker
sudo service docker start
Note: this is an example for volumes in sparse files. You can of course also provide a volume grouped backed by a physical disk.
The lvm volume driver will create volumes with a size of 512MB by default. This can be changed using the --default-size command line parameter.
Another possiblity is to add a postfix to the volume name which specifies the volume size. The following will create a volume of 4 gigabytes:
my-volume-oS4G
The syntax is as follows:
-o : An section follows
S : A size parameters follows
4 : parameter for size (4 GB)
G : Gigabytes
Alternatively one can specify M for megabytes. If no letter G or M is specified M is assumed.
This should allow additional options for the future, e.g. something like Text4 for the file system type ext4.
There is a runtest.sh script which provides an integration test for the lvm volume driver.
The test implements the following checks:
- Validate that some common command line options do work
- Validate that the socket and http modes work
- Creates a lvm volume group and creates volumes inside
- checks all volume driver options and varios error situations
Prerequisites / caveats:
- curl version > 7.40 is required for the socket tests to work
- The setup can be shaky as there are some side effects regarding lvm and loopback devices; especially after failed runs
- lvm2 is required
Create logical volume:
lvcreate -L 1G -ntest services
Volume can now be mounted from
/dev/mapper/services-test
List volumes in a volume group
lvdisplay -v services
Better: list logical volumes
lvs --noheadings -o lv_name -v services
Delete logical volume
lvremove /dev/mapper/service-myvolume
Create volume:
curl -v --header "Content-Type: application/json" -d '{"Name": "myvolume"}' http://localhost:8080/VolumeDriver.Create
List
curl -v --header "Content-Type: application/json" -d '{}' http://localhost:8080/VolumeDriver.List
Create
curl -v --header "Content-Type: application/json" -d '{"Name": "test3"}' http://localhost:8080/VolumeDriver.Create
Mount
curl -v --header "Content-Type: application/json" -d '{"Name": "test3"}' http://localhost:8080/VolumeDriver.Mount
Unmount
curl -v --header "Content-Type: application/json" -d '{"Name": "test3"}' http://localhost:8080/VolumeDriver.Unmount
starting the program
./main --listener=http --default-size=1G --volume-group-name=services-vg --mount-root=/var/volume/mnt-services-vg
If you need any support, have any question or have found a bug, please report it in the GitHub bug tracking system. We shall get back to you.
This project is licensed under the Apache Software License, v. 2 except as noted otherwise in the LICENSE file