CSI plugin for local block devices []
Description
CSI-BlockDevices is a Container Storage Interface
(CSI) plugin for locally
attached block devices. Block devices can be exposed to the plugin by
symlinking them into a directory, by default /dev/disk/csi-blockdevices
. See
sample commands for details.
This project may be compiled as a stand-alone binary using Golang that,
when run, provides a valid CSI endpoint. This project can also be
vendored or built as a Golang plugin in order to extend the functionality
of other programs.
Runtime Dependencies
None
Installation
CSI-BlockDevices can be installed with Go and the following command:
$ go get github.com/thecodeteam/csi-blockdevices
The resulting binary will be installed to $GOPATH/bin/csi-blockdevices
.
If you want to build csi-nblockdevices
with accurate version information,
you'll need to run the go generate
command and build again:
$ go get github.com/thecodeteam/csi-blockdevices
$ cd $GOPATH/src/github.com/thecodeteam/csi-blockdevices
$ go generate && go install
The binary will once again be installed to $GOPATH/bin/csi-blockdevices
.
Start plugin
Before starting the plugin please set the environment variable
CSI_ENDPOINT
to a valid Go network address such as csi.sock
:
$ CSI_ENDPOINT=csi.sock ./csi-blockdevices
INFO[0000] configured com.thecodeteam.blockdevices devicedir=/dev/disk/csi-blockdevices privatedir=/dev/disk/csi-bd-private
INFO[0000] identity service registered
INFO[0000] controller service registered
INFO[0000] node service registered
INFO[0000] serving endpoint="unix://csi.sock"
The server can be shutdown by using Ctrl-C
or sending the process
any of the standard exit signals.
Using plugin
The CSI specification uses the gRPC protocol for plug-in communication.
The easiest way to interact with a CSI plugin is via the Container
Storage Client (csc
) program provided via the
GoCSI project:
$ go get github.com/thecodeteam/gocsi
$ go install github.com/thecodeteam/gocsi/csc
Then, set have csc
use the same CSI_ENDPOINT
, and you can issue commands
to the plugin. Some examples...
Get the plugin's supported versions and plugin info:
$ ./csc -e csi.sock identity supported-versions
0.1.0
$ ./csc -v 0.1.0 -e csi.sock identity plugin-info
"com.thecodeteam.blockdevices" "0.1.0+11"
"commit"="24167e6b3486c7938243c4a97fd5fb410390b8e5"
"formed"="Wed, 14 Feb 2018 18:40:13 UTC"
"semver"="0.1.0+11"
"url"="https://github.com/thecodeteam/csi-nfs"
Create a loopback device and make it available to plugin:
$ mkdir /dev/disk/csi-blockdevices
$ cd /dev/disk/csi-blockdevices
# make 100MiB disk image
$ dd if=/dev/zero of=test.img bs=1024 count=102400
# attach disk image to /dev/loop0
$ losetup /dev/loop0 test.img
# create symlink named loop0 -> /dev/loop0
$ ln -s /dev/loop0
$ csc -e csi.sock -v 0.1.0 c ls
"loop0" 0
Publish the "loop0" volume as a block volume
# create file to mount device to
$ touch /mnt/target
$ csc -v 0.1.0 n publish --cap SINGLE_NODE_WRITER,block --target-path /mnt/target loop0
loop0
$ mount | grep -e loop -e target
devtmpfs on /dev/disk/csi-bd-private/loop0 type devtmpfs (rw,relatime,seclabel,size=241476k,nr_inodes=60369,mode=755)
devtmpfs on /mnt/target type devtmpfs (rw,relatime,seclabel,size=241476k,nr_inodes=60369,mode=755) (rw,relatime,seclabel,size=241476k,nr_inodes=60369,mode=755)
$ csc -v 0.1.0 n unpublish --target-path /mnt/target loop0
loop0
$ mount | grep loop
$
Publish the "loop0" volume as a mount volume, formatted with ext4
# create directory to mount filesystem to
$ mkdir /mnt/test
$ csc -v 0.1.0 n publish --cap SINGLE_NODE_WRITER,mount,ext4 --target-path /mnt/test loop0
loop0
$ mount | grep loop
/dev/loop0 on /dev/disk/csi-bd-private/loop0 type ext4 (rw,relatime,seclabel,data=ordered)
/dev/loop0 on /mnt/test type ext4 (rw,relatime,seclabel,data=ordered)
$ csc -v 0.1.0 n unpublish --target-path /mnt/target loop0
loop0
$ mount | grep loop
$
Parameters
No additional parameters are currently supported/required by the plugin
Configuration
The CSI-BlockDevices SP is built using the GoCSI CSP package. Please see its
configuration section
for a complete list of the environment variables that may be used to
configure this SP.
The following table is a list of this SP's default configuration values:
Name |
Value |
X_CSI_SPEC_REQ_VALIDATION |
true |
X_CSI_SERIAL_VOL_ACCESS |
true |
X_CSI_SUPPORTED_VERSIONS |
0.1.0 |
X_CSI_PRIVATE_MOUNT_DIR |
/dev/disk/csi-bd-private |
The following table is a list of configuration values that are specific
to BlockDevices, their default values, and whether they are required for operation:
Name |
Description |
Default Val |
Required |
X_CSI_BD_DEVDIR |
Directory to scan for block devices |
/dev/disk/csi-blockdevices |
false |
Capable operational modes
The CSI spec defines a set of AccessModes that a volume can have. CSI-BlockDevices
supports the following modes for volumes that will be mounted as a filesystem:
// Can only be published once as read/write on a single node,
// at any given time.
SINGLE_NODE_WRITER = 1;
// Can only be published once as readonly on a single node,
// at any given time.
SINGLE_NODE_READER_ONLY = 2;
This means that mount volumes can be mounted only at one node at a time (because
the disk is local to the node) and can be mounted as read-write or read-only.
For volumes that are used as block devices, only the following are supported:
// Can only be published once as read/write on a single node,
// at any given time.
SINGLE_NODE_WRITER = 1;
This means that giving a workload read-only access to a block device is not
supported.
Support
For any questions or concerns please file an issue with the
csi-blockdevices
project or join the Slack channel #project-rexray at codecommunity.slack.com.