PoC

Author: ashald

.dockerignore

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+.gitignore

.gitignore

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+.idea/
+.vagrant/
+
+docker-volume-loopback
+
+plugin/rootfs
+tmp

Dockerfile

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+# build
+FROM golang:1.11-alpine as builder
+RUN apk --no-cache add make
+ADD ./ /go/src/github.com/ashald/docker-volume-loopback/
+WORKDIR /go/src/github.com/ashald/docker-volume-loopback
+RUN make build && \
+    mv ./docker-volume-loopback /usr/bin/
+
+
+# package
+FROM alpine
+RUN apk --no-cache add e2fsprogs
+COPY --from=builder /usr/bin/docker-volume-loopback /docker-volume-loopback
+CMD [ "/docker-volume-loopback" ]

Makefile

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+VERSION             :=  0
+ROOTFS_IMAGE		:=	ashald/docker-volume-loopback-rootfs
+ROOTFS_CONTAINER	:=	rootfs
+PLUGIN_NAME			:=	docker-volume-loopback
+PLUGIN_FULL_NAME	:=	ashald/docker-volume-loopback
+
+build:
+	GOOS=linux GOARCH=amd64 go build -o $(PLUGIN_NAME)
+
+rootfs-image:
+	docker build -t $(ROOTFS_IMAGE) .
+
+rootfs: rootfs-image
+	docker rm -vf $(ROOTFS_CONTAINER) || true
+	docker create --name $(ROOTFS_CONTAINER) $(ROOTFS_IMAGE) || true
+	mkdir -p plugin/rootfs
+	rm -rf plugin/rootfs/*
+	docker export $(ROOTFS_CONTAINER) | tar -x -C plugin/rootfs
+	docker rm -vf $(ROOTFS_CONTAINER)
+
+
+plugin: rootfs
+	docker plugin disable $(PLUGIN_NAME) || true
+	docker plugin rm --force $(PLUGIN_NAME) || true
+	docker plugin create $(PLUGIN_NAME) ./plugin
+	docker plugin enable $(PLUGIN_NAME)
+
+
+plugin-push: rootfs
+	docker plugin rm --force $(PLUGIN_FULL_NAME) || true
+	docker plugin create $(PLUGIN_FULL_NAME) ./plugin
+	docker plugin create $(PLUGIN_FULL_NAME):$(VERSION) ./plugin
+	docker plugin push $(PLUGIN_FULL_NAME)
+	docker plugin push $(PLUGIN_FULL_NAME):$(VERSION)
+
+
+.PHONY: build rootfs-image rootfs plugin plugin-push

README.md

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+<h1 align="center">xfsvol 📂  </h1>
+
+<h5 align="center">Docker Volume Plugin for managing local XFS-based volumes</h5>
+
+<br/>
+
+[![Build Status](https://travis-ci.org/cirocosta/xfsvol.svg?branch=master)](https://travis-ci.org/cirocosta/xfsvol)
+
+## Quickstart
+
+1. Create a mountpoint at `/mnt/xfs` and a directory `/mnt/xfs/volumes`. 
+
+For testing purposes this mountpoint can be a loopback device (note: use a loopback device for testing purposes only).
+
+```sh
+sudo dd if=/dev/zero of=/xfs.1G bs=1M count=1024
+sudo losetup /dev/loop0 /xfs.1G
+sudo mkfs -t xfs -n ftype=1 /dev/loop0
+sudo mkdir -p /mnt/xfs/volumes
+sudo mount /dev/loop0 /mnt/xfs -o pquota
+```
+
+2. Install the plugin
+
+```
+docker plugin install \
+        --grant-all-permissions \
+        --alias xfsvol \
+        cirocosta/xfsvol
+
+docker plugin ls
+ID                  NAME                DESCRIPTION                                   ENABLED
+06545b643c6a        xfsvol:latest       Docker plugin to manage XFS-mounted volumes   true
+```
+
+3. Create a named volume
+
+```
+docker volume create \
+        --driver xfsvol \
+        --opt size=10M \
+        myvolume1
+```
+
+4. Run a container with the volume attached
+
+```
+docker run -it \
+        -v myvolume1:/myvolume1 \
+        alpine /bin/sh
+
+dd if=/dev/zero of=/myvolume1/file bs=1M count=100
+(fail!)
+```
+
+5. Check the volumes list
+
+```
+docker volume ls
+DRIVER              VOLUME NAME
+xfsvol:latest       myvolume1 (1.004MB)
+local               dockerdev-go-pkg-cache-gopath
+local               dockerdev-go-pkg-cache-goroot-linux_amd64
+local               dockerdev-go-pkg-cache-goroot-linux_amd64_netgo
+```
+
+and the `xfsvolctl` utility:
+
+```
+sudo /usr/bin/xfsvolctl ls --root /mnt/xfs/volumes/
+NAME   QUOTA
+ciro   1.004 MB
+```
+
+## `xfsvolctl`
+
+This tool is made to help inspect the project quotas created under a given root path as well as create/delete others. It's usage is documented under `--help`:
+
+```
+xfsvolctl --help
+NAME:
+   xfsvolctl - Controls the 'xfsvol' volume plugin
+
+USAGE:
+   xfsvolctl [global options] command [command options] [arguments...]
+
+VERSION:
+   0.0.0
+
+COMMANDS:
+     ls       Lists the volumes managed by 'xfsvol' plugin
+     create   Creates a volume with XFS project quota enforcement
+     delete   Deletes a volume managed by 'xfsvol' plugin
+     help, h  Shows a list of commands or help for one command
+
+GLOBAL OPTIONS:
+   --help, -h     show help
+   --version, -v  print the version
+```
+
+### Under the hood
+
+
+```
+$ sudo mkdir -p /mnt/xfs/tmp/bbb
+$ sudo strace -f xfsvolctl create \
+        --root /mnt/xfs/tmp/bbb \
+        --name ccc \
+        --size 1024 \
+        --inode 1024
+
+stat("/mnt/xfs/tmp/bbb", {st_mode=S_IFDIR|0755, st_size=6, ...}) = 0
+unlinkat(AT_FDCWD, "/mnt/xfs/tmp/bbb/backingFsBlockDev", 0) = -1 ENOENT (No such file or directory)
+mknodat(AT_FDCWD, "/mnt/xfs/tmp/bbb/backingFsBlockDev", S_IFBLK|0600, makedev(7, 0)) = 0
+quotactl(Q_XSETQLIM|PRJQUOTA, "/mnt/xfs/tmp/bbb/backingFsBlockDev", 1, {version=1, flags=XFS_PROJ_QUOTA, fieldmask=0xc, id=1, blk_hardlimit=0, blk_softlimit=0, ino_hardlimit=0, ino_softlimit=0, bcount=0, icount=0, ...}) = 0
+...
+mkdirat(AT_FDCWD, "/mnt/xfs/tmp/bbb/ccc", 0755) = 0
+open("/mnt/xfs/tmp/bbb/ccc", O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC) = 3
+fstat(3, {st_mode=S_IFDIR|0755, st_size=6, ...}) = 0
+ioctl(3, FS_IOC_FSGETXATTR, 0xc4201a95e4) = 0
+ioctl(3, FS_IOC_FSSETXATTR, 0xc4201a95e4) = 0
+
+quotactl(Q_XSETQLIM|PRJQUOTA, "/mnt/xfs/tmp/bbb/backingFsBlockDev", 2, {version=1, flags=XFS_PROJ_QUOTA, fieldmask=0xc, id=2, blk_hardlimit=2, blk_softlimit=2, ino_hardlimit=1024, ino_softlimit=1024, bcount=0, icount=0, ...}) = 0
+[pid  6833] ioctl(2, TCGETS, {B38400 opost isig icanon echo ...}) = 0
+
+
+// retrieving (ls)
+
+[pid  8609] quotactl(Q_XGETQUOTA|PRJQUOTA, "/mnt/xfs/tmp/ddd/backingFsBlockDev", 2, {version=1, flags=XFS_PROJ_QUOTA, fieldmask=0, id=2, blk_hardlimit=8, blk_softlimit=8, ino_hardlimit=0, ino_softlimit=0, bcount=8, icount=104, ...}) = 0
+
+
+```
+