[local-volume] Add /dev to volume mount in helm template

[msau42]

To support raw local block, we recommend creating a symlink to the device in the discovery directory. The provisioner daemonset spec needs a hostpath mount to /dev to be able to resolve the symlinks.
/area local-volume

[cofyc]

hi, in which scenario provisioner cannot access device under /dev?

Provisioner runs in privileged mode by using helm chart, in my test, provisioner does not need /dev hostpath mount to access devices under /dev.

$ docker run -it  busybox sh -c 'ls /dev/sd*'
ls: /dev/sd*: No such file or directory
$ docker run -it  --privileged busybox sh -c 'ls /dev/sd*'
/dev/sda   /dev/sda1  /dev/sda2  /dev/sda5  /dev/sdb   /dev/sdc   /dev/sdd

[msau42]

cc @jsafrane

[jsafrane]

Interesting, I did not know about /dev/ in privileged containers. Is is something new? Do all container runtimes support it?

[cofyc]

not sure yet, i'll investigate it
/assign

[k8s-ci-robot]

@cofyc: GitHub didn't allow me to assign the following users: cofyc.

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In response to this:

not sure yet, i'll investigate it
/assign

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[jsafrane]

I stumbled upon this today when testing containerized mounts.

privileged will give a snapshot of /dev to your container at the time when the container is created. Devices created after the container has started are not reflected there. That's not what we want.

[cofyc]

tested locally, you're right!

without -v /dev:/dev

# docker run -it --privileged busybox sh
/ # stat -c %F /dev/testdev
stat: can't stat '/dev/testdev': No such file or directory
# run `mknod /dev/testdev c 1 5` in another terminal
/ # stat -c %F /dev/testdev
stat: can't stat '/dev/testdev': No such file or directory

with -v /dev:dev:

# docker run -it -v /dev:/dev --privileged busybox sh
/ # stat -c %F /dev/testdev
stat: can't stat '/dev/testdev': No such file or directory
# run `mknod /dev/testdev2 c 1 5` in another terminal
/ # stat -c %F /dev/testdev
character special file

I'll add /dev to volume mount.

[cofyc]

/assign