docs: add section for containers

                         changelog.md \

                         compression.md \

                         concurrency.md \

                         containers.md \

                         event.md \

                         ftl.md \

                         gdb_macros.md \

# SPDK and Containers {#containers}

This is a living document as there are many ways to use containers with

SPDK. As new usages are identified and tested, they will be documented

here.

# In this document {#containers_toc}

* @ref spdk_in_docker

# Containerizing an SPDK Application for Docker {#spdk_in_docker}

There are no SPDK specific changes needed to run an SPDK based application in

a docker container, however this quick start guide should help you as you

containerize your SPDK based application.

1. Make sure you have all of your app dependencies identified and included in your Dockerfile

2. Make sure you have compiled your application for the target arch

3. Make sure your host has hugepages enabled

4. Make sure your host has bound your nvme device to your userspace driver

5. Write your Dockerfile. The following is a simple Dockerfile to containerize the nvme `hello_world`

example:

~~~{.sh}

# start with the latest Fedora

FROM fedora

# if you are behind a proxy, set that up now

ADD dnf.conf /etc/dnf/dnf.conf

# these are the min dependencies for the hello_world app

RUN dnf install libaio-devel -y

RUN dnf install numactl-devel -y

# set our working dir

WORKDIR /app

# add the hello_world binary

ADD hello_world hello_world

# run the app

CMD ./hello_world

~~~

6. Create your image

`sudo docker image build -t hello:1.0 .`

7. You docker command line will need to include at least the following:

- the `--privileged` flag to enable sharing of hugepages

- use of the `-v` switch to map hugepages

`sudo docker run --privileged -v /dev/hugepages:/dev/hugepages hello:1.0`

or depending on the needs of your app you may need one or more of the following parameters:

- If you are using the SPDK app framework: `-v /dev/shm:/dev/shm`

- If you need to use RPCs from outside of the container: `-v /var/tmp:/var/tmp`

- If you need to use the host network (i.e. NVMF target application): `--network host`

Your output should look something like this:

~~~{.sh}

$ sudo docker run --privileged -v //dev//hugepages://dev//hugepages hello:1.0

Starting SPDK v20.01-pre git sha1 80da95481 // DPDK 19.11.0 initialization...

[ DPDK EAL parameters: hello_world -c 0x1 --log-level=lib.eal:6 --log-level=lib.cryptodev:5 --log-level=user1:6 --iova-mode=pa --base-virtaddr=0x200000000000 --match-allocations --file-prefix=spdk0 --proc-type=auto ]

EAL: No available hugepages reported in hugepages-1048576kB

Initializing NVMe Controllers

Attaching to 0000:06:00.0

Attached to 0000:06:00.0

Using controller INTEL SSDPEDMD400G4  (CVFT7203005M400LGN  ) with 1 namespaces.

  Namespace ID: 1 size: 400GB

Initialization complete.

INFO: using host memory buffer for IO

Hello world!

~~~

# Miscellaneous {#misc}

- @subpage peer_2_peer

- @subpage containers