Share files between host PC and reference platform

Preface

This document outlines how to share data between a host PC and development/reference platform, such as the Juno development board or Armv8 Base Platform FVP. The following methods are covered:

Network-mounted storage (NFS)
Secure copy (scp)
"Baking" the files into the target filesystem
p9 virtio (models only)

Typographic explanation:

host$    -->  run as regular user on host PC
host#    -->  run as root privilege on host machine (e.g. sudo)
client$  -->  run as regular user in development environment (e.g. Juno)
client#  -->  run as root privilege in development environment

Network-mounted storage

NFS allows a system to share directories and files with others over a network. By using NFS, users and programs can access files on remote systems as if they were local files. This offers great flexibility and scalability. Configuring NFS requires the following steps:

Install the required packages on the host
Configure the host
Configure the client

To do this:

### Install the required packages
host# apt-get update && apt-get install nfs-kernel-server rpcbind

### Configure the directories to be exported by adding them to /etc/exports file by adding the following line like so:
/path/to/dir_shared *(rw,nohide,insecure,no_subtree_check,async,no_root_squash)

### Restart the NFS server
host# service nfs-kernel-server restart

### On the client create a mount point and then use the 'mount' command to mount the shared NFS directory from the host
client$ mkdir mnt_point
client# mount <host_name>:/path/to/dir_shared /path/to/mnt_point

Pros	Cons
Fast and reliable when there is low traffic on the network.	Performance limitation on the network. NFS can experience slowdowns when the network is busy.
Very convenient and efficient for a large network of clients sharing information with one host.	Data is not encrypted and such NFS is insecure and should only be used on a trusted network behind a firewall.
	Requires functional network connection between host and client.

Secure Copy

SCP or secure copy allows secure transferring of files between two networked machines. It uses the same authentication and security as the SSH protocol. SCP comes pre-installed on most Linux distributions so there is no need to install any additional packages. To use SCP:

### Copy a file from the local host (host PC) to the development board (remote host)
host$ scp /path/to/file <client_user>@<client_name>:/path/to/target/directory

The system will ask you to provide a password for <client_user> in order to complete the file transfer.

Pros	Cons
File tranfer through '`scp`' is encrypted.	Because of the encryption the process is slow for very large files or collection of files.
Utilizes the SSH2 port, minimizing the number of ports open on the firewall.	Performance limitation on the network. NFS can experience slowdowns when the network is busy.
Very easy to use. Comes pre-installed on most Linux distributions.	Requires functional network connection between host and client.

"Baking" files into target filesystem

To "bake" files into the target filesystem the following steps need to be followed:

Mount the filesystem image on a local host directory
Edit the mounted filesystem to include the desired files
Unmount it and boot the target as usual

To do this:

### Mount the filesystem image onto a local directory
host$ mkdir mnt_point
host# mount /path/to/target_fs.img mnt_point

### Edit the files on the filesystem.
### For example creating a new directory and tranferring a file on it can be done like so:
host# mkdir /path/to/mnt_point/home/root/test_folder
host# cp /path/to/file1 /path/to/mnt_point/home/root/test_folder/

Pros	Cons
Useful if files are needed to be written permanently.	Need access to the client's storage device.
Relatively secure as there is no data transmission over the network.	Requires caution because the filesystem is directly edited and mistakes may cause errors during boot.

p9 virtio (models only)

P9 virtio allows for sharing data between a host PC and a model (i.e. FVPs). Detailed instruction of setting up and using p9 virtio for the ARM FVPs can be found here.