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Host file access

Getting access to files on your host from the target over a network is very useful. This page lists the ways that this is possible.

USB stick (sneakernet)

You can put files (typically a full ChromiumOS image build with cros build-image) onto a USB stick, insert it into the target, mount the device and access the files from there.

Using sshfs

Since you can use ssh in user space, and we have a 'fuse' module to permit user space filesystems, we can use sshfs to mount directories:


# Make sure fuse is loaded
sudo modprobe fuse
# Create location to mount build directory
mkdir /tmp/chrome
# Mount your dev directory
sshfs username@machine:/path/to/chrome /tmp/chrome
# Take a look
ls /tmp/chrome

You can hope for about 5MB/s over sshfs on a Cortex-A9 with USB Ethernet.

Using NFS

Please see here for full details. NFS requires a lot more setup but has additional features. There are two ways to use NFS from your target:

NFS root - use an NFS mount as your root file system
NFS mount - boot as normal from a USB stick / SSD / eMMC, but then later mount a directory on your host machine

Each option has advantages and disadvantages which will be noted below. Both require a certain amount of setup on both the host and target. In NFS terms the host will be the server (containing the files which we want to export) and the target will be the client.

Transfer speed with NFS is faster than sshfs since CPU overhead is less, but is limited by the USB interface if you are using a 10/100 USB Ethernet dongle. With a Gigabit USB3 dongle it should operate much faster than ssh.

NFS Mount

It is also possible to boot from USB or eMMC, but then later mount a filesystem on your host. This requires some user space utilities to enable portmap, etc. Please add documentation here if you do this.