====== Boot linux over NFS ======
The following text describes on how to use NFS for the root filesystem. For the rest of this text 'client' means the diskless system, and 'server' means the NFS server.
===== NFS server settings =====
Install nfs pakages.
  sudo apt-get install nfs-kernel-server nfs-common

After insert your eMMC or SD card, copy the Root File System.
  # The trusty folder is mounted your RFS by SD card.
  sudo cp -rp /media/$USER/trusty /home/$USER/

Add following line in "/etc/exports"
  /home/$USER/trusty        *(rw,sync,no_root_squash,no_subtree_check)
Restart NFS service.
  sudo service nfs-kernel-server restart
Modify /home/$USER/trusty/etc/network/interfaces
<code>
# This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).

# The loopback network interface
auto lo
iface lo inet loopback

# The primary network interface, commented out for NFS root
#auto eth0
#iface eth0 inet dhcp
iface eth0 inet manual
</code>
===== Kernel configuration =====
To use Ethernet and NFS on initramfs you need to change module to built-in.
==== C1/C2 kernel configuration ====
The C1 Ethernet driver was already built-in.\\
Location:
<code>
-> File systems
  -> Network File Systems
     <*> NFS client support
     <*> NFS client support for NFS version 3
</code>
==== U3 kernel configuration ====
Location:
<code>
-> Device Drivers
  -> Network device support
    -> USB Network Adapters
       <*> Multi-purpose USB Networking Framework
       <*> SMSC LAN95XX based USB 2.0 10/100 ethernet devices
</code>
<code>
-> File systems
  -> Network File Systems
     <*> NFS client support
     <*> NFS client support for NFS version 3
</code>

Then, Update your ODROID's kernel.\\
Refer to the following links How to kernel update.\\
  * [[en:c1_building_kernel | ODROID-C1 kernel update]]
  * [[en:xu3_building_kernel | ODROID-XU3/4 kernel update]]
  * [[en:u3_building_kernel | ODROID-U3 kernel update]]
  * [[en:odroidwkernelcompilation | ODROID-W kernel update]]

===== NFS Client(ODROIDs) settings =====
Append following line to the boot argument.
  boot=nfs root=/dev/nfs ip=dhcp nfsroot=${rfspath} rw
==== How to add the boot argument ====
You should modify boot.ini file or compile to a u-boot script.

e.g. **ODROID-C1**.

Modify "/media/boot/boot.ini"
<code>
setenv rfspath 192.168.0.22:/home/john/trusty
setenv bootargs "boot=nfs root=/dev/nfs ip=dhcp nfsroot=${rfspath} rw rootwait ro ${condev} no_console_suspend vdaccfg=0xa000 logo=osd1,loaded,0x7900000,720p,full dmfc=3 cvbsmode=576cvbs hdmimode=${m} m_bpp=${m_bpp} vout=${vout_mode} ${disableuhs}"
</code>

Reboot.
  sudo reboot

e.g. **ODROID-U3**.

Copy the existing boot script
  cd /media/boot
  cp boot.txt boot-nfs.txt

Modify boot-nfs.txt.
<code>
setenv initrd_high "0xffffffff"
setenv fdt_high "0xffffffff"
setenv rfspath 192.168.0.22:/home/john/trusty
setenv bootcmd "fatload mmc 0:1 0x40008000 zImage; fatload mmc 0:1 0x42000000 uInitrd; bootm 0x40008000"
setenv bootargs "boot=nfs root=/dev/nfs ip=dhcp nfsroot=${rfspath} console=tty1 console=ttySAC1,115200n8 rootwait mem=2047M"
boot
</code>

Install uboot-mkimage package.
  sudo apt-get install uboot-mkimage

Compile to a u-boot script.
  mkimage -T script -A arm -C none -n 'ODROID-U3.Boot NFS-mounted RFS' -d boot-nfs.txt boot-nfs.scr
Copy.
  mv boot.scr boot.scr.orig
  cp boot-nfs.scr boot.scr
Reboot.
  sudo reboot.

Nice to have a lot of disk space:
<code>
root@odroid:~# df -h                                                                                
Filesystem                      Size  Used Avail Use% Mounted on                                    
192.168.0.22:/home/john/trusty  909G  177G  687G  21% /                                             
none                            4.0K     0  4.0K   0% /sys/fs/cgroup                                
udev                            420M  4.0K  420M   1% /dev                                          
tmpfs                           425M  4.0K  425M   1% /tmp                                          
tmpfs                            85M  2.6M   83M   3% /run                                          
none                            5.0M     0  5.0M   0% /run/lock                                     
none                            425M   76K  425M   1% /run/shm                                      
none                            100M   24K  100M   1% /run/user                                     
/dev/mmcblk0p1                  129M  7.4M  122M   6% /media/boot
</code>