NTP server

The [UDOO standard image](Android Installation) comes with ntpd installed. To synchronise the time of Android once, run

su
/system/xbin/ntpd -n -p 0.pool.ntp.org -p 1.pool.ntp.org -p 2.pool.ntp.org -p 3.pool.ntp.org

If other NTP servers will be used, remove the entries -p X.pool.ntp.org in the command above and add -p [LOCAL_NTP_SERVER] where LOCAL_NTP_SERVER is the address of your local NTP server.

To synchronise time indefinitely, the Android RAM-disk must be updated. This involves the large number of steps below.

First, download mkbootimg and boot-extract. The Android debug bridge adb, boot-extract and mkbootimg are assumed to be on the path of your machine; if not, use their full paths instead of the command names in the calls below

# read the boot image on the Udoo Neo
adb -d shell
su
mkdir /data/transfer
dd if=/dev/block/mmcblk0p1 of=/data/transfer/boot_old.img
chmod a+rwx /data/transfer
chmod a+r /data/transfer/boot_old.img
exit
exit

# pull the bootdisk onto a host system (running Linux or MacOSX) and extract ramdisk and kernel from it
adb -d pull /data/transfer/boot_old.img
mkdir tmp
cd tmp
boot-extract ../boot_old.img

# unzip and unpack the ramdisk into a subdirectory
gunzip ramdisk.cpio.gz
mkdir files
cd files
cpio -id < ../ramdisk.cpio

Now modify init.rc as desired (replacing the IP address after -p):

echo $'\nservice ntpd /system/xbin/ntpd -n -p aa.bb.cc.dd\n  class main' >> init.rc

Then repackage and zip the ramdisk

find . | cpio -H newc --owner 0:0 -ov > ../ramdisk.cpio
cd ..
gzip ramdisk.cpio

# combine the ramdisk and the kernel into a complete boot image again
# the arguments for mkbootimg are copied from the output of boot-extract (see sample below), with hexadecimal addresses converted into decimal offsets, relative to base address 0
#
mkbootimg --base 0 --kernel zImage --ramdisk ramdisk.cpio.gz --pagesize 2048 --kernel_offset 2223013888 --ramdisk_offset 2239758336 --second_offset 2238709760 --tags_offset 2222981376 \
          --cmdline 'console=ttymxc0,115200 init=/init vmalloc=256M androidboot.console=ttymxc0 consoleblank=0 androidboot.hardware=freescale cma=128M androidboot.selinux=disabled 
                     androidboot.dm_verity=disabled no_console_suspend uart_from_osc clk_ignore_unused'   -o boot_new.img

# transfer the new boot image to the Udoo Neo and write it to the boot partition
adb -d push boot_new.img /data/transfer/boot_new.img
adb -d shell
su
dd if=/data/transfer/boot_new.img of=/dev/block/mmcblk0p1

# cleanup on the Udoo Neo
rm /data/transfer/boot_old.img
rm /data/transfer/boot_new.img
rmdir /data/transfer
sync

Now reboot the Udoo Neo, automatically using the new boot image. If booting fails, it's still possible to write back the old boot image by connecting the microSD-card of the Udoo Neo to the host system and running a command similar to the following there:

dd if=boot_old.img of=/dev/....

where /dev/.... needs to be replaced by the correct partition name on the specific host system, e.g. /dev/sdb1.

Sample output of boot-extract:

argc 2 optind 1
Boot header
  flash page size	2048
  kernel size		0x570648
  kernel load addr	0x84808000
  ramdisk size		0xde632
  ramdisk load addr	0x85800000
  second size		0xb566
  second load addr	0x85700000
  tags addr		0x84800100
  product name		''
  kernel cmdline	'console=ttymxc0,115200 init=/init vmalloc=256M androidboot.console=ttymxc0 consoleblank=0 androidboot.hardware=freescale cma=128M androidboot.selinux=disabled
                         androidboot.dm_verity=disabled no_console_suspend uart_from_osc clk_ignore_unused'

These notes are based on a set of slides.