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Synopsis:
For many years, my Stratum 1 NTP server was made up of a very old PC running Slackware 11 and
connected to a Motorola GPS receiver. After much loyal service, it was time to retire it.
I already had a new machine running CentOS 7 but I was a bit apprehensive of systemd.
After Googling and testing, I finally got things up and running and decided to share what I found.
Hey, systemd is not so bad after all!
First, here are the details of the old system:
Computer:
* Pentium 4 Motherboard, Single core, 1.4GHz., 1GB memory
* Slackware Linux, 11.0.0
* PPSkit-2.1.7 Kernel
# uname -a:
Linux timelord 2.4.33.3-NANO #1 Fri Nov 12 21:28:51 EST 2010 i686
pentium4 i386 GNU/Linux
For GPS:
Motorola, GPS Receiver Version: 3, Revision: 1, Software Date: 1A30, Model: R5222U1114/[UT], Serial: R0AZSU
PPSKit:
Initial versions of PPSKit did not support 3.6 (and later) kernels. Now, PPSKit is built in to the Linux Kernel.
The Project:
My goal is to build a new machine with CentOS 7 and plenty of memory so it can serve multiple functions.
The initial project to create a Stratum 1 NTP server
is documented here:
https://www.darksmile.net/GPS/gpsindex.html
Setting up the CentOS 7 box.
The new machine has the following setup:
* Intel(R) Pentium(R) 4 CPU 3.20GHz 2 core
* CentOS Linux release 7.0.1406 (Core)
* PPSkit built in.
* 8GB Memory
# uname -a
Linux daedalos 3.10.0-123.9.2.el7.x86_64 #1 SMP Tue Oct 28 18:05:26 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux
For GPS:
The same hardware as the old box.
PPSKit:
PPSKit is built-in to the Linux Kernel.
-----------------------------------------------------------------------------------
OK, lets do this!!!!!
Check PPS on the kernel:
[root@daedalos-n]:/ # cd /lib/modules; pwd
/lib/modules
[root@daedalos-n]:/lib/modules # find `uname -r` | grep -i pps
3.10.0-123.9.2.el7.x86_64/kernel/drivers/pps
3.10.0-123.9.2.el7.x86_64/kernel/drivers/pps/clients
3.10.0-123.9.2.el7.x86_64/kernel/drivers/pps/clients/pps-gpio.ko
3.10.0-123.9.2.el7.x86_64/kernel/drivers/pps/clients/pps-ldisc.ko
3.10.0-123.9.2.el7.x86_64/kernel/drivers/pps/clients/pps_parport.ko
3.10.0-123.9.2.el7.x86_64/kernel/drivers/pps/pps_core.ko
Ok, it's there!
So, I just unplugged the serial cable from the old box and plugged it in to the new box, again, using COM1 --- This is Important!
Next, you must do the following:
# yum -y install setserial.x86_64
# yum -y install pps-tools.x86_64 pps-tools-devel.x86_64
# cat >>/etc/udev/rules.d/09.pps.rules
KERNEL=="ttyS0", SYMLINK+="gps0"
KERNEL=="ttyS0", SYMLINK+="oncore.serial.0"
KERNEL=="pps0", OWNER="root", GROUP="tty", MODE="0660", SYMLINK+="gpspps0"
KERNEL=="pps0", SYMLINK+="oncore.pps.0"
KERNEL=="ttyS0", RUN+="/bin/setserial -v /dev/%k low_latency irq 4"
# cat >/usr/lib/systemd/system/ldattach@.service
[Unit]
Description=Line Discipline for GPS Timekeeping for %i
Before=ntpd.service
[Service]
ExecStart=/sbin/ldattach 18 /dev/%i
Type=forking
[Install]
WantedBy=multi-user.target
# systemctl enable ldattach@ttyS0.service
ln -s '/usr/lib/systemd/system/ldattach@.service' '/etc/systemd/system/multi-user.target.wants/ldattach@ttyS0.service'
# reboot
When the system comes back you should be able to "see" the devices and 1PPS signal.
# ls -latr /dev
crw-rw-rw- 1 root tty 249, 0 Nov 26 14:29 pps0
lrwxrwxrwx 1 root root 5 Nov 26 14:29 gps0 -> ttyS0
lrwxrwxrwx 1 root root 4 Nov 26 14:29 gpspps0 -> pps0
lrwxrwxrwx 1 root root 9 Nov 26 16:24 oncore.pps.0 -> /dev/pps0
lrwxrwxrwx 1 root root 10 Nov 26 16:48 oncore.serial.0 -> /dev/ttyS0
crw-rw-rw- 1 root dialout 4, 64 Dec 10 19:20 ttyS0
NOTE:
oncore.pps.0 -> /dev/pps0
But,
oncore.serial.0 -> /dev/ttyS0
[root@daedalos-n]:/lib/modules # ppstest /dev/pps0
trying PPS source "/dev/pps0"
found PPS source "/dev/pps0"
ok, found 1 source(s), now start fetching data...
source 0 - assert 1418256211.000000287, sequence: 1225504 - clear 1417037578.525918006, sequence: 6957
source 0 - assert 1418256212.000001799, sequence: 1225505 - clear 1417037578.525918006, sequence: 6957
source 0 - assert 1418256212.999999238, sequence: 1225506 - clear 1417037578.525918006, sequence: 6957
…
…
Yup, there it is!
Optional:
CentOS 7 comes with ntpd which you can install via yum.
However, if you want to download a dev NTP version and compile, then
do this section.
Let's configure/compile the latest ntpd -- NOT from yum!
Download the latest NTP and remove any previous NTP package.
Download page is: https://www.ntp.org/downloads.html
# yum erase ntp.x86_64
# mkdir /var/log/ntp; chown -Rh ntp:ntp /var/log/ntp
Below, the {x} should be replaced with the number
of the latest NTP version.
# mkdir /opt/ntp; cd /opt/ntp
# wget https://www.eecis.udel.edu/~ntp/ntp_spool/ntp4/ntp-dev/ntp-dev-4.2.7p48{x}.tar.gz
# tar -xzvf ntp-dev-4.2.7p48{x}.tar.gz
# cd /opt/ntp/ntp-dev-4.2.7p48{x}
# ./configure --enable-all-clocks --with-crypto --enable-parse-clocks --enable-clockctl
# make
# make install
We are almost ready to rock. The install puts the NTP program(s) in /usr/local.
This is where they should go because the yum installed packages go in /usr and this way you can distinguish the two.
# cd /usr/lib/systemd/system
# cat >ntpd.service
[Unit]
Description=Network Time Service
After=syslog.target ntpdate.service sntp.service
[Service]
Type=forking
EnvironmentFile=-/etc/sysconfig/ntpd
ExecStart=/usr/local/bin/ntpd $OPTIONS
PrivateTmp=true
[Install]
WantedBy=multi-user.target
# cat >ntpdate.service
[Unit]
Description=Set time via NTP
After=syslog.target network.target nss-lookup.target
Before=time-sync.target
Wants=time-sync.target
[Service]
Type=oneshot
ExecStart=/usr/local/bin/ntpdate 0.pool.ntp.org
RemainAfterExit=yes
[Install]
WantedBy=multi-user.target
Let's configure from yum!.
# yum -y install ntpd ### That's it. Done!
NTP is installed. Moving on...
# cat > /etc/sysconfig/ntpd
# Command line options for ntpd
OPTIONS="-g -g -g"
Setup the NTP configuration files:
Download these 2 files from my web site.
# cd /etc
# wget https://www.maximaphysics.com/NTP/ntp.conf
# wget https://www.maximaphysics.com/NTP/ntp.oncore0
Ok, let's start ntpd!
# systemctl enable ntpd.service
# systemctl enable ntpdate.service
# systemctl daemon-reload
# systemctl start ntpd.service
# cd /var/log/ntp
# ls -lAtr
-rw-r--r-- 1 root root 6 Dec 11 11:42 ntp.drift
-rw-r--r-- 2 ntp ntp 394577 Dec 11 13:10 peerstats
-rw-r--r-- 2 ntp ntp 232938 Dec 11 13:10 loopstats
-rw-r--r-- 1 ntp ntp 3628 Dec 11 13:11 ONCORE
-rw-r--r-- 1 ntp ntp 215585770 Dec 11 13:11 ntp.log
-rw-r--r-- 2 ntp ntp 14670614 Dec 11 13:11 clockstats
If you tail -f ntp.log you should see:
11 Dec 13:12:15 ntpd[13755]: ONCORE[0]: 3627310334.999999344 2014 345 18 12 15 14 rstat 08 dop 0.0 nsat 9,8 traim 1,0,0 sigma 38 neg-sawtooth 48 sat 88888888
11 Dec 13:12:16 ntpd[13755]: ONCORE[0]: 3627310335.999998902 2014 345 18 12 16 15 rstat 08 dop 0.0 nsat 9,8 traim 1,0,0 sigma 38 neg-sawtooth -19 sat 88888888
11 Dec 13:12:17 ntpd[13755]: ONCORE[0]: 3627310336.999998329 2014 345 18 12 17 16 rstat 08 dop 0.0 nsat 9,8 traim 1,0,0 sigma 38 neg-sawtooth 16 sat 88888888
11 Dec 13:12:18 ntpd[13755]: ONCORE[0]: 3627310338.000000642 2014 345 18 12 18 18 rstat 08 dop 0.0 nsat 9,8 traim 1,0,0 sigma 38 neg-sawtooth -52 sat 88888888
That's it, you're done! Let's check the data:
[root@daedalos-n]:/root # ntpq -c peer -c as -c rl localhost
remote refid st t when poll reach delay offset jitter
==============================================================================
oGPS_ONCORE(0) .GPS. 0 l 3 16 377 0.000 -0.002 0.001
LOCAL(0) .LOCL. 10 l - 64 0 0.000 0.000 0.000
+bindcat.fhsu.ed 132.163.4.103 2 u 57 64 377 62.940 0.571 0.378
+host2.kingrst.c 108.61.73.244 3 u 23 64 377 39.986 1.314 2.451
*propjet.latt.ne 187.253.153.32 2 u 40 64 377 91.905 3.470 0.714
ind assid status conf reach auth condition last_event cnt
===========================================================
1 9580 973a yes yes none pps.peer sys_peer 3
2 9581 8011 yes no none reject mobilize 1
3 9582 9424 yes yes none candidate reachable 2
4 9583 943a yes yes none candidate sys_peer 3
5 9584 963a yes yes none sys.peer sys_peer 3
associd=0 status=0415 leap_none, sync_uhf_radio, 1 event, clock_sync,
version="ntpd 4.2.7p481@1.2483 Wed Nov 26 21:03:23 UTC 2014 (3)",
processor="x86_64", system="Linux/3.10.0-123.9.2.el7.x86_64", leap=00,
stratum=1, precision=-22, rootdelay=0.000, rootdisp=1.045, refid=GPS,
reftime=d83492b1.37a2a583 Thu, Dec 11 2014 17:01:21.217,
clock=d83492b4.9f6ec278 Thu, Dec 11 2014 17:01:24.622, peer=9580, tc=4,
mintc=3, offset=-0.001570, frequency=5.539, sys_jitter=0.000553,
clk_jitter=0.001, clk_wander=0.000
[root@daedalos-n]:/root # ntpdate -bdqv 0.pool.ntp.org | tail -1
host found : bindcat.fhsu.edu
11 Dec 17:01:52 ntpdate[27737]: step time server 216.66.0.142 offset 0.002014 sec
[root@daedalos-n]:/root # ntpdate -bdqv 0.pool.ntp.org | tail -1
host found : tssnet1.tss.net
11 Dec 17:02:11 ntpdate[27743]: step time server 216.66.0.142 offset 0.001892 sec
[root@daedalos-n]:/root # ntpdate -bdqv 0.pool.ntp.org | tail -1
host found : ccadmin.cycoresys.com
11 Dec 17:02:21 ntpdate[27745]: step time server 216.66.0.142 offset 0.003338 sec
Looking Good!!!!!!
Optional:
Now, if you want to see the real time GPS data you must use my darkgps software.
Download and configure as follows:
# cd /opt/ntp
You might have to install:
# yum -y install perl-Curses.x86_64
# wget https://www.maximaphysics.com/NTP/darkgps.tgz
# tar -xzvf darkgps.tgz
# cd darkgps_*
# ./gpsdisplay 47.16.129.9
That's it! Read the readme for a very detailed info n how to create charts, etc.
Here is a screenshot:
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