Hints and tips of system administration

In this page we are giving some hints and tips of system administration. Most of the commands have to be run as root.
The interface with which the ZynqMP is connected to the private network with the host PC is ens6 and the interface with which the host PC is connected to the public network is eno1.
Match those to your respective interfaces.

1 Accept nfs through CentOS firewall

CentOS 7 uses firewalld instead of iptables:
firewall-cmd --permanent --zone=public --add-interface=ens6
firewall-cmd --permanent --add-service=rpc-bind
firewall-cmd --permanent --add-service=mountd
firewall-cmd --permanent --add-port=2049/tcp
firewall-cmd --permanent --add-port=2049/udp
firewall-cmd --permanent --add-port=50000/tcp
firewall-cmd --permanent --add-port=50000/udp
firewall-cmd --reload

2 Set nfs exports

mkdir -p /home/ppapageo/NFS
echo '/home/ppapageo/NFS,sync,no_root_squash,no_subtree_check,no_acl)' >> /etc/exports
exportfs -a

3 Disable the NetworkManager from configuring your interface

If you are using CentOS 7 with the Network Manager, it will periodically overwrite the IP address of the interface where the ZynqMP is conneced, causing serious connection problems. To avoid that disable the Network Manager on that particular interface:
echo "NM_CONTROLLED=no" >> /etc/sysconfig/network-scripts/ifcfg-ens6

4 Setup an ntp server using chrony

On the server side:
Enable ntp through the firewall. Then stop the ntp daemon.
firewall-cmd --permanent --add-service=ntp
firewall-cmd --reload
systemctl stop ntp
systemctl disable ntp

Add the following configuration to the /etc/chrony.conf file:

driftfile /var/lib/chrony/drift
keyfile /etc/chrony.keys
commandkey 1
local stratum 8

Then start the chrony daemon:

systemctl start chronyd
systemctl enable chronyd 

On the ZynqMP side:
Edit the /etc/chrony.conf file:

server pcphl1ct10  iburst prefer minpoll 0 maxpoll 0 xleave
hwtimestamp eth0
allow pcphl1ct10
initstepslew 20 pcphl1ct10
commandkey 24
local stratum 10
log measurements statistics tracking

Edit the /etc/hosts file and add the following line: pcphl1ct10
Then start the chrony daemon:
systemctl start chronyd
systemctl enable chronyd 
You can track the client-host clock syncronization with the command chronyc tracking.

5 Add internet access via IP masquerading

In our configuration the IP address of the ZynqMP is .

On the host PC side:
See the contents of /proc/sys/net/ipv4/ip_forward.

cat /proc/sys/net/ipv4/ip_forward
If the output is not 1.
echo 1 > /proc/sys/net/ipv4/ip_forward
iptables -t nat -I POSTROUTING -s -o eno1 -j MASQUERADE
iptables -I FORWARD -s -j ACCEPT
On the ZynqMP side:
route add default gw
Edit the /etc/resolv.conf file and add the following line(in place of insert the ipv4 of your DNS server):
Special thanks to Piotr Nikiel for providing us with this recipe.

-- PanagiotisPapageorgiou - 2019-02-25
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Topic revision: r10 - 2019-10-11 - unknown
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