Photon OS – no ping and no ICMP replies? Other quick hints on Photon too.

Updated – July 9th, 2020 with password policy and complexity.

So I’ve been playing with Photon OS recently with a few of our Cloud Provider solutions, very nice lightweight appliance.

However, one thing that surprised me is the minimal/lightweight install does not have ping installed nor can you ping it (ICMP echo replies). In my opinion, this is a basic function for any type of network troubleshooting. I understand it’s minimal…but go cut something else out. 🙂

So how do we set up some basic network functions?

Setting up a Static IP

cd to /etc/systemd/network

vi (or use your preferred text editor) a file called 10-eth0.network

There’s three sections required: Match, Network, and DHCP

Below is the code required:

[Match]
Name=eth0
[Network]
Domains=HOSTNAME domain.local
Gateway=192.168.110.1
Address=192.168.110.61/24
DHCP=no
[DHCP]
UseDNS=false

Save it (wq!), and now it’s time to chmod the file so it can be read by the OS

chmod 644 10-eth0.network

Now we should see the correct permissions: 

Now restart the network daemon service.

systemctl restart systemd-networkd

Complete!

Installing Ping on Photon OS

Pretty easy – as you can see, doesn’t exist. 

Now there’s two different versions of Photon – version 1 and 2. On version 1, it’s pretty easy – type in the following:

yum install iputils

Now for Photon 2.0 (which I’m currently using), repos are disabled by default and so I was getting a message stating “package not found” which was odd. However, digging in further, I found the repos were not enabled.

Enabling Repos so we can pull iputils

cd /etc/yum.repos.d/

I enabled three repos:

photon

photon-extras

photon-updates

We need to edit each file and change the enabled=0 to enabled=1

Once I did this, run “tdnf repolist” and we should now see the following:

Now let’s install it!

tdnf install iputils

Now we should see the following: 

Sucess! Ping is available now, along with netstat too.

Allow ICMP echo responses

This is a change in the firewall table. By default, ICMP echo and replies are dropped.

Here are the two commands required to enable ICMP traffic:

iptables -A OUTPUT -p icmp -j ACCEPT

iptables -A INPUT -p icmp -j ACCEPT

Before I make the change on my system, I’m unable to ping

Make the iptables change….

Voila! We now get a response. 

DNS Configuration

Currently, I found a DNS issue with the vami_config_net file with a Photon 3.0 appliance deployment – it was not setting the DNS correctly and resorting to a 127.0.0.53 address. Moreover, the /etc/resolv.conf file should not be modified and if it is, changes do not persist post-reboot.

Two options:

1. Set DNS inside of the /etc/systemd/network/10-eth0-static.network network configuration file
2. Change it under /etc/systemd/resolved.conf

Option 1 Example:

1
2
3
4
5
6
7
[Match]

Name=e*



[Network]

Address=198.51.0.2/24

Gateway=198.51.0.1

DNS=198.51.0.1

Option 2

root@vcav [ ~ ]# more /etc/systemd/resolved.conf 

.......
# See resolved.conf(5) for details

[Resolve]

DNS=10.96.88.2

#DNS=

#FallbackDNS=8.8.8.8 8.8.4.4 2001:4860:4860::8888 2001:4860:4860::8844

#Domains=

LLMNR=false

#MulticastDNS=yes

#DNSSEC=no

#DNSOverTLS=no

#Cache=yes

DNSStubListener=yes

Resetting the Root Password

I’ve had situations where I’ve locked myself out of a Photon instance. The process is pretty simple – follow this link: https://github.com/vmware/photon/blob/master/docs/photon_troubleshoot/resetting-a-lost-root-password.md

Removing Password Expiration Policy

By default, Photon has a one year password expiration policy for accounts, including the root account. One can modify this and establish a no expiration policy, but also adjust other parameters.

From a root account, one can see the following:

root@vcd [ ~ ]# chage -l root

Last password change					: Mar 30, 2020

Password expires					: Mar 30, 2021

Password inactive					: never

Account expires						: never

Minimum number of days between password change		: 0

Maximum number of days between password change		: 365

Number of days of warning before password expires	: 7

One can modify this by using the “chage” command.

chage -m 0 root

From there, we can now see the password expiration has been removed.

root@vcd [ ~ ]# chage -l root

Last password change : Mar 30, 2020

Password expires : never

Password inactive : never

Account expires : never

Minimum number of days between password change : 0

Maximum number of days between password change : 99999

Number of days of warning before password expires : 7

Password Complexity

Photon utilizes the standard PAM modules for password complexity. For those of you in a lab environment that utilize the same password or standard password methodology, one might need to adjust this.

The configuration file is under:

/etc/pam.d/system-password

We can see under this file that we have three lines –

root@usagemeter42 [ /etc/pam.d ]# more system-password 

# Begin /etc/pam.d/system-password

password    requisite   pam_cracklib.so     minlen=8 minclass=4 difok=4 maxsequence=0 retry=3 enforce_for_root

password    requisite   pam_pwhistory.so    retry=3 remember=5 enforce_for_root

password    required    pam_unix.so         sha512 shadow use_authtok

# End /etc/pam.d/system-password

For me, I wanted to just disable the policy in its entirety. To do this, comment out the first line:

# Begin /etc/pam.d/system-password

#password    requisite   pam_cracklib.so     minlen=8 minclass=4 difok=4 maxsequence=0 retry=3 enforce_for_root

password    requisite   pam_pwhistory.so    retry=3 remember=5 enforce_for_root

password    required    pam_unix.so         sha512 shadow use_authtok

# End /etc/pam.d/system-password

From there, one can change their password –

root@usagemeter42 [ /etc/pam.d ]# passwd

New password: 

Retype new password: 

passwd: password updated successfully

Setting the Hostname

Need help changing it from the default photon-appliance hostname?

Hostnamectl is the command for permanently changing the name – not just editing the /etc/hosts file.

hostnamectl set-hostname DanielApp-B

Reboot the system.

One last tidbit – SSHD not starting?

During some of my testing, my lab environment went bottoms up – thanks, Timo 😉

After my Photon appliances started back up, I could not SSH to them. So after some troubleshooting and help from the VMware internal team, figured out what happened.

Steps to resolve:

Log into the console and ls -l /var/vmware/skip_sshd and you can also check the status of sshd by typing “systemctl status sshd”

If the file does exist, you need to remove it. No clue why it was added when I had a hard power outage, but it did.

rm /var/vmware/skip_sshd

Now start up ssh..

systemctl start sshd

Voila! we can now see it’s started

Now, SSH works! 

Other great details on Photon commands can be found here: Photon OS Troubleshooting Guide

Thanks!