After configuring few instances of VMware Skyline I found I am no longer able to login through ssh Root or on web portal through admin, the default password was not working. Another thing was whenever logging through SSH tool I was getting root is locked up. For this skyline has simple and nice knowledge based article https://kb.vmware.com/s/article/52652. Since I was facing recurring issue, I thought of adding few screenshot and write detailed blog about it. 

Reset root password on VMWare PHOTON OS

The first step I will perform is resetting root password on VMware Skyline Collector appliance, Skyline collector uses VMware photon OS. (The same step for resetting root password will also work on other VMware product where Photon OS is used in the appliance for example VCSA (VMware vCenter Server Appliance)). 

Restart appliance from vCenter server (Open web remote console before restart) and when you see the below Photon OS boot screen press e on the keyboard.

On the GNU GRUB screen type rw init=/bin/bash after $systemd_cmdline and Press Ctrl-x or F10 to boot to command prompt.

Once system is loaded on the linux command prompt type passwd to reset root password, type new password twice to confirm. Next unlock root password if it is locked, you can check the status and unlock it with pam_tally command, if it is a recurring issue you will get to know from which ip root account is getting locked up.

passwd
/sbin/pam_tally2 --user root
/sbin/pam_tally2 --user root --reset
/sbin/pam_tally2 --user root
reboot -f

Reboot the server in the last.

Reset Admin password Skyline Controller Web Portal

To reset web portal Admin password of Skyline controller you will require to open remote console and Login with root account.

Provide root account password, change directory to /usr/local/skyline/ccf/config/generated/ locate credentials.json, this file contains Admin password hash. Change the file name of credentials.json to credentials.json.old. and restart server with reboot -f. (File is regenerated upon reboot with "default" password)

cd /usr/local/skyline/ccf/config/generated/
mv credentials.json credentials.json.old
reboot -f

After reboot, open Skyline Collector web portal and use new Admin password "default", once authentication succeeded it asks for resetting new password.

PermitRootLogin ssh

In the last I suspect because by default ssh root login is set to no inside /etc/ssh/sshd_config, this may be the cause of locking out of root user. To give permissions to root to ssh use below commands. restart sshd service and Log to skyline collector from ssh with root.

ls /etc/ssh
vi /etc/ssh/sshd_config 
#change or add line PermitRootLogin yes
systemctl restart sshd

Useful Articles
Part 1 - Copy or clone Distributed Virtual Switch portgroups to standard switch portgroups - Powercli
Migrating move back from Distributed virtual switch to Standard virtual switch - VMKernal Adapter - Part 2
Migrating move back from Distributed virtual switch to Standard virtual switch - VMs (Virtual Machine) - Part 3
Part 4: Remove ESXi Host from Distributed switch and migrate to virtual switch completely