A glance at CentOS 7

For some reason, I've started a CentOS 7 instance to manage some services. It has a bunch of nice features, including LinuX Containers.

However, because of those changes, it is replacing some well-known components to better fit the latest development - specifically the isolation of namespace. Some significant updates includes:

service --> systemctl

This is not a big change, but has more detailed control over different scope management. All the details are stored here: /usr/lib/systemd/system and you can further add new services.
For example, you can start mysql via: systemctl start mariadb.service
Or if you want to start it permanently, via: systemctl enable mariadb.service

iptables --> firewalld

firewalldfeatures zone management, as a better variant of iptables. By default the computer is put to public zone, therefore we will need to add some service and port support. Typically the commands includes:
firewall-cmd --add-port=222/tcp
firewall-cmd --add-service=http
sudo firewall-cmd --permanent --zone=public --add-port=22/tcp

And on my own server it looks like this:
[root@localhost ssh]# firewall-cmd --list-all
public (default, active)
interfaces: ens32 virbr0
services: dhcpv6-client http ssh
ports: 222/tcp 22/tcp
masquerade: no
rich rules:

We will need to restart the firewall after set up: sudo systemctl restart firewalld.service

enhanced selinux

selinux not an easy task for starters, sometimes we are not clear about the which rule is actually blocking the entire thing.
To better deal with selinux (if you do not want to override all the nice settings), this article introduced some nice methods: Where to find SELinux permission denial details
The method includes setting SELINUX=permissive in /etc/selinux/config, and later grep AVC errors from grep "type=AVC" /var/log/audit/audit.log