linuxexpert-practice-labs/labs/linux-plus/2-4-3-infrastructure-services/README.md

Linux+ 2.4.3: DNS, time and DHCP services

Which service keeps the clock in sync, a caching DNS server that another machine can use, and reading a DHCP lease from the client side.

Before you start

The lab sets up a second machine, peer (10.99.0.2), linked to this VM's address 10.99.0.1. It stands in for the chapter's other VM. On RHEL relatives the lab installs bind-utils for dig. Write answers to the files in /root/lab-answers/.

Tasks

1. Find out which service keeps this VM's clock in sync, and write its name (chronyd or systemd-timesyncd) to /root/lab-answers/1.
2. RHEL relatives: build a caching DNS server with Unbound that listens on all addresses and answers clients from 10.0.0.0/8 and 192.168.0.0/16, and that starts at boot. Open the firewall for DNS if it's running. From the peer, dig @10.99.0.1 should get answers.
3. Find the address of the DHCP server that gave this VM its address, and write it to /root/lab-answers/3.

Hints

• chronyc sources -v, chronyc tracking, timedatectl, timedatectl timesync-status, systemctl status.
• A file in /etc/unbound/conf.d/ with interface: and access-control: lines, unbound-checkconf, systemctl enable --now, firewall-cmd --add-service=dns (and --permanent); ip netns exec lepeer dig @10.99.0.1 www.kernel.org.
• nmcli -f DHCP4 device show DEVICE (dhcp_server_identifier); networkctl status, journalctl -u systemd-networkd, /run/systemd/netif/leases/.