Linux Certified System Admin - SA3 (RHEL7)

this lecture introduces systemd as linux service manager in rhel 7, highlighting its role as the first boot process, replacing init, and enabling on-demand, concurrent startup to reduce boot time.

Systemd replaces init as pid 1, enables parallel startup, preserves boot logs with journald, and uses cgroups to start services when dependencies are met.

Explore how systemd uses cgroups to manage service components as units, and use systemctl to view and manage units by status, such as loaded and active.

Check service status with systemctl, interpret active, loaded, and failed states, and use unit listing and status commands to verify and manage service units.

Switch between targets like graphical.target and multi-user.target with systemctl isolate, reboot or suspend to apply changes, and set the default target with systemctl get-default and set-default, configure hostname and time.

Understand the network manager daemon that monitors and configures network settings, and use nmcli to check interface status, add interfaces, activate services, and adjust IP and gateway properties.

Learn to manage network interfaces with nmcli, assign IPs, and activate or deactivate connections, while verifying connected and disconnected states on a Linux server.

View and modify Linux ethernet settings, change IP addresses manual or auto, set the default gateway, update the hostname, and delete a network connection.

Explore how network teaming aggregates multiple interfaces into a single virtual interface. It uses a kernel driver and a userspace daemon, enabling failover and load balancing with round robin.

Explore Linux NIC teaming policies including round robin, active-backup, broadcast, and load balancing, with examples of configuring a team and understanding fault tolerance and throughput.

Configure an active-backup teaming interface in Linux, create team 0, assign interfaces as slaves, set a policy (active-backup or round-robin), and test failover to ensure network resilience.

Test network teaming with an active backup policy, verify port failover between NICs, and review the team configuration file for active backup and round robin options.

Explore how the domain name system maps domain names to IP addresses, resolves queries on port 53, and how DNS servers enable communication.

Explain how a local DNS server resolves domain names to IP addresses. Understand how a client uses iterative lookups and public DNS to reach a remote host.

Explore the root name servers and how the domain name system enables global internet communication, including the structure of top level domains, second level domains, and domain authorities.

Understand how a dns query travels from the client to root servers to locate an ip address. See how the recursive process and dns cache deliver the final ip.

Learn to configure a DNS server with BIND, install the named daemon, edit named.conf and zone files, and manage master/slave servers, forwarders, and domain subdomains.

Explore types of DNS servers, including master and slave for subdomains. See how forwarders, caching, and root and top-level domains resolve queries and hide the local network from the internet.

Learn how DNS resource records map names to IP addresses and services, including A records for hosts, MX records for mail servers, CNAME aliases, and reverse mapping for IP-to-host lookups.

Configure a dns server in a lab by installing the bind package, editing forward and reverse lookup files, and testing name resolution via ping.

Configure dns zone files for forward and reverse lookups, including ttl and serial numbers to manage caching. Learn dns resource records and the roles of primary and slave servers.

Configure a DNS server by editing forward lookup to add A records and canonical name aliases, reverse lookup entries, and mail server priorities; restart the service and test name resolution.

Troubleshoot DNS issues by validating port 53 UDP in firewall rules, verifying DNS lookups and server reachability, and checking SELinux context and named configuration for syntax.

Learn to configure iSCSI targets and initiators, connect storage over IP to Linux systems, and understand how targets and initiators share storage across a SAN.

Explain the core iSCSI concepts, including the initiator and target, unique IQN identifiers, ACL-based access control, and discovery and login processes to share and access storage devices.

Explore iSCSI component terminology, including iqn (qualified name) for initiators and targets, and learn how discovery, login, and lun sharing establish sessions and connections.

Configure and manage target environments using the target cli utility and administration shell. Explore storage objects, including blocks and files, and share them with plane machines.

Configure and manage iSCSI storage by setting up targets and initiators, creating and attaching LUNs, and applying ACLs to map shared storage across nodes.

Lab 3 demonstrates discovering targets, configuring disk partitions, and verifying a shared volume on the target, with start and stop service steps and access checks from the host.

Understand how NFS enables a Linux server to export and share directories with Unix clients over the network, using remote procedure calls to mount them as local file systems.

Explain how NFS services such as rpcbind, mountd, nfs, and idmapd manage port mappings, exports, and file locking to enable secure client file system mounting.

Examine RPC services that process mount requests, verify exported file systems, and manage user IDs, highlighting the role of userspace components like FSD with the kernel interface.

Learn how NFS works by mounting a remote file system on a local directory, using exported file systems and server services, and understanding stateless versus stateful communications.

Install nfs packages with yum, start services with systemctl, and configure /etc/exports to export file systems with rw and sync options. Ensure automatic mounting via fstab and correct permissions.

Set up an nfs export on a rhel7 lab server by creating a filesystem, exporting it with an export file, and enabling rw with no_root_squash.

Mount an exported file system from the server on the Klein client, then create, read, and write files to observe user rights and permissions.

Configure automatic mounting of an nfc network file system by editing /etc/fstab with the server ip, file system name, and mount point, then reboot to verify permanent mounting.

Manage firewalld on Linux by inspecting default and active zones, listing services in the public zone, and configuring rules to enable or disable ports such as 22, including masquerading.

Enable and disable a web server on the firewall, configure public access rules, start the service, and verify browser access while learning to add or remove applications.

Set up firewall port forwarding to map external requests to an internal web server port. Conceal the internal port while routing requests by destination and source IP through the firewall.

Learn to apply firewalld rich rules to permit a specific service for chosen sources while denying all others by default, and manage rules with permanent options and restart.

Configure a firewall to allow a specific server and source IP access to a service, and validate access on port 21.

In this lab, learn to configure a Linux firewall to reject icmp traffic, compare drop versus reject behavior, and test responses to understand the impact on incoming pings.

Explore how masquerading and port forwarding enable access to a private web server behind a firewall by translating public and private IPs and forwarding requests.

Traverse a linux firewall scenario where a LAN uses private and public IPs to reach a web server, showing packet flow, destination and source IPs, and masquerading at the firewall.

Configure a small private web page on an internal server and enable firewall masquerading and port forwarding to expose it to the public internet.

Discover how the Apache httpd web service functions as a cross-platform, open-source web server, configure its files, set up virtual hosts, and secure traffic with HTTP and HTTPS.

Explore the Apache main configuration file, its location, and essential keywords such as server, server name, document root, error log, and pid, plus backup practices and basic setup.

Configure the Apache main conf file by setting the listen directive and log level, enable SSL on port 443, and test a simple website by restarting the service.

Learn how to launch a website with Apache by configuring the Apache configuration file, setting hostname and host entries, installing Apache via yum or rpm, and verifying access through firewall.

Configure Apache access control with order deny, allow. Deny all by default and allow specific hosts, such as Linux or Windows machines, to access the site.

Explore how Apache's indexes directive controls directory listing, enabling web clients to view files when browsing a site, with examples of configuring the document root and index files.

Explore how indexes control directory listing and security in apache, adjust options to deny access, and practice configuring index settings in a hands-on lab session.

Learn to enforce security restrictions on directories using .htaccess, configure basic authentication with a username and password, protect directory indexes, and consider the potential performance overhead.

Configure Apache to restrict access using a password file. Create the password entry, modify the Apache configuration, restart the service, and verify the browser prompts for credentials.

Discover how to secure a web server by verifying server identity, enabling user authentication, and encrypting authentication and session data with ssl or tls.

Learn how a client and a secure web server establish encrypted communication over port 440 using ssl, certificates signed by certificate authorities, and a public key exchange.

Create a self-signed certificate with openssl, generate the certificate and key, and enable encrypted communication between your server and client. Explain browser warnings for unsigned certificates and CSR creation.

Configure postfix to build a Linux mail server and explain how email flows from sender to receiver, including local and remote domains and mail submission checks.

Explore postfix mail server components: mail user agent, mail transport agent, and mail delivery agent, and learn to install, start, enable, and test local mail on a RHEL7 system.

Configure postfix main.cf to listen on all interfaces, set the mail server hostname and domain, and ensure mail from the domain appears correctly.

Configure the mynetworks parameter to specify which networks can use your Postfix server, limiting accepted mail to trusted networks and preventing abuse.

Explore the postfix mydestination parameter, defining which domains are delivered locally versus forwarded, and how to use localhost, example.com, or $mydomain to handle local and remote delivery.

Explore configuring postfix mydestination to accept local and remote mail for example.com, test mail flow with telnet, and examine logs to ensure delivery.

Learn Postfix mail flow in a domain-based setup, covering local user delivery, enabling Postfix, configuring interfaces for external mail, and using a relay host for outbound mail.

Configure Postfix as a null client to relay outbound mail through a central server. Set hostname, domain, and destination, then test mail flow.

Configure dovecot to provide IMAP and POP3 access for Postfix, enabling clients like Thunderbird and Outlook. Learn how IMAP keeps mail on the server and POP3 retrieves messages.

Configure Dovecot by adjusting its configuration file, set mail location to user home directories, and enable authentication and Postfix Unix socket for access via Thunderbird or Outlook.

install the thunderbird mail user agent on linux, download and extract the package, then configure accounts with ssl, authentication, and certificates to access mail and send test messages.