10.3 Start, Stop, and Check Status of Network Services

Red Hat Certified System Administrator RHCSA

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1 Introduction & Exam Overview

1.1 Current Exam Facts 1.2 Lab Setup & Performance-Based Study Strategy

2 Essential Tools: Shell, Redirection & Text Analysis

2.1 Shell Prompt and Command Syntax 2.2 Input-Output Redirection and Pipes 2.3 grep and Regular Expressions for Text Analysis

3 Essential Tools: Remote Access, Users & Text Editing

3.1 Access Remote Systems Using SSH 3.2 Log In and Switch Users in Multiuser Targets 3.3 Create and Edit Text Files

4 Essential Tools: Files, Links & Archives

4.1 Create, Delete, Copy, and Move Files and Directories 4.2 Hard and Soft Links 4.3 Archive and Compress with tar, gzip, and bzip2

5 Essential Tools: Permissions & System Documentation

5.1 List, Set, and Change Standard ugo/rwx Permissions 5.2 System Documentation: man, info, and /usr/share/doc

6 Manage Software: RPM and Flatpak

6.1 Configure Access to RPM Repositories 6.2 Install and Remove RPM Software Packages 6.3 Configure Access to Flatpak Repositories 6.4 Install and Remove Flatpak Software Packages

7 Create Simple Shell Scripts

7.1 Conditional Execution: if, test, and [] 7.2 Looping Constructs for Files and Input 7.3 Process Script Inputs ($1, $2, and Beyond) 7.4 Process Shell Command Output in Scripts

8 Operate Running Systems: Boot and Recovery

8.1 Boot, Reboot, and Shut Down a System Normally 8.2 Boot Systems into Different Targets Manually 8.3 Interrupt the Boot Process to Gain Access

9 Operate Running Systems: Processes and Tuning

9.1 Identify and Kill CPU/Memory Intensive Processes 9.2 Adjust Process Scheduling 9.3 Manage Tuning Profiles

10 Operate Running Systems: Logs, Services & File Transfer

10.1 Locate and Interpret System Log Files and Journals 10.2 Preserve System Journals 10.3 Start, Stop, and Check Status of Network Services 10.4 Securely Transfer Files Between Systems

11 Configure Local Storage: Partitions and LVM

11.1 List, Create, and Delete Partitions on GPT Disks 11.2 Create and Remove Physical Volumes 11.3 Assign Physical Volumes to Volume Groups 11.4 Create and Delete Logical Volumes

12 Configure Local Storage: Mounting and Expansion

12.1 Mount File Systems at Boot by UUID or Label 12.2 Add Partitions, Logical Volumes, and Swap Non-Destructively

13 Create and Configure File Systems: Local FS and Permissions

13.1 Create, Mount, and Use VFAT, ext4, and XFS File Systems 13.2 Extend Existing Logical Volumes 13.3 Diagnose and Correct File Permission Problems

14 Create and Configure File Systems: NFS and autofs

14.1 Mount and Unmount Network File Systems Using NFS 14.2 Configure autofs

15 Deploy and Maintain: Scheduling, Services & Targets

15.1 Schedule Tasks with at, cron, and systemd Timers 15.2 Start, Stop, and Enable Services at Boot 15.3 Configure Systems to Boot into a Specific Target

16 Deploy and Maintain: Time, Software Updates & Bootloader

16.1 Configure Time Service Clients 16.2 Install and Update Software from CDN, Remote Repos, and Local Files 16.3 Modify the System Bootloader

17 Manage Basic Networking

17.1 Configure IPv4 and IPv6 Addresses 17.2 Configure Hostname Resolution 17.3 Configure Network Services to Start Automatically at Boot 17.4 Restrict Network Access Using firewalld and firewall-cmd

18 Manage Users and Groups

18.1 Create, Delete, and Modify Local User Accounts 18.2 Change Passwords and Adjust Password Aging 18.3 Create, Delete, and Modify Local Groups and Memberships 18.4 Configure Privileged Access

19 Manage Security: Firewall, umask & SSH Keys

19.1 Configure Firewall Settings with firewall-cmd and firewalld 19.2 Manage Default File Permissions 19.3 Configure Key-Based Authentication for SSH

20 Manage Security: SELinux Modes and Contexts

20.1 Set Enforcing and Permissive Modes for SELinux 20.2 List and Identify SELinux File and Process Contexts 20.3 Restore Default File Contexts

21 Manage Security: SELinux Ports and Booleans

21.1 Manage SELinux Port Labels 21.2 Use Boolean Settings to Modify SELinux Settings

10.3 Start, Stop, and Check Status of Network Services

Key Takeaways Explain This Topic AI

Use systemctl start, stop, restart, reload, status, is-active, and is-enabled to control and inspect services—including network-facing units like sshd, NetworkManager, and firewalld.

status and is-active answer “is it running now?”; is-enabled answers “will it start on boot?”—EX200 tasks may require both runtime and enablement checks.

NetworkManager manages connectivity (nmcli); firewalld manages packet filtering (firewall-cmd); sshd provides remote shell—know which unit owns which symptom.

Prefer systemctl reload when a daemon supports graceful config reload; use restart when a full stop/start is required; avoid stopping NetworkManager or sshd blindly on a remote exam host.

Failed units show in systemctl --failed and journalctl -u; fix config then start again, and re-verify active state before leaving the task.

Last updated: August 2026

10.3 Start, Stop, and Check Status of Network Services

Quick Answer: Control network services with systemctl start|stop|restart|reload|status UNIT . Confirm with is-active and is-enabled . On RHEL 10, master sshd , NetworkManager , and firewalld as the usual network-related units. Read failures via systemctl status and journalctl -u . Do not stop remote access services without a recovery plan.

Scope of this objective

Under Operate running systems , you must start, stop, and check the status of network services . Related skills appear again under deploy/maintain systems (enable at boot) and networking (addresses, hostname, firewall rules). Here the core is runtime control and status of services that provide or affect network access.

• You will repeatedly use: systemctl status UNIT
• systemctl start UNIT
• systemctl stop UNIT
• systemctl restart UNIT
• systemctl reload UNIT
• systemctl is-active UNIT
• systemctl is-enabled UNIT
• systemctl --failed
• systemctl verbs that matter

• Verb Effect
• start Start unit now
• stop Stop unit now
• restart Stop then start
• reload Ask daemon to reload config without full stop (if supported)
• try-reload-or-restart Reload if possible else restart
• status Human-readable state + recent logs
• is-active Exit code / print active or not—script friendly
• is-enabled Whether enabled for boot
• enable / disable Boot persistence (often paired; full enable patterns also in later chapters)

mask / unmask Hard-block start (mask links to /dev/null )—powerful; use only when required sudo systemctl start sshd

• sudo systemctl stop httpd
• sudo systemctl restart firewalld
• sudo systemctl reload sshd # if unit supports reload
• systemctl status NetworkManager
• systemctl is-active NetworkManager
• systemctl is-enabled NetworkManager

Active means running now . Enabled means started as part of the configured boot target. A service can be active but disabled (started manually) or enabled but failed (should start at boot but is not running).

• The big three network-related services
• 1) sshd — remote login
• Unit name: sshd.service (often referenced as sshd ). systemctl status sshd
• sudo systemctl start sshd
• sudo systemctl reload sshd # common after sshd_config changes when supported
• sudo systemctl restart sshd

After config edits to /etc/ssh/sshd_config or drop-ins under /etc/ssh/sshd_config.d/ : sudo sshd -t # syntax test BEFORE restart

• sudo systemctl reload sshd || sudo systemctl restart sshd
• systemctl is-active sshd

Remote exam danger: Restarting sshd with a broken config can lock you out . Always sshd -t first. Prefer reload when valid. Keep a console session if available.

• 2) NetworkManager — connectivity
• Unit: NetworkManager.service . systemctl status NetworkManager
• systemctl is-active NetworkManager
• nmcli general status
• nmcli device status
• nmcli connection show

Stopping NetworkManager can drop interfaces and kill your SSH session on a DHCP-only remote host. On EX200, start/stop/status tasks are common; do not casually systemctl stop NetworkManager on the only link you use unless the task requires it and you understand the impact.

Bring connections up/down with nmcli (networking chapter depth) while NetworkManager remains running: nmcli connection up "System eth0"

• nmcli device connect eth0
• 3) firewalld — host firewall
• Unit: firewalld.service . systemctl status firewalld
• sudo systemctl start firewalld
• sudo systemctl reload firewalld
• firewall-cmd --state
• firewall-cmd --get-default-zone
• firewall-cmd --list-all

Runtime vs permanent firewall rules are a security/networking objective. Here, ensure you can start/stop/status the service . If firewall-cmd says the firewall is not running, start the unit: sudo systemctl start firewalld

• firewall-cmd --state
• Checking status like an examiner systemctl status sshd -l --no-pager

Read:

Loaded line — unit file path; enabled / disabled / static / masked .

Active line — active (running) , inactive (dead) , failed , activating .

Main PID and tasks .

Recent journal lines attached to the status.

Script-friendly: systemctl is-active sshd; echo $?

systemctl is-enabled sshd; echo $?

• Command result Meaning
• is-active → active Running now
• is-active → inactive Not running
• is-active → failed Stopped in failed state
• is-enabled → enabled Will start at boot (typical)
• is-enabled → disabled Will not
• is-enabled → masked Hard-prevented
• List all failed: systemctl --failed
• systemctl list-units --type=service --state=failed
• restart vs reload vs stop/start

• Situation Prefer
• Apply config, minimize disruption reload if supported
• Unit failed or reload not enough restart
• Task says “stop the service” stop
• Task says “ensure it is running” start or restart then is-active
• Unknown support for reload systemctl reload-or-restart UNIT systemctl show -p CanReload sshd

If reload fails with “Job type reload is not applicable,” use restart .

• Safe workflows on a network host
• Ensure sshd is running (without locking yourself out) sudo sshd -t && sudo systemctl reload sshd
• systemctl is-active sshd
• ss -tlnp | grep ':22' # or the configured port
• Recover a stopped firewalld when a task needs it active systemctl is-active firewalld
• sudo systemctl start firewalld
• firewall-cmd --state
• Inspect NetworkManager after boot systemctl is-enabled NetworkManager
• systemctl is-active NetworkManager
• nmcli -g GENERAL.STATE device show
• journalctl -u NetworkManager -b -p err --no-pager
• Enablement vs this section

Tasks often mix:

• “Start the service now ” → systemctl start / --now
• “Start and enable” → systemctl enable --now UNIT sudo systemctl enable --now firewalld
• systemctl is-enabled firewalld
• systemctl is-active firewalld

Enablement depth continues in deploy chapters; still, you must read is-enabled when checking status of network services on the exam.

• Diagnosing failed network services sudo systemctl start sshd
• systemctl is-active sshd || sudo systemctl status sshd -l --no-pager
• sudo journalctl -u sshd -b -p err --no-pager

Common failure classes:

• Symptom Likely cause
• sshd fails start Syntax error in sshd_config; bad HostKey path; port bind conflict
• firewalld failed Python/backend issue; conflicting nft/iptables manual mess; unit masked

NetworkManager inactive Disabled/masked; replaced by network-scripts legacy in older designs—on RHEL 10 NM is standard

Active but not listening Wrong listen address; firewall blocking; socket unit confusion

Socket-activated services exist on systemd systems; if a task mentions a socket unit, check both .socket and .service . For classic sshd on RHEL exam images, managing sshd.service is the usual path. systemctl cat sshd

• systemctl list-sockets | grep -i ssh
• Other network-adjacent units you may meet

Depending on the lab image:

• Unit Role
• sshd / sshd.service OpenSSH server
• NetworkManager Interface and connection management
• firewalld Dynamic firewall
• nftables / iptables Alternate firewall stacks (know existence; RHEL default path is firewalld)
• chronyd Time (affects certs/logs; not always “network service” wording)
• httpd / nginx Web—network-facing application services
• named / dnsmasq DNS services if installed

Apply the same systemctl discipline to any named unit the task gives you.

• Exam scenarios
• Scenario A — “Start and confirm firewalld” sudo systemctl start firewalld
• systemctl is-active firewalld
• firewall-cmd --state
• Scenario B — “sshd is not running; fix it” systemctl status sshd -l --no-pager
• sudo journalctl -u sshd -b -n 30 --no-pager
• sudo sshd -t
• # fix config errors found
• sudo systemctl start sshd
• systemctl is-active sshd
• Scenario C — “Restart NetworkManager and verify devices” sudo systemctl restart NetworkManager
• systemctl is-active NetworkManager
• nmcli device status

If SSH drops, reconnect after NM settles—wait a few seconds before assuming failure.

• Scenario D — “Show status of all failed services” systemctl --failed --no-pager
• Common traps

Stopping sshd on a remote-only system with a bad config—no way back without console.

Confusing inactive with disabled — start ≠ enable.

Using kill on sshd instead of systemctl—orphans and inconsistent unit state.

Assuming status green means ports open — still verify with ss / firewall-cmd when connectivity is the real issue.

masking a service by accident — systemctl unmask UNIT to recover.

Restarting firewalld mid-rule edit without understanding runtime vs permanent (rule chapters)—still verify --state afterward.

Ignoring systemctl --failed after reboot when a network unit did not come up.

Persistence reminder

start alone does not guarantee the service returns after reboot. If the exam wants both running now and after reboot, use enable --now and verify with a reboot when required. This section still requires you to check enablement status accurately.

Section checkpoint

You should start, stop, restart, and reload network-related units with systemctl; interpret status/active/enabled/failed; operate safely around sshd, NetworkManager, and firewalld; diagnose failures with status plus journals; and verify the runtime end state the task names. That is the EX200 bar for controlling network services.