Chapter 9

Completely disable a service from being started, both manually and at boot

*systemctl mask network*

Reload configuration file of a running sshd service

*systemctl reload sshd.service*

Stop, then start, the sshd service in a single command

*systemctl restart sshd.service*

Set the default target to graphical.target

*systemctl set-default graphical.target*

Display the status of the *chronyd* service

*systemctl status chronyd*

Investigate any units which are in a failed or maintenance state. Show the full output

*systemctl status rngd.service -l*

View the status of a sshd service

*systemctl status sshd.service*

Stop the sshd service

*systemctl stop sshd.service*

Make a masked service available

*systemctl unmask network*

Query the state of all units to verify a system startup

*systemctl*

What will you append to the end of the line starting with *linux16* to get into the emergency target?

*systemd.unit=emergency.target*

What will you add to the end of the line starting with linux16 after pressing *e* to edit the current entry to set the target to rescue target?

*systemd.unit=rescue.target*

Make sure that all unlabeled files (including /etc/shadow at this point) get relabeled during boot

*touch /.autorelabel*

List units which are required and wanted by the sshd service

*systemctl list-dependencies sshd.service*

List the enabled or disabled states of all service units

*systemctl list-unit-files --type=service*

View all targets installed on disk

*systemctl list-unit-files --type=target --all*

Start the sshd service

*systemctl start sshd.service*

List all socket units, active and inactive, on the system

*systemctl list-units --type=socket --all*

View all available targets

*systemctl list-units --type=target --all*

List all service units on the system

*systemctl list-units --type=service*

Switch into a chroot jail, where /sysroot is treated as the root of the file system tree

*chroot /sysroot*

Make changes to the boot loader configuration permanent

*grub2-mkconfig > /boot/grub2/grub.cfg*

Mount all filesystems mentioned in fstab

*mount -a*

Mount the root file system read-write

*mount -o remount,rw /*

Remount /sysroot as read-write

*mount -o remount,rw /sysroot*

Confirm that the listed daemons are running using PID

*ps -p PID*

Display the status of the sshd service

*sudo systemctl status sshd*

View only failed services

*systemctl --failed --type=service*

Query the state of only the service units

*systemctl --type=service*

Disable a sshd service from starting at boot time

*systemctl disable sshd.service*

Configure a sshd service to start at boot time

*systemctl enable sshd.service*

Get the name of the default target

*systemctl get-default*

Determine if sshd is active

*systemctl is-active sshd*

Determine if the sshd service is active without displaying all of the status information

*systemctl is-active sshd*

Determine if the chronyd service is enabled to start at system boot

*systemctl is-enabled chronyd*

Determine if the sshd service is enabled to start at system boot

*systemctl is-enabled sshd*

Show if sshd is enabled to start at boot time

*systemctl is-enabled sshd*

Switch to a multi-user target

*systemctl isolate multi-user.target*

List dependencies for graphical target

*systemctl list-dependencies graphical.target | grep target*

View the enabled and disabled settings for all units

*systemctl list-unit-files*

List the active state of all loaded units and add the option to show inactive units too

*systemctl list-units --all*