updated notes

src/rhcsa.md

@@ -403,4 +403,35 @@ elif [ "$age" -ge 18 ] && [ "$age" -le 20 ]; then
 else
 	echo "You are old enough to vote and enter bars."
 fi
+```
+
+## Boot Process & Targets
+
+### dmesg
+
+> Note: The boot process is the process by which a system starts up. It is a sequence of events that occur when a system is powered on or rebooted.
+
+```bash
+sudo dmesg # Display the kernel messages
+sudo dmesg | tail # Display the last 10 lines of the kernel messages
+sudo dmesg | grep "kernel" # Display the kernel messages that contain the word "kernel"
+
+### /var/log/messages ###
+sudo less /var/log/messages # Display the kernel messages
+```
+
+### systemd targets
+
+> Note: Systemd targets are a way to manage the boot process of a system. They are a way to manage the boot process of a system.
+> multi.target is the default target for the system.
+> graphical.target is the target for the graphical interface.
+> basic.target is the target for the minimal system.
+> rescue.target is the target for the rescue mode.
+> emergency.target is the target for the emergency mode.
+> multi-user.target is the target for the multi-user mode.
+> reboot.target is the target for the reboot mode.
+> poweroff.target is the target for the poweroff mode.
+
+```bash
+systemctl list-units --type=target
 ```