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This article mainly introduces how to start the rescue mode or emergency mode in Ubuntu 18.04. it has a certain reference value, and interested friends can refer to it. I hope you will gain a lot after reading this article.

As you may already know, runlevels have been replaced by systemd targets in many recent Linux distributions, such as RHEL 7 and Ubuntu 16.04 LTS. For more details on them, see this guide. In this short tutorial, we will see how to start rescue mode and emergency mode. This guide was tested in Ubuntu 18.04 LTS, but the steps given below apply to most Linux distributions that use systemd as the default service manager. Before going any further, let me clarify what the rescue model and the emergency model are and what the purpose of these two models is.

What is the rescue mode?

The rescue mode is equivalent to the single-user mode in the Linux distribution that uses SysV as the default service manager. In rescue mode, all local file systems are mounted and only some important services are started. However, normal services (such as network services) will not be started. Rescue mode is useful when the system does not start properly. In addition, we can perform some important rescue operations in rescue mode, such as resetting the root password.

What is emergency mode?

Compared with the rescue mode, nothing is started in emergency mode. There is no service startup, no mount point, no socket establishment, nothing. All you have is a primitive shell. Emergency mode is suitable for debugging purposes.

Enter rescue mode in Ubuntu 18.04LTS

Activate your Ubuntu system. When the Grub menu appears, select the * bar and press e to edit.

If you don't see the Grub menu, just press the ESC key as soon as BIOS's logo disappears.

Locate the line that begins with the word linux and add the following at the end of the line (to reach the end, simply press CTRL+e or use the END key or the left and right arrow keys):

Systemd.unit=rescue.target

After the addition is complete, simply press CTRL+x or F10 to continue to start rescue mode. After a few seconds, you will enter rescue mode (single user mode) as a root user. The following is what the rescue mode looks like in Ubuntu 18.04 LTS server version:

Next, type the following command to mount the root (/) file system back into read / write mode.

Mount-n-o remount,rw / start to emergency mode

Booting Ubuntu to emergency mode is the same as above. You just need to replace systemd.unit=rescue.target with systemd.unit=emergency.target when editing the Grub menu.

After adding systemd.unit=emergency.target, press Ctrl+x or F10 to continue booting to emergency mode.

*, you can use the following command to mount the root file system back to read / write mode:

Mount-n-o remount,rw / switch between rescue mode and emergency mode

If you are in rescue mode, you do not have to edit the Grub entry as mentioned above. Instead, you can immediately switch to emergency mode by entering the following command:

Systemctl emergency

Similarly, to switch from emergency mode to rescue mode, enter:

Systemctl rescue thank you for reading this article carefully. I hope the article "how to start Rescue Mode or Emergency Mode in Ubuntu 18.04" shared by the editor will be helpful to you. At the same time, I hope you will support us and follow the industry information channel. More related knowledge is waiting for you to learn!

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