How do I boot into a root shell?

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When booting to the graphical desktop fails we sometimes are recommended to boot into a "root shell" or to boot in "recovery mode".

How do I do that?

for 12.04.3 LTS and later

During boot press and hold the left Shift key or any other key. This will bring up the Grub2 menu from where we can select "Advanced options for Ubuntu".

After that we will be able to select the kernel we wish to boot in "Recovery mode":

This will lead us to the advanced options. By selecting "Enable networking" we gain access to our network and the internet for upgrades or downloads, and we will also mount our hard drives in read/write mode in case we need to edit files.

After the network has loaded, and fielsystems were mounted we will be presented again with the menu, from where we can choose "Drop to a root shell propmpt":

Note that we are root in this shell. Hence no sudo is needed for administrative tasks. This also means...

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Take the following steps:

1.Reboot server

2. Next, you will see grub-boot loader screen. Select Recovery mode and the version of the kernel that you wish to boot and type 'e' for edit. Select the line that starts with 'kernel' and type 'e' to edit the line.

3. Go to the end of the line and type init=/bin/bash as a separate one word (press the spacebar and then type init=/bin/bash). Press enter key to exit the edit mode.
init=/bin/bash

4. You will be back at the GRUB screen, type 'b' to boot into single user mode. This causes the system to boot the kernel and run /bin/bash instead of its standard init. It will allow us to gain root privileges (w/o password) and a root shell.

Note : This help is for breaking into system for fixing some boot issue , disk issue...

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I had a trouble yesterday. After a motherboard/CPU upgrade, my old network interface eth0 ceased to exist and instead, eth1 appeared. Because the configuration file /etc/network/interfaces referred to eth0, the boot process was permanently stuck on "Configuring Network Interfaces". I could not even log on.

Attempting to do "recovery mode" ended up stuck for the same reason.

Here's what I want to find out: How can I instruct GRUB/kernel to boot into /bin/sh RIGHT AFTER MOUNTING THE ROOT FILESYSTEM.

That is, I want to fully bypass initscripts after mounting root filesystem. In Fedora, I could say init=/bin/sh and it worked.

So, how can I get into the root shell right after kernel initializes and root filesystem is mounted?

Please note: I want to get an answer to my question how to get into root shell right after boot. I am NOT interested in other questions like whether it is a good idea, or how to do other things that are not related to my question, as well...

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Android (and therefore Android Things) does not allow applications to run as the root user for security reasons. If you need this feature for your production apps, feel free to add any comments regarding your use case to the existing feature request in place for this.

Regarding the things you already tried:

-installed an Android app in the /system/app folder with world executable perms

-installed an Android app in the /system/private-app folder with world executable perms

Apps installed in Android's /system partition are allowed privileged access to various Android-level permissions, but this does not affect their Linux UIDs.

-created init.d with a executable shell script file (folder didn't exist before)

Android does not use the same init structure as other Linux distributions. Init instructions are located in various init.rc files on the root file system. In general, again for security reasons, even the processes spawned from init are...

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Can I boot into the EFI shell in order to add a UEFI entry before installing Linux? There won't be GRUB on the Acer laptop initially.

The Acer laptop runs Windows 10.

Once you boot into the EFI shell, add a UEFI boot menu entry:

Shell> bcfg boot add 0 fs1:\EFI\arch_grub\grubx64.efi "Arch Linux (GRUB2)"

where fs1 is the mapping corresponding to the UEFI System Partition and \EFI\arch_grub\grubx64.efi is the the from the --bootloader-id from the grub-install command above.

This will temporarily add a UEFI boot option for the next boot to get into Arch. Once in Arch, modprobe efivars and confirm that efibootmgr creates no errors (no errors meaning you successfully booted in UEFI mode). Then GRUB#UEFI systems can be performed again and should successfully permanently add a boot entry in the UEFI menu.

reference:

https://wiki.archlinux.org/index.php/GRUB/EFI_examples

not specific to...

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How to drop into root shell prompt without going into recovery?

location: ubuntuforums.com - date: October 1, 2013
Hello, I completely hosed my system by installing nvidia-current on 13.10. I need to remove it so my system can boot properly. sudo apt-get remove nvidia_current would do nicely. However, 'm at a los as to how to do this, because the boot freezes on recovery, 6 seconds in, with the message "nvidia: module license 'NVIDIA" taints kernel." I need to remove nvidia so my system can boot, but my system can't boot until I remove nvidia. What Ubuntu sorely needs (if it has, forgive me, I haven't found it) is a failsafe way to boot into shell should the need arise.

How to get a shell prompt back after a shortcut launches a command?

location: linuxquestions.com - date: April 27, 2009
I made a shortcut on the desktop (using RHEL5.1 with KDE) that launches a script to mount a usb device. The shortcut runs the command: "konsole -noclose -e...

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Boot Shell allows you to save Linux Shell commands and execute them at boot. The Pro version allows to execute complete shell scripts at boot.
You can also save your favourite Linux commands and execute them at your will.
It can also eliminate the need of using init.d scripts for basic needs such as setting CPU parameters at boot such as, CPU Frequencies, governors, and also IO Governers,enable/disable Fastcharge, GPU Overclock etc.


REQUIREMENTS -
->ROOT
->BUSYBOX

Pro Version Extras -
-Ability to Execute Scripts at boot
-View outputs and errors after command execution
-Inbuilt Text/Script Editor

For any queries or problems please feel free to E-mail me at k.two.apps@gmail.com

Try not to execute a resource intensive task or scripts at boot, it can slow down your device startup.

Explanation for Permissions -

-> Read/Write USB Storage - Allow the Shell commands to read/write on Device...

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Grub2 - how do i boot into single-user mode from grub, After changing a few lines in xorg.conf, i can no longer boot ubuntu (i assume it breaks when trying to load up x), so i need a way to boot into a single-user mode. Grub2 - ask ubuntu, Ask ubuntu is a question and answer site for ubuntu users and developers. join them; it only takes a minute: sign up Gnu grub manual 2.02, 1.2 history of grub. grub originated in 1995 when erich boleyn was trying to boot the gnu hurd with the university of utah’s mach 4 microkernel (now known as gnu mach).

Grub2 how do i boot into a root shell ask ubuntu images

From Around the Web:

grub2 - How do I boot into single-user mode from GRUB
After changing a few lines in xorg.conf, I can no longer boot Ubuntu (I assume it breaks when trying to load up X), so I need a way to boot into a single-user mode....
Last update Thu, 15 Feb 2018 10:01:00 GMT | Read More...

grub2 - Ask Ubuntu
...

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Post by fedora

Select your boot instance in grub2, type e (for edit) and add "3" at

the end of the line. Then continue booting.


I'd say what he asked for would have been achieved with run level one

(otherwise known as single), not three. Run level three requires a

password, run level one does not.

If you can still boot into run level one, then typing a numeral one,
instead of 3, as you've suggested, ought to work.

The old run level one (whatever they call it, these days), was a basic,
isolated from the network, text-only, login. But I haven't tried that
on a modern system, to see whether it boots up similarly, or into a
newer special login.
--
***@localhost ~]$ uname -rsvp

Linux 3.19.8-100.fc20.i686 #1 SMP Tue May 12 17:42:35 UTC 2015 i686

All mail to my mailbox is automatically deleted, there is no point trying
to privately email me, I will only read messages posted to the public...

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for 12.04.3 LTS and later

During boot press and hold the left Shift key or any other key. This will bring up the Grub2 menu from where we can select "Advanced options for Ubuntu".

After that we will be able to select the kernel we wish to boot in "Recovery mode":

This will lead us to the advanced options. By selecting "Enable networking" we gain access to our network and the internet for upgrades or downloads, and we will also mount our hard drives in read/write mode in case we need to edit files.

After the network has loaded, and fielsystems were mounted we will be presented again with the menu, from where we can choose "Drop to a root shell propmpt":

Note that we are root in this shell. Hence no sudo is needed for administrative tasks. This also means we have full access to all files, and we may cause irreversible damage to our system if we made a mistake.

If we had not enabled read/write access with...

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There may be times where you need or want to boot up a

Linux

system without using a GUI, that is with no X, but rather opt for the command line. Whatever the reason, fortunately, booting straight into the Linux

command-line

is very simple. It requires a simple change to the boot parameter after the other kernel options. This change specifies the runlevel to boot the system into.

Why Do This?

If your system does not run Xorg because the configuration is invalid, or if the display manager is broken, or whatever may prevent the GUI from starting properly, booting into the command-line will allow you to troubleshoot by logging into a terminal (assuming you know what you’re doing to start with) and do whatever you need to do. Booting into the command-line is also a great way to become more familiar with the terminal, otherwise, you can do it just for fun.

Accessing GRUB Menu

On startup, you will need access to the GRUB boot menu. You may...

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