Ubuntu – Add a grub menu entry that boots into the current install but with a different runlevel

14.10grub2initmenurunlevel

I am running the latest Kubuntu (14.10) and would like to add a grub2 menu entry that allows me to boot straight into a different runlevel? I would like to modify /etc/rc3.d or /etc/rc4.d to boot straight into the command line and not load X. I believe the custom menu entry should be placed in /etc/grub.d/40_custom? I assume I can copy my/the default menu entry in /boot/grub/grub.cfg? but then how do i make this entry boot at a different runlevel?

Can I add the command telinit 3 to the end of the custom menu entry?

any help would be appreciated 🙂

Best Answer

The problem with adding an entry using 40_custom is that the entry is static - the contents are copied as-is to grub.cfg, so a new kernel requires re-editing that file. With very slight tinkering of the 10-linux, you can get update-grub to generate an additional entry for each of the installed kernels. Edit /etc/grub.d/10_linux, and after the lines where it says:

linux_entry "${OS}" "${version}" advanced \
            "${GRUB_CMDLINE_LINUX} ${GRUB_CMDLINE_LINUX_DEFAULT}"
if [ "x${GRUB_DISABLE_RECOVERY}" != "xtrue" ]; then
  linux_entry "${OS}" "${version}" recovery \
              "${GRUB_CMDLINE_LINUX_RECOVERY} ${GRUB_CMDLINE_LINUX}"
fi

Add another call to linux_entry:

linux_entry "${OS}, runlevel 3" "${version}" advanced \
          "${GRUB_CMDLINE_LINUX} ${GRUB_CMDLINE_LINUX_DEFAULT} 3"

(Selecting a runlevel is as simple as tacking on the number at the end of the options, IIRC.)

Effect:

Menu entry in the "Advanced options" sub menu: entry
The contents of that entry:

Of course, normally runlevels 2-5 are equivalent, so booting from it made no difference to me, except:

$ runlevel
N 3

Using EasyBCD to Boot to GRUB from Windows Boot Menu

Start Windows and install the free version of EasyBCD.
Open the EasyBCD program and select Add New Entry from the sidebar on the left.
Select the rightmost tab, NeoGrub, under "Operating Systems" and click the Install button.

Note: This adds the NeoGrub bootloader code to your C:\ folder. If the install worked correctly you will see the file C:\NeoGrub and the folder C:\NST.
Select the Linux/BSD tab. Choose GRUB2 as the type of the entry and, optionally, edit the name of the entry you are about to add to the Windows Boot menu.

Click the Add Entry button to add an entry to boot Linux (GRUB menu) to the Windows boot menu.
Select Edit Boot Menu from the sidebar to review your changes.

Note: You can delete the entry for NeoGrub Bootloader if you wish.
You need the bootloader, but you do not need a boot menu entry for it unless you are using it in some other way.
Save your changes and reboot. When the Windows boot menu appears, select the EasyBCD entry you added to boot Linux. You should see something similar to the text below.

Then the GNU GRUB boot menu should appear.

Boot – Add GRUB Menu Item to Boot into Terminal

One

Open the file /boot/grub/grub.cfg and find the section that boots your "regular" Ubuntu.

For me this is:

menuentry 'Ubuntu' --class ubuntu --class gnu-linux --class gnu --class os $menuentry_id_option 'gnulinux-simple-b8f25f1e-a169-4aaa-9f05-90e49359d865' {
        recordfail
        load_video
        gfxmode $linux_gfx_mode
        insmod gzio
        if [ x$grub_platform = xxen ]; then insmod xzio; insmod lzopio; fi
        insmod part_gpt
        insmod ext2
        set root='hd0,gpt2'
        if [ x$feature_platform_search_hint = xy ]; then
          search --no-floppy --fs-uuid --set=root --hint-bios=hd0,gpt2 --hint-efi=hd0,gpt2 --hint-baremetal=ahci0,gpt2  b8f25f1e-a169-4aaa-9f05-90e49359d865
        else
          search --no-floppy --fs-uuid --set=root b8f25f1e-a169-4aaa-9f05-90e49359d865
        fi
        linux   /boot/vmlinuz-4.13.0-39-generic.efi.signed root=UUID=b8f25f1e-a169-4aaa-9f05-90e49359d865 ro  
        initrd  /boot/initrd.img-4.13.0-39-generic
}

Copy that section to a new file, say textmode.txt.

Two

Go to /etc/grub.d and create (or edit) the file 40_custom.

Copy the following "header" to the file:

#!/bin/sh
exec tail -n +3 $0
# This file provides an easy way to add custom menu entries.  Simply type the
# menu entries you want to add after this comment.  Be careful not to change
# the 'exec tail' line above.

Add the menuentry from textmode.txt to the file but change some values (see below):

menuentry 'Ubuntu (text mode)' --class ubuntu --class gnu-linux --class gnu --class os $menuentry_id_option 'gnulinux-simple-b8f25f1e-a169-4aaa-9f05-90e49359d865' {
        recordfail
        load_video
        gfxmode $linux_gfx_mode
        insmod gzio
        if [ x$grub_platform = xxen ]; then insmod xzio; insmod lzopio; fi
        insmod part_gpt
        insmod ext2
        set root='hd0,gpt2'
        if [ x$feature_platform_search_hint = xy ]; then
          search --no-floppy --fs-uuid --set=root --hint-bios=hd0,gpt2 --hint-efi=hd0,gpt2 --hint-baremetal=ahci0,gpt2  b8f25f1e-a169-4aaa-9f05-90e49359d865
        else
          search --no-floppy --fs-uuid --set=root b8f25f1e-a169-4aaa-9f05-90e49359d865
        fi
        linux   /vmlinuz root=UUID=b8f25f1e-a169-4aaa-9f05-90e49359d865 systemd.unit=multi-user.target ro
        initrd  /initrd.img
}

The values that must be changed are:

The menuentry text: change it from 'Ubuntu' to 'Ubuntu (text mode)' (or whatever you like to appear in the menu)
The linux line: change it to linux /vmlinuz root=UUID=... systemd.unit=multi-user.target ro. Make sure the UUID stays the same.
The initrd line: change it to /initrd.img

Make sure you have symlinks in your / directory from /vmlinuz and /initrd.img to the current versions. This is the default, anyway.

Three

Run

sudo update-grub

The difference between this approach and this answer to a very similar question is that in recent versions of Ubuntu the line

linux   /boot/vmlinuz-3.8.0-31-generic root=UUID=... ro quiet splash $vt_handoff

needs to be replaced with

linux   /vmlinuz root=UUID=... systemd.unit=multi-user.target ro

I'm not sure what recent actually means but I guess it's 16.04 when systemd was introduced.

Best Answer

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