The Geek Diary

Solaris 10 (x86/x64) : How to boot into single user mode from the Grub boot loader

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By default, in Solaris x86 10 1/06 the new GRUB boot loader does not provide a fully functional single user boot option in the menu that is presented upon booting. The default menu only has a GRUB “Safe Mode” boot option to choose from, but not the option to choose to boot to single user mode.

A true “Single User” boot option is key for many customers to apply patches and perform other administration needs. The below steps will show you the procedures to boot into single user mode using GRUB. The first method shows how to do this temporarily, and the other shows how to do this permanently by modifying the GRUB menu.lst file.

Temporary method : using GRUB

To boot single user mode temporarily from the GRUB menu, boot the system up and when the GRUB menu appears, type “e” for edit. You will then see a screen that will have 2 booting options as below.

Solaris 10 GRUB boot menu

NOTE: The “findroot (rootfs0,0,a)” line in the example above may look different for your server.

Then use the up and down arrows to highlight the “kernel….multiboot” line entry and then again type “e” for edit.

Solaris 10 kernel multiboot

Once in edit mode add a space and “-s” on the end of the line, and hit enter. The new line should look like this:

solaris 10 x86 boot into single user mode

After doing so, push the enter key. Back at the grub menu type “b” to boot to the modified line item.

solaris 10 x86 single user mode

This will take you into a “real” single user mode boot level.

Solaris 10 single user mode

Permanent method : using /boot/grub/menu.lst file

To be presented with the option to boot in single user mode on every boot, and thus make this change permanent, you would edit the /boot/grub/menu.lst file (grub boot loader) and add the lines below to give the single user mode boot option. If you are using ZFS for your boot disks your menu.lst will be in the location /rpool/boot/grub/menu.lst.

Note: Your entries in the menu.lst file will would look something like the example below, however, the root entry which points to the partition to boot should correspond to your current entries and may vary slightly from this example.

First, be sure to copy your existing menu.lst file:

# cp /boot/grub/menu.lst /boot/grub/menu.lst.old

When that is done, then you can edit the file with vi. You would see 2 entries – for normal booting and a failsafe booting. Make sure you take the entry of “findroot (rootfs0,0,a)” from here. This line may be different in you case. SO make sure you copy it from your menu.lst Rest all lines are same as below :

# vi /boot/grub/menu.lst
title Solaris 10 1/06 Single User Boot
findroot (rootfs0,0,a)
kernel /platform/i86pc/multiboot -s
module /platform/i86pc/boot_archive

solaris 10 menu.lst file

When you add the above to the menu.lst and then boot your server, your GRUB boot menu will have a new line at the bottom reflecting the entry you put after “title”. In this example it will look like this:

Solaris 10 single user boot GRUB menu

You can then boot into single user mode in the future by simply highlighting the “Solaris 10 1/06 Single User Boot” entry and hitting enter.

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