Booting the BIG-IP  V 9-11 system in single-user mode

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On certain occasions, it may be necessary to boot the BIG-IP system into single-user mode to fix operating system issues, such as filesystem or root password issues.
To boot the BIG-IP system into single-user mode, perform the following procedure:

Note: To perform the following steps, you must be local to the BIG-IP system with a console connection or using a console server.

1. Connect a terminal to the BIG-IP serial console port.
2. Reboot the BIG-IP system.While booting, the BIG-IP system displays the GRUB menu and counts down before continuing the boot process.
   
3. Before the countdown expires, use the up and down arrow keys to select the appropriate boot image.
   Note: Alternately, press SHIFT+6 (^) to arrow up, and press the v key to arrow down.
4. Press the e key to edit the boot options.
   
   A new GRUB menu screen displays.
5. Use the up and down arrow keys to select the line that begins with kernel /boot/vmlinuz.
   Note: Alternately, press SHIFT+6 (^) to arrow up and press the v key to arrow down.
6. Press the e key to edit the line.
7. Add the word single to the end of the kernel /boot/vmlinuz line, and then press the Enter key.For example:
   
   kernel /boot/vmlinuz single
   Depending on the platform, the boot command may instead appear similar to the following example:
   
   kernel (hd1,1) /boot/1/vmlinuz ro root=UUID=f6155ffc-db65-46e9-9ba6-7f842a7d06ee console==tty0 console=ttyS0 19200 panic=1 mem=384M platform = D68 quiet single
8. The previous menu screen appears, and the system shows the new boot command.
9. Press the b key to boot the system using the modified options.
10. A prompt displays.

Enabling networking from single user mode in 1.x 4.x

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How do I access the network in single user mode?

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Sometimes it is necessary to utilize network tools while in single user mode. To access the network in single user mode, perform the following steps:

Note: To perform the following steps, you must be local to the BIG-IP or 3-DNS Controller with a console connection. If you have a redundant pair of controllers, you can minimize site down time by using the standby controller.

1. Reboot the controller, by typing the following commands:

   /bin/sync
   /bin/sync
   /sbin/shutdown -r now

2. Press the Spacebar to interrupt the boot up process after the CMOS check, during the BSD boot sequence 4-second countdown.
3. At the boot: prompt, type the following command:
   bsd
4. When you see the following prompt:
   root device?
   Type the following command:
   
   wd0a
5. When prompted for the shell, type the following command:
   /bin/bash
   Or press Enter for the bourne shell.
   
6. Run a filesystem check to assure that the filesystem can be mounted, by typing the following command:
   fsck -y
7. After the filesystem check completes, mount the filesystem by typing the following command:
   /sbin/mount -a
8. Bring up the appropriate interface, by typing the following command:
   /sbin/ifconfig exp0
   Note: Specify the IP address that the device normally uses, so that it can reach the Internet.
9. Add the default route, by typing the following command:
   Note: This is only necessary if you need to access a host outside your subnet, such as ftp.f5.com.
   /sbin/route add default
   Now you can use FTP or other tools that require the use of a network.
   You must use IP addresses rather than domain names because address resolution does not work in single user mode.
   
   For example:
   
   /usr/bin/ftp
   Note: You need to use a different host to look up the names. (For example: nslookup ftp.f5.com)
10. After you perform the necessary tasks in single user mode, you can return to multi-user mode by typing the following command:
    exit