Red Hat LINUX VIRTUAL SERVER 4.6 - ADMINISTRATION Manuale di Installazione Scaricare il pdf (Pagina 239)

Chapter 13. Miscellaneous tasks 219

13.5 Rescuing a Linux system

This section describes how to boot your Linux server into different modes for troubleshooting

purposes. It covers booting Linux into single user mode, and also entering a rescue

environment when you require more advanced troubleshooting.

13.5.1 Entering single user mode

Single user mode is helpful when you need to recover the root password, or if you are having

problems booting Linux into the default run level. To enter single user mode, first perform an

IPL of your Linux server from the 3270 console. You will see a message similar to the

following one:

zIPL v1.8.2-28.el6 interactive boot menu

0. default (linux)

1. linux

Note: VM users please use '#cp vi vmsg <input>'

Please choose (default will boot in 5 seconds):

You can use the #cp vi vmsg command to boot the desired menu option (zero in this example),

followed by the number one for single user mode:

==> #cp vi vmsg 0 1

In single user mode, you are logged in as the root user. You can use the passwd command to

set the root password. All of the file systems in /etc/fstab are mounted, but networking has

not been started. To exit single user mode, you can type reboot, or enter init 3 to continue

booting normally.

13.5.2 Entering a rescue environment

If you encounter errors while mounting the root file system, or have other problems that

prevent you from entering single user mode, you can enter a rescue environment. This

environment loads a Linux image in memory, and does not attempt to mount the root file

system.

To enter a rescue environment, initiate an interactive Linux installation. Perform the following

steps to enter a rescue environment on the LINUX023 user ID:

1. Log on to LNXMAINT. Copy the RHEL6 EXEC file to a new file named RESCUE EXEC, and

copy the user’s PARM-RH6 file to a new file (LINUX02 RESCUE in this example):

==> copy rhel6 exec d rescue = =

==> copy linux02 parm-rh6 d = rescue =

2. Edit RESCUE EXEC to point to the new RESCUE file:

==> x rescue exec

/* EXEC to punch a RHEL 6 install system to reader and IPL from it */

Address 'COMMAND'

'CP SPOOL PUN *'

'CP CLOSE RDR'

'CP PURGE RDR ALL'

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Red Hat LINUX VIRTUAL SERVER 4.6 - ADMINISTRATION Manuale di Installazione Pagina 239