Red Hat Enterprise Linux 4: Installation Guide for the IBM® POWER Architecture
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# 2.25. Rescue Mode on POWER Systems

You can use the installation disks in rescue mode, in case your system does not boot. Rescue mode gives you access to the disk partitions on your system so you can make any changes necessary to rescue your installation.

To boot in rescue mode on iSeries or i5 with power control NWSD , follow the instructions for booting the installation program, with this change: In the NWSD, set the IPL parameters field to `'rescue'` (including the quotes), or to `'dd rescue'` if you need to load the SCSI driver. On other systems, specify the `rescue` or `dd rescue` (without quotes) after the default kernel name at the YABOOT prompt.

After the Language Selection screen (Section 2.10 Language Selection), the installation program attempts to mount the disk partitions on your system. It then presents you with a shell prompt where you can make the changes you need. These changes may include storing the kernel and command line into the IPL source, as described in the Installation Complete section (Section 2.23 Installation Complete).

When your changes are complete, you can exit the shell using `exit 0`. This causes a reboot from the C side. To reboot from the A or B side or from *NWSSTG, you should vary off the system instead of exiting the shell.

## 2.25.1. Special Considerations for Accessing the SCSI Utilities from Rescue Mode

If your system uses Native DASD disks, you may need access to the SCSI utilities from rescue mode. These utilities are located on the driver disc CD. The driver disc CD cannot be mounted from rescue mode unless special steps are taken. These steps are described below.

If you have a second CD-ROM drive assigned to your Linux system, you can mount the driver disc CD in the second drive.

If you have only one CD-ROM drive, you must set up an NFS boot, using the following steps:

1. For OpenPower, p5, i5, and pSeries:

   Boot from the CD-ROM with the `linux rescue askmethod` command. This allows you to manually select NFS as the source of your rescue media instead of defaulting to the CD-ROM drive.

2. For iSeries:

   Copy `/qopt/red_hat/ppc/iSeries/boot.img` to the IFS of the iSeries system containing your Linux system. You can do this with a command like:

       COPY OBJ ('/qopt/red_hat/ppc/iSeries/boot.img') TODIR('/tmp')

   Note that `/tmp` can be replaced with any location on your IFS.

3. Copy the first installation disc onto a file system of another Linux system.

4. Make this copy of the installation disc available through NFS or FTP.

5. Vary off or power down the system you need to rescue. Set its IPL parameters as instructed for booting the Installation discs in rescue mode, except that the IPL source should point to the copy of `boot.img` on your IFS (from step 1, above).

6. Make sure the installation disc is not in your CD-ROM drive.

7. IPL the Linux system.

8. Follow the prompts as decribed in Section 2.25 Rescue Mode on POWER Systems. An additonal prompt for the installation source appears. Select NFS or FTP (as appropriate) and complete the following network configuration screen.

9. When the Linux system has booted into rescue mode, the CD-ROM drive is available for use and you can mount the driver media to access the SCSI utilities.

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