Red Hat ENTERPRISE LINUX 4 System Administration Manual page 80

Chapter 5. Basic System Recovery
As the name implies, rescue mode is provided to rescue you from something. During normal
operation, your Red Hat Enterprise Linux system uses files located on your system's hard drive to do
everything — run programs, store your files, and more.
However, there may be times when you are unable to get Red Hat Enterprise Linux running
completely enough to access files on your system's hard drive. Using rescue mode, you can access
the files stored on your system's hard drive, even if you cannot actually run Red Hat Enterprise Linux
from that hard drive.
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To boot into rescue mode, you must be able to boot the system using one of the following methods :
• By booting the system from an installation boot CD-ROM.
• By booting the system from other installation boot media, such as USB flash devices.
• By booting the system from the Red Hat Enterprise Linux CD-ROM #1.
Once you have booted using one of the described methods, add the keyword rescue as a kernel
parameter. For example, for an x86 system, type the following command at the installation boot
prompt:
linux rescue
You are prompted to answer a few basic questions, including which language to use. It also prompts
you to select where a valid rescue image is located. Select from Local CD-ROM, Hard Drive, NFS
image, FTP, or HTTP. The location selected must contain a valid installation tree, and the installation
tree must be for the same version of Red Hat Enterprise Linux as the Red Hat Enterprise Linux
disk from which you booted. If you used a boot CD-ROM or other media to start rescue mode, the
installation tree must be from the same tree from which the media was created. For more information
about how to setup an installation tree on a hard drive, NFS server, FTP server, or HTTP server, refer
to the earlier section of this guide.
If you select a rescue image that does not require a network connection, you are asked whether or not
you want to establish a network connection. A network connection is useful if you need to backup files
to a different computer or install some RPM packages from a shared network location, for example.
The following message is displayed:
The rescue environment will now attempt to find your Linux installation
and mount it under the directory /mnt/sysimage. You can then make any
changes required to your system. If you want to proceed with this step
choose 'Continue'. You can also choose to mount your file systems read-
only instead of read-write by choosing 'Read-only'. If for some reason this
process fails you can choose 'Skip' and this step will be skipped and you
will go directly to a command shell.
If you select Continue, it attempts to mount your file system under the directory /mnt/sysimage/.
If it fails to mount a partition, it notifies you. If you select Read-Only, it attempts to mount your file
system under the directory /mnt/sysimage/, but in read-only mode. If you select Skip, your file
system is not mounted. Choose Skip if you think your file system is corrupted.
Refer to the earlier sections of this guide for more details.
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