9.2. Booting into Rescue Mode
Rescue mode provides the ability to boot a small Red Hat Linux environment
entirely from a diskette, CD-ROM, or some other boot method instead of
the system's hard drive.
As the name implies, rescue mode is provided to rescue you from
something. During normal operation, your Red Hat 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 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 Linux from that hard drive.
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 diskette made
from the bootdisk.img image.
[1]
By booting the system from an installation boot CD-ROM.
[2]
By booting the system from the Red Hat Linux CD-ROM #1.
Once you have booted using one of the described methods, enter the
following command at the installation boot prompt:
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 Linux as the Red Hat Linux CD-ROM #1 from
which you booted. If you used a boot CD-ROM or diskette 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 Red Hat Linux Installation Guide.
If you select a rescue image that does not require a network connect,
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.
You will also see the following message:
The rescue environment will now attempt to find your Red Hat
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 will attempt to mount
your file system under the directory
/mnt/sysimage. If it fails to mount a partition, it
will notify you. If you select Read-Only, it will
attempt to mount your file system under the directory
/mnt/sysimage, but in read-only mode. If you
select Skip, your file system will not be
mounted. Choose Skip if you think your file system
is corrupted.
Once you have your system in rescue mode, a prompt appears on VC
(virtual console) 1 and VC 2 (use the
[Ctrl]-[Alt]-[F1] key
combination to access VC 1 and
[Ctrl]-[Alt]-[F2]
to access VC 2):
If you selected Continue to mount your
partitions automatically and they were mounted successfully, you are
in single-user mode.
Even if your file system is mounted, the default root partition while in
rescue mode is a temporary root partition, not the root partition of the
file system used during normal user mode (runlevel 3 or 5). If you
selected to mount your file system and it mounted successfully, you can
change the root partition of the rescue mode environment to the root
partition of your file system by executing the following command:
This is useful if you need to run commands such as
rpm that require your root partition to be mounted as
/. To exit the chroot environment, type
exit, and you will return to the prompt.
If you selected Skip, you can still try to mount
a partition manually inside rescue mode by creating a directory such
as /foo, and typing the
following command:
mount -t ext3 /dev/hda5 /foo |
In the above command,
/foo is a directory
that you have created and
/dev/hda5 is the
partition you want to mount. If the partition is of type
ext2, replace ext3 with
ext2.
If you do not know the names of your partitions, use the following
command to list them:
From the prompt, you can run many useful commands such as
list-harddrives to list the hard drives in
the system
ssh,scp, and
ping if the network is started
dump and restore for users with
tape drives
parted and fdisk for
managing partitions
rpm for installing or upgrading
software
joe for editing configuration files (If you
try to start other popular editors such as emacs,
pico, or vi, the
joe editor will be started.)
