Red Hat Enterprise Linux 5 Administration Unleashed

12CHAPTER 1Installing Red Hat Enterprise LinuxTIPThis page also provides a link to a page with instructions for properly downloading theISO image files with curl or wget. Read it carefully before downloading the ISO files.Download times will vary and depend on the speed of your Internet connection.In the table containing the links to the ISO images, notice the third column. This longstring of numbers and letters is called a checksum, which can be used to verify that theISO file you downloaded hasn’t been corrupted. If the column contains MD5 checksums,check the MD5 checksum of an ISO file after downloading it with the followingcommand, replacing with the filename of the ISO image downloaded (repeat foreach ISO file):md5sum If the column contains SHA1 checksums, check the SHA1 checksum of an ISO file afterdownloading it with the following command, replacing with the filename of theISO image downloaded (repeat for each ISO file):sha1sum When the utility is finished computing the checksum, it is displayed at the commandline. Compare it to the checksum listed on the RHN page. If they match exactly, thedownload was successful in retrieving the entire file without corruption. If they do notmatch exactly, remove the ISO file and download it again until the MD5 checksumreturned matches the checksum on the RHN page exactly.Creating a Boot DiscNetwork installations, including kickstart installations, can be started with a boot CDcreated from the boot.iso image found in the images/ directory on the first installationCD. Instead of creating the first installation CD to access this file, the files from the ISOimage of the disc can be loopback mounted so the boot.iso file can be retrieved and usedto create a boot disc.When an ISO image is loopback mounted, the files from the image are listed in a dedicateddirectory as they would appear on the disc if the image was written to disc. The filesdo not actually exist as separate files in this directory on the filesystem. When they areaccessed, the files are read from the ISO image. If they are copied to the filesystem, eachfile copied will actually exist on the filesystem.To loopback mount an ISO image, use the following steps:1. Create an empty directory to mount the image into, such as /tmp/rhel/.2. Mount the image into this new directory (if the image is not in the current directory,provide its full path so it can be found):mount -o loop .iso /tmp/rhel/