3.2. Making Installation USB Media

Procedure 3.1. Making USB Media on Linux

1. Connect a USB flash drive to the system and execute the dmesg command. A log detailing all recent events will be displayed. At the bottom of this log, you will see a set of messages caused by the USB flash drive you just connected. It will look like a set of lines similar to the following:

   [ 170.171135] sd 5:0:0:0: [sdb] Attached SCSI removable disk

   Note the name of the connected device - in the above example, it is sdb.
2. Log in as root:

   $ su -

   Provide your root password when prompted.
3. Make sure that the device is not mounted. First, use the findmnt device command and the device name you found in the earlier steps. For example, if the device name is sdb, use the following command:

   # findmnt /dev/sdb

   If the command displays no output, you can proceed with the next step. However, if the command does provide output, it means that the device was automatically mounted and you must unmount it before proceeding. A sample output will look similar to the following:

   # findmnt /dev/sdb
   TARGET   SOURCE   FSTYPE  OPTIONS
   /mnt/iso /dev/sdb iso9660 ro,relatime
   

   Note the TARGET column. Next, use the umount target command to unmount the device:

   # umount /mnt/iso

4. Use the dd command to write the installation ISO image directly to the USB device:

   # dd if=/image_directory/image.iso of=/dev/device bs=blocksize

   Replace /image_directory/image.iso with the full path to the ISO image file you downloaded, device with the device name as reported by the dmesg command earlier, and blocksize with a reasonable block size (for example, 512k) to speed up the writing process. The bs parameter is optional, but it can speed up the process considerably.

   Important

   Make sure to specify the output as the device name (for example, /dev/sda), not as a name of a partition on the device (for example, /dev/sda1).
   For example, if the ISO image is located in /home/testuser/Downloads/rhel-server-7-x86_64-boot.iso and the detected device name is sdb, the command will look like the following:

   # dd if=/home/testuser/Downloads/rhel-server-7-x86_64-boot.iso of=/dev/sdb bs=512k

5. Wait for dd to finish writing the image to the device. Note that no progress bar is displayed; the data transfer is finished when the # prompt appears again. After the prompt is displayed, log out from the root account and unplug the USB drive.

Procedure 3.2. Making USB Media on Windows

1. Download and install Fedora Media Writer.
2. Download the Red Hat Enterprise Linux ISO image you want to use to create the media. (See Chapter 2, Downloading Red Hat Enterprise Linux for instructions on obtaining ISO images.)
3. Plug in the USB drive you will be using to create bootable media.
4. Open Fedora Media Writer.
5. In the main window, click Custom Image and select the downloaded Red Hat Enterprise Linux ISO image.
6. From the drop-down menu, select the drive you want to use. If the drive does not appear, verify that the USB drive is connected and restart Fedora Media Writer.
7. Click Write to disk. The boot media creation process will begin. Do not unplug the drive until the operation completes. Depending on the size of the ISO image and the write speed of the USB drive, writing the image can take several minutes.
   

   Figure 3.1. Fedora Media Writer

8. When the creation process finishes and the Complete! message appears, unmount the USB drive using the Safely remove hardware icon in the system's notification area.

Procedure 3.3. Making USB Media on Mac OS X

1. Connect a USB flash drive to the system and identify the device path with the diskutil list command. The device path has the format of /dev/disknumber, where number is the number of the disk. The disks are numbered starting at zero (0). Disk 0 is likely to be the OS X recovery disk, and Disk 1 is likely to be your main OS X installation. In the following example, it is disk2:

   $ diskutil list
   /dev/disk0
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *500.3 GB   disk0
   1:                        EFI EFI                     209.7 MB   disk0s1
   2:          Apple_CoreStorage                         400.0 GB   disk0s2
   3:                 Apple_Boot Recovery HD             650.0 MB   disk0s3
   4:          Apple_CoreStorage                         98.8 GB    disk0s4
   5:                 Apple_Boot Recovery HD             650.0 MB   disk0s5
   /dev/disk1
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:                  Apple_HFS YosemiteHD             *399.6 GB   disk1
   Logical Volume on disk0s1
   8A142795-8036-48DF-9FC5-84506DFBB7B2
   Unlocked Encrypted
   /dev/disk2
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:     FDisk_partition_scheme                        *8.0 GB     disk2
   1:               Windows_NTFS SanDisk USB             8.0 GB     disk2s1

   To identify your USB flash drive, compare the NAME, TYPE and SIZE columns to what you know about your flash drive. For example, the NAME should be the same as the title of the flash drive icon in the Finder. You can also compare these values to those in the flash drive's information panel; right-click on the drive icon and select Get Info.
2. Use the diskutil unmountDisk command to unmount the flash drive's filesystem volumes:

   $ diskutil unmountDisk /dev/disknumber
   					Unmount of all volumes on disknumber was successful

   When you do this, the icon for the flash drive disappears from your desktop. If it does not, you might have identified the wrong disk. If you attempt to unmount the system disk accidentally, you get a failed to unmount error.
3. Use the dd command as a parameter of the sudo command to write the ISO image to the flash drive:

   $ sudo dd if=/path/to/image.iso of=/dev/rdisknumber bs=1m>

   Note

   Mac OS X provides both a block (/dev/disk*) and character device (/dev/rdisk*) file for each storage device. Writing an image to the /dev/rdisknumber character device is faster than to the /dev/disknumber block device.

   Example 3.1. Writing an ISO Image to a Disk

   To write the /Users/user_name/Downloads/rhel-server-7-x86_64-boot.iso file to the /dev/rdisk2 device:

   $ sudo dd if=/Users/user_name/Downloads/rhel-server-7-x86_64-boot.iso of=/dev/rdisk2

4. Wait for the command to finish. Note that no progress bar is displayed; however, to check the status of the operation while it is still running, press Ctrl+t in the terminal:

   load: 1.02  cmd: dd 3668 uninterruptible 0.00u 1.91s
   112+0 records in
   111+0 records out
   116391936 bytes transferred in 114.834860 secs (1013559 bytes/sec)

5. The speed of the data transfer depends on the speed of your USB ports and the flash drive. After the prompt is displayed again, the data transfer is finished. You can then unplug the flash drive.