Making Installation USB Media on Linux
The following procedure assumes you are using a Linux system and that you have downloaded an appropriate ISO image as described in Downloading CentOS. On most Linux distributions, it will work without the need for installing any additional packages.
This procedure is destructive. Any data on the USB flash drive will be destroyed with no warning. Make sure that you specify the correct drive, and make sure that this drive does not contain any data you want to preserve.
Many Linux distributions provide their own tools for creating live USB media, for example, usb-creator on Ubuntu. Describing these tools is beyond the scope of this book; the following procedure will work on most Linux systems.
Connect a USB flash drive to the system and execute the
dmesgcommand. 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
Log in as
Provide your root password when prompted.
Make sure that the device is not mounted. First, use the
findmnt devicecommand 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/sdbTARGET SOURCE FSTYPE OPTIONS /mnt/iso /dev/sdb iso9660 ro,relatime
TARGETcolumn. Next, use the
umount targetcommand to unmount the device:
# umount /mnt/iso
ddcommand 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
dmesgcommand earlier, and blocksize with a reasonable block size (for example,
512k) to speed up the writing process. The
bsparameter is optional, but it can speed up the process considerably.
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,
For example, if the ISO image is located in
/home/testuser/Downloads/CentOS-server-x86_64-boot.isoand the detected device name is
sdb, the command will look like the following:
# dd if=/home/testuser/Downloads/CentOS-server-x86_64-boot.iso of=/dev/sdb bs=512k
ddto 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
rootaccount and unplug the USB drive.
The USB drive is now ready to be used as a boot device. You can continue with Booting the Installation on 64-bit AMD, Intel, and ARM systems on AMD, Intel, and ARM systems, or Booting the Installation on IBM Power Systems on IBM Power Systems servers.
Non-virtualized installations (known as "bare metal" installations) on IBM Power Systems servers require that the