First, we create 2 partitions on the USB stick that is let's say 16GB.

first partition is let's say only 1GB
and the second partition is the rest of what is available.

after we "w" write the changes, the USB now has 2 partitions.

  • 1 is 1GB
  • 1 is more than 14GB

so , we have... sdb1 and sdb2 now.

now we need to turn these partitions into filesystems some say i should run these commands after those procedures.

mkfs.vfat -F 32 /dev/sdb1
mkfs.ext3 /dev/sdb2

but some web pages recommend using:

mkfs.vfat -n BOOT /dev/sdb1
mkfs.ext2 -m 0 -b 4096 -L DATA /dev/sdb2

which is it?

so let's say the DVDs are called:

  • CentOS-6.4-x86_64-bin-DVD1.iso
  • CentOS-6.4-x86_64-bin-DVD2.iso

so we make a directory:

mkdir -p /mnt/dvd1

and then mount it:

mount -o loop CentOS-6.4-x86_64-bin-DVD1.iso /mnt/dvd1

and i suppose we don't make a directory for dvd2 and we don't have to mount it ?

at this point i do not know what should be done.

but i think this step might be next:

we make the USB bootable by finding the file named mbr.bin and then moving it to there via these commnad.

dd conv=notrunc bs=440 count=1 if=/usr/lib/syslinux/mbr.bin of=/dev/sdb
parted /dev/sdb set 1 boot on

in other words we are "dd-ing it to 'sdb' not sdb1' or 'sdb2'. and then we use parted to set the boot to on for sdb

so far everything looks good?

here is the confusing parts..

how exactly do i move these iso files to the usb drive?


so at this point i should

  • copy the folder /mnt/dvd1/isolinux to usb's sdb1 or sdb2 ?
  • rename it to syslinux ?
  • and then inside this syslinux folder there will be a file called...
  • isolinux.cfg ?
  • which should be renamed to syslinux.cfg ?

  • and then copy the contents of /mnt/dvd1/images/* to USB's sdb2 ?

but i think i am also suppose to copy and paste the both

  • CentOS-6.4-x86_64-bin-DVD1.iso
  • CentOS-6.4-x86_64-bin-DVD2.iso

somewhere into this USB's sdb2 partition, correct ? almost like a drag and drop kind of a thing?

or do they go into any folders ?

centos' own web site has some instructions but those instructions do not work.


i once got this working but things got ruined, i have to do it again and this time take notes.

2 Answers 2


You can use dd to copy burn the ISO in the USB stick. It's pretty easy and always work:

Assuming the .iso file is in your home folder, open the terminal and write:

sudo dd bs=4M if=[ur .iso] of=/dev/sd[that 1 letter]


sudo dd bs=4M if=centos.iso of=/dev/sdc
  • That does not address the key point of the question, which is merging the isos of both DVD1 and DVD2 to the same usb stick.
    – Igb
    Commented Nov 8, 2018 at 9:13

Why do you have 2 DVDs? There is an Everything "DVD" image with all of CentOS (of some 16GiB in size), that is all you could need (I write "DVD" because it won't fit on a real DVD). You certainly could write a boot ISO image to one partition of the USB stick and place further stuff in the remainder, but that setup I've never seen as installation media (I suspect it would be too much hassle; just stash everything needed into the ISO, that shouldn't change anyway).

Please refer to the installation guide, it should answer all questions. If not, ask around there, perhaps even report a bug/suggest a clarification. Feel free to ask pointed further questions here.

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