Instructions for making USB-Bootable installation disk for 64bit CentOS7 with custom kickstart
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0a. These instructions are intended for making a USB-bootable kickstart installer for CentOS7.
0b. 16GB USB flash media is recommended (8GB is too small)
0c. On el7, do "yum install glibc.i686" or extlinux will not run

1. Get a copy of CentOS-7-x86_64-Everything-1810.iso

2. Prepare the USB disk:
a) su -
b) fdisk -H224 -S56 /dev/sdX, make one partition of type "83-Linux", mark it bootable. Result should look like this:

root# fdisk -l /dev/sdX

[root@daq06 ~]# fdisk -l /dev/sdc

Disk /dev/sdc: 15.5 GB, 15518924800 bytes, 30310400 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk label type: dos
Disk identifier: 0x01f2198f

   Device Boot      Start         End      Blocks   Id  System
/dev/sdc1   *        2048    30310399    15154176   83  Linux
[root@daq06 ~]# 

***IMPORTANT***

The one partition ***must*** be marked "bootable", see "*" under "Boot",
use the fdisk command "a" to toggle the "bootable" flag.

***IMPORTANT***

ext4 partition should have the "64bit" feature disabled. It is not compatible
with the present version of extlinux.


b) mkfs.ext4 -O ^64bit /dev/sdX1; tune2fs -c0 -i0 /dev/sdX1; e2label /dev/sdX1 USB
c) mkdir /mnt/tmp
d) mount LABEL=USB /mnt/tmp

3. Copy the CentOS ISO data:
0) cd to directory with the CentOS ISO file
a) mkdir -p /mnt/iso; mount -o loop,ro CentOS-7-x86_64-Everything-1810.iso /mnt/iso
b) rsync -av --progress /mnt/iso/ /mnt/tmp; sync ### trailing slash is important!
c) rsync -av --progress extlinux /mnt/tmp ### notice there is no trailing slash here!
d) cp -pv ks.cfg /mnt/tmp
e) cd /mnt/tmp; chown -R root.root .

4. Make disk bootable
a) cd /mnt/tmp/extlinux
b) cp -pv ../isolinux/{memtest,initrd.img,vmlinuz} .
c) cat ./mbr.bin > /dev/sdX ### (*NOT* /dev/sdX1)
d) ./extlinux -i .

5. cd /; umount /mnt/tmp; umount /mnt/iso
6. try to boot from the newly made USB disk.

//KO 4JAN2019