Preseed Linux USB Create

To create an Auto-Install USB Stock with Mint 21.2 or later, use the following steps.

Download latest Linux Mint iso file https://www.linuxmint.com/edition.php?id=305
Insert USB stick, check with dmesg | tail to identify the usb device
Delete/Create FAT32 partition
```
su -
fdisk /dev/xxx
```
create type c (Win95 FAT32 LBA) partition
See for details: https://askubuntu.com/questions/1064278/how-to-create-win95-fat32-lba-partition-type-on-32-gb-usb
create vfat filesystem on new partition
```
mkfs.vfat /dev/xxx1
```
mount disk
```
mount /dev/xxx1 /mnt
```
rename usb stick label if necessary/desired
```
mlabel -i /dev/xxx1 -s ::"CST_MINT212"
```
mount iso and copy iso content directly to usb stick partition. Ensure hidden files/directories are copied as well.
copy custom_install directory to usb stick root
copy custom preseed files to usb stick preseed directory

edit /boot/grub/grub.cfg and add to end:

menuentry "Install Custom Linux Mint 21.2 Cinnamon 64-bit" {
	set gfxpayload=keep
	linux	/casper/vmlinuz  file=/cdrom/preseed/mint_allinone.seed boot=casper debian-installer/locale=en keyboard-configuration/layoutcode=en_GB console-setup/layoutcode=en_GB automatic-ubiquity quiet splash --
	initrd	/casper/initrd.lz
}

add syslinux.cfg to root with content:

default vesamenu.c32
timeout 100

menu background splash.png
menu title Welcome to Linux Mint Cinnamon 64-bit

menu color screen	37;40      #80ffffff #00000000 std
MENU COLOR border       30;44   #40ffffff #a0000000 std
MENU COLOR title        1;36;44 #ffffffff #a0000000 std
MENU COLOR sel          7;37;40 #e0ffffff #20ffffff all
MENU COLOR unsel        37;44   #50ffffff #a0000000 std
MENU COLOR help         37;40   #c0ffffff #a0000000 std
MENU COLOR timeout_msg  37;40   #80ffffff #00000000 std
MENU COLOR timeout      1;37;40 #c0ffffff #00000000 std
MENU COLOR msg07        37;40   #90ffffff #a0000000 std
MENU COLOR tabmsg       31;40   #ffDEDEDE #00000000 std
MENU WIDTH 78
MENU MARGIN 15
MENU ROWS 7
MENU VSHIFT 10
MENU TABMSGROW 12
MENU CMDLINEROW 12
MENU HELPMSGROW 16
MENU HELPMSGENDROW 29


label custom
menu label Automated installation (Everything in one partition) (syslinux)
kernel casper/vmlinuz
append  file=/cdrom/preseed/mint_allinone.seed boot=casper initrd=/casper/initrd.lz debian-installer/locale=en keyboard-configuration/layoutcode=en_GB console-setup/layoutcode=en_GB automatic-ubiquity quiet splash --
label live
  menu label Start Linux Mint
  kernel /casper/vmlinuz
  append  file=/cdrom/preseed/linuxmint.seed boot=casper initrd=/casper/initrd.lz quiet splash -- persistent
menu default
label xforcevesa
  menu label Start in compatibility mode
  kernel /casper/vmlinuz
  append  file=/cdrom/preseed/linuxmint.seed boot=casper initrd=/casper/initrd.lz noapic noacpi nosplash irqpoll nomodeset --
label oem
  menu label OEM install (for manufacturers)
  kernel /casper/vmlinuz
  append  file=/cdrom/preseed/linuxmint.seed oem-config/enable=true only-ubiquity boot=casper initrd=/casper/initrd.lz quiet splash --
label check
  menu label Integrity check
  kernel /casper/vmlinuz
  append  boot=casper integrity-check initrd=/casper/initrd.lz quiet splash --
label hdt
  menu label Hardware Detection
  kernel hdt.c32
label local
  menu label Boot from local drive
  COM32 chain.c32
  APPEND hd0
label memtest
  menu label Memory test
  kernel /casper/memtest

add mint_allinone.seed file to preseed folder. Example:

### Set language and keyboard layout
d-i debian-installer/locale string en_GB.UTF-8
d-i keyboard-configuration/xkb-keymap select gb
d-i keyboard-configuration/layoutcode string gb
d-i keyboard-configuration/modelcode string pc105
d-i console-setup/layoutcode string en_GB
d-i console-setup/ask_detect boolean false

### Timezone and NTP
d-i time/zone string Europe/London
d-i clock-setup/ntp boolean true

### Mirror settings
d-i mirror/country string GB

### Enable extras.ubuntu.com.
d-i apt-setup/extras boolean true

### Disable nonfree multimedia codecs
ubiquity ubiquity/use_nonfree boolean false

### Avoid EFI warning if bios set or allowed to use legacy BIOS boot as well
d-i partman-efi/non_efi_system true

### Partitioning
d-i partman-auto/method string lvm
d-i partman-auto/choose_recipe select atomic
partman-basicfilesystems partman-basicfilesystems/no_mount_point boolean false
d-i partman-basicfilesystem/no_swap boolean false
d-i partman-lvm/device_remove_lvm boolean true
d-i partman-md/device_remove_md boolean true
d-i partman-lvm/confirm boolean true
d-i partman-partitioning/confirm_write_new_label boolean true
d-i partman/choose_partition select finish
d-i partman/confirm boolean true
d-i partman/confirm_nooverwrite boolean true
d-i grub-installer/only_debian boolean true
d-i grub-installer/bootdev string /dev/sda
d-i partman-crypto/passphrase password
d-i partman-crypto/passphrase-again password

### allow root account
d-i passwd/root-login boolean true

### Root password 
d-i passwd/root-password password rootpassword
d-i passwd/root-password-again password rootpassword

### To create a normal user account.
d-i passwd/user-fullname string XXXFULLNAMEXXX
d-i passwd/username string XXXUSERNAMEXXX

### Normal user's password, either in clear text or encrypted using a crypt(3) hash. i.e mkpasswd -m sha-512
d-i passwd/user-password-crypted password XXXUSERPASSWORDXXX

### The installer will warn about weak passwords. If you are sure you know what you're doing and want to override it, uncomment this.
d-i user-setup/allow-password-weak boolean true

### setup groups for user
d-i passwd/user-default-groups string audio cdrom video dip plugdev lpadmin sambashare

### set Hostname
d-i netcfg/get_hostname string XXXPCHOSTNAMEXXX

### Auto Login after first boot
d-i passwd/auto-login boolean true

### Trigger reboot
ubiquity ubiquity/reboot boolean true


### Custom Commands
ubiquity ubiquity/success_command string \
  cp /cdrom/auto_install/auto* /target/root/ ;\
  cp -a /cdrom/auto_install/config-files /target/root/config-files ;\
  cp -a /cdrom/auto_install/scripts /target/root/scripts ;\
  cp -a /cdrom/auto_install/dpkg /target/root/dpkg ;\
  chroot /target /root/auto.sh

Finally, proceed with pre-config as per CUSTOM USB INSTALL instructions (to follow)