Make USB boot key

Format as vfat, copy image, make bootable:

disk=/dev/sdb; label=CZ_2021
sudo apt install gparted
sudo gparted $disk 
sudo fatlabel ${disk}1 $label

unzip Downloads/clonezilla-live-2.7.1-22-amd64.zip -d /media/$USER/$label/
cd /media/$USER/$label/utils/linux/
sudo bash makeboot.sh ${disk}1

Boot parameters

/syslinux/isolinux.cfg when booting from CD on a MBR machine
/syslinux/syslinux.cfg when booting from USB flash drive on a MBR machine
/boot/grub/grub.cfg when booting from a uEFI machine
/tftpboot/pxelinux.cfg/default or similar on PXE server, when booting from PXE on a MBR machine
/tftpboot/grub/grub.cfg or similar on PXE server, when booting from a uEFI netboot machine