docs: add further and improve existing usage examples

There's no reason to say "use /dev/sda1 as system partition"
all the time, when we already mention that we "Install Debian on /dev/sda1".

Provide usage examples for mmdebstrap and LVM devices.

The --iso option also accepts mountpoint without any file: syntax,
which is more human-friendly.

grml-debootstrap.8.txt

@@ -269,46 +269,51 @@ Usage examples
 
   grml-debootstrap --target /dev/sda1 --grub /dev/sda
 
-Install default Debian release (buster) on /dev/sda1 and install bootmanager
-GRUB in MBR (master boot record) of /dev/sda and use /dev/sda1 as system partition.
+Install default Debian release (buster) on /dev/sda1 and install bootmanager GRUB in MBR (master boot record) of /dev/sda.
 
-  grml-debootstrap --release stretch --target /dev/sda1 --grub /dev/sda --hostname foobar --password changeme
+  grml-debootstrap --release stretch --target /dev/sda1 --grub /dev/sda --hostname debian01 --password changeme
 
-Install Debian release stretch on /dev/sda1 and install bootmanager
-GRUB in MBR (master boot record) of /dev/sda and use /dev/sda1 as system partition.
-Set hostname to 'foobar' and password for user root to 'changeme'.
+Install Debian release stretch on /dev/sda1 and install bootmanager GRUB in MBR (master boot record) of /dev/sda.
+Set hostname to 'debian01' and password for user root to 'changeme'.
 
   grml-debootstrap --target /dev/sda6 --grub /dev/sda --release sid
 
-Install Debian unstable/sid on /dev/sda6, install bootmanager GRUB in MBR
-(master boot record) of /dev/sda and use /dev/sda6 as system partition.
+Install Debian unstable/sid on /dev/sda6 and install bootmanager GRUB in MBR (master boot record) of /dev/sda.
+
+  DEBOOTSTRAP=mmdebstrap grml-debootstrap --target /dev/sda1 --grub /dev/sda
+
+Install default Debian release (buster) on /dev/sda1 and install bootmanager GRUB in MBR (master boot record) of /dev/sda.
+Use mmdebstrap instead of default debootstrap tool for bootstrapping.
+
+  grml-debootstrap --target /dev/mapper/vg0-rootfs --grub /dev/sda
+
+Install default Debian release (buster) on LVM device /dev/mapper/vg0-rootfs and install bootmanager GRUB in MBR (master boot record) of /dev/sda.
+
+  grml-debootstrap --efi /dev/sda1 --target /dev/sda2 --grub /dev/sda --efi
+
+Install default Debian release (buster) on /dev/sda2 and install bootmanager GRUB in MBR (master boot record) of /dev/sda.
+Use /dev/sda1 as EFI partition (requires EFI support in booted system).
 
   mount /dev/sda1 /data/chroot
   grml-debootstrap --target /data/chroot
 
-Install default Debian release (buster) in directory /data/chroot (without
-any bootloader).
+Install default Debian release (buster) in directory /data/chroot (without any bootloader).
 
   grml-debootstrap --target /dev/sda3 --grub /dev/sda  --mirror ftp://ftp.tugraz.at/mirror/debian
 
-Install default Debian release (buster) on /dev/sda3 and install bootmanager
-GRUB in MBR (master boot record) of /dev/sda and use /dev/sda3 as system partition.
+Install default Debian release (buster) on /dev/sda3 and install bootmanager GRUB in MBR (master boot record) of /dev/sda.
 Use specified mirror instead of the default (http://deb.debian.org/debian) one.
 
   mount /dev/sda1 /mnt/sda1
   grml-debootstrap --vmfile --vmsize 3G --target /mnt/sda1/qemu.img
 
-Install default debian release (buster) in a Virtual Machine file with
-3GB disk size (including GRUB as bootmanager in MBR of the virtual disk file):
+Install default debian release (buster) in a Virtual Machine file with 3GB disk size (including GRUB as bootmanager in MBR of the virtual disk file):
 
-  mount -o loop /mnt/sda6/debian-CD-1.iso /mnt/iso
-  grml-debootstrap --target /dev/sda1 --grub /dev/sda --iso file:/mnt/iso/debian/
+  mount -o loop ./debian-CD-1.iso /media/cdrom
+  grml-debootstrap --target /dev/sda1 --grub /dev/sda --iso /media/cdrom
 
-Install Debian on /dev/sda1 using the loopback mounted Debian-ISO
-for the base-system and install bootmanager GRUB in MBR (master boot record) of
-/dev/sda and use /dev/sda1 as system partition. Please notice, that the chroot
-system requires network access for all packages which are not part of the
-ISO.
+Install Debian on /dev/sda1 using the loopback mounted Debian-ISO for the base-system and install bootmanager GRUB in MBR (master boot record) of /dev/sda.
+Please notice, that the chroot system requires network access for all packages which are not part of the ISO.
 
 Files
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