Refine boot process of build target and allow config of /boot fstype and mount-options

- Add env-vars BOOT_FSTYPE and BOOT_FSOPTIONS, supporting customizing the boot filesystem type and options
- FAT_CODEPAGE (if using BOOT_FSTYPE vfat, default) is hardcoded '437'

- Add 'lsof', allowing to check open listening ports (besides netstat)

- On Raspi: Use plymouth splash screen for all configurations, theme 'pix'

- Add systemd resize2fs_once.service to have it start very early
  to resize the rootfs partition for RW rootfs

- No kernel argument 'rootwait' for initramfs/grub root=file boot

loop_rootfs (initram):
- kill spawn-off pipe copy process (LOOP_ROOTFS_LOG_PIDS)
- Use BOOT_FSTYPE, BOOT_FSOPTIONS (incl mounting /boot)..
- Use dedicated fsck.BOOT_FSTYPE if possible (and quiet)
- Log fsck and mount attempts, failure and success
-

Stage2 01-sys-tweaks fixes:
- Only disable systemd-remount-fs for ROOTFS_RO
- Only generate /boot/loop_rootfs.id for ROOTFS_RO
- Kernel Modules: Add codepage 437 and 850, drm and vc4 (raspi only)
- Use TARGET_ARCH in all situations
- On RW rootfs, grub-install with ext2 module
-

1 files changed, 12 insertions, 0 deletions

diff --git a/README.md b/README.md
index c0a3f25..ac2bf84 100644
--- a/README.md
+++ b/README.md
@@ -119,6 +119,18 @@ The following environment variables are supported:
    If using `ROOTFS_RO`, this variable specifies the shared `tmpfs` size
    for the overlays - see above.
 
+ * `BOOT_FSTYPE` (Default: `vfat`)
+
+   Allows user to define the `/boot` filesystem type. For Raspberry this **must** be `vfat`, the default.
+   However, as we support other target system, this may be one of: `vfat`, `ext2`, `ext4` or `xfs`.
+
+ * `BOOT_FSOPTIONS` (Default: `rw,noatime,fmask=0022,dmask=0022,codepage=437,iocharset=ascii,shortname=mixed,errors=remount-ro`)
+
+   Allows user to define the mount options for the `/boot` filesystem, see `BOOT_FSTYPE`.
+   For `vfat`, only the `codepage 437` is being hardcoded in the `initrd` `loop_rootfs` and scripts, as it is the default for GNU/Linux.
+
+   Further more, producing the image failed with `codepage 850` on `vfat` operations on the `overlay` diversions within `pi-gen`.
+
  * `REDUCED_FOOTPRINT` (Default: unset)
 
    If set to one, i.e. `REDUCED_FOOTPRINT=1`,