UC20 initrd misses modules to boot from USB disk

[Oliver Grawert]

Trying to use a default USB boot on a Raspberry Pi using either an USB3 UAS SSD enclosure or even a simple USB 2 stick fails (due to the missing console output it simply hangs indefinitely with a black screen https://bugs.launchpad.net/ubuntu/+source/linux-raspi/+bug/1914608).

seemingly neither the usb_storage module nor uas, enclosure or required scsi drivers are included in the initrd, this makes using the UC20 images with a fast USB3 disk impossible.

[Oliver Grawert (ogra)]

USB3 SATA disk needs:

$ diff -ruN mods1.txt mods2.txt
--- mods1.txt 2021-02-14 11:46:00.578329987 +0000
+++ mods2.txt 2021-02-14 11:46:23.422140313 +0000
@@ -1,4 +1,5 @@
 Module Size Used by
+uas 28672 0
 rtl8xxxu 139264 0
 rtl8192cu 77824 0
 rtl_usb 24576 1 rtl8192cu
@@ -113,7 +114,7 @@
 virtio_blk 20480 0
 virtio_scsi 24576 0
 nls_iso8859_1 16384 0
-usb_storage 81920 0
+usb_storage 81920 1 uas
 libahci 40960 0
 hid_generic 16384 0
 usbhid 69632 0

USB3 NVME enclosure disk needs:

$ diff -ruN mods1.txt mods3.txt
--- mods1.txt 2021-02-14 11:46:00.578329987 +0000
+++ mods3.txt 2021-02-14 11:52:09.191046939 +0000
@@ -1,4 +1,8 @@
 Module Size Used by
+ses 20480 0
+enclosure 20480 1 ses
+scsi_transport_sas 49152 1 ses
+uas 28672 0
 rtl8xxxu 139264 0
 rtl8192cu 77824 0
 rtl_usb 24576 1 rtl8192cu
@@ -113,7 +117,7 @@
 virtio_blk 20480 0
 virtio_scsi 24576 0
 nls_iso8859_1 16384 0
-usb_storage 81920 0
+usb_storage 81920 1 uas
 libahci 40960 0
 hid_generic 16384 0
 usbhid 69632 0

[Juerg Haefliger (juergh)]

The initrd for UC20 is generated by ubuntu-core-initramfs.