I'm trying to get my own init script running on some ARM hardware and Debian Jessie with systemd. The overall boot concept and init script is almost identical to a x86 variant, which works fine. For both hardwares the whole SD card image is pre-built on a x86 host.

When running on the ARM hardware, having serial console access I see that my init script runs fine up to the point where switch_root is called:

exec switch_root -c /dev/console /newroot /sbin/init

Nothing happens after that. No error message is printed - which makes it difficult to find the problem.

The kernel command line is...

ro root=LABEL=IM_BOOT1 panic=10 mem=256M console=ttyS0,115200 systemd.log_level=debug

...and AFAIK this should make systemd print maximum debug messages. Unfortunately nothing is printed.

Any idea/hint what I could do to understand what could be causing the freeze, or with other words - understand what is going on?

The only strange detail are some warnings in the kernel log before calling switch_root:

<snip> ext4: Unknown symbol jbd2_journal_errno (err 0) ext4: Unknown symbol jbd2_journal_begin_ordered_truncate (err 0) ext4: Unknown symbol jbd2_journal_flush (err 0) ext4: Unknown symbol mb_cache_entry_find_next (err 0) squashfs: version 4.0 (2009/01/31) Phillip Lougher aufs 3.16-20150928 usbhid: Unknown symbol hid_output_report (err 0) usbhid: Unknown symbol hidinput_count_leds (err 0) usbhid: Unknown symbol hid_allocate_device (err 0) usbhid: Unknown symbol hid_destroy_device (err 0) usbhid: Unknown symbol hid_alloc_report_buf (err 0) usbhid: Unknown symbol hid_set_field (err 0) usbhid: Unknown symbol hid_check_keys_pressed (err 0) usbhid: Unknown symbol hid_input_report (err 0) usbhid: Unknown symbol hid_debug (err 0) usbhid: Unknown symbol __hid_request (err 0) usbhid: Unknown symbol hid_parse_report (err 0) usbhid: Unknown symbol hid_add_device (err 0) usbcore: registered new interface driver usbhid usbhid: USB HID core driver usb_storage: Unknown symbol scsi_report_device_reset (err 0) usb_storage: Unknown symbol scsi_remove_host (err 0) usb_storage: Unknown symbol scsi_report_bus_reset (err 0) usb_storage: Unknown symbol scsi_sense_desc_find (err 0) usb_storage: Unknown symbol scsi_eh_prep_cmnd (err 0) usb_storage: Unknown symbol scsi_host_put (err 0) usb_storage: Unknown symbol scsi_scan_host (err 0) usb_storage: Unknown symbol scsi_is_host_device (err 0) <snip>

...however these modules appear to work fine anyway. I don't know if that is related.

Some additional details:

  • Debian installation is prepared using debootstrap (same method works perfectly with x86)
  • Custom built Kernel: Linux (none) 3.16.7 #1 Mon Nov 16 08:32:55 UTC 2015 armv5tejl GNU/Linux, patched with AUFS and hardware-specific device tree
  • both Kernel and root fs are built with help of QEMU on a x86 host
  • initramfs boots with BusyBox, sets up the AUFS final root fs and finally invokes switch_root. The same method (nearly 100% identical init script) works fine on x86
  • I can run an interactive shell just before running switch_root and I can't find anything that isn't working as expected at that point
  • Cool toy. I am myself running here an ARM lamobo R1.Does it seems something should be compiled in the kernel not as module, or am I with the wrong impression? Try the armbian forum, it seems the guys have tried to make systemd work. – Rui F Ribeiro Nov 16 '15 at 11:03
  • What makes you think modules are missing? At least in the /newroot environment there should be all modules. There aren't all modules in the initramfs, though, however enough for my init script to run fine. BTW, the HW manufacturer provides a Debian Jessie image w/ systemd, but they are booting from the second partition directly, without an initramfs. BTW, Lamobo R1 looks interesting. – Udo G Nov 16 '15 at 12:59
  • The errors. But I have not dealt with kernel full compilations for a long time in Linux. Lamobo R1 is very interesting, internal switch a boon, pity the wifi is braindead. The HW manufacturer also provides Bananian and openwrt, which are too sloppy hacked for my taste. I prefer so much the work the armbian guys have done. – Rui F Ribeiro Nov 16 '15 at 13:47
  • Tried with a RAMdisk that includes all Kernel modules (19 MB compressed), however the same warnings keep appearing in Kernel log and systemd still freezes... :-( Any idea whatsoever? – Udo G Nov 17 '15 at 8:16
  • Besides one last try about compiling a kernel with them instead of using them as modules, not really. – Rui F Ribeiro Nov 17 '15 at 8:19

It turned out that the Kernel was missing some important settings, that are required by systemd.

http://cgit.freedesktop.org/systemd/systemd/tree/README shows what Kernel config settings were necessary.

Once configured, systemd started working immediately.

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