wic:generic:x86-64: Update kernel cmdline parameter when bootlower with grub

[masami256]

This PR contains two commits.

commit: fc5cd6f

This commit added ADDITIONAL_KERNEL_CMDLINE variable to customize kernel cmdline.

Use ADDITIONAL_KERNEL_CMDLINE variable to append kernel cmdline. This variable is used in meta-isar/scripts/lib/wic/canned-wks/installer-efi.wks.in and meta-isar/recipes-core/images/isar-image-installer.bb so we use same variable.

commit: bf7050c

This commit added "rw" option in the kernel cmdline to solve following issue.

Without rw option, rootfs will be mounted read only first, the re-mount with read/write option.
In this case, firstboot which is run at fisrt time, will run on ro rootfs. In the result, some firstboot process fails because it cannot create symbolic link onto the rootfs.

Current problem

In the kernel cmdline, rw option is not set.

root@EMLinux3:~# cat /proc/cmdline 
BOOT_IMAGE=/vmlinuz-6.1.159-cip49 root=PARTUUID=3d221ac1-96fe-47f8-b46b-eecc81f8c092 rootwait console=ttyS0,115200 console=tty0

The firstboot process couldn't create symbolic link file so that systemd-networkd is not running even though preset is enabeld.

root@EMLinux3:~# systemctl status systemd-networkd
○ systemd-networkd.service - Network Configuration
     Loaded: loaded (/lib/systemd/system/systemd-networkd.service; disabled; preset: enabled)
     Active: inactive (dead)
TriggeredBy: ○ systemd-networkd.socket
       Docs: man:systemd-networkd.service(8)
             man:org.freedesktop.network1(5)

Test

qemu command line is here.

sudo qemu-system-x86_64 \                                                                                                                                                    
  -drive file=./tmp/deploy/images/generic-x86-64/emlinux-image-base-emlinux-bookworm-generic-x86-64.wic,discard=unmap,if=none,id=disk,format=raw \                           
  -m 1G \                                                                                                                                                                    
  -serial mon:stdio \                                                                                                                                                        
  -cpu qemu64 \                                                                                                                                                              
  -smp 4 \                                                                                                                                                                   
  -machine q35,accel=kvm:tcg \                                                                                                                                               
  -global ICH9-LPC.noreboot=off \                                                                                                                                            
  -device ide-hd,drive=disk \                                                                                                                                                
  -nographic \                                                                                                                                                               
  -drive if=pflash,format=raw,readonly=on,file=/usr/share/OVMF/OVMF_CODE.fd \                                                                                                
  -drive if=pflash,format=raw,file=/usr/share/OVMF/OVMF_VARS.fd  

Checking rw option

1. Bulid emlinux-image-base
2. Run qemu to boot emlinux-image-base
3. Check /proc/cmdline
4. Check status of systemd-networkd

Checking additional kernel cmdline options

1. Add 'ADDITIONAL_KERNEL_CMDLINE:append = " earlyprintk"' in local.conf
2. Run qemu to boot emlinux-image-base
3. Check /proc/cmdline

Test Result

Test result of Checking rw option

rw option is set.

root@EMLinux3:~# cat /proc/cmdline 
BOOT_IMAGE=/vmlinuz-6.1.159-cip49 root=PARTUUID=f5da7416-d04b-4616-8e7f-8075bc21eec0 rootwait rw console=ttyS0,115200 console=tty0

systemd-networkd is running.

root@EMLinux3:~# systemctl status systemd-networkd
● systemd-networkd.service - Network Configuration
     Loaded: loaded (/lib/systemd/system/systemd-networkd.service; enabled; preset: enabled)
     Active: active (running) since Wed 2026-01-07 04:22:38 UTC; 52s ago
TriggeredBy: ● systemd-networkd.socket
       Docs: man:systemd-networkd.service(8)
             man:org.freedesktop.network1(5)
   Main PID: 302 (systemd-network)
     Status: "Processing requests..."
      Tasks: 1 (limit: 1087)
     Memory: 3.0M
        CPU: 13ms
     CGroup: /system.slice/systemd-networkd.service
             └─302 /lib/systemd/systemd-networkd

Jan 07 04:22:38 EMLinux3 systemd[1]: Starting systemd-networkd.service - Network Configuration...
Jan 07 04:22:38 EMLinux3 systemd-networkd[302]: lo: Link UP
Jan 07 04:22:38 EMLinux3 systemd-networkd[302]: lo: Gained carrier
Jan 07 04:22:38 EMLinux3 systemd-networkd[302]: Enumeration completed
Jan 07 04:22:38 EMLinux3 systemd[1]: Started systemd-networkd.service - Network Configuration.

Test result of Checking additional kernel cmdline options

ealryprintk option is set.

root@EMLinux3:~# cat /proc/cmdline 
BOOT_IMAGE=/vmlinuz-6.1.159-cip49 root=PARTUUID=5efc325c-ceb8-42c0-b88e-56425fa49ef8 rootwait rw console=ttyS0,115200 console=tty0 earlyprintk