i tried overlayroot on JetPack 4.5.1 by this step ( overlayfs for Jetson - #5 by juerg ) . but after reading extlinux.conf, startup fails and reboot.
the last line before rebooting(by serial console):
[ 0.018254] bootconsole [uart8250] disabled
messages after reading extlinux.conf:
U-Boot 2020.04-g6b630d64fd (Feb 19 2021 - 08:37:46 -0800)
SoC: tegra210
Model: NVIDIA Jetson Nano Developer Kit
Board: NVIDIA P3450-0000
DRAM: 4 GiB
MMC: sdhci@700b0000: 1, sdhci@700b0600: 0
Loading Environment from SPI Flash... SF: Detected mx25u3235f with page size 256 Bytes, erase size 4 KiB, total 4 MiB
*** Warning - bad CRC, using default environment
In: serial
Out: serial
Err: serial
Net: No ethernet found.
Hit any key to stop autoboot: 2 1 0
switch to partitions #0, OK
mmc1 is current device
Scanning mmc 1:1...
Found /boot/extlinux/extlinux.conf
Retrieving file: /boot/extlinux/extlinux.conf
843 bytes read in 26 ms (31.3 KiB/s)
1: primary kernel
Retrieving file: /boot/initrd.img
20042806 bytes read in 901 ms (21.2 MiB/s)
Retrieving file: /boot/Image
34338824 bytes read in 1505 ms (21.8 MiB/s)
append: tegraid=21.1.2.0.0 ddr_die=4096M@2048M section=512M memtype=0 vpr_resize usb_port_owner_info=0 lane_owner_info=0 emc_max_dvfs=0 touch_id=0@63 video=tegrafb no_console_suspend=1 console=ttyS0,115200n8 debug_uartport=lsport,4 earlyprintk=uart8250-32bit,0x70006000 maxcpus=4 usbcore.old_scheme_first=1 lp0_vec=0x1000@0xff780000 core_edp_mv=1075 core_edp_ma=4000 gpt tegra_fbmem=0x800000@0x92ca9000 is_hdmi_initialised=1 earlycon=uart8250,mmio32,0x70006000 root=/dev/mmcblk0p1 rw rootwait rootfstype=ext4 console=ttyS0,115200n8 console=tty0 fbcon=map:0 net.ifnames=0 root=/dev/mmcblk0p1 ro rootwait rootfstype=ext4 console=ttyS0,115200n8 console=tty0 fbcon=map:0 net.ifnames=0
## Flattened Device Tree blob at 83100000
Booting using the fdt blob at 0x83100000
ERROR: reserving fdt memory region failed (addr=0 size=0)
ERROR: reserving fdt memory region failed (addr=0 size=0)
Using Device Tree in place at 0000000083100000, end 000000008317e68d
copying carveout for /host1x@50000000/dc@54200000...
copying carveout for /host1x@50000000/dc@54240000...
Starting kernel ...
[ 0.000000] Booting Linux on physical CPU 0x0
[ 0.000000] Linux version 4.9.201-tegra (buildbrain@mobile-u64-5294-d8000) (gcc version 7.3.1 20180425 [linaro-7.3-2018.05 revision d29120a424ecfbc167ef90065c0eeb7f91977701] (Linaro GCC 7.3-2018.05) ) #1 SMP PREEMPT Fri Feb 19 08:40:32 PST 2021
[ 0.000000] Boot CPU: AArch64 Processor [411fd071]
[ 0.000000] OF: fdt:memory scan node memory@80000000, reg size 32,
[ 0.000000] OF: fdt: - 80000000 , 7ee00000
[ 0.000000] OF: fdt: - 100000000 , 7f200000
[ 0.000000] Found tegra_fbmem: 00800000@92ca9000
[ 0.000000] earlycon: uart8250 at MMIO32 0x0000000070006000 (options '')
[ 0.000000] bootconsole [uart8250] enabled
[ 0.000000] OF: fdt:Reserved memory: failed to reserve memory for node 'fb0_carveout': base 0x0000000000000000, size 0 MiB
[ 0.000000] OF: fdt:Reserved memory: failed to reserve memory for node 'fb0_carveout': base 0x0000000000000000, size 0 MiB
[ 0.000000] OF: fdt:Reserved memory: failed to reserve memory for node 'fb1_carveout': base 0x0000000000000000, size 0 MiB
[ 0.000000] OF: fdt:Reserved memory: failed to reserve memory for node 'fb1_carveout': base 0x0000000000000000, size 0 MiB
[ 0.000000] OF: reserved mem: initialized node vpr-carveout, compatible id nvidia,vpr-carveout
[ 0.000000] OF: reserved mem: initialized node iram-carveout, compatible id nvidia,iram-carveout
[ 0.000000] OF: reserved mem: initialized node ramoops_carveout, compatible id nvidia,ramoops
[ 0.000000] cma: Reserved 64 MiB at 0x00000000fac00000
[ 0.000000] psci: probing for conduit method from DT.
[ 0.000000] psci: PSCIv1.0 detected in firmware.
[ 0.000000] psci: Using standard PSCI v0.2 function IDs
[ 0.000000] psci: MIGRATE_INFO_TYPE not supported.
[ 0.000000] psci: SMC Calling Convention v1.1
[ 0.000000] percpu: Embedded 24 pages/cpu s57560 r8192 d32552 u98304
[ 0.000000] CPU features: enabling workaround for ARM erratum 832075
[ 0.000000] Speculative Store Bypass Disable mitigation not required
[ 0.000000] Built 1 zonelists in Zone order, mobility grouping on. Total pages: 1023544
[ 0.000000] Kernel command line: tegraid=21.1.2.0.0 ddr_die=4096M@2048M section=512M memtype=0 vpr_resize usb_port_owner_info=0 lane_owner_info=0 emc_max_dvfs=0 touch_id=0@63 video=tegrafb no_console_suspend=1 console=ttyS0,115200n8 debug_uartport=lsport,4 earlyprintk=uart8250-32bit,0x70006000 maxcpus=4 usbcore.old_scheme_first=1 lp0_vec=0x1000@0xff780000 core_edp_mv=1075 core_edp_ma=4000 gpt tegra_fbmem=0x800000@0x92ca9000 is_hdmi_initialised=1 earlycon=uart8250,mmio32,0x70006000 root=/dev/mmcblk0p1 rw rootwait rootfstype=ext4 console=ttyS0,115200n8 console=tty0 fbcon=map:0 net.ifnames=0 root=/dev/mmcblk0p1 ro rootwait rootfstype=ext4 console=ttyS0,115200n8 console=tty0 fbcon=map:0 net.ifnames=0
[ 0.000000] log_buf_len individual max cpu contribution: 32768 bytes
[ 0.000000] log_buf_len total cpu_extra contributions: 98304 bytes
[ 0.000000] log_buf_len min size: 32768 bytes
[ 0.000000] log_buf_len: 131072 bytes
[ 0.000000] early log buf free: 29256(89%)
[ 0.000000] PID hash table entries: 4096 (order: 3, 32768 bytes)
[ 0.000000] Dentry cache hash table entries: 524288 (order: 10, 4194304 bytes)
[ 0.000000] Inode-cache hash table entries: 262144 (order: 9, 2097152 bytes)
[ 0.000000] Memory: 3552524K/4159488K available (15294K kernel code, 2942K rwdata, 6664K rodata, 8576K init, 609K bss, 131828K reserved, 475136K cma-reserved)
[ 0.000000] Virtual kernel memory layout:
[ 0.000000] modules : 0xffffff8000000000 - 0xffffff8008000000 ( 128 MB)
[ 0.000000] vmalloc : 0xffffff8008000000 - 0xffffffbebfff0000 ( 250 GB)
[ 0.000000] .text : 0xffffff8008080000 - 0xffffff8008f70000 ( 15296 KB)
[ 0.000000] .rodata : 0xffffff8008f70000 - 0xffffff8009600000 ( 6720 KB)
[ 0.000000] .init : 0xffffff8009600000 - 0xffffff8009e60000 ( 8576 KB)
[ 0.000000] .data : 0xffffff8009e60000 - 0xffffff800a13f808 ( 2943 KB)
[ 0.000000] .bss : 0xffffff800a13f808 - 0xffffff800a1d7cbc ( 610 KB)
[ 0.000000] fixed : 0xffffffbefe7fd000 - 0xffffffbefec00000 ( 4108 KB)
[ 0.000000] PCI I/O : 0xffffffbefee00000 - 0xffffffbeffe00000 ( 16 MB)
[ 0.000000] vmemmap : 0xffffffbf00000000 - 0xffffffc000000000 ( 4 GB maximum)
[ 0.000000] 0xffffffbf00000000 - 0xffffffbf03fc8000 ( 63 MB actual)
[ 0.000000] memory : 0xffffffc000000000 - 0xffffffc0ff200000 ( 4082 MB)
[ 0.000000] SLUB: HWalign=64, Order=0-3, MinObjects=0, CPUs=4, Nodes=1
[ 0.000000] Preemptible hierarchical RCU implementation.
[ 0.000000] Build-time adjustment of leaf fanout to 64.
[ 0.000000] RCU restricting CPUs from NR_CPUS=64 to nr_cpu_ids=4.
[ 0.000000] RCU: Adjusting geometry for rcu_fanout_leaf=64, nr_cpu_ids=4
[ 0.000000] NR_IRQS:64 nr_irqs:64 0
[ 0.000000] /interrupt-controller@60004000: 192 interrupts forwarded to /interrupt-controller
[ 0.000000] t210 clock and reset probe
[ 0.000000] tegra-pmc: get_secure_pmc_setting: done secure_pmc=1
[ 0.000000] clk_cbus_recalc_rate: no gbus parent
[ 0.000000] clk_cbus_recalc_rate: no gbus parent
[ 0.000000] clk_cbus_recalc_rate: no gbus parent
[ 0.000000] clk_cbus_recalc_rate: no gbus parent
[ 0.000000] clk_cbus_recalc_rate: no gbus parent
[ 0.000000] arm_arch_timer: Architected cp15 timer(s) running at 19.20MHz (phys).
[ 0.000000] clocksource: arch_sys_counter: mask: 0xffffffffffffff max_cycles: 0x46d987e47, max_idle_ns: 440795202767 ns
[ 0.000006] sched_clock: 56 bits at 19MHz, resolution 52ns, wraps every 4398046511078ns
[ 0.010098] Console: colour dummy device 80x25
[ 0.014746] console [tty0] enabled
[ 0.018254] bootconsole [uart8250] disabled
[0000.159] [L4T TegraBoot] (version 00.00.2018.01-l4t-e82258de)
(...snip...)