Buildroot NFS boot failure - can't open /run/nfs/xtab for reading

I am trying to boot a machine into a NFS root built by buildroot, but it crashes at a step near NFS mount. It seems like it wants to read a file, but fails to read it.

Boot log:

[    0.000000] Linux version 4.19.57 (user@kernelbuildhost) (gcc version 7.4.0 (Buildroot 2019.02.4)) #4 SMP Sat Aug 10 14:18:02 PDT 2019
[    0.000000] Command line: root=/dev/nfs ip=dhcp nfsroot=192.168.2.8:/images/dev/nfsroots/buildroot/8a:4b:84:c8:e2:b9/,nfsvers=3 rw console=tty0 console=ttyS0,115200
[    0.000000] x86/fpu: x87 FPU will use FXSAVE
[    0.000000] BIOS-provided physical RAM map:
[    0.000000] BIOS-e820: [mem 0x0000000000000000-0x000000000009c3ff] usable
[    0.000000] BIOS-e820: [mem 0x00000000000f0000-0x00000000000fffff] reserved
[    0.000000] BIOS-e820: [mem 0x0000000000100000-0x00000000bfed8fff] usable
[    0.000000] BIOS-e820: [mem 0x00000000bff91000-0x00000000bffdffff] usable
[    0.000000] BIOS-e820: [mem 0x00000000bffe0000-0x00000000bfffffff] reserved
[    0.000000] BIOS-e820: [mem 0x00000000feffc000-0x00000000feffffff] reserved
[    0.000000] BIOS-e820: [mem 0x00000000fffc0000-0x00000000ffffffff] reserved
[    0.000000] BIOS-e820: [mem 0x0000000100000000-0x000000013fffffff] usable
[    0.000000] NX (Execute Disable) protection: active
[    0.000000] SMBIOS 2.8 present.
[    0.000000] DMI: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.11.0-0-g63451fca13-prebuilt.qemu-project.org 04/01/2014
[    0.000000] tsc: Fast TSC calibration using PIT
[    0.000000] tsc: Detected 4008.451 MHz processor
[    0.000926] last_pfn = 0x140000 max_arch_pfn = 0x400000000
[    0.000952] x86/PAT: Configuration [0-7]: WB  WC  UC- UC  WB  WC  UC- UC
[    0.000956] last_pfn = 0xbffe0 max_arch_pfn = 0x400000000
[    0.005453] found SMP MP-table at [mem 0x000f5b60-0x000f5b6f]
[    0.005493] Scanning 1 areas for low memory corruption
[    0.005599] ACPI: Early table checksum verification disabled
[    0.005628] ACPI: RSDP 0x00000000000F5940 000014 (v00 BOCHS )
[    0.005633] ACPI: RSDT 0x00000000BFFE2563 000030 (v01 BOCHS  BXPCRSDT 00000001 BXPC 00000001)
[    0.005637] ACPI: FACP 0x00000000BFFE23A7 000074 (v01 BOCHS  BXPCFACP 00000001 BXPC 00000001)
[    0.005641] ACPI: DSDT 0x00000000BFFE0040 002367 (v01 BOCHS  BXPCDSDT 00000001 BXPC 00000001)
[    0.005643] ACPI: FACS 0x00000000BFFE0000 000040
[    0.005645] ACPI: APIC 0x00000000BFFE249B 000090 (v01 BOCHS  BXPCAPIC 00000001 BXPC 00000001)
[    0.005647] ACPI: HPET 0x00000000BFFE252B 000038 (v01 BOCHS  BXPCHPET 00000001 BXPC 00000001)
[    0.005860] No NUMA configuration found
[    0.005861] Faking a node at [mem 0x0000000000000000-0x000000013fffffff]
[    0.005863] NODE_DATA(0) allocated [mem 0x13fff9000-0x13fffcfff]
[    0.005889] Zone ranges:
[    0.005890]   DMA      [mem 0x0000000000001000-0x0000000000ffffff]
[    0.005891]   DMA32    [mem 0x0000000001000000-0x00000000ffffffff]
[    0.005891]   Normal   [mem 0x0000000100000000-0x000000013fffffff]
[    0.005892] Movable zone start for each node
[    0.005893] Early memory node ranges
[    0.005893]   node   0: [mem 0x0000000000001000-0x000000000009bfff]
[    0.005894]   node   0: [mem 0x0000000000100000-0x00000000bfed8fff]
[    0.005894]   node   0: [mem 0x00000000bff91000-0x00000000bffdffff]
[    0.005895]   node   0: [mem 0x0000000100000000-0x000000013fffffff]
[    0.005898] Reserved but unavailable: 101 pages
[    0.005899] Initmem setup node 0 [mem 0x0000000000001000-0x000000013fffffff]
[    0.019622] ACPI: PM-Timer IO Port: 0x608
[    0.019628] ACPI: LAPIC_NMI (acpi_id[0xff] dfl dfl lint[0x1])
[    0.019646] IOAPIC[0]: apic_id 0, version 17, address 0xfec00000, GSI 0-23
[    0.019647] ACPI: INT_SRC_OVR (bus 0 bus_irq 0 global_irq 2 dfl dfl)
[    0.019648] ACPI: INT_SRC_OVR (bus 0 bus_irq 5 global_irq 5 high level)
[    0.019649] ACPI: INT_SRC_OVR (bus 0 bus_irq 9 global_irq 9 high level)
[    0.019650] ACPI: INT_SRC_OVR (bus 0 bus_irq 10 global_irq 10 high level)
[    0.019650] ACPI: INT_SRC_OVR (bus 0 bus_irq 11 global_irq 11 high level)
[    0.019654] Using ACPI (MADT) for SMP configuration information
[    0.019655] ACPI: HPET id: 0x8086a201 base: 0xfed00000
[    0.019659] smpboot: Allowing 4 CPUs, 0 hotplug CPUs
[    0.019664] PM: Registered nosave memory: [mem 0x00000000-0x00000fff]
[    0.019665] PM: Registered nosave memory: [mem 0x0009c000-0x000effff]
[    0.019666] PM: Registered nosave memory: [mem 0x000f0000-0x000fffff]
[    0.019666] PM: Registered nosave memory: [mem 0xbfed9000-0xbff90fff]
[    0.019667] PM: Registered nosave memory: [mem 0xbffe0000-0xbfffffff]
[    0.019668] PM: Registered nosave memory: [mem 0xc0000000-0xfeffbfff]
[    0.019668] PM: Registered nosave memory: [mem 0xfeffc000-0xfeffffff]
[    0.019668] PM: Registered nosave memory: [mem 0xff000000-0xfffbffff]
[    0.019669] PM: Registered nosave memory: [mem 0xfffc0000-0xffffffff]
[    0.019670] [mem 0xc0000000-0xfeffbfff] available for PCI devices
[    0.019672] clocksource: refined-jiffies: mask: 0xffffffff max_cycles: 0xffffffff,max_idle_ns: 1910969940391419 ns
[    0.082346] setup_percpu: NR_CPUS:64 nr_cpumask_bits:64 nr_cpu_ids:4 nr_node_ids:1
[    0.083290] percpu: Embedded 43 pages/cpu s138392 r8192 d29544 u524288
[    0.083306] Built 1 zonelists, mobility grouping on.  Total pages: 1031853
[    0.083307] Policy zone: Normal
[    0.083308] Kernel command line: root=/dev/nfs ip=dhcp nfsroot=192.168.2.8:/images/dev/nfsroots/buildroot/8a:4b:84:c8:e2:b9/,nfsvers=3 rw console=tty0 console=ttyS0,115200
[    0.127844] Memory: 4019620K/4193036K available (12300K kernel code, 1314K rwdata,2908K rodata, 15004K init, 1976K bss, 173416K reserved, 0K cma-reserved)
[    0.127876] SLUB: HWalign=64, Order=0-3, MinObjects=0, CPUs=4, Nodes=1
[    0.127881] Kernel/User page tables isolation: enabled
[    0.128084] rcu: Hierarchical RCU implementation.
[    0.128084] rcu:     RCU event tracing is enabled.
[    0.128085] rcu:     RCU restricting CPUs from NR_CPUS=64 to nr_cpu_ids=4.
[    0.128086] rcu: Adjusting geometry for rcu_fanout_leaf=16, nr_cpu_ids=4
[    0.128215] NR_IRQS: 4352, nr_irqs: 456, preallocated irqs: 16
[    0.134863] Console: colour VGA+ 80x25
[    0.156297] console [tty0] enabled
[    0.194862] console [ttyS0] enabled
[    0.195361] ACPI: Core revision 20180810
[    0.196008] clocksource: hpet: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 19112604467 ns
[    0.197106] APIC: Switch to symmetric I/O mode setup
[    0.198388] ..TIMER: vector=0x30 apic1=0 pin1=2 apic2=-1 pin2=-1
[    0.203280] clocksource: tsc-early: mask: 0xffffffffffffffff max_cycles: 0x39c78c545a3, max_idle_ns: 440795353506 ns
[    0.204445] Calibrating delay loop (skipped), value calculated using timer frequency.. 8016.90 BogoMIPS (lpj=4008451)
[    0.205435] pid_max: default: 32768 minimum: 301
[    0.206452] Security Framework initialized
[    0.206964] SELinux:  Initializing.
[    0.208367] Dentry cache hash table entries: 524288 (order: 10, 4194304 bytes)
[    0.210795] Inode-cache hash table entries: 262144 (order: 9, 2097152 bytes)
[    0.211476] Mount-cache hash table entries: 8192 (order: 4, 65536 bytes)
[    0.212244] Mountpoint-cache hash table entries: 8192 (order: 4, 65536 bytes)
[    0.212591] Last level iTLB entries: 4KB 0, 2MB 0, 4MB 0
[    0.213435] Last level dTLB entries: 4KB 0, 2MB 0, 4MB 0, 1GB 0
[    0.214435] Spectre V2 : Mitigation: Full generic retpoline
[    0.215064] Spectre V2 : Spectre v2 / SpectreRSB mitigation: Filling RSB on context switch
[    0.215435] Speculative Store Bypass: Vulnerable
[    0.216461] MDS: Vulnerable: Clear CPU buffers attempted, no microcode
[    0.217523] Freeing SMP alternatives memory: 40K
[    0.218433] smpboot: CPU0: Intel Common KVM processor (family: 0xf, model: 0x6, stepping: 0x1)
[    0.218572] Performance Events: unsupported Netburst CPU model 6 no PMU driver, software events only.
[    0.219477] rcu: Hierarchical SRCU implementation.
[    0.220489] smp: Bringing up secondary CPUs ...
[    0.221175] x86: Booting SMP configuration:
[    0.221435] .... node  #0, CPUs:      #1 #2 #3
[    0.258444] smp: Brought up 1 node, 4 CPUs
[    0.259436] smpboot: Max logical packages: 1
[    0.260435] smpboot: Total of 4 processors activated (32067.60 BogoMIPS)
[    0.261513] devtmpfs: initialized
[    0.261981] random: get_random_u32 called from bucket_table_alloc.isra.18+0x86/0x170 with crng_init=0
[    0.262511] clocksource: jiffies: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 1911260446275000 ns
[    0.262788] kworker/u8:0 (32) used greatest stack depth: 14648 bytes left
[    0.263439] futex hash table entries: 1024 (order: 4, 65536 bytes)
[    0.263557] RTC time: 21:46:05, date: 08/10/19
[    0.265529] NET: Registered protocol family 16
[    0.266143] audit: initializing netlink subsys (disabled)
[    0.266454] audit: type=2000 audit(1565473565.070:1): state=initialized audit_enabled=0 res=1
[    0.266710] kworker/u8:2 (45) used greatest stack depth: 14232 bytes left
[    0.272295] cpuidle: using governor menu
[    0.272510] ACPI: bus type PCI registered
[    0.273107] PCI: Using configuration type 1 for base access
[    0.278467] HugeTLB registered 2.00 MiB page size, pre-allocated 0 pages
[    0.279499] ACPI: Added _OSI(Module Device)
[    0.280045] ACPI: Added _OSI(Processor Device)
[    0.280439] ACPI: Added _OSI(3.0 _SCP Extensions)
[    0.281435] ACPI: Added _OSI(Processor Aggregator Device)
[    0.282095] ACPI: Added _OSI(Linux-Dell-Video)
[    0.282095] ACPI: Added _OSI(Linux-Lenovo-NV-HDMI-Audio)
[    0.282095] ACPI: 1 ACPI AML tables successfully acquired and loaded
[    0.282309] ACPI: Interpreter enabled
[    0.283444] ACPI: (supports S0 S3 S4 S5)
[    0.283996] ACPI: Using IOAPIC for interrupt routing
[    0.284456] PCI: Using host bridge windows from ACPI; if necessary, use "pci=nocrs" and report a bug
[    0.285515] ACPI: Enabled 2 GPEs in block 00 to 0F
[    0.287267] ACPI: PCI Root Bridge [PCI0] (domain 0000 [bus 00-ff])
[    0.287267] acpi PNP0A03:00: _OSC: OS supports [ASPM ClockPM Segments MSI]
[    0.288688] acpi PNP0A03:00: _OSC failed (AE_NOT_FOUND); disabling ASPM
[    0.289448] acpi PNP0A03:00: fail to add MMCONFIG information, can't access extended PCI configuration space under this bridge.
[    0.290533] PCI host bridge to bus 0000:00
[    0.290533] pci_bus 0000:00: root bus resource [io  0x0000-0x0cf7 window]
[    0.291260] pci_bus 0000:00: root bus resource [io  0x0d00-0xffff window]
[    0.292435] pci_bus 0000:00: root bus resource [mem 0x000a0000-0x000bffff window]
[    0.293438] pci_bus 0000:00: root bus resource [mem 0xc0000000-0xfebfffff window]
[    0.294435] pci_bus 0000:00: root bus resource [mem 0x140000000-0x1bfffffff window]
[    0.295436] pci_bus 0000:00: root bus resource [bus 00-ff]
[    0.298139] pci 0000:00:01.1: legacy IDE quirk: reg 0x10: [io  0x01f0-0x01f7]
[    0.299435] pci 0000:00:01.1: legacy IDE quirk: reg 0x14: [io  0x03f6]
[    0.300435] pci 0000:00:01.1: legacy IDE quirk: reg 0x18: [io  0x0170-0x0177]
[    0.301435] pci 0000:00:01.1: legacy IDE quirk: reg 0x1c: [io  0x0376]
[    0.303470] pci 0000:00:01.3: quirk: [io  0x0600-0x063f] claimed by PIIX4 ACPI
[    0.304420] pci 0000:00:01.3: quirk: [io  0x0700-0x070f] claimed by PIIX4 SMB
[    0.329187] pci_bus 0000:01: extended config space not accessible
[    0.330600] pci 0000:00:1e.0: PCI bridge to [bus 01]
[    0.331826] pci_bus 0000:02: extended config space not accessible
[    0.332597] pci 0000:00:1f.0: PCI bridge to [bus 02]
[    0.334482] ACPI: PCI Interrupt Link [LNKA] (IRQs 5 *10 11)
[    0.336505] ACPI: PCI Interrupt Link [LNKB] (IRQs 5 *10 11)
[    0.338482] ACPI: PCI Interrupt Link [LNKC] (IRQs 5 10 *11)
[    0.339220] ACPI: PCI Interrupt Link [LNKD] (IRQs 5 10 *11)
[    0.340463] ACPI: PCI Interrupt Link [LNKS] (IRQs *9)
[    0.341476] pci 0000:00:02.0: vgaarb: setting as boot VGA device
[    0.341476] pci 0000:00:02.0: vgaarb: VGA device added: decodes=io+mem,owns=io+mem,locks=none
[    0.342447] pci 0000:00:02.0: vgaarb: bridge control possible
[    0.343100] vgaarb: loaded
[    0.344532] SCSI subsystem initialized
[    0.345068] ACPI: bus type USB registered
[    0.345479] usbcore: registered new interface driver usbfs
[    0.346452] usbcore: registered new interface driver hub
[    0.347113] usbcore: registered new device driver usb
[    0.347468] pps_core: LinuxPPS API ver. 1 registered
[    0.347468] pps_core: Software ver. 5.3.6 - Copyright 2005-2007 Rodolfo Giometti <giometti@linux.it>
[    0.349446] PTP clock support registered
[    0.349983] EDAC MC: Ver: 3.0.0
[    0.350591] Advanced Linux Sound Architecture Driver Initialized.
[    0.351454] PCI: Using ACPI for IRQ routing
[    0.352233] NetLabel: Initializing
[    0.352438] NetLabel:  domain hash size = 128
[    0.352988] NetLabel:  protocols = UNLABELED CIPSOv4 CALIPSO
[    0.353446] NetLabel:  unlabeled traffic allowed by default
[    0.354555] HPET: 3 timers in total, 0 timers will be used for per-cpu timer
[    0.355455] hpet0: at MMIO 0xfed00000, IRQs 2, 8, 0
[    0.356035] hpet0: 3 comparators, 64-bit 100.000000 MHz counter
[    0.361634] clocksource: Switched to clocksource tsc-early
[    0.368716] VFS: Disk quotas dquot_6.6.0
[    0.369278] VFS: Dquot-cache hash table entries: 512 (order 0, 4096 bytes)
[    0.370151] pnp: PnP ACPI init
[    0.370927] pnp: PnP ACPI: found 5 devices
[    0.379624] clocksource: acpi_pm: mask: 0xffffff max_cycles: 0xffffff, max_idle_ns: 2085701024 ns
[    0.381285] pci 0000:00:1e.0: PCI bridge to [bus 01]
[    0.381894] pci 0000:00:1e.0:   bridge window [io  0xd000-0xdfff]
[    0.382954] pci 0000:00:1e.0:   bridge window [mem 0xfe800000-0xfe9fffff]
[    0.384265] pci 0000:00:1e.0:   bridge window [mem 0xfe200000-0xfe3fffff 64bit pref]
[    0.385764] pci 0000:00:1f.0: PCI bridge to [bus 02]
[    0.386410] pci 0000:00:1f.0:   bridge window [io  0xc000-0xcfff]
[    0.387540] pci 0000:00:1f.0:   bridge window [mem 0xfe600000-0xfe7fffff]
[    0.388544] pci 0000:00:1f.0:   bridge window [mem 0xfe000000-0xfe1fffff 64bit pref]
[    0.390110] NET: Registered protocol family 2
[    0.390845] tcp_listen_portaddr_hash hash table entries: 2048 (order: 3, 32768 bytes)
[    0.392835] TCP established hash table entries: 32768 (order: 6, 262144 bytes)
[    0.393858] TCP bind hash table entries: 32768 (order: 7, 524288 bytes)
[    0.394733] TCP: Hash tables configured (established 32768 bind 32768)
[    0.395564] UDP hash table entries: 2048 (order: 4, 65536 bytes)
[    0.396313] UDP-Lite hash table entries: 2048 (order: 4, 65536 bytes)
[    0.397123] NET: Registered protocol family 1
[    0.397922] RPC: Registered named UNIX socket transport module.
[    0.399346] RPC: Registered udp transport module.
[    0.399915] RPC: Registered tcp transport module.
[    0.400479] RPC: Registered tcp NFSv4.1 backchannel transport module.
[    0.401423] pci 0000:00:01.0: PIIX3: Enabling Passive Release
[    0.402099] pci 0000:00:00.0: Limiting direct PCI/PCI transfers
[    0.402779] pci 0000:00:01.0: Activating ISA DMA hang workarounds
[    0.414171] PCI Interrupt Link [LNKD] enabled at IRQ 11
[    0.425572] pci 0000:00:01.2: quirk_usb_early_handoff+0x0/0x670 took 21563 usecs
[    0.426529] pci 0000:00:02.0: Video device with shadowed ROM at [mem 0x000c0000-0x000dffff]
[    0.579118] PCI-DMA: Using software bounce buffering for IO (SWIOTLB)
[    0.579881] software IO TLB: mapped [mem 0xbbed9000-0xbfed9000] (64MB)
[    0.581339] Scanning for low memory corruption every 60 seconds
[    0.582555] Initialise system trusted keyrings
[    0.583233] workingset: timestamp_bits=56 max_order=20 bucket_order=0
[    0.585641] NFS: Registering the id_resolver key type
[    0.586295] Key type id_resolver registered
[    0.586850] Key type id_legacy registered
[    0.589596] Key type asymmetric registered
[    0.590159] Asymmetric key parser 'x509' registered
[    0.590782] Block layer SCSI generic (bsg) driver version 0.4 loaded (major 251)
[    0.591688] io scheduler noop registered
[    0.592201] io scheduler deadline registered
[    0.592764] io scheduler cfq registered (default)
[    0.593336] io scheduler mq-deadline registered
[    0.593896] io scheduler kyber registered
[    0.594637] input: Power Button as /devices/LNXSYSTM:00/LNXPWRBN:00/input/input0
[    0.595552] ACPI: Power Button [PWRF]
[    0.596404] Serial: 8250/16550 driver, 4 ports, IRQ sharing enabled
[    0.619819] 00:04: ttyS0 at I/O 0x3f8 (irq = 4, base_baud = 115200) is a 16550A
[    0.621753] Non-volatile memory driver v1.3
[    0.622429] Linux agpgart interface v0.103
[    0.627107] loop: module loaded
[    0.628207] scsi host0: ata_piix
[    0.628900] scsi host1: ata_piix
[    0.629731] ata1: PATA max MWDMA2 cmd 0x1f0 ctl 0x3f6 bmdma 0xe080 irq 14
[    0.630674] ata2: PATA max MWDMA2 cmd 0x170 ctl 0x376 bmdma 0xe088 irq 15
[    0.631742] e100: Intel(R) PRO/100 Network Driver, 3.5.24-k2-NAPI
[    0.632621] e100: Copyright(c) 1999-2006 Intel Corporation
[    0.633467] e1000: Intel(R) PRO/1000 Network Driver - version 7.3.21-k8-NAPI
[    0.634465] e1000: Copyright (c) 1999-2006 Intel Corporation.
[    0.645993] PCI Interrupt Link [LNKB] enabled at IRQ 10
[    0.944408] e1000 0000:00:12.0 eth0: (PCI:33MHz:32-bit) 8a:4b:84:c8:e2:b9
[    0.945252] e1000 0000:00:12.0 eth0: Intel(R) PRO/1000 Network Connection
[    0.946109] e1000e: Intel(R) PRO/1000 Network Driver - 3.2.6-k
[    0.946836] e1000e: Copyright(c) 1999 - 2015 Intel Corporation.
[    0.947567] sky2: driver version 1.30
[    0.948244] ehci_hcd: USB 2.0 'Enhanced' Host Controller (EHCI) Driver
[    0.949054] ehci-pci: EHCI PCI platform driver
[    0.949660] ohci_hcd: USB 1.1 'Open' Host Controller (OHCI) Driver
[    0.950387] ohci-pci: OHCI PCI platform driver
[    0.950998] uhci_hcd: USB Universal Host Controller Interface driver
[    0.962621] uhci_hcd 0000:00:01.2: UHCI Host Controller
[    0.963390] uhci_hcd 0000:00:01.2: new USB bus registered, assigned bus number 1
[    0.964451] uhci_hcd 0000:00:01.2: irq 11, io base 0x0000e040
[    0.965225] usb usb1: New USB device found, idVendor=1d6b, idProduct=0001, bcdDevice= 4.19
[    0.966274] usb usb1: New USB device strings: Mfr=3, Product=2, SerialNumber=1
[    0.967282] usb usb1: Product: UHCI Host Controller
[    0.967925] usb usb1: Manufacturer: Linux 4.19.57 uhci_hcd
[    0.968613] usb usb1: SerialNumber: 0000:00:01.2
[    0.969372] hub 1-0:1.0: USB hub found
[    0.969924] hub 1-0:1.0: 2 ports detected
[    0.970603] usbcore: registered new interface driver usblp
[    0.971296] usbcore: registered new interface driver usb-storage
[    0.972071] i8042: PNP: PS/2 Controller [PNP0303:KBD,PNP0f13:MOU] at 0x60,0x64 irq1,12
[    0.973654] serio: i8042 KBD port at 0x60,0x64 irq 1
[    0.974399] serio: i8042 AUX port at 0x60,0x64 irq 12
[    0.975335] rtc_cmos 00:00: RTC can wake from S4
[    0.976354] input: AT Translated Set 2 keyboard as /devices/platform/i8042/serio0/input/input1
[    0.977164] rtc_cmos 00:00: registered as rtc0
[    0.979501] rtc_cmos 00:00: alarms up to one day, y3k, 114 bytes nvram, hpet irqs
[    0.980550] device-mapper: ioctl: 4.39.0-ioctl (2018-04-03) initialised: dm-devel@redhat.com
[    0.981581] hidraw: raw HID events driver (C) Jiri Kosina
[    0.982387] usbcore: registered new interface driver usbhid
[    0.983032] usbhid: USB HID core driver
[    0.984077] Initializing XFRM netlink socket
[    0.984741] NET: Registered protocol family 10
[    0.985569] Segment Routing with IPv6
[    0.986305] sit: IPv6, IPv4 and MPLS over IPv4 tunneling driver
[    0.987067] NET: Registered protocol family 17
[    0.987645] Key type dns_resolver registered
[    0.988417] mce: Using 10 MCE banks
[    0.988886] sched_clock: Marking stable (920364329, 68028548)->(1103199312, -114806435)
[    0.990290] registered taskstats version 1
[    0.990868] Loading compiled-in X.509 certificates
[    0.991628]   Magic number: 15:228:803
[    0.992260] console [netcon0] enabled
[    0.992739] netconsole: network logging started
[    0.995103] IPv6: ADDRCONF(NETDEV_UP): eth0: link is not ready
[    1.293481] usb 1-1: new full-speed USB device number 2 using uhci_hcd
[    1.456904] usb 1-1: New USB device found, idVendor=0627, idProduct=0001, bcdDevice= 0.00
[    1.457973] usb 1-1: New USB device strings: Mfr=1, Product=3, SerialNumber=5
[    1.458763] usb 1-1: Product: QEMU USB Tablet
[    1.459297] usb 1-1: Manufacturer: QEMU
[    1.459787] usb 1-1: SerialNumber: 42
[    1.468622] input: QEMU QEMU USB Tablet as /devices/pci0000:00/0000:00:01.2/usb1/1-1/1-1:1.0/0003:0627:0001.0001/input/input4
[    1.470258] hid-generic 0003:0627:0001.0001: input,hidraw0: USB HID v0.01 Mouse [QEMU QEMU USB Tablet] on usb-0000:00:01.2-1/input0
[    1.596065] input: ImExPS/2 Generic Explorer Mouse as /devices/platform/i8042/serio1/input/input3
[    1.635519] tsc: Refined TSC clocksource calibration: 4008.083 MHz
[    1.637366] clocksource: tsc: mask: 0xffffffffffffffff max_cycles: 0x39c63125c49, max_idle_ns: 440795404658 ns
[    1.639785] clocksource: Switched to clocksource tsc
[    3.043902] e1000: eth0 NIC Link is Up 1000 Mbps Full Duplex, Flow Control: RX
[    3.045486] IPv6: ADDRCONF(NETDEV_CHANGE): eth0: link becomes ready
[    3.057461] Sending DHCP requests ., OK
[    4.062045] IP-Config: Got DHCP answer from 192.168.2.1, my address is 192.168.2.72
[    4.063206] IP-Config: Complete:
[    4.065670]      device=eth0, hwaddr=8a:4b:84:c8:e2:b9, ipaddr=192.168.2.72, mask=255.255.255.0, gw=192.168.2.1
[    4.066907]      host=192.168.2.72, domain=, nis-domain=(none)
[    4.067636]      bootserver=192.168.2.8, rootserver=192.168.2.8, rootpath=
[    4.067637]      nameserver0=192.168.2.1
[    4.068977] cfg80211: Loading compiled-in X.509 certificates for regulatory database
[    4.071495] cfg80211: Loaded X.509 cert 'sforshee: 00b28ddf47aef9cea7'
[    4.072256] ALSA device list:
[    4.072693]   No soundcards found.
[    4.075016] Freeing unused kernel image memory: 15004K
[    4.076158] platform regulatory.0: Direct firmware load for regulatory.db failed with error -2
[    4.077620] cfg80211: failed to load regulatory.db
[    4.081551] Write protecting the kernel read-only data: 18432k
[    4.083028] Freeing unused kernel image memory: 2004K
[    4.084171] Freeing unused kernel image memory: 1188K
[    4.084950] Run /init as init process
Starting syslogd: [    4.091103] random: fast init done
OK
Starting klogd: OK
Initializing random number generator... [    4.095140] random: dd: uninitialized urandom read (512 bytes read)
done.
Starting rpcbind: OK
Starting network: ip: RTNETLINK an[    4.102817] ip (1157) used greatest stack depth:14184 bytes left
swers: File exists
FAIL
Starting NFS statd: OK
Starting NFS services: exportfs: can't open /run/nfs/xtab for reading
FAIL
Starting NFS daemon: rpc.nfsd: Unable to access /proc/fs/nfsd errno 2 (No such file or directory).
Please try, as root, 'mount -t nfsd nfsd /proc/fs/nfsd' and then restart rpc.nfsd to correct the problem
FAIL
Starting NFS mountd: OK

Welcome to Buildroot
buildroot login:

I checked the file /run/nfs/xtab. It does exist, but may be protected by a lock file.

# ls -lah /run/nfs
total 4
drwxr-xr-x    4 root     root         200 Aug 10 22:01 .
drwxr-xr-x    4 root     root         240 Aug 10 22:01 ..
-rw-------    1 root     root           0 Aug 10 22:01 .etab.lock
-rw-------    1 root     root           0 Aug 10 22:01 .xtab.lock
-rw-r--r--    1 root     root           0 Aug 10 22:01 etab
-rw-r--r--    1 root     root           0 Aug 10 22:01 rmtab
drwxr-xr-x    2 root     root          40 Aug 10 22:01 sm
drwxr-xr-x    2 root     root          40 Aug 10 22:01 sm.bak
-rw-r--r--    1 root     root           4 Aug 10 22:01 state
-rw-r--r--    1 root     root           0 Aug 10 22:01 xtab

I do not know what to debug next. Have I screwed up my boot arguments (see top of boot log)? Could this be an issue with the build configuration? Everything happening here is within bzImage, so not too many variables are at play.