I'm Trying to mount rootfile system using NFS in my SAM9G25 Evaluation board( AT91SAM9x5-EK).

I'm getting error "Cannot open root device "nfs" or unknown-block(0,255)", and kernel goes PANIC!!.

Please help in this regard.

I have already exported my root file system path in my PC (NFS server)

U-Boot bootargs are below:

bootargs=mem=128M console=ttyS0,115200 mtdparts=atmel_nand:8M(bootstrap/uboot/ kernel)ro,-(rootfs) ip=192.168.1.174 root=/dev/nfs rw nfsroot=192.168.1.147:/ rootfs/rfs_samg25

Kernel boot messages are below:

U-Boot> boot
NAND read: device 0 offset 0x200000, size 0x220000 atmel_nand : one bit error on data. (data byte : f3, in page offset : 200, bit o
ffset : 0x4) atmel_nand : error corrected 2228224 bytes read: OK ## Booting kernel from Legacy Image at 22000000 ... Image Name: Angstrom/2.6.39/at91sam9x5ek
Image Type: ARM Linux Kernel Image (uncompressed)
Data Size: 2220296 Bytes = 2.1 MiB
Load Address: 20008000
Entry Point: 20008000
Verifying Checksum ... OK
Loading Kernel Image ... OK OK
Starting kernel ...
Uncompressing Linux... done, booting the kernel. Linux version 2.6.39 (nferre@RFOLXTS02.rfo.atmel.com) (gcc version 4.5.3 2011022
3 (prerelease) (GCC) ) #1 Wed Jun 1 19:01:01 CEST 2011 CPU: ARM926EJ-S [41069265] revision 5 (ARMv5TEJ), cr=00053177 CPU: VIVT data cache, VIVT instruction cache Machine: Atmel AT91SAM9X5-EK Memory policy: ECC disabled, Data cache writeback Clocks: CPU 400 MHz, master 133 MHz, main 12.000 MHz Built 1 zonelists in Zone order, mobility grouping on. Total pages: 32512 Kernel command line: mem=128M console=ttyS0,115200 mtdparts=atmel_nand:8M( bootstrap/uboot/kernel)ro,-(rootfs) ip=192.168.1.174 root=/dev/nfs rw nfsroot=192.168.1.147:/rootfs/rfs_samg25 PID hash table entries: 512 (order: -1, 2048 bytes) Dentry cache hash table entries: 16384 (order: 4, 65536 bytes) Inode-cache hash table entries: 8192 (order: 3, 32768 bytes) Memory: 128MB = 128MB total Memory: 125488k/125488k available, 5584k reserved, 0K highmem Virtual kernel memory layout: vector : 0xffff0000 - 0xffff1000 ( 4 kB)
fixmap : 0xfff00000 - 0xfffe0000 ( 896 kB)
DMA : 0xffa00000 - 0xffe00000 ( 4 MB)
vmalloc : 0xc8800000 - 0xfee00000 ( 870 MB)
lowmem : 0xc0000000 - 0xc8000000 ( 128 MB)
modules : 0xbf000000 - 0xc0000000 ( 16 MB) .init : 0xc0008000 - 0xc0029000 ( 132 kB)
.text : 0xc0029000 - 0xc041282c (4007 kB)
.data : 0xc0414000 - 0xc043bb00 ( 159 kB) NR_IRQS:192 AT91: 128 gpio irqs in 4 banks Console: colour dummy device 80x30 console [ttyS0] enabled Calibrating delay loop... 199.06 BogoMIPS (lpj=995328) pid_max: default: 32768 minimum: 301 Mount-cache hash table entries: 512 CPU: Testing write buffer coherency: ok devtmpfs: initialized NET: Registered protocol family 16 AT91: CM rev B and higher AT91: EK rev B and higher AT91: Power Management (with slow clock mode) AT91: Starting after user reset bio: create slab <bio-0> at 0 SCSI subsystem initialized usbcore: registered new interface driver usbfs usbcore: registered new interface driver hub usbcore: registered new device driver usb i2c-gpio i2c-gpio.0: using pins 62 (SDA) and 63 (SCL) at_hdmac at_hdmac.0: Atmel AHB DMA Controller ( cpy slave ), 8 channels at_hdmac at_hdmac.1: Atmel AHB DMA Controller ( cpy slave ), 8 channels Advanced Linux Sound Architecture Driver Version 1.0.24. Switching to clocksource tcb_clksrc NET: Registered protocol family 2 IP route cache hash table entries: 1024 (order: 0, 4096 bytes) TCP established hash table entries: 4096 (order: 3, 32768 bytes) TCP bind hash table entries: 4096 (order: 2, 16384 bytes) TCP: Hash tables configured (established 4096 bind 4096) TCP reno registered UDP hash table entries: 256 (order: 0, 4096 bytes) UDP-Lite hash table entries: 256 (order: 0, 4096 bytes) NET: Registered protocol family 1 RPC: Registered udp transport module. RPC: Registered tcp transport module. RPC: Registered tcp NFSv4.1 backchannel transport module. JFFS2 version 2.2. (NAND) (SUMMARY) © 2001-2006 Red Hat, Inc. msgmni has been set to 245 Block layer SCSI generic (bsg) driver version 0.4 loaded (major 253) io scheduler noop registered (default) atmel_usart.0: ttyS0 at MMIO 0xfefff200 (irq = 1) is a ATMEL_SERIAL cfg80211: Calling CRDA to update world regulatory domain atmel_usart.1: ttyS1 at MMIO 0xf801c000 (irq = 5) is a ATMEL_SERIAL brd: module loaded loop: module loaded ssc ssc.0: Atmel SSC device at 0xc8870000 (irq 28) atmel_nand atmel_nand: Using dma0chan0 for DMA transfers. ONFI flash detected ONFI param page 0 valid NAND device: Manufacturer ID: 0x2c, Chip ID: 0xda (Micron MT29F2G08AAD) atmel_pmecc_init_params Scanning device for bad blocks 2 cmdlinepart partitions found on MTD device atmel_nand Creating 2 MTD partitions on "atmel_nand": 0x000000000000-0x000000800000 : "bootstrap/uboot/kernel" 0x000000800000-0x000010000000 : "rootfs" macb macb.0: eth0: Features changed: 0x00004800 -> 0x00004000 MACB_mii_bus: probed eth0: Atmel MACB at 0xf802c000 irq 24 (82:8a:d6:84:e7:3a) eth0: attached PHY driver [Davicom DM9161A] (mii_bus:phy_addr=0:00, irq=-1) ehci_hcd: USB 2.0 'Enhanced' Host Controller (EHCI) Driver atmel-ehci atmel-ehci: Atmel EHCI UHP HS atmel-ehci atmel-ehci: new USB bus registered, assigned bus number 1 atmel-ehci atmel-ehci: irq 22, io mem 0x00700000 atmel-ehci atmel-ehci: USB 2.0 started, EHCI 1.00 hub 1-0:1.0: USB hub found hub 1-0:1.0: 3 ports detected ohci_hcd: USB 1.1 'Open' Host Controller (OHCI) Driver at91_ohci at91_ohci: AT91 OHCI at91_ohci at91_ohci: new USB bus registered, assigned bus number 2 at91_ohci at91_ohci: irq 22, io mem 0x00600000 hub 2-0:1.0: USB hub found hub 2-0:1.0: 3 ports detected Initializing USB Mass Storage driver... usbcore: registered new interface driver usb-storage USB Mass Storage support registered. atmel_usba_udc atmel_usba_udc: MMIO registers at 0xf803c000 mapped at c887a000 atmel_usba_udc atmel_usba_udc: FIFO at 0x00500000 mapped at c8900000 qt1070 0-001b: can not read register, returned -6 qt1070 0-001b: ID -6 not supported at91_rtc at91_rtc: rtc core: registered at91_rtc as rtc0 AT91 Real Time Clock driver. i2c /dev entries driver usbcore: registered new interface driver usbhid usbhid: USB HID core driver asoc: wm8731-hifi <-> atmel-ssc-dai.0 mapping ok ASoC: at91sam9x5ek_init ok ALSA device list: #0: AT91SAM9X5 nf_conntrack version 0.5.0 (1960 buckets, 7840 max) ip_tables: (C) 2000-2006 Netfilter Core Team TCP cubic registered NET: Registered protocol family 17 lib80211: common routines for IEEE802.11 drivers Registering the dns_resolver key type at91_rtc at91_rtc: setting system clock to 2011-06-01 16:27:53 UTC (1306945673) atmel_mci atmel_mci.0: Using dma0chan1 for DMA transfers atmel_mci atmel_mci.0: Atmel MCI controller at 0xf0008000 irq 12, 1 slots atmel_mci atmel_mci.1: Using dma1chan0 for DMA transfers atmel_mci atmel_mci.1: Atmel MCI controller at 0xf000c000 irq 26, 1 slots
VFS: Cannot open root device "nfs" or unknown-block(0,255)
Please append a correct "root=" boot option; here are the available partitions:
1f00 8192 mtdblock0 (driver?)
1f01 253952 mtdblock1 (driver?)
Kernel panic - not syncing:
VFS: Unable to mount root fs on unknown-block(0, 255)
[<c002dce0>] (unwind_backtrace+0x0/0xe0) from [<c03101fc>] (panic+0x50/0x170) [<c03101fc>] (panic+0x50/0x170) from [<c0008d20>] (mount_block_root+0x234/ 0x284)
[<c0008d20>] (mount_block_root+0x234/0x284) from [<c0009028>] ( prepare_namespace
+0x160/0x1c0) [<c0009028>] (prepare_namespace+0x160/0x1c0) from [<c00089ac>] (kernel_init+ 0x10
0/0x13c) [<c00089ac>] (kernel_init+0x100/0x13c) from [<c002a754>] (kernel_thread_exit+ 0x0
/0x8)

Thanks..

So did you build the kernel with NFS support/driver?

The kernel crashed complaining about a missing driver, how did you build the kernel, and with what options, packages, etc.

I'm NOT able to see "Root File system on NFS" option in Network File System part of linux menuconfig..

Is there any patch to enable it?

I have built the kernel(2.6.39) using buildroot builder with at91sam9x5ek_defconfig configuration
I followed the below link:

http://www.at91.com/linux4sam/bin/view/ ... ldRoot_9x5

My kernel version is 2.6.39.. I selected this version using the buildroot menuconfig.
Even the patches are applied through buildroot builder I suppose..

Got the solution how to mount Root File System on NFS:

Add CONFIG_IP_PNP=y and CONFIG_ROOT_NFS=y in at91sam9x5ek_defconfig

"make at91sam9x5ek_defconfig" in the linux source directory..

Thanks for the support!!