On Apr 21, 2015, at 10:45 AM, Mason <slash.tmp@xxxxxxx> wrote: > Hello Chuck, > > On 21/04/2015 16:07, Chuck Lever wrote: > >> On Apr 21, 2015, at 4:37 AM, Mason wrote: >> >>> Hello, >>> >>> On 01/04/2015 11:55, Mason wrote: >>> >>>> My embedded system is supposed to mount the rootfs via NFS. >>>> https://www.kernel.org/doc/Documentation/filesystems/nfs/nfsroot.txt >>>> >>>> So I set these options in my kernel .config >>>> >>>> CONFIG_IP_PNP=y >>>> CONFIG_IP_PNP_DHCP=y >>>> CONFIG_ROOT_NFS=y >>>> CONFIG_NFS_V4=y >>>> >>>> But it didn't work, the system would panic after a long time out >>>> (around 95 seconds) >>>> >>>> [ 98.567037] VFS: Unable to mount root fs via NFS, trying floppy. >>>> [ 98.573238] Freeing unused kernel memory: 144K (c0332000 - c0356000) >>>> [ 98.579698] Kernel panic - not syncing: No working init found. >>>> Try passing init= option to kernel. See Linux Documentation/init.txt for guidance. >>>> >>>> I then enabled NFSv2 and NFSv3, and then it worked. >>>> >>>> When I was debugging the problem, I ran across NFS_DEF_OPTIONS >>>> in fs/nfs/nfsroot.c >>>> >>>> #define NFS_DEF_OPTIONS "vers=2,udp,rsize=4096,wsize=4096" >>>> >>>> IIUC, we are explicitly requesting NFSv2? >>>> >>>> Would that explain why it fails when NFSv2 support is not compiled in? >>>> >>>> Would it make sense to use version 3? >>>> (So NFSv2 is not needed just to load the rootfs.) >>> >>> I saw commit 4251c94833aa (NFS: Revert NFSROOT default mount options) >>> which states: >>> >>> Last fall we removed the ad hoc mount option parser in >>> fs/nfs/nfsroot.c in favor of using the main parser in fs/nfs/super.c >>> (see commit 56463e50 "NFS: Use super.c for NFSROOT mount option >>> parsing"). That commit changed the default NFSROOT mount options to >>> be the same as those employed by user space mounts. >>> As it turns out, these new default mount options are not tolerated by >>> many embedded systems. So far these problems have been due to >>> specific behavior of certain embedded NICs. The NFS community does >>> not have such hardware on hand for running tests. >>> Commit 53d47375 recently introduced a clean way to specify default >>> mount options for NFSROOT, so we can now easily restore the >>> traditional defaults for NFSROOT: >>> vers=2,udp,rsize=4096,wsize=4096 >>> This should revert the new default NFSROOT mount options introduced >>> with commit 56463e50. >>> >>> I guess this explains why vers=3 is not the default? >>> >>> I'm now wondering how to override the mount options on the boot command >>> line. Looking more closely at commit 53d473758053 (NFS: NFSROOT should >>> default to "proto=udp") nothing jumps out at me. >>> >>> My current boot command line is >>> "root=/dev/nfs ip=:::::eth0:dhcp rdinit=/none console=ttyS0,115200 mem=512M earlyprintk" >>> >>> Looking at the documentation >>> https://www.kernel.org/doc/Documentation/filesystems/nfs/nfsroot.txt >>> I don't see where the protocol version is specified. >>> >>> Where am I supposed to add the vers=3 option? >> >> Let's try that again. >> >> Specifying “vers=3” in the nfs-options section of the nfsroot= boot >> parameter should work. > > Hmmm, I don't have nfsroot= in my boot command line. > nfsroot=[<server-ip>:]<root-dir>[,<nfs-options>] nfsroot= is the way that NFSROOT mount options are specified. Without that kernel boot parameter, NFSROOT won’t work. > In U-Boot, DHCP sets a root-path environment variable to > "172.27.64.1:/export/roots/6_2_0_8756" > > Is root-path an alias for nfsroot? RFC 2132 Section 3.19 defines Root Path as option 17, which provides a DHCP client with the location of it’s root disk. root-path is the API on your DHCP server that lets you specify the contents of option 17. DHCP clients use the contents of option 17 to construct a kernel boot command line. > I tried > root-path = "172.27.64.1:/export/roots/6_2_0_8756,vers=3" > root-path = "172.27.64.1:/export/roots/6_2_0_8756,v3" > (second form suggested in the link below) > but neither worked :-( > > This page mentions root-path > http://developer.toradex.com/software-resources/arm-family/linux/linux-booting > option root-path "192.168.10.1:/srv/nfs/rootfs,wsize=1024,rsize=1024,v3”; You might have better luck with this: http://wiki.emacinc.com/wiki/Booting_with_an_NFS_Root_Filesystem It explains how to specify client kernel boot commandline parameters on your DHCP server that will make NFSROOT work. -- Chuck Lever chuck[dot]lever[at]oracle[dot]com -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
