[Qemu-devel] NFS-root

[Qemu-devel] NFS-root

[Alexander E. Patrakov]

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I have experimented with NFS-root linux installations in qemu recently. 
Results follow. All of them are obtained with this command or its 
variations:

qemu -nographic -hda hda.dsk -m 64 -kernel bzImage -append 
"console=ttyS0 root=/dev/nfs ro nfsroot=10.0.2.2:/jail 
ip=10.0.2.15:10.0.2.2:::::off init=/bin/sh ide0=noprobe ide1=noprobe 
ide2=noprobe ide3=noprobe ide4=noprobe ide5=noprobe" -user-net

In /jail, there are dev/console, dev/null, bin/sh and libraries it 
depends upon. The directory is exported in /etc/exports in the following 
way:

/jail        (ro,insecure)

The .config file for 2.6.6 linux kernel used for this experiment is 
attached.

1) I have to create a dummy hard disk image because of that "-kernel 
requires -hda" check. The diskless configuration is perfectly valid, 
please remove the check.

2) Everything works perfectly with tun-tap networking (of course with IP 
addresses adjusted).

3) I cannot make the kernel mount the root filesystem via NFS over UDP 
if I use -user-net. However, if I replace nfsroot=10.0.2.2:/jail with 
nfsroot=10.0.2.2:/jail,tcp everything works.

Why does the difference exist between tun-tap and slirp cases when UDP 
is used? Is this a bug?

-- 
Alexander E. Patrakov

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