> elm and mutt fail when they use fcntl() to lock the mail spool file which
> is mounted over NFS in our case (/var/spool/mail served by SunOS 4.1.3 and
> mounted by Linux clients). strace shows that after fcntl() the variable
> errno is set to "No locks available". It worked when 2.0.36 kernel was
> used. It also works from SunOS clients.
> On Linux side: kernel 2.2.7, latest userland nfsd, lockd is compiled into
> the kernel. A test program showed that Linux-Linux locking didn't work
> Can someone explain it or point to relevant information sources?
File locking is not supported by the userland nfsd. If you want true
file locking, use knfsd. 2.0.x kernels supported local file locks
only: this is why they 'worked' (not at all), and 2.2.x will do the
same if you use the 'nolock' mount option.
In other words: Always compile mutt/elm/pine etc to use dotlocking or
some such workaround when you think you might want to use the userland
nfsd or a 2.0.x kernel, since posix file locking will never be
reliable in that case. (BSD file locking is not supported for 2.2.x
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