Broken NFS server (or client?)
mrp at sonic.net
Thu Aug 9 17:33:48 PDT 2001
Should you be exporting the server's root fs? I occurs to me that
unix/linux weren't designed with the idea that multiple machines banging
on the same filesystem. At the very least, the /var and /tmp
should be different for different clients.
When I've seen diskless client setups, each client usually has an
individual /var mount (or /var is on a ramdisk, and created at boot).
I would create a single client root partition, and put that in something
like /export/clientroot/ on the server and export that. I'd also create
a per-client /var partition, and have /tmp put on a ramdisk on the
On Thursday, August 9, 2001, at 02:58 PM, Lincoln Peters wrote:
>> From: ME <dugan at passwall.com>
>> Reply-To: <talk at nblug.org>
>> To: talk at nblug.org
>> Subject: Re: Broken NFS server (or client?)
>> Date: Wed, 8 Aug 2001 21:50:37 -0700 (PDT)
>> On Wed, 8 Aug 2001, Lincoln Peters wrote:
>> > >I assume the test client has a local HD since you have LILO being
>> used for
>> > >the netboot testing. This is true?
>> > No, LILO is installed on the boot floppy. There is no hard disk.
>> > (although since it's a VMWare virtual machine, I can add one with
>> > difficulty)
>> Might be an option, but check other things for now. :-)
>> > >When you boot the client from the local disk, are you able to nfs
>> > >the exported volume and use it as you desire to use with a netbooted
>> > >system?
>> > When I tried to mount the root filesystem on another client (it is
>> > to be mountable to any system that wants to mount it), I got a
>> similar error
>> > message.
>> Ahhhh. This is a good pointer. Lets have a look at the list of NFS
>> exports. Not sure if this is still going to be /etc/exports on your
>> NFS server, but it is a place to look. I really want to see what
>> rules/permissions you have for the export (who can look at it as well
>> ro?rw?) also could you show the ls -l of the volume and make sure that
>> of the dirs leading up to the volume share point are at the very
>> least +x
>> for everyone and just for testing rwxr-xr-x (755).
> There is only one line in /etc/exports:
> / (rw) # Root filesystem (for diskless clients)
>> As the other poster wrote:
>> > From: Mark Street <jet at sonic.net>
>> > Do you have portmapper running? Is it started before nfsutils?
>> which is another very good point in this same direction.
>> Also, related to the excellent point from Mark:
>> Do you have any firewall rules on the server that we should know about?
>> Really, it gets to the direction of thought:
>> Can you do it with another non-NFSroot client? If you can't, then
>> focus on
>> the server side. Once you can get a different disk based client to NFS
>> mount the export from the server, then we can look back at the client
> There is no firewalling set up on the NFS server (I use a different
> computer as a firewall). However, I tried mounting the NFS filesystem
> on my other test client (the one with a hard disk), and got a
> "Connection refused" error.
> Perhaps the server is malfunctioning rather than the client.
>> > >When you write about this error, are you saying that you can't even
>> > >your root filesystem via NFS from the client, or once you have the
>> > >machine net-booted in Linux you get this error when you ry to start
>> up the
>> > >vmware application?
>> > I can't mount the root filesystem via NFS. I don't think that
>> VMWare is
>> > causing any problems.
>> I agree with your conclusion based on the data we have so far. :-)
>> > >Does the client get a different IP address fron the network when it
>> > >netboots vs. when it is running from a local HD?
>> > It does not have a local HD, but since each system that I run with
>> > always seems to get the same IP address every time I run it (I'm not
>> > that they all share a single IP address), I can (hopefully) safely
>> > that the IP addresses are the same.
>> This would be another point for testing. Fire up your test-NFS client
>> one with a disk) and bind the same IP address you will use for the
>> that will be netbooting and mounting its root via NFS. This helps to
>> sure any IP based authentication or checks would otherwise pass when
>> IP is moved to the real netbooting client.
> There are not supposed to be any IP-based authentication checks, at
> least not yet. Although I supopse if the server is misconfigured, it
> might be trying to perform IP-based authentication using an empty list
> of valid machines.
> BTW, I can't have my test client with a hard disk bind to the address
> of the diskless test client because I don't know what the IP address
> is. I'm not even sure that the test client it is getting an IP address
> because I can't see any DHCP activity on the DHCP server when the
> client boots.
>> > >Is the error logged from the server or the client or both?
>> > The error can't be logged by the client since it has nowhere to log
>> to; it
>> > just gave me that "Error -101" message that I already described.
>> And I
>> > cannot find any NFS logs on the server.
>> So, the client just hangs in the middle of the kernel loading giving
>> grand message like
>> "Kernel panic unable to mount /"
> It gives me the NFS error I described earlier, then asks me to insert a
> floppy disk with a root filesystem.
>> > >"The client IP address is in the lilo configuration" how? is this an
>> > >"append=" statement? Often those are passed to scripts that do the
>> > >work of setting up your interfaces. Is it just getting its IP and
>> nfs root
>> > >server/volume from bootp/dhcp?
>> > The appended lines are:
>> > root=/dev/nfs
>> > nfsroot=192.168.0.6:/
>> This concerns me greatly. Are you really exporting your root "/" file
>> system from your server over NFS? Usually, you create a second system
>> in a new location off of the root file system like /usr/export/system1
>> then have your nfsroot= entry on the client look like:
>> and then have an entry in your /etc/exports on the server like:
>> /usr/export/system1 *.yourdomain.com(ro,insecure,all_squash)
>> or perhaps
>> /usr/export/system1 *.yourdomain.com(ro,all_squash)
>> and then make sure that either:
>> all of the ip addresses of client that will connect to NFS have valid
>> entires in the server's /etc/host file with FQDN (Fully Qualified
>> Names) *or* a DNS server that will provide zone support for reverse
>> of the IPs and make the *.yourdomain.com check for the incoming IP
>> (There are other ways, but this is the most common I think.)
>> One big issue with exporting your server's root over NFS is that even
>> is is ro, you may not have all_squash and an evil user may be able to
>> files they should not= from a client machine. Perhaps password files,
> This server probably does not have enough disk space to hold two
> operating system as you described. I see why it would be a good idea
> to use a different filesystem than the root filesystem, but I doubt
> that any of the users of this system would know anything about cracking
> Linux (although I recognize the possibility).
> Since nobody else is using either the client or the server at the
> moment, I'll worry about security once I have them working in some
>> > It is configured to get its network configuration from a DHCP server.
>> > However, I did notice that there is no entry in the DHCP log that
>> looks like
>> > my test client. The problem still appeared on the test client as an
>> > error, though.
>> This part confuses me:
>> > The problem still appeared on the test client as an NFS error,
>> So the problem and error appear on the screen of the test client, or
>> symptoms appear on the test client? The Server does still log the error
>> message in a server log file too, eh?
> The error I described appeared on the client's monitor. I could not
> find any records that refer to the test client on the DHCP server or
> the NFS server. Although I would expect that if neither was working,
> the DHCP error would stop the system before the NFS error would come up.
>> Mark Street <jet at sonic.net> has some good thoughts on troubleshooting
>> too. I'd go through his suggestions and look at his questions as well.
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