Eee 701 Planetoid

2011/07/29

Troubleshooting NFS access problems on a Synology NAS device

Filed under: Software — Tags: , , — Tim @ 12:33

(I found this post in the blog’s “drafts” area; it seems I wrote it back in April (hence the references to my 701 still running Eeebuntu), but for some reason the piece was never published. I reckon it could still be of use to someone, and I don’t like to waste things I’ve spent time writing, so here is a quick delve into the Planetoid’s very own “dead letter office”…)

One of the things I really like about our Synology DS110j NAS device—being a user of at least two Linux-based PCs around the house—is that it offers just about every option for sharing files over a network that you can think of: SMB (Windows), AFP (Mac), WebDAV, FTP, SCP (I think) and NFS, to name just the ones that came to my mind. Most network-attached storage devices just give you Windows file-sharing (and if you’re lucky, FTP)—as, well, all computers “speak” SMB, don’t they?—so it’s welcome to find a NAS box which speaks so many “languages”!

Having two PCs running Linux in our house—my Eee 701 (Eeebuntu v3) and a “nettop” (Ubuntu Maverick Meerkat)—it made sense to set up NFS file-sharing, so that the machines could access the storage on the Synology box.

To cut a long story short, I managed to get this all working (in retrospect, I don’t quite know how it did), and all was well for a while. Then, a few weeks ago, our old ADSL modem/wireless router died on us, and we replaced it with a BT Home Hub 3 (very nice, does the job well, etc.).

It was around this time that I noticed something: the nettop PC was no longer mounting the NFS shares. Either the mount request would just sit there for ages and do nothing, or I was getting the dreaded “nfs.mount: access denied” message. I pored over the settings on the PCs and the Synology; everything seemed to match up, and there were no firewalls I was aware of on either side, which could be getting in the way.

For a while, I was even suspecting the Home Hub—there is a firewall on the device, and I wondered if, somehow, it could be blocking the ports required for NFS. I couldn’t see why this would be necessary within a home network, but I couldn’t think of any other possibility, so I started querying Web forums, to no immediate avail.

Last night, I was re-checking the NFS exports settings on the Synology (for what felt like the umpteenth time), and noticed something that had always been there, but which I hadn’t paid attention to before. The settings window contains some suggestions for valid syntax for specifying the IP address range, which will be allowed to access the NFS shares. I had specified the IP address range in the format XXX.XXX.XXX.*, which I thought would mean “all machines on our home LAN”… but this format wasn’t in the suggestions list.

I noticed one of the “valid syntax” suggestions was XXX.XXX.XXX.0/24, which I seemed to recall means “all machines in that range”, so I entered this into one of the NFS exports, and tried mounting the share from the Eee. Almost instantly, it worked… which led me to wonder why the old setting worked before but then suddenly didn’t, but I’m not going to look a gift horse in the mouth 🙂

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5 Comments »

  1. Amazing, thanks a lot.

    I’ve had the very same configuration (i.e 192.168.2.*) for over a year, and it has worked really well, and today it stopped working.

    What I did change in my setup, was that I added the two hosts which started misbehaving to my DNS server, then deconfigured an iSCSI device in one of my LINUX boxes. There and then, my NFS setup just died.

    I strongly suspect the DNS config more than my iSCSI config, though. It all started working again after I changed the nfs/exports configuration on my Synology DS1511+ to 192.168.2.0/24.

    //magnus

    Comment by Magnus — 2012/02/19 @ 17:10

  2. Thanks for commenting – I’m glad it helped you! 🙂

    Comment by Tim — 2012/02/19 @ 20:00

  3. I am sure now, the issue started after I added the two systems to my internal DNS, after which they were denied access by the Synology disk station. The reason why it worked with the 192.168.2.* entry, was that this matches the hostname if it is not in the DNS for any host in the range.

    As soon as it was entered in the DNS, the reverse lookup for the ip address (which the Synology tries to match as I configured the 192.168.2.*) will actually return something, which was not in the config. So it is actually working as designed, and the only solution (since I really do want to export the nfs share to all hosts on that network segment) was to configure it as 192.168.2.0/24. Problem solved.

    Thanks again!

    Comment by Magnus — 2012/02/20 @ 18:55

  4. Thanks !

    Issue here was the NAS own firewall that was active after upgrading from DSM 3.2 to 4.0.
    After deactivating it, i was able to access the Diskstation again via NFS….

    Comment by Akay Seyrek — 2012/04/06 @ 22:21

  5. Same problem here! But with a Drobo 5N and a BT Homehub 5 Infinity router – after switching router, the NFS mappings wouldn’t connect to the NAS, but changing from xxx.xxx.xxx.* to xxx.xxx.xxx.0/24 worked a treat!
    CrashPlan is now backing up all my stuff again 🙂

    Sorted!

    Comment by Dave Rix — 2016/08/27 @ 18:31


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