NFS Troubleshooting

NFS Troubleshooting

As you recall the setting up NFS on clients and a storage system involves:

1.       Licensing NFS on the storage system.

2.       Configuring and starting the NFS services.

3.       Exporting the file system on the storage system.

4.       Mounting file systems on clients.

Steps To configure NFS:

Step1: licensing NFS on storage system.

license add command

Step2: configure the NFS service:

Set the version of NFS to use.

Set the transport protocol (TCP,User Datagram Protocol, or UDP)

Nfs on command.

Step3: Exporting file system to the storage system:

Updating /etc/exports file as needed.

Running the exportfs command

Filerview administration tool

Step 4: Mounting file system on clients

Running mount command

Updating /etc/fstab

During the troubleshooting the NFS we need to investigate on storage system, client, Network.

Storage system:

1 Verify NFS service

-NFS licensed

-NFS properly configured

-Interface properly configured.

2. Verify export

-exportfs –v

-/etc/exports

Hostname to IP resolution

Can you turn hostnames into IP addresses?

-          If not, look at:

. nsswitch.conf

. hosts file

. resolv.conf

. On the storage system , DNS or NIS options

. Changing the order of DNS or NIS servers

. Consider circumventing DNS/NIS by temporarily entering hosts into the hosts file.

Remember:

-Data ontap caches NIS maps in slave mode.

-Data ONTAP caches DNS.

The nsswitch.conf file is the place to start when troubleshooting name-resolution issues. Make sure that you are using the name services you intend to be using. If that file is correct, move to the services listed: files= /etc/hosts, DNS=/etc/resolv.conf , NIS= domainname and ypwhich for starters.

Remember, there are several options in Data ONTAP used to configure and manage DNS:

dns.cache.enable – used to enable/disable DNS name –resolution caching.

dns.domainname – the storage system DNS domain name.

dns.enable – enable /disable DNS name resolution.

dns.update.enable – used to dynamically update the storage system ‘A’ record.

dns.update.ttl – time to live for a dynamically inserted ‘A’ record.

One troubleshooting method when dealing with name resolution problem is to enter hostname/addresses in the /etc/hosts file to the storage system or hosts, thereby eliminating the external name resolution services.

Remember that Network information service (NIS) maps in slave mode are cache as well as DNS. You can flush the DNS cache at any time by entering the “dns flush” command.

Client system:

-ping, dig, host, getnet

-ypwhich, ypcat, domainanme

- showmount –e|-a

- /etc/init.d/autofs start|stop

-nfsstat –m

Check:

- /etc/nsswitch.conf

- /etc/vfstab or /etc/fstab

- /etc/resolv.conf

- /etc/mtab

Dig – Use dig (domain information groper) to gather information from the DNS servers.

Host – A simple utility for performing DNS lookups. It is normally used to convert names to IP addresses and vice versa.

Getent- gets a list of entries from the administrative databases. For exp:

# getent passwd

Or

# getent hosts v210- inst

The yp* commands are used to examine the NIS configuration.

ypwhich – rename the name of the NIS server that supplies the NIS name services to the NIS client.

ypcat mapname- prints the values of all keys from the NIS database specified by mapname.

domainname- show or sets the system NIS domain name.

showmount- Queries the mount daemon on a remote host for information about the state of the NFS server on that machine

Autofs – controls the operation of the automount daemons.

nfsstat –display statistical information about the NFS and remote procedure call(RPC) interface to the kernel.

Check for the ports they must be open on clients and storage systems.

Portmap TCP 111

Nfsd TCP 2049

Mountd TCP 4046

Hard Mount and soft mount

Unix client can mount either:

Soft:- clients try to mount export a few times and then return an error.

Hard:- clients will continue to send out mount request indefinitely until the server responds.

Automounter:- Using the NFS automounter feature on NFS clients generates an automount map file on the NFS server that contains entries for every file system that is permanently exported for NFS access, after creating and resolving conflicts in the file , this map file can be copied to NFS clients or the Network information service (NIS) server to use as input to the automounter configuration.

Network:

The “cleaner” the better

-Matched parameters all the way through

-Not saturated (no quality of service in Ethernet)

-Auto versus half/full duplex.

Use TCP instead of UDP

-TCP is acknowledged

-UDP is not acknowledged

Are there firewalls (network or clients) in the way?

-Remember RPC ports should not be blocked.