Support #251
Updated by Daniel Curtis over 10 years ago
NFS mounts work to share a directory between several virtual servers. This has the advantage of saving disk space, as the home directory is only kept on one virtual private server, and others can connect to it over the network. When setting up mounts, NFS is most effective for permanent fixtures that should always be accessible. Setup An NFS mount is set up between at least two virtual servers. The machine hosting the shared network is called the server, while the ones that connect to it are called ‘clients’. This tutorial requires 2 servers: one acting as the server and one as the client. We will set up the server machine first, followed by the client. The following IP addresses will refer to each one: * Master: 192.168.10.10 * Client: 192.168.10.200 The system should be set up as root. You can access the root user by typing: <pre> sudo su- </pre> h1. Setting Up the NFS Server h2. 1 - Download the Required Software Start off by using @apt-get@ to install the nfs programs. <pre> apt-get install nfs-kernel-server portmap </pre> h2. 2 - Export the Shared Directory The next step is to decide which directory we want to share with the client server. The chosen directory should then be added to the @/etc/exports@ file, which specifies both the directory to be shared and the details of how it is shared. Suppose we wanted to share two directories: @/home@ and @/var/nfs@. Because the @/var/nfs/@ does not exist, we need to do two things before we can export it. First, we need to create the directory itself: <pre> mkdir /var/nfs/ </pre> Second, we should change the ownership of the directory to the user, nobody and the group, no group. These represent the default user through which clients can access a directory shared through NFS. Go ahead and chown the directory: <pre> chown nobody:nogroup /var/nfs </pre> After completing those steps, it’s time to export the directories to the other VPS: <pre> nano /etc/exports </pre> Add the following lines to the bottom of the file, sharing both directories with the client: <pre> /home 192.168.10.200(rw,sync,no_root_squash,no_subtree_check) /var/nfs 192.168.10.200(rw,sync,no_subtree_check) </pre> These settings accomplish several tasks: * *rw*: This option allows the client server to both read and write within the shared directory * *sync*: Sync confirms requests to the shared directory only once the changes have been committed. * *no_subtree_check*: This option prevents the subtree checking. When a shared directory is the subdirectory of a larger filesystem, nfs performs scans of every directory above it, in order to verify its permissions and details. Disabling the subtree check may increase the reliability of NFS, but reduce security. * *no_root_squash*: This phrase allows root to connect to the designated directory *Note*: An export can be set to individual IP addresses or networks: > NFS clients may be specified in a number of ways: > single host > You may specify a host either by an abbreviated name recognized be the resolver, the fully qualified domain name, an IPv4 address, or an IPv6 address. IPv6 addresses must not be inside square brackets in /etc/exports lest they be confused with character-class wildcard matches. > netgroups > NIS netgroups may be given as @group. Only the host part of each netgroup members is consider in checking for membership. Empty host parts or those containing a single dash (-!) (-) are ignored. > wildcards > +Machine names may contain the wildcard characters * and ?, or may contain character class lists within [square brackets]. This can be used to make the exports file more compact; for instance, *.cs.foo.edu matches all hosts in the domain cs.foo.edu. As these characters also match the dots in a domain name, the given pattern will also match all hosts within any subdomain of cs.foo.edu. > IP networks > You can also export directories to all hosts on an IP (sub-!) (sub-) network simultaneously. This is done by specifying an IP address and netmask pair as address/netmask where the netmask can be specified in dotted-decimal format, or as a contiguous mask length. For example, either '/255.255.252.0' or '/22' appended to the network base IPv4 address results in identical subnetworks with 10 bits of host. IPv6 addresses must use a contiguous mask length and must not be inside square brackets to avoid confusion with character-class wildcards. Wildcard characters generally do not work on IP addresses, though they may work by accident when reverse DNS lookups fail. Once you have entered in the settings for each directory, run the following command to export them: <pre> exportfs -a </pre> If any mistakes are mades, you can unmount the exports via: <pre> exportfs -ua </pre> h1. Setting Up the NFS Client h2. 1 - Download the Required Software Start off by using @apt-get@ to install the nfs programs. <pre> apt-get install nfs-common portmap </pre> h2. 2 - Mount the Directories Once the programs have been downloaded to the the client server, create the directories that will contain the NFS shared files <pre> mkdir -p /mnt/nfs/home mkdir -p /mnt/nfs/var/nfs </pre> Then go ahead and mount them <pre> mount 192.168.10.10:/home /mnt/nfs/home mount 192.168.10.10:/var/nfs /mnt/nfs/var/nfs </pre> You can use the @df -h@ command to check that the directories have been mounted. You will see them last on the list. <pre> df -h </pre> <pre> Filesystem Size Used Avail Use% Mounted on /dev/sda 100G 9480M 90G 5% / udev 119M 4.0K 119M 1% /dev tmpfs 49M 208K 49M 1% /run none 5.0M 0 5.0M 0% /run/lock none 122M 0 122M 0% /run/shm 192.168.10.10:/home 500G 510M 499.5G 5% /mnt/nfs/home 192.168.10.10:/var/nfs 500G 510M 499.5G 5% /mnt/nfs/var/nfs </pre> Additionally, use the mount command to see the entire list of mounted file systems. <pre> mount </pre> Your list should look something like this: > /dev/sda on / type ext4 (rw,errors=remount-ro,barrier=0) [DOROOT] > proc on /proc type proc (rw,noexec,nosuid,nodev) > sysfs on /sys type sysfs (rw,noexec,nosuid,nodev) > none on /sys/fs/fuse/connections type fusectl (rw) > none on /sys/kernel/debug type debugfs (rw) > none on /sys/kernel/security type securityfs (rw) > udev on /dev type devtmpfs (rw,mode=0755) > devpts on /dev/pts type devpts (rw,noexec,nosuid,gid=5,mode=0620) > tmpfs on /run type tmpfs (rw,noexec,nosuid,size=10%,mode=0755) > none on /run/lock type tmpfs (rw,noexec,nosuid,nodev,size=5242880) > none on /run/shm type tmpfs (rw,nosuid,nodev) > rpc_pipefs on /run/rpc_pipefs type rpc_pipefs (rw) > 192.168.10.10:/home on /mnt/nfs/home type nfs (rw,vers=4,addr= 192.168.10.10,clientaddr=192.168.10.200) > 192.168.10.10:/var/nfs on /mnt/nfs/var/nfs type nfs (rw,vers=4,addr=192.168.10.10,clientaddr=192.168.10.200) h2. Testing the NFS Mount Once you have successfully mounted your NFS directories, you can test that they work by creating files on the Client and checking their availability on the Server. Create a file in each directory to try it out: <pre> touch /mnt/nfs/home/example /mnt/nfs/var/nfs/example </pre> You should then be able to find the files on the Server in the /home and /var/nfs directories. <pre> ls /home ls /var/nfs/ </pre> You can ensure that the mount is always active by adding the directories to the fstab file on the client. This will ensure that the mounts start up after the server reboots. <pre> nano /etc/fstab </pre> Then add the following at the end <pre> 192.168.10.10:/home /mnt/nfs/home nfs auto,noatime,nolock,bg,nfsvers=3,intr,tcp,actimeo=1800 0 0 192.168.10.10:/var/nfs /mnt/nfs/var/nfs nfs auto,noatime,nolock,bg,nfsvers=3,intr,tcp,actimeo=1800 0 0 </pre> You can learn more about the fstab options by typing in: <pre> man nfs </pre> Any subsequent restarts will include the NFS mount—although the mount may take a minute to load after the reboot You can check the mounted directories with the two earlier commands: df -h mount h3. Removing the NFS Mount Should you decide to remove a directory, you can unmount it using the @umount@ command: <pre> cd sudo umount /directory name </pre> You can see that the mounts were removed by then looking at the filesystem again. <pre> df -h </pre> You should find your selected mounted directory gone. h1. Resources * https://www.digitalocean.com/community/articles/how-to-set-up-an-nfs-mount-on-ubuntu-12-04 * http://linux.die.net/man/5/exports