man > nfs.systemd(7)

NFS.SYSTEMD(7)                    Miscellaneous Information Manual                    NFS.SYSTEMD(7)

NAME
       nfs.systemd - managing NFS services through systemd.

SYNOPSIS
       nfs-utils.service
       nfs-server.service
       nfs-client.target
       etc

DESCRIPTION
       The nfs-utils package provides a suite of systemd unit files which allow the various services
       to be started and managed.  These unit files ensure that the services are started in the cor‐
       rect  order,  and the prerequisites are active before dependant services start.  As there are
       quite  few unit files, it is not immediately obvious how best  to  achieve  certain  results.
       The following subsections attempt to cover the issues that are most likely to come up.

   Configuration
       The  standard  systemd  unit files do not provide any easy way to pass any command line argu‐
       ments to daemons so as to configure their behavior.  In many case such configuration  can  be
       performed  by making changes to /etc/nfs.conf or other configuration files.  When that is not
       convenient, a distribution might provide systemd "drop-in" files which replace the ExecStart=
       setting to start the program with different arguments.   For  example  a  drop-in  file  sys‐
       temd/system/nfs-mountd.service.d/local.conf containing
              [Service]
              EnvironmentFile=/etc/sysconfig/nfs
              ExecStart=
              ExecStart= /usr/sbin/rpc.mountd $RPCMOUNTDOPTS
       would  cause  the nfs-mountd.service unit to run the rpc.mountd program using, for arguments,
       the value given for RPCMOUNTDOPTS in /etc/sysconfig/nfs.  This allows for  seamless  integra‐
       tion with existing configuration tools.

   Enabling unit files
       There  are  three unit files which are designed to be manually enabled.  All others are auto‐
       matically run as required.  The three are:

       nfs-client.target
              This should be enabled on any host which ever serves as an NFS client.  There is  lit‐
              tle cost in transparently enabling it whenever NFS client software is installed.

       nfs-server.service
              This  must be enabled to provide NFS service to clients.  It starts and configures the
              required daemons in the required order.

       nfs-blkmap.service
              The blkmapd daemon is only required on NFS clients  which  are  using  pNFS  (parallel
              NFS),  and  particularly using the blocklayout layout protocol.  If you might use this
              particular extension to NFS, the nfs-blkmap.service unit should be enabled.

       Several other units which might be considered to be optional, such  as  rpc-gssd.service  are
       careful  to  only start if the required configuration file exists.  rpc-gssd.service will not
       start if the krb5.keytab file does not exist (typically in /etc).

   Restarting NFS services
       Most NFS daemons can be restarted at any time.  They will reload any state  that  they  need,
       and continue servicing requests.  This is rarely necessary though.

       When  configuration changesare make, it can be hard to know exactly which services need to be
       restarted to ensure that the configuration takes effect.  The simplest approach, which is of‐
       ten the best, is to restart everything.  To help with this,  the  nfs-utils.service  unit  is
       provided.  It declares appropriate dependencies with other unit files so that
              systemctl restart nfs-utils
       will  restart all NFS daemons that are running.  This will cause all configuration changes to
       take effect except for changes to mount options lists in  /etc/fstab  or  /etc/nfsmount.conf.
       Mount  options  can  only  be changed by unmounting and remounting filesystem.  This can be a
       disruptive operation so it should only be done when the value justifies the cost.   The  com‐
       mand
              umount -a -t nfs; mount -a -t nfs
       should unmount and remount all NFS filesystems.

   Masking unwanted services
       Rarely  there  may  be  a desire to prohibit some services from running even though there are
       normally part of a working NFS system.  This may be needed to reduce system load  to  an  ab‐
       solute  minimum,  or  to reduce attack surface by not running daemons that are not absolutely
       required.

       Three particular services which this can apply to are rpcbind, idmapd, and rpc-gssd.  rpcbind
       is not part of the nfs-utils package, but it used by several NFS services.  However it is not
       needed when only NFSv4 is in use.  If a site will never use NFSv3 (or  NFSv2)  and  does  not
       want rpcbind to be running, the correct approach is to run
              systemctl mask rpcbind
       This  will  disable  rpcbind,  and  the various NFS services which depend on it (and are only
       needed for NFSv3) will refuse to start, without interfering with the operation of NFSv4  ser‐
       vices.  In particular, rpc.statd will not run when rpcbind is masked.

       idmapd is only needed for NFSv4, and even then is not needed when the client and server agree
       to  use  user-ids  rather  than user-names to identify the owners of files.  If idmapd is not
       needed and not wanted, it can be masked with
              systemctl mask idmapd
       rpc-gssd is assumed to be needed if the krb5.keytab file is present.  If a  site  needs  this
       file present but does not want rpc-gssd running, it can be masked with
              systemctl mask rpc-gssd

FILES
       /etc/nfs.conf
       /etc/nfsmount.conf
       /etc/idmapd.conf

SEE ALSO
       systemd.unit(5), nfs.conf(5), nfsmount.conf(5).

                                                                                      NFS.SYSTEMD(7)