plucky (7) nfs.systemd.7.gz

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 correct 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 arguments 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  (see  nfs.conf(5)).   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   systemd/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 integration with existing
       configuration tools.

   Enabling unit files
       There are three unit files which are designed to be manually enabled.  All others are  automatically  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 little 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 often 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 command
              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 absolute 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  services.   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

       Also similar files in /usr/etc and in related conf.d drop-in directories.

SEE ALSO

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

                                                                                                  NFS.SYSTEMD(7)