oracular (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.  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

SEE ALSO

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

                                                                                                  NFS.SYSTEMD(7)