Provided by: corosync_3.0.3-2ubuntu2_amd64 bug

NAME

       corosync.conf - corosync executive configuration file

SYNOPSIS

       /etc/corosync/corosync.conf

DESCRIPTION

       The  corosync.conf  instructs  the  corosync  executive about various parameters needed to
       control the corosync executive.  Empty lines and  lines  starting  with  #  character  are
       ignored.  The configuration file consists of bracketed top level directives.  The possible
       directive choices are:

       totem { }
              This top level directive contains configuration options for the totem protocol.

       logging { }
              This top level directive contains configuration options for logging.

       quorum { }
              This top level directive contains configuration options for quorum.

       nodelist { }
              This top level directive contains configuration options for nodes in cluster.

       system { }
              This top level directive contains configuration options related to system.

       resources { }
              This top level directive contains configuration options for resources.

       nozzle { }
              This top level directive contains configuration options for a libnozzle device.

       The interface sub-directive of totem is optional for UDP and knet transports.

       For knet, multiple interface subsections define parameters  for  each  knet  link  on  the
       system.

       For  UDPU  an  interface  section is not needed and it is recommended that the nodelist is
       used to define cluster nodes.

       linknumber
              This specifies the link number for the interface.  When using  the  knet  protocol,
              each  interface  should  specify  separate link numbers to uniquely identify to the
              membership protocol which interface to use for which  link.   The  linknumber  must
              start at 0. For UDP the only supported linknumber is 0.

       knet_link_priority
              This  specifies the priority for the link when knet is used in 'passive' mode. (see
              link_mode below)

       knet_ping_interval
              This specifies the  interval  between  knet  link  pings.   knet_ping_interval  and
              knet_ping_timeout  are  a  pair,  if  one  is  specified  the  other should be too,
              otherwise one will be calculated from the token timeout and one will be taken  from
              the config file.  (default is token timeout / (knet_pong_count*2))

       knet_ping_timeout
              If  no  ping  is  received  within  this  time,  the  knet  link  is declared dead.
              knet_ping_interval and knet_ping_timeout are a pair, if one is specified the  other
              should be too, otherwise one will be calculated from the token timeout and one will
              be taken from the config file.  (default is token timeout / knet_pong_count)

       knet_ping_precision
              How many values of latency are used to calculate the average link latency. (default
              2048 samples)

       knet_pong_count
              How many valid ping/pongs before a link is marked UP. (default 2)

       knet_transport
              Which  IP  transport  knet  should use. valid values are "sctp" or "udp". (default:
              udp)

       bindnetaddr (udp only)
              This specifies the network address the corosync executive should bind to when using
              udp.

              bindnetaddr  (udp  only)  should  be  an  IP address configured on the system, or a
              network address.

              For example, if the local interface is 192.168.5.92 with netmask 255.255.255.0, you
              should  set  bindnetaddr to 192.168.5.92 or 192.168.5.0.  If the local interface is
              192.168.5.92 with netmask  255.255.255.192,  set  bindnetaddr  to  192.168.5.92  or
              192.168.5.64, and so forth.

              This  may  also be an IPV6 address, in which case IPV6 networking will be used.  In
              this case, the exact address must be specified and there is no automatic  selection
              of the network interface within a specific subnet as with IPv4.

              If IPv6 networking is used, the nodeid field in nodelist must be specified.

       broadcast (udp only)
              This is optional and can be set to yes.  If it is set to yes, the broadcast address
              will be used for communication.  If this option is set,  mcastaddr  should  not  be
              set.

       mcastaddr (udp only)
              This  is the multicast address used by corosync executive.  The default should work
              for most networks,  but  the  network  administrator  should  be  queried  about  a
              multicast  address  to  use.   Avoid 224.x.x.x because this is a "config" multicast
              address.

              This may also be an IPV6 multicast address, in which case IPV6 networking  will  be
              used.  If IPv6 networking is used, the nodeid field in nodelist must be specified.

              It's  not  necessary  to  use  this  option if cluster_name option is used. If both
              options are used, mcastaddr has higher priority.

       mcastport (udp only)
              This specifies the UDP port number.  It is  possible  to  use  the  same  multicast
              address on a network with the corosync services configured for different UDP ports.
              Please note corosync  uses  two  UDP  ports  mcastport  (for  mcast  receives)  and
              mcastport - 1 (for mcast sends).  If you have multiple clusters on the same network
              using the same mcastaddr please configure the mcastports with a gap.

       ttl (udp only)
              This specifies the Time To Live (TTL). If you run your cluster on a routed  network
              then  the  default of "1" will be too small. This option provides a way to increase
              this up to 255. The valid range is 0..255.

       Within the totem directive,  there  are  seven  configuration  options  of  which  one  is
       required,  five are optional, and one is required when IPV6 is configured in the interface
       subdirective.  The required directive controls the version  of  the  totem  configuration.
       The  optional option unless using IPV6 directive controls identification of the processor.
       The optional options control secrecy and authentication, the network mode of operation and
       maximum network MTU field.

       version
              This  specifies  the  version  of the configuration file.  Currently the only valid
              version for this directive is 2.

       clear_node_high_bit
              This configuration option is optional and  is  only  relevant  when  no  nodeid  is
              specified.   Some  corosync  clients require a signed 32 bit nodeid that is greater
              than zero however by default corosync uses all 32 bits of the  IPv4  address  space
              when  generating a nodeid.  Set this option to yes to force the high bit to be zero
              and therefore ensure the nodeid is a positive signed 32 bit integer.

              WARNING: Cluster behavior is undefined if this option is enabled on only  a  subset
              of the cluster (for example during a rolling upgrade).

       crypto_model
              This  specifies which cryptographic library should be used by knet. Options are nss
              and openssl.

              The default is nss.

       crypto_hash
              This specifies which  HMAC  authentication  should  be  used  to  authenticate  all
              messages.  Valid values are none (no authentication), md5, sha1, sha256, sha384 and
              sha512. Encrypted transmission is only supported for the knet transport.

              The default is none.

       crypto_cipher
              This specifies which cipher should be used to encrypt all messages.   Valid  values
              are  none  (no  encryption),  aes256,  aes192  and aes128.  Enabling crypto_cipher,
              requires also enabling of crypto_hash. Encrypted transmission is only supported for
              the knet transport.

              The default is none.

       secauth
              This  implies crypto_cipher=aes256 and crypto_hash=sha256, unless those options are
              explicitly set. Encrypted transmission is only supported for the knet transport.

              The default is off.

       keyfile
              This specifies the fully qualified path to the shared key used to authenticate  and
              encrypt data used within the Totem protocol.

              The default is /etc/corosync/authkey.

       key    Shared  key  stored in configuration instead of authkey file. This option has lower
              precedence than keyfile option so it's used only when  keyfile  is  not  specified.
              Using this option is not recommended for security reasons.

       link_mode
              This  specifies  the  Kronosnet  mode,  which may be passive, active, or rr (round-
              robin).  passive: the active link with the highest priority will be used. If one or
              more  links  share  the same priority the one with the lowest link ID will be used.
              active: All active links  will  be  used  simultaneously  to  send  traffic.   link
              priority  is ignored.  rr: Round-Robin policy. Each packet will be sent to the next
              active link in order.

              If only one interface directive is specified, passive is automatically chosen.

              The maximum number of interface directives that is allowed with Kronosnet is 8. For
              other transports it is 1.

       netmtu This  specifies  the network maximum transmit unit.  To set this value beyond 1500,
              the regular frame MTU, requires ethernet devices that support large, or also called
              jumbo,  frames.   If  any  device  in the network doesn't support large frames, the
              protocol will not operate properly.  The hosts must also have their  mtu  size  set
              from 1500 to whatever frame size is specified here.

              Please  note  while  some  NICs or switches claim large frame support, they support
              9000 MTU as the maximum frame size including the IP header.  Setting the netmtu and
              host  MTUs  to 9000 will cause totem to use the full 9000 bytes of the frame.  Then
              Linux will add a 18 byte header moving the full frame size to 9018.   As  a  result
              some  hardware  will not operate properly with this size of data.  A netmtu of 8982
              seems to work for the  few  large  frame  devices  that  have  been  tested.   Some
              manufacturers  claim  large  frame support when in fact they support frame sizes of
              4500 bytes.

              When sending multicast traffic, if the network frequently reconfigures, chances are
              that some device in the network doesn't support large frames.

              Choose hardware carefully if intending to use large frame support.

              The default is 1500.

       transport
              This  directive  controls  the transport mechanism used.  The default is knet.  The
              transport type can also be set to udpu or udp.  Only knet allows crypto or multiple
              interfaces per node.

       cluster_name
              This  specifies  the  name  of  cluster  and  it's used for automatic generating of
              multicast address.

       config_version
              This specifies version of config file. This is converted to  unsigned  64-bit  int.
              By  default it's 0. Option is used to prevent joining old nodes with not up-to-date
              configuration. If value is not 0, and node is going for first time (only for  first
              time,  join  after  split doesn't follow this rules) from single-node membership to
              multiple nodes membership, other nodes config_versions are  collected.  If  current
              node  config_version  is  not  equal  to highest of collected versions, corosync is
              terminated.

       ip_version
              This specifies version of IP to ask DNS resolver for.  The value can be one of ipv4
              (look only for an IPv4 address) , ipv6 (check only IPv6 address) , ipv4-6 (look for
              all address families and use first IPv4 address found in the list if there is  such
              address,  otherwise  use  first  IPv6  address)  and  ipv6-4  (look for all address
              families and use first IPv6 address found in the list if  there  is  such  address,
              otherwise use first IPv4 address).

              Default (if unspecified) is ipv6-4 for knet and udpu transports and ipv4 for udp.

              The knet transport supports IPv4 and IPv6 addresses concurrently, provided they are
              consistent on each link.

              Within the totem directive, there are several configuration options which are  used
              to  control  the  operation  of  the  protocol.  It is generally not recommended to
              change any of these values without proper guidance and  sufficient  testing.   Some
              networks  may  require  larger  values if suffering from frequent reconfigurations.
              Some applications may require faster failure detection times which can be  achieved
              by reducing the token timeout.

       token  This  timeout  is  used  directly  or  as a base for real token timeout calculation
              (explained in token_coefficient section). Token timeout specifies  in  milliseconds
              until a token loss is declared after not receiving a token.  This is the time spent
              detecting a failure of a processor in the current configuration.  Reforming  a  new
              configuration takes about 50 milliseconds in addition to this timeout.

              For  real  token  timeout  used  by  totem  it's  possible  to  read  cmap value of
              runtime.config.totem.token key.

              Be careful to use the same timeout values on each of the nodes in  the  cluster  or
              unpredictable results may occur.

              The default is 1000 milliseconds.

       token_warning
              Specifies  the interval between warnings that the token has not been received.  The
              value is a percentage of the token timeout and can be set to 0 to disable warnings.

              The default is 75%.

       token_coefficient
              This value is used only when nodelist section is specified and contains at least  3
              nodes.  If so, real token timeout is then computed as token + (number_of_nodes - 2)
              * token_coefficient.  This allows cluster to scale without manually changing  token
              timeout  every  time  new  node  is  added. This value can be set to 0 resulting in
              effective removal of this feature.

              The default is 650 milliseconds.

       token_retransmit
              This timeout specifies in milliseconds after how long before receiving a token  the
              token  is  retransmitted.   This  will  be  automatically  calculated  if  token is
              modified.  It is not recommended to alter this  value  without  guidance  from  the
              corosync community.

              The  minimum  is  30  milliseconds.  If  not set and error occur, make sure token /
              (token_retransmits_before_loss_const + 0.2) is more than 30.

              The default is 238  milliseconds  for  two  nodes  cluster.  Three  or  more  nodes
              reference token_coefficient.

       knet_compression_model
              Type of compression used by Kronosnet. Supported values depend on the libknet build
              and on the  installed  compression  libraries.  Typically  zlib  and  lz4  will  be
              available but bzip2 and others could also be allowed. The default is 'none'.

       knet_compression_threshold
              Tells  knet  to NOT compress any packets that are smaller than the value indicated.
              Default 100 bytes.

              Set to 0 to reset to the default.  Set to 1 to compress everything.

       knet_compression_level
              Many compression libraries allow tuning of compression parameters. For example 0 or
              1  ...  9  are  commonly  used to determine the level of compression. This value is
              passed unmodified to the compression library so it is recommended  to  consult  the
              library's documentation for more detailed information.

       hold   This  timeout  specifies  in  milliseconds how long the token should be held by the
              representative when the protocol is under low utilization.   It is not  recommended
              to alter this value without guidance from the corosync community.

              The default is 180 milliseconds.

       token_retransmits_before_loss_const
              This value identifies how many token retransmits should be attempted before forming
              a new configuration. It is also used for token_retransmit and hold calculations.

              The default is 4 retransmissions.

       join   This timeout specifies in milliseconds how long to wait for join  messages  in  the
              membership protocol.

              The default is 50 milliseconds.

       send_join
              This  timeout  specifies  in milliseconds an upper range between 0 and send_join to
              wait before sending a join message.  For configurations with less  than  32  nodes,
              this  parameter is not necessary.  For larger rings, this parameter is necessary to
              ensure the NIC is not overflowed with join messages on formation of a new ring.   A
              reasonable  value  for large rings (128 nodes) would be 80msec.  Other timer values
              must also change if this value is changed.  Seek advice from the  corosync  mailing
              list if trying to run larger configurations.

              The default is 0 milliseconds.

       consensus
              This  timeout  specifies  in  milliseconds  how  long  to  wait for consensus to be
              achieved before starting a new round  of  membership  configuration.   The  minimum
              value  for  consensus  must  be  1.2  *  token.   This  value will be automatically
              calculated at 1.2 * token if the user doesn't specify a consensus value.

              For two node clusters, a consensus larger than the join timeout but less than token
              is safe.  For three node or larger clusters, consensus should be larger than token.
              There is an increasing risk  of  odd  membership  changes,  which  still  guarantee
              virtual synchrony,  as node count grows if consensus is less than token.

              The default is 1200 milliseconds.

       merge  This  timeout  specifies  in  milliseconds  how  long to wait before checking for a
              partition when no multicast traffic is being sent.  If multicast traffic  is  being
              sent, the merge detection happens automatically as a function of the protocol.

              The default is 200 milliseconds.

       downcheck
              This  timeout  specifies  in  milliseconds  how long to wait before checking that a
              network interface is back up after it has been downed.

              The default is 1000 milliseconds.

       fail_recv_const
              This constant specifies how many rotations of the token without  receiving  any  of
              the  messages when messages should be received may occur before a new configuration
              is formed.

              The default is 2500 failures to receive a message.

       seqno_unchanged_const
              This constant specifies how many rotations  of  the  token  without  any  multicast
              traffic should occur before the hold timer is started.

              The default is 30 rotations.

       heartbeat_failures_allowed
              [HeartBeating  mechanism] Configures the optional HeartBeating mechanism for faster
              failure detection. Keep in mind that engaging  this  mechanism  in  lossy  networks
              could  cause  faulty  loss  declaration  as the mechanism relies on the network for
              heartbeating.

              So as a rule of thumb use this mechanism if you require improved failure in low  to
              medium utilized networks.

              This constant specifies the number of heartbeat failures the system should tolerate
              before declaring heartbeat failure e.g 3. Also if this value is not  set  or  is  0
              then the heartbeat mechanism is not engaged in the system and token rotation is the
              method of failure detection

              The default is 0 (disabled).

       max_network_delay
              [HeartBeating mechanism] This constant specifies in  milliseconds  the  approximate
              delay  that your network takes to transport one packet from one machine to another.
              This value is to be set by system engineers and please don't change if not sure  as
              this effects the failure detection mechanism using heartbeat.

              The default is 50 milliseconds.

       window_size
              This  constant  specifies  the  maximum  number of messages that may be sent on one
              token rotation.  If all processors perform equally well, this value could be  large
              (300),  which  would introduce higher latency from origination to delivery for very
              large rings.  To reduce latency in  large  rings(16+),  the  defaults  are  a  safe
              compromise.   If  1  or  more  slow processor(s) are present among fast processors,
              window_size should be no larger than 256000 /  netmtu  to  avoid  overflow  of  the
              kernel  receive  buffers.   The  user  is  notified  of  this  by  the display of a
              retransmit list  in  the  notification  logs.   There  is  no  loss  of  data,  but
              performance is reduced when these errors occur.

              The default is 50 messages.

       max_messages
              This  constant  specifies  the  maximum  number of messages that may be sent by one
              processor on receipt of the token.  The max_messages parameter is limited to 256000
              / netmtu to prevent overflow of the kernel transmit buffers.

              The default is 17 messages.

       miss_count_const
              This  constant  defines the maximum number of times on receipt of a token a message
              is checked for retransmission before a retransmission occurs.   This  parameter  is
              useful  to  modify  for  switches  that delay multicast packets compared to unicast
              packets.  The default setting works well for nearly all modern switches.

              The default is 5 messages.

       knet_pmtud_interval
              How often the knet PMTUd runs to look for network MTU changes.  Value  in  seconds,
              default: 30

       block_unlisted_ips
              Allow  UDPU  and  KNET  to drop packets from IP addresses that are not known (nodes
              which don't exist in the nodelist) to corosync.  Value is yes or no.

              This feature is mainly to protect  against  the  joining  of  nodes  with  outdated
              configurations  after  a  cluster  split.   Another use case is to allow the atomic
              merge of two independent clusters.

              Changing the default value is not recommended, the overhead is tiny and an existing
              cluster  may  fail  if  corosync  is  started  on  an  unlisted  node  with  an old
              configuration.

              The default value is yes.

       Within the logging directive, there  are  several  configuration  options  which  are  all
       optional.

       The following 3 options are valid only for the top level logging directive:

       timestamp
              This specifies that a timestamp is placed on all log messages. It can be one of off
              (no timestamp), on (second precision timestamp)  or  hires  (millisecond  precision
              timestamp - only when supported by LibQB).

              The default is hires (or on if hires is not supported).

       fileline
              This specifies that file and line should be printed.

              The default is off.

       function_name
              This specifies that the code function name should be printed.

              The default is off.

       blackbox
              This specifies that blackbox functionality should be enabled.

              The default is on.

       The  following  options  are  valid  both  for top level logging directive and they can be
       overridden in logger_subsys entries.

       to_stderr

       to_logfile

       to_syslog
              These specify the destination of logging output. Any combination of  these  options
              may be specified. Valid options are yes and no.

              The default is syslog and stderr.

              Please  note,  if  you  are  using  to_logfile  and  want  to  rotate the file, use
              logrotate(8) with the option copytruncate.  eg.
              /var/log/corosync.log {
                   missingok
                   compress
                   notifempty
                   daily
                   rotate 7
                   copytruncate
              }

       logfile
              If the to_logfile directive is set to yes , this option specifies the  pathname  of
              the log file.

              No default.

       logfile_priority
              This specifies the logfile priority for this particular subsystem. Ignored if debug
              is on.  Possible values are: alert, crit, debug (same as debug = on),  emerg,  err,
              info, notice, warning.

              The default is: info.

       syslog_facility
              This  specifies the syslog facility type that will be used for any messages sent to
              syslog. options are daemon, local0, local1, local2, local3, local4, local5,  local6
              & local7.

              The default is daemon.

       syslog_priority
              This  specifies the syslog level for this particular subsystem. Ignored if debug is
              on.  Possible values are: alert, crit, debug (same as  debug  =  on),  emerg,  err,
              info, notice, warning.

              The default is: info.

       debug  This  specifies whether debug output is logged for this particular logger. Also can
              contain value trace, what is highest level of debug information.

              The default is off.

       Within the logging directive, logger_subsys directives are optional.

       Within the logger_subsys sub-directive, all of the above logging configuration options are
       valid  and  can  be  used  to  override the default settings.  The subsys entry, described
       below, is mandatory to identify the subsystem.

       subsys This specifies the subsystem identity (name) for which logging is  specified.  This
              is the name used by a service in the log_init() call. E.g. 'CPG'. This directive is
              required.

       Within the quorum directive it is possible to specify the quorum algorithm to use with the

       provider
              directive. At the time of  writing  only  corosync_votequorum  is  supported.   See
              votequorum(5) for configuration options.

       Within  the  nodelist directive it is possible to specify specific information about nodes
       in cluster. Directive can contain only node sub-directive, which specifies every node that
       should be a member of the membership, and where non-default options are needed. Every node
       must have at least ring0_addr field filled.

       Every node that should be a member of the membership must be specified.

       Possible options are:

       ringX_addr
              This specifies IP or network hostname address of the particular node.  X is a  link
              number.

       nodeid This configuration option is required for each node for Kronosnet mode.  It is a 32
              bit value specifying the  node  identifier  delivered  to  the  cluster  membership
              service.  The  node identifier value of zero is reserved and should not be used. If
              knet is set, this field must be set.

       name   This option is used mainly with knet transport to identify local node.   It's  also
              used  by  client  software  (pacemaker).   Algorithm  for identifying local node is
              following:

              1.     Looks up $HOSTNAME in the nodelist

              2.     If this fails strip the domain name from $HOSTNAME and looks up that in  the
                     nodelist

              3.     If  this  fails  look in the nodelist for a fully-qualified name whose short
                     version matches the short version of $HOSTNAME

              4.     If all this fails then search  the  interfaces  list  for  an  address  that
                     matches a name in the nodelist

       Within the system directive it is possible to specify system options.

       Possible options are:

       qb_ipc_type
              This  specifies type of IPC to use. Can be one of native (default), shm and socket.
              Native means one of shm or socket, depending on what is supported by OS. On systems
              with  support  for  both,  SHM  is  selected.  SHM is generally faster, but need to
              allocate ring buffer file in /dev/shm.

       sched_rr
              Should be set to yes (default) if corosync should try to set round  robin  realtime
              scheduling  with  maximal  priority  to  itself.  When  setting of scheduler fails,
              fallback to set maximal priority.

       priority
              Set priority of corosync process. Valid only when sched_rr is set to  no.   Can  be
              ether  numeric value with similar meaning as nice(1) or max / min meaning maximal /
              minimal priority (so minimal / maximal nice value).

       move_to_root_cgroup
              Should be set to yes (default) if corosync  should  try  to  move  itself  to  root
              cgroup.  This  feature  is  available  only  for systems with cgroups with RT sched
              enabled (Linux with CONFIG_RT_GROUP_SCHED kernel option).

       state_dir
              Existing directory where corosync should  chdir  into.  Corosync  stores  important
              state files and blackboxes there.

              The default is /var/lib/corosync.

       Within the resources directive it is possible to specify options for resources.

       Possible option is:

       watchdog_device
              (Valid only if Corosync was compiled with watchdog support.)
              Watchdog  device  to  use, for example /dev/watchdog.  If unset, empty or "off", no
              watchdog is used.

              In a cluster  with  properly  configured  power  fencing  a  watchdog  provides  no
              additional  value.  On the other hand, slow watchdog communication may incur multi-
              second delays in the Corosync main  loop,  potentially  breaking  down  membership.
              IPMI   watchdogs   are   particularly   notorious   in   this  regard:  read  about
              kipmid_max_busy_us in IPMI.txt in the Linux kernel documentation.

       Within the nozzle directive it is possible to specify options for a libnozzle device. This
       is  a pseudo ethernet device that routes network traffic through a channel on the corosync
       knet network (NOT cpg or any corosync internal service) to other  nodes  in  the  cluster.
       This  allows  applications  to  take  advantage  of  knet  features  such as multipathing,
       automatic failover, link switching etc. Note that libnozzle is not a  reliable  transport,
       but you can tunnel TCP through it for reliable communications.
       libnozzle  also  supports  optional  interface  up/down  scripts  that  are  kept  under a
       /etc/corosync/updown.d/ directory. See the knet documentation for more information.
       Only one nozzle device is allowed.
       The nozzle stanza takes several options:

       name   The name of the network device to be created. On Linux this may be any name at all,
              other platforms have restrictions on the name.

       ipaddr The  IP  address  (IPv6  or IPv4) of the interface. The bottom part of this address
              will be replaced by the local node's nodeid in conjunction with  ipprefix.  so,  eg
              ipaddr:  192.168.1.0  ipprefix:  24  will  make  nodeids  1,2,5  use  IP  addresses
              192.168.1.1, 192.168.1.2 & 192.168.1.5.  If a prefix length of 16 is used then  the
              bottom two bytes will be filled in with nodeid numbers.  IPv6 addresses must end in
              '::', the nodeid will be added after the two colons to make the local  IP  address.
              Only one IP address is currently supported in the corosync.conf file. Additional IP
              addresses can be added in the ifup script if necessary.

       ipprefix
              specifies the IP address prefix for the nozzle device (see above)

       macaddr
              Specifies the MAC address prefix for the nozzle device. As for the IP address,  the
              bottom  part of the MAC address will be filled in with the node id. In this case no
              prefix applies, the bottom two bytes of the MAC address will always be  overwritten
              with  the node id. So specifying macaddr: 54:54:12:24:12:12 on nodeid 1 will result
              in it having a MAC address of 54:54:12:24:00:01

TO ADD A NEW NODE TO THE CLUSTER

       For example to add a node with address 10.24.38.108 with nodeid 3. The node has  the  name
       NEW   (in  DNS  or  /etc/hosts)  and  is  not  currently  running  corosync.  The  current
       corosync.conf nodelist looks like this:

              nodelist {
                  node {
                      nodeid: 1
                      ring0_addr: 10.24.38.101
                      name: node1
                  }
                  node {
                      nodeid: 2
                      ring0_addr: 10.24.38.102
                      name: node2

                  }
              }

       Add a new entry for the node below the existing nodes. Node entries don't have  to  be  in
       nodeid order, but it will help keep you sane. So the nodelist now looks like this:

              nodelist {
                  node {
                      nodeid: 1
                      ring0_addr: 10.24.38.101
                      name: node1
                  }
                  node {
                      nodeid: 2
                      ring0_addr: 10.24.38.102
                      name: node2

                  }
                  node {
                      nodeid: 3
                      ring0_addr: 10.24.38.108
                      name: NEW

                  }
              }

       This  file must then be copied onto all three nodes -  the existing two nodes, and the new
       one.  On one of the existing corosync nodes, tell corosync to re-read the  updated  config
       file into memory:

              corosync-cfgtool -R

       This  command only needs to be run on one node in the cluster. You may then start corosync
       on the NEW node and it should join the cluster. If this  doesn't  work  as  expected  then
       check the communications between all three nodes is working, and check the syslog files on
       all nodes for more information. It's important to note that the  key  bit  of  information
       about a node failing to join might be on a different node than you expect.

TO REMOVE A NODE FROM THE CLUSTER

       This  is  the  reverse procedure to 'Adding a node' above. First you need to shut down the
       node you will be removing from the cluster.

              corosync-cfgtool -H

       Then delete the nodelist stanza from corosync.conf and  finally  update  corosync  on  the
       remaining nodes by running

              corosync-cfgtool -R

       on one of them.

ADDRESS RESOLUTION

       corosync resolves ringX_addr names/IP addresses using the getaddrinfo(3) call with respect
       of totem.ip_version setting.

       getaddrinfo() function uses a sophisticated  algorithm  to  sort  node  addresses  into  a
       preferred order and corosync always chooses the first address in that list of the required
       family.  As such it  is  essential  that  your  DNS  or  /etc/hosts  files  are  correctly
       configured  so  that  all addresses for ringX appear on the same network (or are reachable
       with minimal hops) and over the same IP protocol. If this is not the case then some  nodes
       might not be able to join the cluster. It is possible to override the search order used by
       getaddrinfo() using the configuration file /etc/gai.conf(5) if necessary, but this is  not
       recommended.

       If  there  is  any  doubt about the order of addresses returned from getaddrinfo() then it
       might be simpler to use IP addresses (v4 or v6) in the ringX_addr field.

FILES

       /etc/corosync/corosync.conf
              The corosync executive configuration file.

SEE ALSO

       corosync_overview(7),  votequorum(5),  corosync-qdevice(8),  logrotate(8)   getaddrinfo(3)
       gai.conf(5)