CMAN_TOOL(8)CMAN_TOOL(8)NAMEcman_tool - Cluster Management Tool
SYNOPSIScman_tool join | leave | kill | expected | votes | version | wait |
status | nodes | services | debug [options]
DESCRIPTIONcman_tool is a program that manages the cluster management subsystem
CMAN. cman_tool can be used to join the node to a cluster, leave the
cluster, kill another cluster node or change the value of expected
votes of a cluster.
Be careful that you understand the consequences of the commands issued
via cman_tool as they can affect all nodes in your cluster. Most of the
time the cman_tool will only be invoked from your startup and shutdown
scripts.
SUBCOMMANDS
join This is the main use of cman_tool. It instructs the cluster man‐
ager to attempt to join an existing cluster or (if no existing
cluster exists) then to form a new one on its own.
If no options are given to this command then it will take the
cluster configuration information from cluster.conf. However, it
is possible to provide all the information on the command-line
or to override cluster.conf values by using the command line.
leave Tells CMAN to leave the cluster. You cannot do this if there are
subsystems (eg DLM, GFS) active. You should dismount all GFS
filesystems, shutdown CLVM, fenced and anything else using the
cluster manager before using cman_tool leave. Look at
'cman_tool status' and group_tool to see how many (and which)
subsystems are active.
When a node leaves the cluster, the remaining nodes recalculate
quorum and this may block cluster activity if the required num‐
ber of votes is not present. If this node is to be down for an
extended period of time and you need to keep the cluster run‐
ning, add the remove option, and the remaining nodes will recal‐
culate quorum such that activity can continue.
kill Tells CMAN to kill another node in the cluster. This will cause
the local node to send a "KILL" message to that node and it will
shut down. Recovery will occur for the killed node as if it had
failed. This is a sort of remote version of "leave force" so
only use if if you really know what you are doing.
expected
Tells CMAN a new value of expected votes and instructs it to
recalculate quorum based on this value.
Use this option if your cluster has lost quorum due to nodes
failing and you need to get it running again in a hurry.
version
Used alone this will report the major, minor, patch and config
versions used by CMAN (also displayed in 'cman_tool status'). It
can also be used with -r to tell cluster members to update the
cluster configuration.
If -r is specified, cman will read the configuration file, vali‐
date it, distribute it around the cluster (if necessary) an
activate it. See the VERSION OPTIONS section below for addi‐
tional options to the version command.
wait Waits until the node is a member of the cluster and then
returns.
status Displays the local view of the cluster status.
nodes Displays the local view of the cluster nodes.
services
Displays the local view of subsystems using cman (deprecated,
group_tool should be used instead).
debug Sets the debug level of the running cman daemon. Debug output
will be sent to syslog level LOG_DEBUG. the -d switch specifies
the new logging level. This is the same bitmask used for
cman_tool join -d
LEAVE OPTIONS-w Normally, "cman_tool leave" will fail if the cluster is in tran‐
sition (ie another node is joining or leaving the cluster). By
adding the -w flag, cman_tool will wait and retry the leave
operation repeatedly until it succeeds or a more serious error
occurs.
-t <seconds>
If -w is also specified then -t dictates the maximum amount of
time cman_tool is prepared to wait. If the operation times out
then a status of 2 is returned.
force Shuts down the cluster manager without first telling any of the
subsystems to close down. Use this option with extreme care as
it could easily cause data loss.
remove Tells the rest of the cluster to recalculate quorum such that
activity can continue without this node.
EXPECTED OPTIONS-e <expected-votes>
The new value of expected votes to use. This will usually be
enough to bring the cluster back to life. Values that would
cause incorrect quorum will be rejected.
KILL OPTIONS-n <nodename>
The node name of the node to be killed. This should be the
unqualified node name as it appears in 'cman_tool nodes'.
VERSION OPTIONS-r Update config version. You don't need to use this when adding a
new node, the new cman node will tell the rest of the cluster to
read the latest version of the config file automatically. The
version present in the new configuration must be higher than the
one currently in use by cman.
cman_tool version on its own will always show the current ver‐
sion and not the one being looked for. So be aware that the dis‐
play will possibly not update immediately after you have run
cman_tool version -r.
-D<option>
see "JOIN" options
-S By default cman_tool version will try to distribute the new
cluster.conf file using ccs_sync and ricci. If you have distrib‐
uted the file yourself and/or do not have ricci installed then
the -S option will skip this step. NOTE: it is still important
that all nodes in the cluster have the same version of the file.
Make sure that this is the case before using this option.
WAIT OPTIONS-q Waits until the cluster is quorate before returning. -t <sec‐
onds> Dictates the maximum amount of time cman_tool is prepared
to wait. If the operation times out then a status of 2 is
returned.
JOIN OPTIONS-c <clustername>
Provides a text name for the cluster. You can have several clus‐
ters on one LAN and they are distinguished by this name. Note
that the name is hashed to provide a unique number which is what
actually distinguishes the cluster, so it is possible that two
different names can clash. If this happens, the node will not be
allowed into the existing cluster and you will have to pick
another name or use different port number for cluster communica‐
tion.
-p <port>
UDP port number used for cluster communication. This defaults to
5405.
-v <votes>
Number of votes this node has in the cluster. Defaults to 1.
-e <expected votes>
Number of expected votes for the whole cluster. If different
nodes provide different values then the highest is used. The
cluster will only operate when quorum is reached - that is more
than half the available votes are available to the cluster. The
default for this value is the total number of votes for all
nodes in the configuration file.
-2 Sets the cluster up for a special "two node only" mode. Because
of the quorum requirements mentioned above, a two-node cluster
cannot be valid. This option tells the cluster manager that
there will only ever be two nodes in the cluster and relies on
fencing to ensure cluster integrity. If you specify this you
cannot add more nodes without taking down the existing cluster
and reconfiguring it. Expected votes should be set to 1 for a
two-node cluster.
-n <nodename>
Overrides the node name. By default the unqualified hostname is
used. This option is also used to specify which interface is
used for cluster communication.
-N <nodeid>
Overrides the node ID for this node. Normally, nodes are
assigned a node id in cluster.conf. If you specify an incorrect
node ID here, the node might not be allowed to join the cluster.
Setting node IDs in the configuration is a far better way to do
this. Note that the node's application to join the cluster may
be rejected if you try to set the nodeid to one that has already
been used, or if the node was previously a member of the cluster
but with a different nodeid.
-o <nodename>
Override the name this node will have in the cluster. This will
normally be the hostname or the first name specified by -n.
Note how this differs from -n: -n tells cman_tool how to find
the host address and/or the entry in the configuration file. -o
simply changes the name the node will have in the cluster and
has no bearing on the actual name of the machine. Use this
option will extreme caution.
-m <multicast-address>
Specifies a multicast address to use for cluster communication.
This is required for IPv6 operation. You should also specify an
ethernet interface to bind to this multicast address using the
-i option.
-w Join and wait until the node is a cluster member.
-q Join and wait until the cluster is quorate. If the cluster join
fails and -w (or -q) is specified, then it will be retried. Note
that cman_tool cannot tell whether the cluster join was rejected
by another node for a good reason or that it timed out for some
benign reason; so it is strongly recommended that a timeout is
also given with the wait options to join. If you don't want join
to retry on failure but do want to wait, use the cman_tool join
command without -w followed by cman_tool wait.
-k <keyfile>
All traffic sent out by cman/corosync is encrypted. By default
the security key used is simply the cluster name. If you need
more security you can specify a key file that contains the key
used to encrypt cluster communications. Of course, the contents
of the key file must be the same on all nodes in the cluster. It
is up to you to securely copy the file to the nodes.
-t <seconds>
If -w or -q is also specified then -t dictates the maximum
amount of time cman_tool is prepared to wait. If the operation
times out then a status of 2 is returned. Note that just
because cman_tool has given up, does not mean that cman itself
has stopped trying to join a cluster.
-X Tells cman not to use the configuration file to get cluster
information. If you use this option then cman will apply several
defaults to the cluster to get it going. The cluster name will
be "RHCluster", node IDs will default to the IP address of the
node and remote node names will show up as Node<nodeid>. All of
these, apart from the node names can be overridden on the
cman_tool command-line if required.
If you have to set up fence devices, services or anything else
in cluster.conf then this option is probably not worthwhile to
you - the extra readability of sensible node names and numbers
will make it worth using cluster.conf for the cluster too. But
for a simple failover cluster this might save you some effort.
On each node using this configuration you will need to have the
same authorization key installed. To create this key run
corosync-keygen
mv /etc/ais/authkey /etc/cluster/cman_authkey
then copy that file to all nodes you want to join the cluster.
-C Overrides the default configuration module. Usually cman uses
xmlconfig (cluster.conf) to load its configuration. If you have
your configuration database held elsewhere (eg LDAP) and have a
configuration plugin for it, then you should specify the name of
the module (see the documentation for the module for the name of
it - it's not necessarily the same as the filename) here.
It is possible to chain configuration modules by separating them
with colons. So to add two modules (eg) 'configloader' and 'con‐
figpreproc' to the chain start cman with -C configloader:config‐
preproc
The default value for this is 'xmlconfig'. Note that if the -X
is on the command-line then -C will be ignored.
-A Don't load openais services. Normally cman_tool join will load
the configuration module 'openaisserviceenablestable' which will
load the services installed by openais. If you don't want to
use these services or have not installed openais then this
switch will disable them.
-D Tells cman_tool whether to validate the configuration before
loading or reloading it. By default the configuration is vali‐
dated, which is equivalent to -Dfail.
-Dwarn will validate the configuration and print any messages
arising, but will attempt to use it regardless of its validity.
-Dnone (or just -D) will skip the validation completely.
The -D switch does not take a space between -D and the parame‐
ter. so '-D fail' will cause an error. Use -Dfail.
NODES OPTIONS-a Shows the IP address(es) the nodes are communicating on.
-n <nodename>
Shows node information for a specific node. This should be the
unqualified node name as it appears in 'cman_tool nodes'.
-F <format>
Specify the format of the output. The format string may contain
one or more format options, each separated by a comma. Valid
format options include: id, name, type, and addr.
DEBUG OPTIONS
-d<value>
The value is a bitmask of
2 Barriers
4 Membership messages
8 Daemon operation, including command-line interaction
16 Interaction with Corosync
32 Startup debugging (cman_tool join operations only)
NOTES
the nodes subcommand shows a list of nodes known to cman. the state is
one of the following:
M The node is a member of the cluster
X The node is not a member of the cluster
d The node is known to the cluster but disallowed access to it.
ENVIRONMENT VARIABLEScman_tool removes most environment variables before forking and running
Corosync, as well as adding some of its own for setting up configura‐
tion parameters that were overridden on the command-line, the exception
to this is that variable with names starting COROSYNC_ will be passed
down intact as they are assumed to be used for configuring the daemon.
DISALLOWED NODES
Occasionally (but very infrequently I hope) you may see nodes marked as
"Disallowed" in cman_tool status or "d" in cman_tool nodes. This is a
bit of a nasty hack to get around mismatch between what the upper lay‐
ers expect of the cluster manager and corosync.
If a node experiences a momentary lack of connectivity, but one that is
long enough to trigger the token timeouts, then it will be removed from
the cluster. When connectivity is restored corosync will happily let it
rejoin the cluster with no fuss. Sadly the upper layers don't like this
very much. They may (indeed probably will have) have changed their
internal state while the other node was away and there is no straight‐
forward way to bring the rejoined node up-to-date with that state. When
this happens the node is marked "Disallowed" and is not permitted to
take part in cman operations.
If the remainder of the cluster is quorate the the node will be sent a
kill message and it will be forced to leave the cluster that way. Note
that fencing should kick in to remove the node permanently anyway, but
it may take longer than the network outage for this to complete.
If the remainder of the cluster is inquorate then we have a problem.
The likelihood is that we will have two (or more) partitioned clusters
and we cannot decide which is the "right" one. In this case we need to
defer to the system administrator to kill an appropriate selection of
nodes to restore the cluster to sensible operation.
The latter scenario should be very rare and may indicate a bug some‐
where in the code. If the local network is very flaky or busy it may be
necessary to increase some of the protocol timeouts for corosync. We
are trying to think of better solutions to this problem.
Recovering from this state can, unfortunately, be complicated. Fortu‐
nately, in the majority of cases, fencing will do the job for you, and
the disallowed state will only be temporary. If it persists, the recom‐
mended approach it is to do a cman tool nodes on all systems in the
cluster and determine the largest common subset of nodes that are valid
members to each other. Then reboot the others and let them rejoin cor‐
rectly. In the case of a single-node disconnection this should be
straightforward, with a large cluster that has experienced a network
partition it could get very complicated!
Example:
In this example we have a five node cluster that has experienced a net‐
work partition. Here is the output of cman_tool nodes from all systems:
Node Sts Inc Joined Name
1 M 2372 2007-11-05 02:58:55 node-01.example.com
2 d 2376 2007-11-05 02:58:56 node-02.example.com
3 d 2376 2007-11-05 02:58:56 node-03.example.com
4 M 2376 2007-11-05 02:58:56 node-04.example.com
5 M 2376 2007-11-05 02:58:56 node-05.example.com
Node Sts Inc Joined Name
1 d 2372 2007-11-05 02:58:55 node-01.example.com
2 M 2376 2007-11-05 02:58:56 node-02.example.com
3 M 2376 2007-11-05 02:58:56 node-03.example.com
4 d 2376 2007-11-05 02:58:56 node-04.example.com
5 d 2376 2007-11-05 02:58:56 node-05.example.com
Node Sts Inc Joined Name
1 d 2372 2007-11-05 02:58:55 node-01.example.com
2 M 2376 2007-11-05 02:58:56 node-02.example.com
3 M 2376 2007-11-05 02:58:56 node-03.example.com
4 d 2376 2007-11-05 02:58:56 node-04.example.com
5 d 2376 2007-11-05 02:58:56 node-05.example.com
Node Sts Inc Joined Name
1 M 2372 2007-11-05 02:58:55 node-01.example.com
2 d 2376 2007-11-05 02:58:56 node-02.example.com
3 d 2376 2007-11-05 02:58:56 node-03.example.com
4 M 2376 2007-11-05 02:58:56 node-04.example.com
5 M 2376 2007-11-05 02:58:56 node-05.example.com
Node Sts Inc Joined Name
1 M 2372 2007-11-05 02:58:55 node-01.example.com
2 d 2376 2007-11-05 02:58:56 node-02.example.com
3 d 2376 2007-11-05 02:58:56 node-03.example.com
4 M 2376 2007-11-05 02:58:56 node-04.example.com
5 M 2376 2007-11-05 02:58:56 node-05.example.com
In this scenario we should kill the node node-02 and node-03. Of
course, the 3 node cluster of node-01, node-04 & node-05 should remain
quorate and be able to fenced the two rejoined nodes anyway, but it is
possible that the cluster has a qdisk setup that precludes this.
CONFIGURATION SYSTEMS
This section details how the configuration systems work in cman. You
might need to know this if you are using the -C option to cman_tool, or
writing your own configuration subsystem.
By default cman uses two configuration plugins to corosync. The first,
'xmlconfig', reads the configuration information stored in cluster.conf
and stores it in an internal database, in the same schema as it finds
in cluster.conf. The second plugin, 'cmanpreconfig', takes the infor‐
mation in that the database, adds several cman defaults, determines the
corosync node name and nodeID and formats the information in a similar
manner to corosync.conf(5). Corosync then reads those keys to start the
cluster protocol. cmanpreconfig also reads several environment vari‐
ables that might be set by cman_tool which can override information in
the configuration.
In the absence of xmlconfig, ie when 'cman_tool join' is run with -X
switch (this removes xmlconfig from the module list), cmanpreconfig
also generates several defaults so that the cluster can be got running
without any configuration information - see above for the details.
Note that cmanpreconfig will not overwrite corosync keys that are
explicitly set in the configuration file, allowing you to provide cus‐
tom values for token timeouts etc, even though cman has its own
defaults for some of those values. The exception to this is the node
name/address and multicast values, which are always taken from the cman
configuration keys.
Most of the extra keys that cmanpreconfig adds are outside of the
/cluster/ tree and will only be seen if you dump the whole of
corosync's object database. However it does add some keys into /clus‐
ter/cman that you would not normally see in a normal cluster.conf file.
These are harmless, though could be confusing. The most obvious of
these is the "nodename" option which is passed from cmanpreconfig to
the name cman module, to save it recalculating the node name again.
Cluster utilities Nov 8 2007 CMAN_TOOL(8)
