mon(1)

Global Variables

The following variables may be set to override compiled-in defaults. Command-line options will have a higher precedence than these definitions.

alertdir = dir

dir is the full path to the alert scripts. This is the value set by the -a command-line parameter.

Multiple alert paths may be specified by separating them with a colon. Non-absolute paths are taken to be relative to the base directory (/usr/lib/mon by default).

When the configuration file is read, all alerts referenced from the configuration will be looked up in each of these paths, and the full path to the first instance of the alert found is stored in a hash. This hash is only generated upon startup or after a "reset" command, so newly added alert scripts will not be recognized until a "reset" is performed.

mondir = dir

dir is the full path to the monitor scripts. This value may also be set by the -s command-line parameter.

Multiple alert paths may be specified by separating them with a colon. Non-absolute paths are taken to be relative to the base directory (/usr/lib/mon by default).

When the configuration file is read, all monitors referenced from the configuration will be looked up in each of these paths, and the full path to the first instance of the monitor found is stored in a hash. This hash is only generated upon startup or after a "reset" command, so newly added monitor scripts will not be recognized until a "reset" is performed.

statedir = dir

dir is the full path to the state directory. mon uses this directory to save various state information.

logdir = dir

dir is the full path to the log directory. mon uses this directory to save various logs, including the downtime log.

basedir = dir

dir is the full path for the state, script, and alert directory.

authfile = file

file is the full path to the authentication file.

authtype = type

type is the type of authentication to use. If type is getpwnam, then the standard Unix passwd file authentication method will be used (calls getpwnam(3) on the user and compares the crypt(3)ed version of the password with what it gets from getpwnam). This will not work if shadow passwords are enabled on the system.

If type is userfile, then usernames and hashed passwords are read from userfile, which is defined via the userfile configuration variable.

If type is shadow, then shadow password may be used (NOT IMPLEMENTED).

userfile = file

This file is used when authtype is set to userfile. It consists of a sequence of lines of the format 'username : password'. password is stored as the hash returned by the standard Unix crypt(3) function.

Blank lines and lines beginning with # are ignored.

snmpport = portnum

Set the SNMP port that the server binds to.

serverbind = addr

trapbind = addr

serverbind and trapbind specify which address to bind the server and trap ports to, respectively. If these are not defined, the default address is INADDR_ANY, which allows connections on all interfaces. For security reasons, it could be a good idea to bind only to the loopback interface.

use SNMP

Turn on SNMP support.

dtlogfile = file

file is a file which will be used to record the downtime log. Whenever a service fails for some amount of time and then stop failing, this event is written to the log. If this parameter is not set, no logging is done. The format of the file is as follows (# is a comment and may be ignored):

timenoticed group service firstfail downtime interval summary.

timenoticed is the time(2) the service came back up.

group service is the group and service which failed.

firstfail is the time(2) when the service began to fail.

downtime is the number of seconds the service failed.

interval is the frequency (in seconds) that the service is polled.

summary is the summary line from when the service was failing.

dtlogging = yes/no

Turns downtime logging on or off. The default is off.

histlength = num

num is the the maximum number of events to be retained in history list. The default is 100. This value may also be set by the -k command-line parameter.

historicfile = file

If this variable is set, then alerts are logged to file, and upon startup, some (or all) of the past history is read into memory.

historictime = timeval

num is the amount of the history file to read upon startup. "Now" - timeval is read. See the explanation of interval in the "Service Definitions" section for a description of timeval.

serverport = port

port is the TCP port number that the server should bind to. This value may also be set by the -p command-line parameter. Normally this port is looked up via getservbyname(3), and it defaults to 2583.

trapport = port

port is the UDP port number that the trap server should bind to. Normally this port is looked up via getservbyname(3), and it defaults to 2583.

pidfile = path

path is the file the sever will store its pid in. This value may also be set by the -P command-line parameter.

maxprocs = num

Throttles the number of concurrently forked processes to num. The intent is to provide a safety net for the unlikely situation when the server tries to take on too many tasks at once. Note that this situation has only been reported to happen when trying to use a garbled configuration file! You don't want to use a garbled configuration file now, do you?

cltimeout = secs

Sets the client inactivity timeout to secs. This is meant to help thwart denial of service attacks or recover from crashed clients. secs is interpreted as a "1h/1m/1s" string, where "1m" = 60 seconds.

randstart = secs

When the server starts, normally all services will not be scheduled until the interval defined in the respective service section. This can cause long delays before the first check of a service, and possibly a high load on the server if multiple things are scheduled at the same intervals. This option is used to randomize the scheduling of the first test for all services during the startup period, and immediately after the reset command. If randstart is defined, the scheduled run time of all services of all watch groups will be a random number between zero and randstart seconds.

dep_recur_limit = depth

Limit dependency recursion level to depth. If dependency recursion (dependencies which depend on other dependencies) tries to go beyond depth, then the recursion is aborted and a messages is logged to syslog. The default limit is 10.

dep_behavior = {a|m}

dep_behavior controls whether the dependency expression suppresses either the running of alerts or monitors when a node in the dependency graph fails. Read more about the behavior in the "Service Definitions" section below.

This is a global setting which controls the default settings for the service-specified variable.

Hostgroup Entries

Hostgroup entries begin with the keyword hostgroup, and are followed by a hostgroup tag and one or more hostnames or IP addresses, separated by whitespace. The hostgroup tag must be composed of alphanumeric characters, a dash ("-"), a period ("."), or an underscore ("_"). Non-blank lines following the first hostgroup line are interpreted as more hostnames. The hostgroup definition ends with a blank line. For example:

hostgroup servers nameserver smtpserver nntpserver
	nfsserver httpserver smbserver
hostgroup router_group cisco7000 agsplus

Watch Group Entries

Watch entries begin with a line that starts with the keyword watch, followed by whitespace and a single word which normally refers to a pre-defined hostgroup. If the second word is not recognized as a hostgroup tag, a new hostgroup is created whose tag is that word, and that word is its only member.

Watch entries consist of one or more service definitions.

Service Definitions

service servicename

A service definition begins with they keyword service followed by a word which is the tag for this service.

The components of a service are an interval, monitor, and one or more time period definitions, as defined below.

interval timeval

The keyword interval followed by a time value specifies the frequency that a monitor script will be triggered. Time values are defined as "30s", "5m", "1h", or "1d", meaning 30 seconds, 5 minutes, 1 hour, or 1 day. The numeric portion may be a fraction, such as "1.5h" or an hour and a half. This format of a time specification will be referred to as timeval.

traptimeout timeval

This keyword takes the same time specification argument as interval, and makes the service expect a trap from an external source at least that often, else a failure will be registered. This is used for a heartbeat-style service.

trapduration timeval

If a trap is received, the status of the service the trap was delivered to will normally remain constant. If trapduration is specified, the status of the service will remain in a failure state for the duration specified by timeval, and then it will be reset to "success".

randskew timeval

Rather than schedule the monitor script to run at the start of each interval, randomly adjust the interval specified by the interval parameter by plus-or-minus randskew . The skew value is specified as the interval parameter: "30s", "5m", etc... For example if interval is 1m, and randskew is "5s", then mon will schedule the monitor script some time between every 55 seconds and 65 seconds. The intent is to help distribute the load on the server when many services are scheduled at the same intervals.

monitor monitor-name [arg...]

The keyword monitor followed by a script name and arguments specifies the monitor to run when the timer expires. Shell-like quoting conventions are followed when specifying the arguments to send to the monitor script. The script is invoked from the directory given with the -s argument, and all following words are supplied as arguments to the monitor program, followed by the list of hosts in the group referred to by the current watch group. If the monitor line ends with ";;" as a separate word, the host groups are not appended to the argument list when the program is invoked.

allow_empty_group

The allow_empty_group option will allow a monitor to be invoked even when the hostgroup for that watch is empty because of disabled hosts. The default behavior is not to invoke the monitor when all hosts in a hostgroup have been disabled.

description descriptiontext

The text following description is queried by client programs, passed to alerts and monitors via an environment variable. It should contain a brief description of the service, suitable for inclusion in an email or on a web page.

depend dependexpression

The depend keyword is used to specify a dependency expression, which evaluates to either true of false, in the boolean sense. Dependencies are actual Perl expressions, and must obey all syntactical rules. The expressions are evaluated in their own package space so as to not accidentally have some unwanted side-effect. If a syntax error is found when evaluating the expression, it is logged via syslog.

Before evaluation, the following substitutions on the expression occur: phrases which look like "group:service" are substituted with the value of the current operational status of that specified service. These opstatus substitutions are computed recursively, so if service A depends upon service B, and service B depends upon service C, then service A depends upon service C. Successful operational statuses (which evaluate to "1") are "STAT_OK", "STAT_COLDSTART", "STAT_WARMSTART", and "STAT_UNKNOWN".

This feature can be used to control alerts for services which are dependent on other services, e.g. an SMTP test which is dependent upon the machine being ping-reachable.

dep_behavior {a|m}

The evaluation of dependency graphs can control the suppression of either alert or monitor invocations.

Alert suppression. If this option is set to "a", then the dependency expression will be evaluated after the monitor for the service exits or after a trap is received. An alert will only be sent if the evaluation succeeds, meaning that none of the nodes in the dependency graph indicate failure.

Monitor suppression. If it is set to "m", then the dependency expression will be evaulated before the monitor for the service is about to run. If the evaulation succeeds, then the monitor will be run. Otherwise, the monitor will not be run and the status of the service will remain the same.

Period Definitions

Periods are used to define the conditions which should allow alerts to be delivered.

period [label:] periodspec

A period groups one or more alarms and variables which control how often an alert happens when there is a failure. The period keyword has two forms. The first takes an argument which is a period specification from Patrick Ryan's Time::Period Perl 5 module. Refer to "perldoc Time::Period" for more information.

The second form requires a label followed by a period specification, as defined above. The label is a tag consisting of an alphabetic character or underscore followed by zero or more alphanumerics or underscores and ending with a colon. This form allows multiple periods with the same period definition. One use is to have a period definition which has no alertafter or alertevery parameters for a particular time period, and another for the same time period with a different set of alerts that does contain those parameters.

alertevery timeval

The alertevery keyword (within a period definition) takes the same type of argument as the interval variable, and limits the number of times an alert is sent when the service continues to fail. For example, if the interval is "1h", then only the alerts in the period section will only be triggered once every hour. If the alertevery keyword is omitted in a period entry, an alert will be sent out every time a failure is detected. By default, if the output of two successive failures changes, then the alertevery interval is overridden. If the word "summary" is the last argument, then only the summary output lines will be considered when comparing the output of successive failures.

alertafter num

alertafter num timeval

The alertafter keyword (within a period section) has two forms: only with the "num" argument, or with the "num timeval" arguments. In the first form, an alert will only be invoked after "num" consecutive failures.

In the second form, the arguments are a positive integer followed by an interval, as described by the interval variable above. If these parameters are specified, then the alerts for that period will only be called after that many failures happen within that interval. For example, if alertafter is given the arguments "3 30m", then the alert will be called if 3 failures happen within 30 minutes.

numalerts num

This variable tells the server to call no more than num alerts during a failure. The alert counter is kept on a per-period basis, and is reset upon each success.

comp_alerts

If this option is specified, then upalerts will only be called if a corresponding "down" alert has been called.

alert alert [arg...]

A period may contain multiple alerts, which are triggered upon failure of the service. An alert is specified with the alert keyword, followed by an optional exit parameter, and arguments which are interpreted the same as the monitor definition, but without the ";;" exception. The exit parameter takes the form of exit=x or exit=x-y and has the effect that the alert is only called if the exit status of the monitor script falls within the range of the exit parameter. If, for example, the alert line is alert exit=10-20 mail.alert mis then mail-alert will only be invoked with mis as its arguments if the monitor program's exit value is between 10 and 20. This feature allows you to trigger different alerts at different severity levels (like when free disk space goes from 8% to 3%).

Alert programs are invoked with the following command-line parameters:

-s service name

The service tag for this failure.

-g hostgroup

The tag of the host group for this service.

-h hostgroup expansion

All of the members in this hostgroup.

-t time

The time (in time(2) format) of when this failure condition was detected.

-l alertevery

The number of seconds until the next alarm will be sent.

-u

This option is supplied to an alert only if it is being called as an upalert.

upalert alert [arg...]

An upalert is the compliment of an alert. An upalert is called when a services makes the state transition from failure to success. The upalert script is called supplying the same parameters as the alert script, with the addition of the -u parameter which is simply used to let an alert script know that it is being called as an upalert. Multiple upalerts may be specified for each period definition. Please note that the default behavior is that an upalert will be sent regardless if there were any prior "down" alerts sent, since upalerts are triggered on a state transition. Set the per-period comp_alerts option to pair upalerts with "down" alerts.

startupalert alert [arg...]

A startupalert is only called when the mon server starts execution.

upalertafter timeval

The upalertafter parameter is specified as a string that follows the syntax of the interval parameter ("30s", "1m", etc.), and controls the triggering of an upalert. If a service comes back up after being down for a time greater than or equal to the value of this option, an upalert will be called. Use this option to prevent upalerts to be called because of "blips" (brief outages).