Monitoring::Sneck

SYNOPSIS

sneck -u [-C <cache file>] [-f <config file>] [-p] [-i] [-d] [-q] [-l|-L] [-P <pid dir>] [-r] [-T <seconds>] [-s <signal>] [-k|-K]

sneck -c [-C <cache file>] [-f <config file>] [-b]

sneck [-f <config file>] [-p] [-i] [-d] [-q] [-r] [-T <seconds>] [-s <signal>] [-k|-K]

sneck -t [-f <config file>]

sneck -h

sneck -v

FLAGS

The cache file, PID dir, locking, and check timeout settings may also be set in the config file. Flags override those. See OPTIONS.

-f config_file

The config file to use.

Files ending in .yaml or .yml are read as YAML, which needs YAML::XS.

Default :: /usr/local/etc/sneck.conf

-p

Pretty print the JSON.

-C cache_file

The cache file to use.

Overrides cache_file in the config.

Default :: /var/cache/sneck.cache

A secondary cache file based on this name is also created. By default it is /var/cache/sneck.cache.snmp and always holds the GZip+BASE64 compressed version.

Compliance check state, used for interval, is kept in the cache file name with .compliance added, so by default /var/cache/sneck.cache.compliance. It is only used if a compliance check has a interval.

-u

Update the cache file. Will also print what was written to it.

-c

Print the cache file. Please note that -p or -i won't affect this as this flag only reads/prints the cache file.

If the cache file does not exist or can't be read, error JSON saying so is printed and it exits 3.

-b

When used with -c, print the LibreNMS style GZip+BASE64 compressed cache instead.

-i

Includes the config file used.

-d

Print debugging info to stderr.

-q

Don't print the results. Exit quietly. Meant for use with -u.

-l

Enable locking for -u so more than one instance can't run at a time. Overrides locking in the config.

The PID file is sneck.pid in the directory set by -P.

-L

Disable locking, overriding locking in the config. Can not be used with -l.

-P pid_dir

The directory for the PID file used by -l. The user running sneck must be able to write to it.

Overrides pid_dir in the config.

Default :: /var/run

-r

Run any restarts whose checks failed. Without this, restarts are only reported as restarts disabled. Meant to be used with -u from cron. Never use it from snmpd.

Restart state, used for min_interval and max_retries, is kept in the cache file name with .restarts added, so by default /var/cache/sneck.cache.restarts.

Use locking with this to make sure two runs can't restart things at the same time. Without it, a warning saying so is printed to stderr.

-T seconds

Seconds to wait on each check before giving up on it. Overrides check_timeout in the config.

Default :: 30

-s signal

Signal to send a check on timeout, such as TERM. Overrides check_timeout_signal in the config. none sends no signal, even if the config sets one.

Default :: none

-k

Also send the timeout signal to all child processes of a check. Overrides check_kill_sub_pids in the config. Does nothing without a timeout signal. This is the default.

-K

Do not send the timeout signal to child processes of a check. Overrides check_kill_sub_pids in the config. Can not be used with -k.

-t

Test the config file. Prints any errors and warnings, then exits 0 if there are no errors and 1 if there are or the file can't be read. Warnings, such as a check using a undefined variable, do not affect the exit code.

-h, --help

Print the help.

-v, --version

Print the version.

CONFIG FORMAT

The sneck format is described below. Files ending in .yaml or .yml use the YAML format instead, described under YAML CONFIG.

Each line has leading spaces and tabs removed before it is looked at. A trailing \r is also removed, so files with CRLF line endings work.

Blank lines are ignored.

Lines starting with # are comments and are ignored.

• env NAME=value :: Sets a environment variable. The env is case insensitive. The value may be empty. These may be set more than once, with the last one winning. They are only applied if the whole config is valid.

• $name=value :: A option. See OPTIONS.

• NAME=value :: A variable. The name is before the first =, the value is everything after it. The value may be empty.

• name|command :: A check. The command is everything after the first | with leading whitespace removed. It may not be empty.

• %name|command :: A debug check. Same as a check, but not counted towards any of the counts. It exists purely for debugging. The leading % is not part of the name, so a check and a debug check may share a name.

• @name|options|command :: A restart. Options are space separated key=value, with checks and depends being comma separated lists. Values containing spaces may be quoted with " or '. See RESTARTS.

• !name|options|command :: A compliance check. Laid out the same as a restart. The options may be empty, but the second | is still needed, such as !foo||/bin/true. See COMPLIANCE.

Names are made up of A-Z, a-z, 0-9, and _.

Any other sort of line is an error. Every bad line is reported, along with its line number.

Variables are used in commands in the form %NAME%. A reference to a variable that is not defined is left as written and produces a warning, as it may just be part of the command, such as date +%Y%m%d. Use -t to see warnings.

Option, variable, check, debug check, compliance check, and restart names may not be redefined. A compliance check may share a name with a check or debug check.

Checks, debug checks, and compliance checks starting with perl: are perl checks, run in process. See PERL CHECKS.

EXAMPLE CONFIG

env PATH=/sbin:/bin:/usr/sbin:/usr/bin:/usr/local/sbin:/usr/local/bin
# this is a comment
GEOM_DEV=foo
geom_foo|/usr/local/libexec/nagios/check_geom mirror %GEOM_DEV%
does_not_exist|/bin/this_will_error yup... that it will

does_not_exist_2|/usr/bin/env /bin/this_will_also_error

#includes route info
%routes|netstat -rn

php_check|/usr/local/libexec/nagios/check_procs -C php-fpm -c 1:
@php_fpm|checks=php_check|/usr/sbin/service php_fpm restart

The first line sets the environment variable PATH.

The second is ignored as it is a comment.

The third sets the variable GEOM_DEV to 'foo'.

The fourth creates a check named geom_foo that calls check_geom with the value of the variable GEOM_DEV.

The fifth is an example of a check that calls a file that does not exist.

The sixth line is ignored as it is blank.

The seventh is an example of another command erroring.

The eighth is ignored as it is blank.

The ninth is ignored as it is a comment.

The tenth creates a debug check named routes.

The eleventh is ignored as it is blank.

The twelfth creates a check named php_check.

The thirteenth creates a restart named php_fpm that runs the command when php_check is critical, if restarts are enabled.

When it is run, errors for the fifth and seventh lines are printed to STDERR. For this reason, use 2> /dev/null when calling it from snmpd or 2> /dev/null > /dev/null when calling it from cron.

YAML CONFIG

YAML configs need YAML::XS, which is optional and only loaded when a YAML config is used.

env:
  PATH: /sbin:/bin:/usr/sbin:/usr/bin:/usr/local/sbin:/usr/local/bin
vars:
  GEOM_DEV: foo
checks:
  geom_foo: /usr/local/libexec/nagios/check_geom mirror %GEOM_DEV%
  does_not_exist: /bin/this_will_error yup... that it will
  php_check: '/usr/local/libexec/nagios/check_procs -C php-fpm -c 1:'
debugs:
  routes: netstat -rn
restarts:
  php_fpm:
    command: /usr/sbin/service php_fpm restart
    checks: [php_check]

• options :: Options. See OPTIONS.

• env :: Environment variables to set, in sorted name order. Only applied if the whole config is valid.

• vars :: Variables.

• checks :: Checks, with the command as the value.

• debugs :: Debug checks, with the command as the value.

• compliance :: Compliance checks, each a mapping of options plus command. See COMPLIANCE.

• restarts :: Restarts, each a mapping of options plus command. See RESTARTS.

Any other top level key is an error. Any section may be left out or empty. An empty file is a valid config with nothing in it.

Names, variables, and undefined variable warnings work the same as the sneck format. Errors and warnings point to a path, such as checks.geom_foo, as YAML::XS does not give line numbers.

Values must be strings or numbers. An empty value is an empty string for env and vars and an error for checks and debugs.

Some things to watch for.

• Unquoted true becomes 1 and false becomes an empty string. Quote values like those.

• A value starting with % must be quoted, as % can't start a plain YAML value.

• A value containing : or ending in :, such as -c 1:, must be quoted, or it is read as a mapping.

• Duplicate keys are not caught. YAML::XS silently keeps the last one.

OPTIONS

Options are settings for sneck itself. Flags override them.

• cache_file :: The cache file. The same as -C. May not be empty.

• pid_dir :: The directory for the PID file used for locking. The same as -P. May not be empty.

• locking :: If 1, locking is enabled. The same as -l. -L disables it. Takes true and false in YAML.

• check_timeout :: Seconds to wait on each check, debug check, and compliance check before giving up on it. Compliance checks may override it via their timeout option. Works the same as timeout for restarts. A timeout counts as errored, with a exit of -1. The same as -T. Default :: 30

• check_timeout_signal :: Signal to send a check, debug check, or compliance check on timeout. Works the same as timeout_signal for restarts. The same as -s. Default :: none

• check_kill_sub_pids :: If 1, the timeout signal is also sent to all child processes of the check, debug check, or compliance check. Works the same as kill_sub_pids for restarts. The same as -k. -K disables it. Takes true and false in YAML. Default :: 1

• compliance_alert :: If 1, compliance checks that are not ok and not waived also set .data.alert and are added to .data.alertString. Takes true and false in YAML. Default :: 0

Any other option is an error.

$cache_file=/var/db/sneck/sneck.cache
$pid_dir=/var/run/sneck
$locking=1
$check_timeout=60
$check_timeout_signal=TERM

options:
  cache_file: /var/db/sneck/sneck.cache
  pid_dir: /var/run/sneck
  locking: true
  check_timeout: 60
  check_timeout_signal: TERM

COMPLIANCE

A compliance check is a nagios style check for how a system is set up, such as root logins being off or a file having the right mode, rather than if something is working. They run the same as checks, but are counted separately and set .data.compliance_alert instead of .data.alert. Set the compliance_alert option to have them set .data.alert as well.

!ssh_no_root|control=CIS-5.2.10 framework=CIS severity=high|sshd -T | grep -qi '^permitrootlogin no$'
!pkg_vulns|control=VULN-1 severity=high interval=86400 timeout=300|/usr/local/libexec/nagios/check_pkg_audit
!telnet_off|control=CIS-2.2.18 framework=CIS waived_until=2026-12-31 waiver="legacy box, ticket 1234"|/usr/local/libexec/sneck/check_telnet_off

compliance:
  ssh_no_root:
    command: sshd -T | grep -qi '^permitrootlogin no$'
    control: CIS-5.2.10
    framework: CIS
    severity: high
  pkg_vulns:
    command: /usr/local/libexec/nagios/check_pkg_audit
    control: VULN-1
    severity: high
    interval: 86400
    timeout: 300
  telnet_off:
    command: /usr/local/libexec/sneck/check_telnet_off
    control: CIS-2.2.18
    framework: CIS
    waived_until: 2026-12-31
    waiver: legacy box, ticket 1234

All options are optional.

• control :: The ID of the control it checks, such as CIS-5.2.10. Used in place of the name in .data.compliance_alertString. Default :: none

• framework :: The framework the control is from, such as CIS or STIG. Ones with a framework also get counts and a score for it under .data.compliance_frameworks. Default :: none

• severity :: One of low, medium, high, or critical, in any case. Only used for reporting. It does not change how the exit code is counted. Default :: none

• interval :: Minimum seconds between runs. Until it is due again, the last result is reused and marked as cached. A change to the command, after variables are put in place, makes it run right away. 0 runs it every time. Default :: 0

• timeout :: Seconds to wait on it. Works the same as check_timeout, which is used if this is not set. Default :: check_timeout

• waived_until :: A date as YYYY-MM-DD. Through the end of that day, local time, warning, critical, and unknown count as waived instead. Errored is never waived, as that means the check itself is broken. Once the date passes, it counts as normal again. Default :: none

• waiver :: Why it is waived, such as a ticket number. Needs waived_until. Default :: none

Restarts can't watch compliance checks.

State for interval is kept in the cache file name with .compliance added, so by default /var/cache/sneck.cache.compliance. It is only used if a compliance check has a interval.

PERL CHECKS

A check, debug check, or compliance check in the form perl:$name $args runs the check $name from Monitoring::Sneck::Checks inside of sneck, instead of starting a program for it. Each is a module, such as Monitoring::Sneck::Checks::http, whose POD lists its args.

www|perl:http -H www.example.org -S -w 1 -c 2
www_cert|perl:https_cert -H www.example.org -w 30 -c 14
!hosts_file|control=LOCAL-1|perl:hosts -e db.example.org=%DB_IP%

Variables are put in place first, then the args are split as a shell would, so quote args with spaces in them.

The name must be a-z, 0-9, and _, starting with a letter, which is checked along with the args having balanced quotes when the config is read. Whether the check is there is only known when it is run.

The exit is what the check returns, as for any other command, with two differences. A exit of -1, which is errored, means the check, or Monitoring::Sneck::Checks, could not be loaded, such as it not being installed or the name being base. Running past check_timeout, or the timeout of a compliance check, is UNKNOWN, a exit of 3, as nothing is forked to be killed. Each check passes the timeout on to what it talks to the network through, so this is rare. check_timeout_signal and check_kill_sub_pids do not apply.

Monitoring::Sneck::Checks is optional and only loaded once a perl check is run.

Restarts can't be perl checks, as they are commands to run, not checks. A restart command starting with perl: is a error. Restarts may watch perl checks though, and check_restart reruns them in process.

RESTARTS

A restart is a command run when enough of the checks it watches fail. They only run with -r. Otherwise they are just reported.

The command can't be a perl check. See PERL CHECKS.

http_check|/usr/local/libexec/nagios/check_http -H localhost
php_check|/usr/local/libexec/nagios/check_procs -C php-fpm -c 1:
@php_fpm|checks=php_check|/usr/sbin/service php_fpm restart
@httpd|checks=http_check,php_check threshold=2 depends=php_fpm cascade=1 timeout=60|/usr/sbin/service apache24 restart

restarts:
  php_fpm:
    command: /usr/sbin/service php_fpm restart
    checks: [php_check]
  httpd:
    command: /usr/sbin/service apache24 restart
    checks: [http_check, php_check]
    threshold: 2
    depends: [php_fpm]
    cascade: true
    timeout: 60

• checks :: Required. The checks to watch. Debug checks and compliance checks can't be watched.

• threshold :: How many of the watched checks must fail for it to trigger. Must be between 1 and the number of checks. Default :: 1

• depends :: Other restarts this one depends on. When both trigger, the ones depended on run first. A depend that didn't trigger is assumed fine and isn't run. If a depend runs and fails, or was itself skipped for that reason, this one is skipped. Cycles are errors. Default :: none

• cascade :: If 1, this also runs when any of its depends ran without failing, even if its own threshold wasn't met. Default :: 0

• ignore_unknown :: If 0, unknown, exit 3, counts as failed. Default :: 1

• ignore_errored :: If 0, errored counts as failed. This is any exit other than 0 to 3, dying on a signal, or not being able to run the check. Default :: 1

• min_interval :: Minimum seconds from when this restart last finished to when it may run again. 0 turns it off. Default :: 180

• max_retries :: How many times in a row it will run for its threshold before giving up until its checks recover. 0 means always retry. Runs from cascade don't count. Default :: 0

• timeout :: Seconds to wait on the command before giving up on it. On timeout its output pipes are closed and it is left running, unless timeout_signal is set. If it writes again it gets SIGPIPE, or whatever it does when the reader goes away. A timeout counts as failed, with an exit of -1. Default :: 30

• timeout_signal :: Signal to send the command on timeout, as a name such as TERM or SIGTERM, or a number. 0 is not allowed. It is sent to the PID of the command and it is not waited on afterwards. If the command has shell metacharacters in it, that PID is the /bin/sh running it, so use kill_sub_pids to reach the command. Default :: none

• kill_sub_pids :: If 1, the timeout signal is also sent to all child processes of the command, found via pgrep and signaled via pkill, deepest first. Does nothing without timeout_signal. Default :: 1

• check_restart :: If 1, its checks are rerun after the command finishes and their results replace the earlier ones in what is returned. If they still meet the threshold, the restart counts as failed, the same as the command failing. Default :: 0

• check_restart_delay :: Seconds to wait after the command finishes before rerunning its checks. Does nothing without check_restart. Default :: 5

• not_every :: A maintenance window, as a five field cron spec of minute, hour, day of month, month, and day of week. While local time matches it, the restart doesn't run. Numbers only, no names like sat or jan. Sunday is 0 or 7. If both day of month and day of week are given, either matching is enough, same as cron. Restarts depending on one held back by this act as if it didn't trigger. Must be quoted, such as not_every="* 2-3 * * 0", or in YAML not_every: '* 2-3 * * 0'. Default :: none

Critical always counts as failed. Ok and warning never do.

The 0/1 options also take true and false in YAML.

Restart commands get variables put in place the same as checks. A restart does not wait for its output to be closed once its command has exited, so a daemon started by it holding stdout open is fine.

The command is also given the environment variables below, describing why it is running.

• SNECK_RESTART :: The name of the restart.

• SNECK_REASON :: Either threshold or cascade.

• SNECK_CASCADE_FROM :: The depend it cascaded from, or empty.

• SNECK_FAILED_CHECKS :: Comma separated list of its checks that counted as failed. May be empty for a cascade.

• SNECK_CHECKS :: Comma separated list of the checks it watches.

• SNECK_THRESHOLD :: The threshold.

• SNECK_ATTEMPTS :: Runs for its threshold since its checks last recovered, this one included.

@php_fpm|checks=php_check timeout=60 timeout_signal=TERM check_restart=1|/usr/sbin/service php_fpm restart
@php_fpm|checks=php_check not_every="* 2-3 * * 0"|/usr/sbin/service php_fpm restart

restarts:
  php_fpm:
    command: /usr/sbin/service php_fpm restart
    checks: [php_check]
    timeout: 60
    timeout_signal: TERM
    check_restart: true
    not_every: '* 2-3 * * 0'

The last two never restart between 02:00 and 03:59 on Sundays.

A restart that ran and failed sets .data.alert and adds a line to .data.alertString, along with any output from the command.

USAGE

snmpd just needs to print the cache. The simplest way is to cat the GZip+BASE64 compressed cache, which avoids starting perl at all.

extend sneck /bin/cat /var/cache/sneck.cache.snmp

sneck -c may be used instead. It reports a missing cache file as error JSON instead of printing nothing, but has to start perl and read the config on each poll.

extend sneck /usr/bin/env PATH=/sbin:/bin:/usr/sbin:/usr/bin:/usr/local/sbin:/usr/local/bin /usr/local/bin/sneck -c

If the cache file is changed via cache_file or -C, cat its .snmp file instead, or give -c the same -C.

Then just setup a entry in like cron such as below.

*/5 * * * * /usr/bin/env PATH=/sbin:/bin:/usr/sbin:/usr/bin:/usr/local/sbin:/usr/local/bin /usr/local/bin/sneck -u 2> /dev/null > /dev/null

Most likely want to run it once per polling interval.

You can use it in a non-cached manner with out cron, but this will result in a longer polling time for LibreNMS or the like when it queries it.

RETURN HASH/JSON

The generated JSON/hash is as below in jpath notation.

• .data.alert :: 0/1 boolean for if there is a alert or not.

• .data.ok :: Count of the number of ok checks.

• .data.warning :: Count of the number of warning checks.

• .data.critical :: Count of the number of critical checks.

• .data.unknown :: Count of the number of unknown checks.

• .data.errored :: Count of the number of errored checks.

• .data.alertString :: The cumulative outputs of anything that returned a warning, critical, or unknown.

• .data.vars :: A hash with the variables to use.

• .data.time :: Time since epoch.

• .data.hostname :: The hostname the check was ran on.

• .data.config :: The raw config file if told to include it.

• .data.run_time :: How long it took to run all checks.

• .data.restarted :: Count of the number of restarts ran.

• .data.restart_state_error :: Only present if the restart state file could not be read or written. Restarts still run if it can't be read, as if there was no state.

• .data.compliance_ok, .data.compliance_warning, .data.compliance_critical, .data.compliance_unknown, .data.compliance_errored :: Counts of compliance checks, the same as for checks. Waived ones are not included.

• .data.compliance_waived :: Count of compliance checks that were not ok but are waived. These are not counted anywhere else.

• .data.compliance_alert :: 0/1 for if any compliance check is not ok and not waived. Only sets .data.alert as well if the compliance_alert option is set.

• .data.compliance_alertString :: The outputs of compliance checks that are warning, critical, or unknown and not waived, each prefixed with the control, or the name if there is none, and the severity, such as [CIS-5.2.10 high] . Added to .data.alertString if the compliance_alert option is set.

• .data.compliance_score :: Percent of compliance checks that are ok, leaving out waived ones, to two decimal places. null if there are none to score.

• .data.compliance_frameworks.$framework :: The same counts as above for compliance checks with that framework, as ok, warning, critical, unknown, errored, waived, and score.

• .data.compliance_state_error :: Only present if the compliance state file could not be read or written. Compliance checks are run as if there was no state.

For the following $name is the name of the check ran.

• .data.checks.$name :: A hash with info on the checks ran.

• .data.checks.$name.check :: The command pre-variable substitution.

• .data.checks.$name.ran :: The command ran.

• .data.checks.$name.output :: The output of the check.

• .data.checks.$name.exit :: The exit code. If it died on a signal, this is 128 plus the signal number. If it could not be executed or timed out, this is -1. For a perl check, -1 is it not being able to be loaded and timing out is 3, see PERL CHECKS.

• .data.checks.$name.error :: Only present if it died on a signal, timed out, or could not be executed. Provides a brief description.

• .data.checks.$name.run_time :: How long it took to run the check.

• .data.checks.$name.rechecked_by :: Only present if it was rerun after a restart with check_restart set. The name of that restart. The rest of the results are from the rerun.

For the following $name is the name of the debug check ran. Debug checks are run the same as checks, including check_timeout, check_timeout_signal, and check_kill_sub_pids.

• .data.debugs.$name :: A hash with info on the checks ran.

• .data.debugs.$name.check :: The command pre-variable substitution.

• .data.debugs.$name.ran :: The command ran.

• .data.debugs.$name.output :: The output of the check.

• .data.debugs.$name.exit :: The exit code. Same as for checks.

• .data.debugs.$name.error :: Only present if it died on a signal, timed out, or could not be executed. Provides a brief description.

• .data.debugs.$name.run_time :: How long it took to run the debug.

For the following $name is the name of the compliance check. They are run the same as checks, except timeout may override check_timeout.

• .data.compliance.$name.check, ran, output, exit, error, run_time :: The same as for checks. For a cached result, these are from when it last ran.

• .data.compliance.$name.last_ran :: Time since epoch of when it last started running.

• .data.compliance.$name.cached :: 0/1 for if this is a earlier result reused because of interval.

• .data.compliance.$name.waived :: 0/1 for if it is not ok and counted as waived. Errored is never waived.

• .data.compliance.$name.control, framework, severity, waived_until, waiver :: Only present if set in the config.

For the following $name is the name of the restart. Every restart has an entry, even when restarts are disabled.

• .data.restarts.$name.triggered :: 0/1 for if enough of its checks failed to meet its threshold.

• .data.restarts.$name.ran :: 0/1 for if it ran.

• .data.restarts.$name.reason :: Why it did or didn't run. One of threshold, cascade from $depend, cooldown, $N seconds left, max retries reached, skipped, dependency $depend failed, maintenance window, not triggered, or restarts disabled.

• .data.restarts.$name.failed_checks :: Array of the watched checks that counted as failed.

• .data.restarts.$name.threshold :: The threshold.

• .data.restarts.$name.attempts :: Runs for its threshold since its checks last recovered.

• .data.restarts.$name.command :: The command pre-variable substitution.

The rest are only present if it ran.

• .data.restarts.$name.ran_command :: The command ran.

• .data.restarts.$name.output :: The output of the command.

• .data.restarts.$name.exit :: The exit code. Same as for checks.

• .data.restarts.$name.error :: Only present if it timed out, died on a signal, or could not be executed. If it timed out and timeout_signal is set, also says the signal was sent, plus any problems sending it. Also present if check_restart is set and its checks still met the threshold afterwards, unless one of the above already set it.

• .data.restarts.$name.run_time :: How long the command took to run, not counting check_restart.

• .data.restarts.$name.recheck_failed_checks :: Only present if check_restart is set. Array of the watched checks that still counted as failed when rerun.

A restart that ran and failed, including timing out or its checks still failing with check_restart, sets .data.alert and adds a line to .data.alertString along with any output from the command. Check results, counts, and .data.alertString reflect any checks rerun by check_restart.

INSTALLING

FreeBSD

pkg install p5-JSON p5-JSON-XS p5-File-Slurp p5-Proc-PID-File p5-DateTime-Event-Cron p5-App-cpanminus
cpanm Monitoring::Sneck

Debian

apt-get install libjson-perl libjson-xs-perl libfile-slurp-perl libproc-pid-file-perl libdatetime-event-cron-perl cpanminus
cpanm Monitoring::Sneck

YAML Support

For YAML configs, also install YAML::XS.

# FreeBSD
pkg install p5-YAML-LibYAML

# Debian
apt-get install libyaml-libyaml-perl

Perl Checks

For perl: checks, run in process instead of as a program, also install Monitoring::Sneck::Checks. See PERL CHECKS.

www|perl:http -H www.example.org -S -w 1 -c 2

From Source

perl Makefile.PL
make
make test
make install