How to monitor SSL certificates using icinga2

Create custom data field to define multiple domain names and service apply rule to verify those SSL certificates.

Log in to web-interface to use icinga director.

Open data fields form.

Create custom ssl_domains data field as an array.

It will be used to directly define particular domain names.

Create custom config data field as an string.

It will be used indirectly inside service apply rule to pass each domain name.

Open host templates form.

Assign custom ssl_domains data field to a host template.


template Host "notebook" {
    check_command = "hostalive"
    enable_active_checks = true
    enable_passive_checks = true

Open hosts form.

Define domain names on a particular host.


object Host "milosz-XPS-13-9343" {
    import "notebook"

    display_name = "milosz-XPS-13-9343"
    address = ""
    vars.ssl_domains = [ "", "" ]


object Endpoint "milosz-XPS-13-9343" {
    host = ""
    log_duration = 0s


object Zone "milosz-XPS-13-9343" {
    parent = ""
    endpoints = [ "milosz-XPS-13-9343" ]

Open commands form.

Define plugin check command using check_http command which is provided by monitoring-plugins-basic package.


object CheckCommand "Check SSL certificate" {
    import "plugin-check-command"
    command = [ PluginDir + "/check_http" ]
    arguments += {
        "--sni" = {
            order = 3
        "-C" = {
            order = 4
            value = "30,14"
        "-H" = {
            order = 1
            required = true
            value = "$config$"
        "-S" = {
            order = 2

Open service templates form.

Define basic service template that will be executed on agent.


template Service "Check SSL certificates" {
    check_command = "Check SSL certificate"
    check_interval = 1d
    retry_interval = 12h
    command_endpoint = host_name

Open service apply rules form.

Create service apply rule to verify SSL certificates on hosts where custom ssl_domains data field is defined.


apply Service "Check SSL certificate for " for (config in host.vars.ssl_domains) {
    import "Check SSL certificates"

    assign where host.vars.ssl_domains
    vars.config = config

    import DirectorOverrideTemplate

Apply changes.

Verify SSL certificates using web-interface.

check_http command reference.

$ /usr/lib/nagios/plugins/check_http --help
check_http v2.2 (monitoring-plugins 2.2)
Copyright (c) 1999 Ethan Galstad <>
Copyright (c) 1999-2013 Monitoring Plugins Development Team

This plugin tests the HTTP service on the specified host. It can test
normal (http) and secure (https) servers, follow redirects, search for
strings and regular expressions, check connection times, and report on
certificate expiration times.

 check_http -H <vhost> | -I <IP-address> [-u <uri>] [-p <port>]
       [-J <client certificate file>] [-K <private key>]
       [-w <warn time>] [-c <critical time>] [-t <timeout>] [-L] [-E] [-a auth]
       [-b proxy_auth] [-f <ok|warning|critcal|follow|sticky|stickyport>]
       [-e <expect>] [-d string] [-s string] [-l] [-r <regex> | -R <case-insensitive regex>]
       [-P string] [-m <min_pg_size>:<max_pg_size>] [-4|-6] [-N] [-M <age>]
       [-A string] [-k string] [-S <version>] [--sni] [-C <warn_age>[,<crit_age>]]
       [-T <content-type>] [-j method]
NOTE: One or both of -H and -I must be specified

 -h, --help
    Print detailed help screen
 -V, --version
    Print version information
    Read options from an ini file. See
    for usage and examples.
 -H, --hostname=ADDRESS
    Host name argument for servers using host headers (virtual host)
    Append a port to include it in the header (eg:
 -I, --IP-address=ADDRESS
    IP address or name (use numeric address if possible to bypass DNS lookup).
 -p, --port=INTEGER
    Port number (default: 80)
 -4, --use-ipv4
    Use IPv4 connection
 -6, --use-ipv6
    Use IPv6 connection
 -S, --ssl=VERSION[+]
    Connect via SSL. Port defaults to 443. VERSION is optional, and prevents
    auto-negotiation (2 = SSLv2, 3 = SSLv3, 1 = TLSv1, 1.1 = TLSv1.1,
    1.2 = TLSv1.2). With a '+' suffix, newer versions are also accepted.
    Enable SSL/TLS hostname extension support (SNI)
 -C, --certificate=INTEGER[,INTEGER]
    Minimum number of days a certificate has to be valid. Port defaults to 443
    (when this option is used the URL is not checked.)
 -J, --client-cert=FILE
   Name of file that contains the client certificate (PEM format)
   to be used in establishing the SSL session
 -K, --private-key=FILE
   Name of file containing the private key (PEM format)
   matching the client certificate
 -e, --expect=STRING
    Comma-delimited list of strings, at least one of them is expected in
    the first (status) line of the server response (default: HTTP/1.)
    If specified skips all other status line logic (ex: 3xx, 4xx, 5xx processing)
 -d, --header-string=STRING
    String to expect in the response headers
 -s, --string=STRING
    String to expect in the content
 -u, --url=PATH
    URL to GET or POST (default: /)
 -P, --post=STRING
    URL encoded http POST data
 -j, --method=STRING  (for example: HEAD, OPTIONS, TRACE, PUT, DELETE, CONNECT)
    Set HTTP method.
 -N, --no-body
    Don't wait for document body: stop reading after headers.
    (Note that this still does an HTTP GET or POST, not a HEAD.)
 -M, --max-age=SECONDS
    Warn if document is more than SECONDS old. the number can also be of
    the form "10m" for minutes, "10h" for hours, or "10d" for days.
 -T, --content-type=STRING
    specify Content-Type header media type when POSTing

 -l, --linespan
    Allow regex to span newlines (must precede -r or -R)
 -r, --regex, --ereg=STRING
    Search page for regex STRING
 -R, --eregi=STRING
    Search page for case-insensitive regex STRING
    Return CRITICAL if found, OK if not

 -a, --authorization=AUTH_PAIR
    Username:password on sites with basic authentication
 -b, --proxy-authorization=AUTH_PAIR
    Username:password on proxy-servers with basic authentication
 -A, --useragent=STRING
    String to be sent in http header as "User Agent"
 -k, --header=STRING
    Any other tags to be sent in http header. Use multiple times for additional headers
 -E, --extended-perfdata
    Print additional performance data
 -L, --link
    Wrap output in HTML link (obsoleted by urlize)
 -f, --onredirect=<ok|warning|critical|follow|sticky|stickyport>
    How to handle redirected pages. sticky is like follow but stick to the
    specified IP address. stickyport also ensures port stays the same.
 -m, --pagesize=INTEGER<:INTEGER>
    Minimum page size required (bytes) : Maximum page size required (bytes)
 -w, --warning=DOUBLE
    Response time to result in warning status (seconds)
 -c, --critical=DOUBLE
    Response time to result in critical status (seconds)
 -t, --timeout=INTEGER
    Seconds before connection times out (default: 10)
 -v, --verbose
    Show details for command-line debugging (output may be truncated by
    the monitoring system)

 This plugin will attempt to open an HTTP connection with the host.
 Successful connects return STATE_OK, refusals and timeouts return STATE_CRITICAL
 other errors return STATE_UNKNOWN.  Successful connects, but incorrect response
 messages from the host result in STATE_WARNING return values.  If you are
 checking a virtual server that uses 'host headers' you must supply the FQDN
 (fully qualified domain name) as the [host_name] argument.

 This plugin can also check whether an SSL enabled web server is able to
 serve content (optionally within a specified time) or whether the X509 
 certificate is still valid for the specified number of days.

 Please note that this plugin does not check if the presented server
 certificate matches the hostname of the server, or if the certificate
 has a valid chain of trust to one of the locally installed CAs.

 CHECK CONTENT: check_http -w 5 -c 10 --ssl -H

 When the '' server returns its content within 5 seconds,
 a STATE_OK will be returned. When the server returns its content but exceeds
 the 5-second threshold, a STATE_WARNING will be returned. When an error occurs,
 a STATE_CRITICAL will be returned.

 CHECK CERTIFICATE: check_http -H -C 14

 When the certificate of '' is valid for more than 14 days,
 a STATE_OK is returned. When the certificate is still valid, but for less than
 14 days, a STATE_WARNING is returned. A STATE_CRITICAL will be returned when
 the certificate is expired.

 CHECK CERTIFICATE: check_http -H -C 30,14

 When the certificate of '' is valid for more than 30 days,
 a STATE_OK is returned. When the certificate is still valid, but for less than
 30 days, but more than 14 days, a STATE_WARNING is returned.
 A STATE_CRITICAL will be returned when certificate expires in less than 14 days

 check_http -I -p 80 -u -S -j CONNECT -H 
 all these options are needed: -I <proxy> -p <proxy-port> -u <check-url> -S(sl) -j CONNECT -H <webserver>
 a STATE_OK will be returned. When the server returns its content but exceeds
 the 5-second threshold, a STATE_WARNING will be returned. When an error occurs,
 a STATE_CRITICAL will be returned.

Send email to if you have questions regarding
use of this software. To submit patches or suggest improvements, send email
Milosz Galazka's Picture

About Milosz Galazka

Milosz is a Linux Foundation Certified Engineer working for a successful Polish company as a system administrator and a long time supporter of Free Software Foundation and Debian operating system. He is also open for new opportunities and challenges.

Gdansk, Poland