How-To Tutorials - IoT and Hardware

How SNMP Behaves in the CUPS Web Interface In the CUPS web interface under the Administration tab, the option Find New Printers is used to discover printers that support SNMPv1. This will search and list the available network printers. The discovery of printers is based on the directive configuration done in the /etc/cups/snmp.conf file. On the basis of the search list, you can add a printer using the Add This Printer option. The process is very similar to the Add Printer wizard. Overview of Basic Debugging in CUPS-SNMP In the snmp.conf, we started discussion about various debugging levels in CUPS support. If the directive DebugLevel is set to anything other than 0, you will get the output accordingly. The debugging mode can be made active using the following command. As the SNMP backend supports debugging mode, the command for setting up debugging mode changes depending on the shell prompt. The SNMP backend is located at /usr/lib/cups/backend/snmp when using the Bourne, Bash, Z, or Korn shells. The following command will output verbose debugging information into the cupssnmp.log file when using those shells: $CUPS_DEBUG_LEVEL=1 /usr/lib/cups/backend/snmp 2>&1 | tee cupssnmp.log On Mac OS X, the SNMP backend is located /usr/libexec/cups. The following command will be used: $CUPS_DEBUG_LEVEL=1 /usr/libexec/cups/backend/snmp 2>&1 | tee cupssnmp.log If you are using the C or Tcsh shells, you can use the following command. $(setenv CUPS_DEBUG_LEVEL 1; /usr/lib/cups/backend/snmp) |& tee cupssnmp.log An example of the output might look like this: DEBUG: Scanning for devices in "public" via "@LOCAL"... DEBUG: 0.000 Sending 46 bytes to 192.168.0.255... DEBUG: 0.001 Received 50 bytes from 192.168.0.250... DEBUG: community="public" DEBUG: request-id=1213875587 DEBUG: error-status=0 DEBUG: 1.001 Scan complete! The above output shows that doesn't find any printer at the specified DeviceURI. The above shows the output at the basic debugging level; more information can be found if we use level 2 or 3. Overview of mailto.conf The CUPS provides the facility to send notifications through email. It can be done by integrating the local mail server with CUPS. The configuration file is /etc/cups/mailto.conf, and contains several directives and the characteristics and behavior of the local mail server and email notification for CUPS. We normally use each of the following directives in our daily communication done through mail. The Cc Directive The directive Cc (carbon copy) is used to specify an additional recipient for all email notifications. By default, the value directive is not set and the email is sent only to the administrator. The following examples shows that how email IDs can be specified with this directive. Cc kajol@cupsgrp.com Cc Kajol Shah <ks@cupsgrp.com> The From Directive This directive is used to specify the sender's name in the email notifications. By default, the ServerAdmin address specified in the cupsd.conf file is used. The following are some examples that show how the sender's email is specified with this directive: From cupsadmin@cupsgrp.com From Your CUPS Printer <cupsadmin@cupsgrp.com> The Sendmail Directive The directive Sendmail specifies the command to run and deliver an email locally. If there is an SMTPServer directive, then this directive cannot be used. If both directives appear in the mailto.conf file, then only the last directive is used. The following example shows how this directive can be specified. The default value for this directive is /usr/sbin/sendmail. Sendmail /usr/sbin/sendmail Sendmail /usr/lib/sendmail -bm -i The SMTPServer Directive This directive is used to specify an IP address or hostname of an SMTP mail server. As we have seen previously, this directive cannot be used with the Sendmail directive, and if both Sendmail and SMTPServer directives don't appear in the mailto.conf file, then the default Sendmail will be considered. The following are examples of the SMTP server: SMTPServer mail.mailforcups.com SMTPServer 192.168.0.17 The Subject Directive The Subject directive is used if you want to prefix some text to the subject line in each email that CUPS sends out. The following examples show how a prefix can be specified with this directive. By default, no prefix string is added: Subject [CUPS_ALERTS] Subject URGENT CUPS NOTICE Monitoring SNMP Printers As discussed, CUPS supports SNMPv1 for discovering SNMP enabled printers. This Simple Network Management Protocol-SNMP is used for managing networking printers. We can use any network monitoring tools that supports SNMP for monitoring these SNMP-enabled printers. You can check various open-source network monitoring tools at: http://www.openxtra.co.uk/network-management/monitor/open-source/ I would recommend you to use Cacti, which is a frontend to an RRDTool (Round Robin Database Tool) that collects and stores data in a MySQL database. The frontend is completely written in PHP. The advantage of Cacti over other network monitoring tool is that it has built-in SNMP capabilities and like other monitoring tools such as Nagios, it has its internal mechanism to check certain aspects of the infrastructure. It also provides a frontend for maintaining customized scripts, which an administrator normally creates. But the most important factor is that it is much easier to configure than Nagios. RRDTool is a system that stores high performance logging data and displays related time-series graphs. You can get more information about RRDTool from: http://oss.oetiker.ch/rrdtool/ Downloading and Installing Cacti The pre-requisites of Cacti include MySQL database, PHP, RRDTool, net-snmp, and PHP supported web servers such as Apache or IIS. You can get detailed information about the pre-requisites for Cacti installation at: http://www.cacti.net/downloads/docs/html/requirements.html The current stable release of Cacti is 0.8.7b. You can download various versions of Cacti for different platforms from: http://www.cacti.net/download_cacti.php You can get installation information for Cacti and its pre-requisites on the UNIX/Linux platform from: http://www.cacti.net/downloads/docs/html/install_unix.html The following URL will help you install Cacti on the Windows platform: http://www.cacti.net/downloads/docs/html/install_windows.html You can proceed further by clicking on Next. The next screen shows two options for a new install or an upgrade. If you want to do fresh installation, use the option New Install and click on Next. The screen also displays some useful information such as database user, database hostname, database name, and OS that was specified while configuring Cacti. If you want to upgrade the Cacti, follow the instructions mentioned here: http://www.cacti.net/downloads/docs/html/upgrade.html And then select the upgrade from cacti-current-version option and click on Next to proceed further. The following screen appears, which shows the recommended path of the binary files such as RRDTool, PHP, snmpwalk, snmpgetV, snmpbulkwalk, snmpgetnext, and information related to the Cacti log file and versions for net-snmp and RRDTool. If you found any change in the path with your installation, it should be modified first. Otherwise, Cacti may not work properly. Click on Finish to complete the installation procedure. Once the installation is finished and the next screen will ask for authentication. You need to use the username and the password mentioned in your database configuration to log into a Cacti application: You can use default login information to log in for the first time. Once you click on Login, the next screen will force you to change your password. Once the password is changed, you can see the main page of Cacti that contains two major tabs: console and graphs apart from other generalized options. The console tab contains various options related to the template and graphs management, whereas the graphs tab contains related graphs.  

The Common UNIX Printing System (CUPS) is actually a printer management tool, and thus monitoring CUPS always remains a very essential activity to to make the best use of the resources available. Monitoring CUPS will allow us to take action quickly should something go wrong. Using the lpstat Command The lpstat command displays the status of the CUPS service, printers, classes, and jobs. It supports a number of options. If the command is used without any options, it displays the job queues for the current user: $lpstatcupstest-3 kajol 8192 Tue Aug 05 13:24:43 2008cupstest-4 kajol 8192 Tue Aug 05 13:25:34 2008 To check whether the CUPS server is running, use the -r option. $lpstat -rscheduler is running$lpstat -dsystem default destination: cupsclass The above command gives information about the default destination printer or class. The output following the command shows that the default destination of the system is cupsclass. $lpstat -c cupsclass This shows the printer class and the member printers belonging to that class. If a particular class is not specified, then the output shows all classes along with their member printers. members of class cupsclass:cupsprinter1cupsprinter2$lpstat -v cupsprinter2 The command above will show the device to which cupsprinter1 is attached. If no printers are specified, then the output will list all printers along with device-uri information. device for cupsprinter2: ipp://cupsserver.cupsgroup.org/printers/cupsprinter2$lpstat -s This shows a status summary for all printers and classes on the network. The summary includes the default destination, a list of classes and their member printers, and a list of printers and their associated devices. The output is equivalent to using the -d, -c, and -v options simultaneously. system default destination: cupsclassmembers of class cupsclass:cupsprinter1cupsprinter2device for cupsprinter1: lpd://192.168.0.11/printers/cupsprinter1device for cupsprinter2: ipp://cupsserver.cupsgroup.org/printers/cupsprinter2$lpstat -a This command shows if printers are currently accepting jobs. If no printers are specified, then it will list all printers. cupsprinter1 accepting requests since Mon 16 Jun 2008 02:28:14 PM ISTcupsprinter2 accepting requests since Wed 18 Jun 2008 11:07:23 AM IST$lpstat -p cupsprinter1 This shows whether the printer cupsprinter1 is enabled and if it is currently printing a job. If no printers are specified then all the printers are listed. printer cupsprinter1 is idle. enabled since Mon 16 Jun 2008 02:28:14 PM IST$lpstat -o This shows the job queues on the specified destinations. If no destinations are specified then all jobs are shown. $lpstat -t This displays status information for all printers, which is equivalent to using the -r, -d, -c, -v, -a, -p, and -o options. scheduler is runningsystem default destination: cupsclassmembers of class cupsclass:cupsprinter1cupsprinter2device for cupsprinter1: lpd://192.168.0.11/printers/cupsprinter1device for cupsprinter2: ipp://cupsserver.cupsgroup.org/printers/cupsprinter2cupsprinter1 accepting requests since Mon 16 Jun 2008 02:28:14 PM ISTcupsprinter2 accepting requests since Wed 18 Jun 2008 11:07:23 AM ISTprinter cupsprinter1 is idle. enabled since Mon 16 Jun 2008 02:28:14 PM ISTprinter cupsprinter2 now printing cupsprinter2-5711. enabled since Wed 18 Jun 2008 03:12:55 PM ISTPrinter is now on-line.cupsprinter2-5711 kajol 1449984 Wed 18 Jun 2008 03:12:55 PM IST$lpstat -l This command displays printers, classes, or jobs in a long list. $lpstat -u This shows a list of print jobs queued by the specified users. If no users are specified, it lists the jobs queued by the current user. cupsprinter2-5711 kajol 1449984 Wed 18 Jun 2008 03:12:55 PM IST$lpstat -h 192.168.0.11:631 The above command specifies an alternative server for CUPS. It uses the port number that is specified along with the server. If no port is specified, then it will connect to the default port 631. $lpstat -U username You can specify an alternative username with the -U option $lpstat -R : $lpstat -W all This shows the ranking of print jobs. This command specifies which jobs to show, complete, incomplete (the default), or all. This option must appear before the -o option and any printer names: $lpstat -W completed -o cupsprinter2 The output will be as follows cupsprinter2-5709 kajol 483328 Wed 18 Jun 2008 03:10:45 PM ISTcupsprinter2-5710 kajol 97280 Wed 18 Jun 2008 03:12:18 PM ISTcupsprinter2-5711 kajol 1449984 Wed 18 Jun 2008 03:12:55 PM ISTcupsprinter2-5712 kajol 8192 Wed 18 Jun 2008 03:22:31 PM ISTcupsprinter2-5713 kajol 9216 Wed 18 Jun 2008 03:23:38 PM ISTcupsprinter2-5714 kajol 9216 Wed 18 Jun 2008 03:24:23 PM IST$lpstat -E This command forces encryption when connecting to a print server.