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><H1
><A
NAME="FAQ"
></A
>Chapter 17. Frequently Asked Questions</H1
><DIV
CLASS="QANDASET"
><DL
><DT
>1. <A
HREF="faq.html#AEN2406"
>Using Cacti</A
></DT
><DD
><DL
><DT
> <A
HREF="faq.html#AEN2409"
> How do I create traffic graphs?
</A
></DT
></DL
></DD
><DT
>2. <A
HREF="faq.html#AEN2436"
>General</A
></DT
><DD
><DL
><DT
> <A
HREF="faq.html#AEN2439"
> I get a "Undefined variable: _SERVER" error message from Cacti.
</A
></DT
><DT
> <A
HREF="faq.html#AEN2444"
> I get a "Call to undefined function: mysql_connect()" error message from Cacti.
</A
></DT
><DT
> <A
HREF="faq.html#AEN2449"
> I have forgotten my 'admin' password to Cacti, how do I reset it?
</A
></DT
></DL
></DD
><DT
>3. <A
HREF="faq.html#AEN2460"
>Monitoring</A
></DT
><DD
><DL
><DT
> <A
HREF="faq.html#AEN2463"
> I am polling thousands of items and poller.php takes more than 5 minutes to run.
</A
></DT
><DT
> <A
HREF="faq.html#AEN2471"
> I changed x, and now some of my graphs are not updating.
</A
></DT
><DT
> <A
HREF="faq.html#AEN2478"
> I am using <SPAN
CLASS="APPLICATION"
>Redhat 8.0</SPAN
> and SNMP is not working.
</A
></DT
><DT
> <A
HREF="faq.html#AEN2485"
> How do I configure <SPAN
CLASS="APPLICATION"
>net-snmp</SPAN
> so it will work with Cacti?
</A
></DT
></DL
></DD
><DT
>4. <A
HREF="faq.html#AEN2496"
>Graphs</A
></DT
><DD
><DL
><DT
> <A
HREF="faq.html#AEN2499"
> I just installed Cacti and all of my graphs appear as broken images.
</A
></DT
><DT
> <A
HREF="faq.html#AEN2512"
> My graphs render, but they do not contain any data.
</A
></DT
><DT
> <A
HREF="faq.html#AEN2524"
> A lot of my graphs contain long ifAlias names, but they are being truncated to 15 characters.
</A
></DT
><DT
> <A
HREF="faq.html#AEN2532"
> One of my devices rebooted and now I have a huge spike on my graph!
</A
></DT
><DT
> <A
HREF="faq.html#AEN2541"
> RRDTool Says: ERROR: unknown option '--slope-mode' or RRDTool Says: ERROR: Garbage ':39:24 To 2005/10/22 16:39:24\c' after command: COMMENT:From 2005/10/21 16:39:24 To 2005/10/22 16:39:24\c
</A
></DT
></DL
></DD
><DT
>5. <A
HREF="faq.html#AEN2545"
>Windows Related</A
></DT
><DD
><DL
><DT
> <A
HREF="faq.html#AEN2548"
> I get a "Fatal error: Cannot redeclare title_trim()" error message from Cacti.
</A
></DT
></DL
></DD
></DL
><DIV
CLASS="QANDADIV"
><H3
><A
NAME="AEN2406"
></A
>1. Using Cacti</H3
><DIV
CLASS="QANDAENTRY"
><DIV
CLASS="QUESTION"
><P
><A
NAME="AEN2409"
></A
><B
> </B
> How do I create traffic graphs?
</P
></DIV
><DIV
CLASS="ANSWER"
><P
><B
> </B
> Before you can create traffic graphs, Cacti must have working SNMP support. One way to do this is to compile
PHP with SNMP support built in, many times you can install the 'php-snmp' package to do this. The second option
is to have Cacti call the snmpget and snmpwalk binaries from your ucd-snmp or <SPAN
CLASS="APPLICATION"
>net-snmp</SPAN
>
installation. You can use the about page to determine whether to are using "built-in" or "external" SNMP support.
</P
><P
> Now that you have working SNMP support, follow these steps.
</P
><P
></P
><OL
TYPE="1"
><LI
><P
>Click <SPAN
CLASS="GUILABEL"
>Devices</SPAN
> on Cacti's menu.</P
></LI
><LI
><P
>Click <SPAN
CLASS="GUILABEL"
>Add</SPAN
> to add a new device.</P
></LI
><LI
><P
>Type a description, hostname, management IP, and SNMP community. Make sure to select "Generic SNMP-enabled Host" under <SPAN
CLASS="GUILABEL"
>Host Template</SPAN
> and click <SPAN
CLASS="GUILABEL"
>Create</SPAN
>.</P
></LI
><LI
><P
>Click <SPAN
CLASS="GUILABEL"
>Create Graphs for this Host</SPAN
> at the top of the page.</P
></LI
><LI
><P
>You should see one or more interfaces listed under the <SPAN
CLASS="GUILABEL"
>Data Query [SNMP - Interface Statistics]</SPAN
> box. Place a check next to each interface that you want to graph. Below the box, select type of graph that you want to create (bits, bytes, summation, etc).</P
></LI
><LI
><P
>Click <SPAN
CLASS="GUILABEL"
>Create</SPAN
>, and <SPAN
CLASS="GUILABEL"
>Create</SPAN
> again on the following screen to create your graphs.</P
></LI
></OL
></DIV
></DIV
></DIV
><DIV
CLASS="QANDADIV"
><H3
><A
NAME="AEN2436"
></A
>2. General</H3
><DIV
CLASS="QANDAENTRY"
><DIV
CLASS="QUESTION"
><P
><A
NAME="AEN2439"
></A
><B
> </B
> I get a "Undefined variable: _SERVER" error message from Cacti.
</P
></DIV
><DIV
CLASS="ANSWER"
><P
><B
> </B
> Cacti 0.8.6 and above requires that you have at least PHP 4.1 or greater installed.
</P
></DIV
></DIV
><DIV
CLASS="QANDAENTRY"
><DIV
CLASS="QUESTION"
><P
><A
NAME="AEN2444"
></A
><B
> </B
> I get a "Call to undefined function: mysql_connect()" error message from Cacti.
</P
></DIV
><DIV
CLASS="ANSWER"
><P
><B
> </B
> Your installation of PHP does not have MySQL installed or enabled. On binary-based distributions, make
sure you have the 'php-mysql' package installed. Also make sure that 'extension=mysql.so' is uncommented
in your php.ini file.
</P
></DIV
></DIV
><DIV
CLASS="QANDAENTRY"
><DIV
CLASS="QUESTION"
><P
><A
NAME="AEN2449"
></A
><B
> </B
> I have forgotten my 'admin' password to Cacti, how do I reset it?
</P
></DIV
><DIV
CLASS="ANSWER"
><P
><B
> </B
> To reset the admin account password back to the default of 'admin', connect to your Cacti database at the
command line.
</P
><PRE
CLASS="SCREEN"
><SAMP
CLASS="PROMPT"
>shell></SAMP
> <KBD
CLASS="USERINPUT"
>mysql -u root -p cacti</KBD
></PRE
><P
> Now execute the following SQL:
</P
><PRE
CLASS="SCREEN"
><SAMP
CLASS="PROMPT"
>mysql></SAMP
> <KBD
CLASS="USERINPUT"
>update user_auth set password=md5('admin') where username='admin';</KBD
></PRE
></DIV
></DIV
></DIV
><DIV
CLASS="QANDADIV"
><H3
><A
NAME="AEN2460"
></A
>3. Monitoring</H3
><DIV
CLASS="QANDAENTRY"
><DIV
CLASS="QUESTION"
><P
><A
NAME="AEN2463"
></A
><B
> </B
> I am polling thousands of items and poller.php takes more than 5 minutes to run.
</P
></DIV
><DIV
CLASS="ANSWER"
><P
><B
> </B
> Give <SPAN
CLASS="APPLICATION"
>Spine</SPAN
>, the fast replacement for poller.php a try. Unlike poller.php, <SPAN
CLASS="APPLICATION"
>Spine</SPAN
> is written in c and makes use
of pthreads. On a typical installation, it is not uncommon for <SPAN
CLASS="APPLICATION"
>Spine</SPAN
> to poll about 500 items in less then 10
seconds.
</P
></DIV
></DIV
><DIV
CLASS="QANDAENTRY"
><DIV
CLASS="QUESTION"
><P
><A
NAME="AEN2471"
></A
><B
> </B
> I changed x, and now some of my graphs are not updating.
</P
></DIV
><DIV
CLASS="ANSWER"
><P
><B
> </B
> The best thing to do here is to force Cacti to rebuild its poller cache. To do this click <SPAN
CLASS="GUILABEL"
>Utilities</SPAN
> on the Cacti menu, and select <SPAN
CLASS="GUILABEL"
>Clear Poller Cache</SPAN
>.
</P
></DIV
></DIV
><DIV
CLASS="QANDAENTRY"
><DIV
CLASS="QUESTION"
><P
><A
NAME="AEN2478"
></A
><B
> </B
> I am using <SPAN
CLASS="APPLICATION"
>Redhat 8.0</SPAN
> and SNMP is not working.
</P
></DIV
><DIV
CLASS="ANSWER"
><P
><B
> </B
> <SPAN
CLASS="APPLICATION"
>Redhat 8.0</SPAN
> comes with a broken php-snmp package. Updating your 'php-snmp' and 'net-snmp'
packages to their latest versions should fix this problem.
</P
></DIV
></DIV
><DIV
CLASS="QANDAENTRY"
><DIV
CLASS="QUESTION"
><P
><A
NAME="AEN2485"
></A
><B
> </B
> How do I configure <SPAN
CLASS="APPLICATION"
>net-snmp</SPAN
> so it will work with Cacti?
</P
></DIV
><DIV
CLASS="ANSWER"
><P
><B
> </B
> Run <B
CLASS="COMMAND"
>snmpconf -g basic_setup</B
> and follow the prompts. Also check that the file being used by snmpd
is the correct config file. For Redhat Linux, snmpconf creates the <TT
CLASS="FILENAME"
>/etc/snmpd.conf</TT
>, but snmpd
uses <TT
CLASS="FILENAME"
>/etc/snmpd/snmpd.conf</TT
>.
</P
><P
> If this doesn't work a very simple config file is:
</P
><PRE
CLASS="SCREEN"
><KBD
CLASS="USERINPUT"
># contact
syslocation Something
syscontact "root@someone.com"
# auth
rocommunity public
# disk monitoring
disk /</KBD
></PRE
></DIV
></DIV
></DIV
><DIV
CLASS="QANDADIV"
><H3
><A
NAME="AEN2496"
></A
>4. Graphs</H3
><DIV
CLASS="QANDAENTRY"
><DIV
CLASS="QUESTION"
><P
><A
NAME="AEN2499"
></A
><B
> </B
> I just installed Cacti and all of my graphs appear as broken images.
</P
></DIV
><DIV
CLASS="ANSWER"
><P
><B
> </B
> For you to actually get graph images, poller.php must run at least once so it can create .rrd files in Cacti's 'rra/'
directory. Double check that you configured your <TT
CLASS="FILENAME"
>/etc/crontab</TT
> file to execute poller.php every
five minutes. Also make sure that the user poller.php runs as has permission to create new files in Cacti's 'rra/'
directory.
</P
><P
> If all of your settings appear correct, try running poller.php manually by cd'ing to Cacti's directory and typing:
</P
><PRE
CLASS="SCREEN"
><SAMP
CLASS="PROMPT"
>shell></SAMP
> <KBD
CLASS="USERINPUT"
>php poller.php</KBD
></PRE
><P
> If you have files in your 'rra/' directory, but your graphs still appear as broken images, you should enable graph
debug mode see exactly why the graphs are not rendering. To do this go into Cacti, select <SPAN
CLASS="GUILABEL"
>Graph Management</SPAN
>
from the menu, select any graph listed, and select <SPAN
CLASS="GUILABEL"
>Turn On Graph Debug Mode</SPAN
>.
</P
></DIV
></DIV
><DIV
CLASS="QANDAENTRY"
><DIV
CLASS="QUESTION"
><P
><A
NAME="AEN2512"
></A
><B
> </B
> My graphs render, but they do not contain any data.
</P
></DIV
><DIV
CLASS="ANSWER"
><P
><B
> </B
> More often than not, this problem's cause is permissions. For instance if you run poller.php manually as root for testing, any
.rrd files that it creates will be owned by root. Now when poller.php runs from cron, it will not be able to update these .rrd
files because they are owned by root. You can double check the owner of your .rrd files by running the following command in
your Cacti directory:
</P
><PRE
CLASS="SCREEN"
><SAMP
CLASS="PROMPT"
>shell></SAMP
> <KBD
CLASS="USERINPUT"
>ls -al rra/</KBD
></PRE
><P
> If only some of your graphs are not updating correctly, double check the <SPAN
CLASS="GUILABEL"
>Maximum Value</SPAN
> field for all data
sources used by these graphs. If the value being fed to the .rrd file exceeds its <SPAN
CLASS="GUILABEL"
>Maximum Value</SPAN
>, RRDTool
will insert an <SPAN
CLASS="GUILABEL"
>Unknown</SPAN
> and you will see no data on the graph.
</P
></DIV
></DIV
><DIV
CLASS="QANDAENTRY"
><DIV
CLASS="QUESTION"
><P
><A
NAME="AEN2524"
></A
><B
> </B
> A lot of my graphs contain long ifAlias names, but they are being truncated to 15 characters.
</P
></DIV
><DIV
CLASS="ANSWER"
><P
><B
> </B
> Cacti does this by default to better control graph title formatting. You can change this limit, by going to <SPAN
CLASS="GUILABEL"
>Cacti
Settings</SPAN
> on the Cacti menu, selecting the <SPAN
CLASS="GUILABEL"
>Visual</SPAN
> tab, and changing the value for <SPAN
CLASS="GUILABEL"
>Data
Queries - Maximum Field Length</SPAN
>.
</P
></DIV
></DIV
><DIV
CLASS="QANDAENTRY"
><DIV
CLASS="QUESTION"
><P
><A
NAME="AEN2532"
></A
><B
> </B
> One of my devices rebooted and now I have a huge spike on my graph!
</P
></DIV
><DIV
CLASS="ANSWER"
><P
><B
> </B
> This occurs because the reboot causes SNMP's counters to reset, which can cause a rather large spike on the graph when
<SPAN
CLASS="APPLICATION"
>RRDTool</SPAN
> tries to determine the change between the new small counter value and the large
previous value. One way to combat this issue is to specify realistic maximum values for your data sources.
<SPAN
CLASS="APPLICATION"
>RRDTool</SPAN
> will ignore any value that is larger than the maximum value.
</P
><P
> If you already have a spike on one or more of your graphs, there is a really <A
HREF="http://cricket.sourceforge.net/contrib/files/killspike2"
TARGET="_top"
>useful Perl script</A
> that will remove them for you.
</P
></DIV
></DIV
><DIV
CLASS="QANDAENTRY"
><DIV
CLASS="QUESTION"
><P
><A
NAME="AEN2541"
></A
><B
> </B
> RRDTool Says: ERROR: unknown option '--slope-mode' or RRDTool Says: ERROR: Garbage ':39:24 To 2005/10/22 16:39:24\c' after command: COMMENT:From 2005/10/21 16:39:24 To 2005/10/22 16:39:24\c
</P
></DIV
><DIV
CLASS="ANSWER"
><P
><B
> </B
> This occurs because the version of RRDTool that you are running does not match the RRDTool version Cacti is configured to use. Double check your Cacti Settings and make sure that the RRDTool version matches what version of RRDTool you are running.
</P
></DIV
></DIV
></DIV
><DIV
CLASS="QANDADIV"
><H3
><A
NAME="AEN2545"
></A
>5. Windows Related</H3
><DIV
CLASS="QANDAENTRY"
><DIV
CLASS="QUESTION"
><P
><A
NAME="AEN2548"
></A
><B
> </B
> I get a "Fatal error: Cannot redeclare title_trim()" error message from Cacti.
</P
></DIV
><DIV
CLASS="ANSWER"
><P
><B
> </B
> Contrary to previous versions of Cacti, you must not put Cacti in your PHP include path. Check your <TT
CLASS="FILENAME"
>php.ini</TT
> file to make sure there is not something like <KBD
CLASS="USERINPUT"
>include_path = C:/Apache2/htdocs/cacti</KBD
>.
</P
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