# Frequently Asked Questions

## Using Cacti

**Q:** How do I create traffic graphs?

**A:** 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 net-snmp
installation. You can use the about page to determine whether to are using
"built-in" or "external" SNMP support.

Now that you have working SNMP support, follow these steps.

1. Click Devices on Cacti's menu.

2. Click Add to add a new device.

3. Type a description, hostname, management IP, and SNMP community. Make sure to
   select "Generic SNMP-enabled Host" under Host Template and click Create.

4. Click Create Graphs for this Host at the top of the page.

5. You should see one or more interfaces listed under the Data Query [SNMP -
   Interface Statistics] 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).

6. Click Create, and Create again on the following screen to create your graphs.

## General

**Q:** When I visit the Cacti Monitoring Website, I see garbage instead of a
login prompt.

**A:** Starting with Cacti 1.2.x, the first thing you should always see is a
login prompt asking for your admin credentials before the installation wizard
will be displayed. However, if you fail to see the login prompt, you may be
presented with text that looks like:

```php
<?php
/*
 +-------------------------------------------------------------------------+
 | Copyright (C) 2004-2026 The Cacti Group                                 |
 |                                                                         |
 | This program is free software; you can redistribute it and/or           |
 | modify it under the terms of the GNU General Public License             |
 | as published by the Free Software Foundation; either version 2          |
 | of the License, or (at your option) any later version.                  |
```

If this happens, it usually means that you have not enabled the PHP module to
work with your web server software. This can be as simple as running `a2enmod`
on Ubuntu, or having to manually create a configuration for nginx under another
flavour of Linux. For specific help on enabling PHP, search the internet using
your favourite search engine with keywords such as:

> How do I enable PHP under ...

Replacing the three dots with your operating system and web server software
should reveal many results on how to do this. The specific steps are outside of
the scope of Cacti's FAQ documentation, though there are several How To
installation documents included that may also help.

---

**Q:** I have forgotten my 'admin' password to Cacti, how do I reset it?

**A:** To reset the admin account password back to the default of 'admin',
connect to your Cacti database at the command line.

```sql
shell> mysql -u root -p cacti
```

Now execute the following SQL:

```sql
MySQL> update user_auth set password=md5('admin') where username='admin';
```

## Monitoring

**Q:** I am polling thousands of items and poller.php takes more than 5 minutes
to run.

**A:** Give Spine, the fast replacement for poller.php a try. Unlike poller.php,
Spine is written in c and makes use of threads. On a typical installation, it is
not uncommon for Spine to poll about 50000 items in less then 10 seconds. Spine
supports upto several threads per poller process and can also poll a single
hosts with more than a single thread.

If using spine alone does not help, look to both the amount of memory and CPU
threads are available on your Cacti server. You should generally not use more
than 2 times the number of CPU threads as you have spine threads. Remember,
every spine thread has to also talk to the database, so having more CPU threads
on your Cacti server has a direct impact on performance. If you make the thread
setting too high, it will actually decrease performance. So, be careful.

---

**Q:** I changed x, and now some of my graphs are not updating.

**A:** First, check your Poller Cache to see if the poller entries for the Data
Sources in question are still found there. Then, if you find that they are
missing, you can either resave the Device in question, if it's a single device,
or Repopulate the Poller cache if it impacts multiple Devices. If you have a
large installation with thousands or tens of thousands of devices you should use
the CLI script `rebuild_poller_cache.php` to perform this action.

Often times, if you have changed a Template, bad things can happen. So, it's
always advisable to have a backup of your Graph and Data Templates as well as
any Script or XML files you used to create the Templates. Another good practice
is to perform database backups daily just in case of either an unintended
change, or a disaster.

---

**Q:** I am using Redhat 8.0 and SNMP is not working.

**A:** Redhat 8.0 comes with a broken php-snmp package. Updating your 'php-snmp'
and 'net-snmp' packages to their latest versions should fix this problem.

---

**Q:** How do I configure net-snmp so it will work with Cacti?

**A:** Run `snmpconf -g basic_setup` and follow the prompts. Also check that the
file being used by snmpd is the correct config file. For Redhat Linux, snmpconf
creates the `/etc/snmpd.conf`, but snmpd uses `/etc/snmpd/snmpd.conf`.

If this doesn't work a very simple config file is:

```console
    # contact
    syslocation Something
    syscontact "root@someone.com"

    # auth
    rocommunity public

    # disk monitoring
    disk /

    # Don't monitor NFS
    skipNFSInHostResources true

    # Allow for real big disk volumes
    realStorageUnits 0
```

After you have made the changes to the net-snmp configuration file, you should
restart the service using the following command:

```sh
systemctl enable snmpd
systemctl restart snmpd
```

Though there are many more advanced settings available in net-snmp, it generally
recommended to keep a simpler configuration unless your information security
policies require more stringent settings.

---

**Q:** I've installed Cacti, and scheduled a network discovery, but nothing is
happening. Where should I go to see the issue?

**A:** You should click the **Log** tab at the top of the page. When you get to
the **Log** tab, you should search for an entry "SYSTEM STATS:". If you do not
find that entry, it means that you Cacti Data Collector, otherwise known as the
Cacti Poller is not running.

This can happen if you have neglected to create either a CRON entry for the
Cacti Poller, or registered and started the `cactid` service available in the
latest Cacti. If you find that the CRON entry is there, you should look at your
systems CRON log for entries like **permission denied**. Sometimes the user
accounts you have selected to run the CRON are not permitted to do so. We
strongly recommend that you use the `cactid` service with Cacti 1.x though and
avoid CRON based Data Collection though.

## Graphs

**Q:** I just installed Cacti and all of my graphs appear as broken images.

**A:** 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 `/etc/crontab` file or the `cactid` service to execute
poller.php at the desired frequency, normally either every 1 or 5 minutes. Also
make sure that the user poller.php runs as has permission to create new files in
Cacti's 'rra/' directory. In the modern Cacti, both the Web Server account and
Cacti's Poller account must have write access.

If all of your settings appear correct, try running poller.php manually by
cd'ing to Cacti's directory and typing:

```sh
shell> php poller.php
```

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 Graph Management from the menu,
select any graph listed, and select Turn On Graph Debug Mode.

---

**Q:** My graphs render, but they do not contain any data.

**A:** 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:

```sh
shell> ls -al rra/
```

If only some of your graphs are not updating correctly, double check the Maximum
Value field for all data sources used by these graphs. If the value being fed to
the .rrd file exceeds its Maximum Value, RRDtool will insert an Unknown and you
will see no data on the graph.

---

**Q:** A lot of my graphs contain long ifAlias names, but they are being
truncated to 15 characters.

**A:** Cacti does this by default to better control graph title formatting. You
can change this limit, by going to Cacti Settings on the Cacti menu, selecting
the Visual tab, and changing the value for Data Queries - Maximum Field Length.

---

**Q:** One of my devices rebooted and now I have a huge spike on my graph!

**A:** This occurs because the reboot causes SNMP counters to reset, which can
cause a rather large spike on the graph when RRDtool 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. RRDtool will ignore any value that is larger than the maximum value.

If you already have a spike on one or more of your graphs, there is a really
[useful Perl script](http://cricket.sourceforge.net/contrib/files/killspike2)
that will remove them for you.

---

**Q:** I have a remote poller that is timing out but SNMP timing to the devices
is fine

**A:** Check that the network connection between the Remote poller and Main
poller is working ok if the link has very high latency this can cause the
polling times to increase as the data being transferred from the remote poller
will be slowed causing the poll not to finish in time

---

**Q:** 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:** 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.

## Windows Related

**Q:** I get a "Fatal error: Cannot redeclare title_trim()" error message from
Cacti.

**A:** Contrary to previous versions of Cacti, you must not put Cacti in your
PHP include path. Check your `php.ini` file to make sure there is not something
like `include_path = C:/Apache2/htdocs/cacti`.

## Common Problems

### I see "MySQL server has gone away" in cacti log and cacti does not work as expected

Check the following in MySQL/MariaDB
```
SHOW GLOBAL VARIABLES LIKE 'max_connections';
SHOW GLOBAL STATUS LIKE 'max_used_connections';
```

If they are close, increase the max_connections in the server.cnf (mysql.cnf, my.cnf) 
and restart MariaDB/MySQL.

### Cron is out of sync with the Poller Interval

```shell
WARNING: Cron is out of sync with the Poller Interval! The Poller Interval is
'15' seconds, with a maximum of a '60' second Cron, but 300.9 seconds have
passed since the last poll!
```

This warning message may be recorded in the Cacti logs if you have a mismatch
between the cron file that runs the poller.php and the settings within Cacti
itself. Browse to **Console > Configuration > Settings > Poller** _(tab)_ and
check that the Cron Interval is defined as either 1 minute or 5 minutes.

If the cron interval is 5 minutes, then the schedule within the cron
configuration file (normally /etc/cron.d/cacti) should be set to:

```console
*/5 * * * *
```

For 1 minute intervals, this should be:

```console
* * * * *
```

### Poller Runtime exceeded

```shell
POLLER: Poller[0] Maximum runtime of xxx seconds exceeded.
```

This error indicates that Cacti was unable to finish the polling cycle in time.
This can be for a few reasons.

- You are using spine and have not entered the correct mysql credentials in
  spine.conf
- You do not have an adaquete process setting for cmd.php or thread/process
  count for spine
- Network related issue either an network outage or a network slowdown
- System related trouble cpu/memory exhaustion
- Insufficient MySQL connections resulting in spine failing

### RRDtool reports Unknown Error

Sometimes, RRDtool can be rather unhelpful and display the simple error within
the graph image of "Unknown Error". When this occurs, the best course of action
would be to grab the command that Cacti uses and see if any more information is
given at the command line level.

To do this, edit a graph that has the issue, select **Turn On Graph Debug** and
a new section should appear beneath the graph. This should show both the command
and what output we received from the tool.

```console
RRDtool Command:
  /usr/bin/rrdtool graph - \
  --imgformat=PNG \
  --start='-86400' \
  --end='-60' \
  --pango-markup  \
  --title='localhost - CPU Usage' \
  --vertical-label='percent' \
  --slope-mode \
  --base=1000 \
  --height=200 \
  --width=700 \
  --tabwidth '40' \
  --rigid \
  --alt-autoscale-max \
  --lower-limit='0' \
  COMMENT:"From 2019/10/19 12\:37\:00 To 2019/10/20 12\:36\:00\c" \
  COMMENT:"  \n" \
  --color BACK#F3F3F3 \
  --color CANVAS#FDFDFD \
  --color SHADEA#CBCBCB \
  --color SHADEB#999999 \
  --color FONT#000000 \
  --color AXIS#2C4D43 \
  --color ARROW#2C4D43 \
  --color FRAME#2C4D43 \
  --border 1 --font TITLE:11:'Arial' \
  --font AXIS:8:'Arial' \
  --font LEGEND:8:'Courier' \
  --font UNIT:8:'Arial' \
  --font WATERMARK:6:'Arial' \
  --slope-mode \
  --watermark 'Generated by Cacti' \
  DEF:a='/usr/share/cacti/site/rra/127_0_0_1_5min_cpu_40.rrd':'5min_cpu':MAX \
  AREA:a#FF0000FF:'CPU Usage'  \
  GPRINT:a:LAST:'Current\:%8.0lf'  \
  GPRINT:a:AVERAGE:'Average\:%8.0lf'  \
  GPRINT:a:MAX:'Maximum\:%8.0lf\n'

RRDtool Says:
  OK
```

If the output above isn't helpful, simply copy the command section and then run
it as the user which the website runs as. For Linux, you can do this by either
`su - <user>` and then running the command, or `sudo -u <user> <command>` to
stay as your current user but run the command as the website user.

For Windows, the following command will allow you to spawn a command prompt as
the website user, from which you can then run the above command to see the
output.

```console
runas /user:<machine or domain>\<user> cmd.exe
```

The newly created command prompt should show the user name if you have entered
the correct password.

---

Copyright (c) 2004-2026 The Cacti Group
