ClickHouse DB Installation for Nectus Netflow & Syslog Storage

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Requirements:  Operating System: Ubuntu 22.04.1 LTS       RAM: 16GB   vCPU: 2

More information about installation:

Step 1

Open terminal and install required packages:

sudo apt-get update
sudo apt-get install -y apt-transport-https ca-certificates dirmngr

Step 2

Import the ClickHouse public key:

sudo apt-key adv –keyserver hkp:// –recv 8919F6BD2B48D754

NOTE: It is recommended to import the public key if it’s a fresh Ubuntu install.

Otherwise, you may get the following error when adding the repository:

GPG error:
The following signatures couldn’t be verified because the public key is not available:

NO_PUBKEY 8919F6BD2B48D754

Step 3

Add ClickHouse repository:

echo “deb stable main” | sudo tee \

Step 4

Install ClickHouse:

NOTE: During the installation you will be asked to create a password for default user.

Generate a strong password and save it, it will be used for further configuration.

sudo apt-get update
sudo apt-get install -y clickhouse-server clickhouse-client

Step 5

Start ClickHouse server as a daemon:

sudo service clickhouse-server start

Step 6

Now after installation it is time to test connection to ClickHouse database.

Start client (use password generated on Step 4):

clickhouse-client –password

NOTE: Use Ctrl+D to exit ClickHouse client.
NOTE: TCP ports 8123 and 9000 must be open

Step 7

NOTE: Use Ctrl+D to exit ClickHouse client.

While being connected to the ClickHouse, create required Netflow & Syslog databases:


ClickHouse Configuration

Step 8

By default, ClickHouse allows inbound connections from localhost only.

To allow connections from remote IP-s

edit /etc/clickhouse-server/config.xml:

sudo vim /etc/clickhouse-server/config.xml

Find <listen_host> parameters (one for IPv6 and one for IPv4) allowing all connections after <logger> section, and uncomment them.

Also uncomment and change to 1 <listen_reuse_port> tag for allowing simultaneous IPv4 and IPv6 interfaces:


<!– Same for hosts without support for IPv6: –>


Step 9

Restart ClickHouse to apply new parameters:

sudo service clickhouse-server restart

Step 10

Add internal ClickHouse user “root” for Nectus server to connect to DB.

For that edit users.xml file:

sudo vi /etc/clickhouse-server/users.xml

Find <users> section right after <profiles> section.

Add code snippet with user configuration from below, right between </users> and <default> tags, as on a screenshot below.

Generate strong password, replace it in snippet below, and then save file:

<networks incl=”networks” replace=”replace”>

NOTE: If file was overwritten by WinSCP or any other similar tool, verify that file has correct ownership:

sudo chown clickhouse:clickhouse /etc/clickhouse-server/users.xml

Step 11

Restart ClickHouse to apply new user:

sudo service clickhouse-server restart

Step 12

Verify newly created user able to log in:

clickhouse-client -u root –password

Step 13

Disable limit of max database size to drop. By default, ClickHouse doesn’t allow to drop table bigger than 50 Gb to prevent occasional data loss.

NOTE: More info here:

To disable it, edit config file /etc/clickhouse-server/config.xml:

sudo vi /etc/clickhouse-server/config.xml

Find and uncomment line to disable limit of max table size to drop:


Restart ClickHouse to apply change:

sudo service clickhouse-server restart

Nectus Configuration

Step 14

We have completed the ClickHouse installation. This last step requires login to Nectus to finish the NetFlow/Syslog integration.

Open to “Nectus Settings -> General Settings -> Netflow Integration” page:

Enter the required information and click Test DB Connection (Remote Server IP is the IP address of the Ubuntu/ClickHouse server). The result should be “Test DB Connection OK”

Click “Run Integration Scripts” and finally Save.

Step 15

Restart Nectus NetFlow and Syslog Services.