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4. Configuration

Redis configuration

Set the maximum size of memory allocated for data storage and policy of work when this limit will be achieved in /etc/redis/redis.conf the file. To prevent loss of data you should use these settings:

maxmemory 2GB 
maxmemory-policy noeviction

To apply the settings restart Redis server service:

service redis-server restart

ISP Go modules configuration

All the modules read the same configuration file /etc/isp-go/config.ini
The file consists of several sections.

[dnscache] section
[dnscache] section

This section is used by isp-go-dnsproxy and contains only one key - forward. As a value, you should set an IP address and a port of caching DNS server which will be used to resolve all non-blocked DNS requests.


forward =

[proxy] section

[proxy] section

This section is used by isp-go-dnsproxy and contains listen blockpage-ip, log, and PID keys.
The ‘Listen’ key contains an IP address and a port on which isp-go-dnsproxy should get DNS requests from users. It can be duplicated to accept requests on several addresses at once, for example, IPv4 and IPv6 at the same time. The number of keys, as well as the number of listening addresses, is unlimited

blockpage-ip key contains an IP address of a block page, which should be passed to users in answers to blocked requests. This is the IP address where Nginx accepts requests to the block page. In general, case when filtering DNS server and Nginx are on the same server you should set for this key the same IP address as for the listening key. The key can be duplicated to specify an alternative address for the block pages, for example, for IPv6. It is allowed to use at least one key only for A redirects or only AAAA packets, but no more than two to support both IP versions.

log, pid keys contain the absolute path to the log file and PID file accordingly. To prevent loss of compatibility with init scripts from the ISP Go package you should not change the path to the PID file.


listen = ; IPv4 
listen = [4321:a:bcde:1::2020]:53 ; IPv6 
blockpage-ip = ; IPv4 to forwarding A 
blockpage-ip = abcd:1234:zyxw::9876 ; IPv6 to forwarding AAAA 
log = /var/log/isp-go/isp-go-dnsproxy.log 
pid = /var/log/isp-go/

[datafiles] section

[datafiles] section

This section contains 'path', 'file', 'cats' keys. ‘file’ key can be used several times in this section.

The ‘path’ key contains the absolute path to the directory with the SafeDNS domain database. Files, that database is made of, should be enumerated in the ‘file’ keys. The order of these keys is important for correct work. Each top-listed file is processed as a correction to all bottom-listed files. To maintain the correct work of the database we prohibit the change of default values for these keys.

The ‘cats’ key contains the absolute path to the JSON file with the list of supported categories. You cannot change this file, because all changes made to it, will be lost on the ISP Go package update. If you need to hide some categories or translate them to some other language you should create a copy of the catgroups.json file and make all changes in the copy. The numbers of the categories should not be changed because they are linked to the content of the master database of SafeDNS.


path = /var/lib/isp-go/filter/ 
file = host2cat-fast.dat file = host2cat.dat 
cats = /usr/share/isp-go/config/

[blockpage] section

[blockpage] section

This section is used by the isp-go-blockpage application and contains 'listen', 'templates', 'log', and 'pid' keys.
‘listen’ key contains an IP address (usually and a port that isp-go-blockpage daemon listens on for HTTP requests to block page.

Daemon isp-go-blockpage does not accept requests from users. All requests should be passed through Nginx.

The ‘templates’ key contains the absolute path to the directory with templates of block page. Do not change templates installed with the package, because all changes made will be lost on the ISP Go package update. We recommend copying the whole directory /usr/share/isp-go/templates and changing templates in this copy.

‘log’ and ‘pid’ keys contain the absolute path to log and PID files accordingly. To prevent loss of compatibility with init scripts from the ISP Go package you should not change the path to pidfile.


listen = 
templates = /usr/share/isp-go/templates/ 
log = /var/log/isp-go/isp-go-blockpage.log 
pid = /var/run/isp-go/

[api] section

[api] section

This section is used by the web application isp-go-api and contains 'listen', 'log', and 'pid' keys.
listen key contains an IP address (usually and a port that isp-go-api daemon listens on for HTTP requests to API. An IP address or a port should be different from the set in the [blockpage] section

Listening on an externally accessible IP address will be a security problem. The isp-go-api daemon does not contain any authorization mechanisms, so anyone who can send a request can make any changes to user settings (including someone else's). To prevent such a situation, it is recommended to use the IP address here and to implement external access (with authorization) at the Nginx level.


listen = 
log = /var/log/isp-go/isp-go-api.log 
pid = /var/run/isp-go/

[common] section
[common] section

The section is used by all three daemons and contains the keys 'redis-ip' and 'redis-port'.

The 'redis-ip' and 'redis-port' keys specify which Redis server the daemons that are part of ISP Go should connect to. For performance reasons, it is recommended to run the Redis server on the same machine where ISP Go is installed.


redis-ip = 
redis-port = 6379

Enabling ISP Go services

To enable ISP Go services automatic startup please run the following commands:

systemctl enable isp-go-dnsproxy
systemctl enable isp-go-blockpage
systemctl enable isp-go-api

Applying settings

After changing the configuration file you should restart all ISP Go services:

service isp-go-dnsproxy restart 
service isp-go-blockpage restart 
service isp-go-api restart

Nginx configuration

Nginx is used in ISP Go for the following tasks:
• separation of API requests from requests to the block page and to the administrative web interface
• proxying requests to corresponding web applications
• restricting access to the API and to the administrative web interface

For correct separation of requests, you need to register the domain name used to manage filtering through the API in the server_name directive of the file /etc/nginx/sites-available/isp-go-api instead of the value 'api.ispgo'.

All other requests will go to the virtual host configured in the file /etc/nginx/sites-available/isp-go-blocked due to the presence of the default_server modifier in the listen directive.

You can create additional virtual hosts with the following exceptions:
• each additional virtual host should contain the server_name directive
default_server option cannot be used
• HTTPS usage is not recommended, because users who are requesting blocked websites via HTTPS will get browser warnings of an invalid SSL certificate.

IP addresses and ports in the proxy_pass directive in Nginx configuration files should correspond with IP addresses and ports on which web applications were launched (see listen key in /etc/isp-go/config.ini file).

API access is restricted using the allow and deny directives. Directives are processed in turn from top to bottom until the first match. The default configuration allows access only from the address You must allow access from the server where the billing system is installed.

In no case, access should be allowed to the API from untrusted (including user) systems, because if access to the API is provided an attacker can change any filtering settings for any users.

To apply changes reload Nginx:

service nginx reload

Database update

In the installation process demo version of the database will be copied to  /var/lib/isp-go/filter/ folder. For production deployment, you should replace the demo version with the full one and configure automatic updates.
The domain database is updated by cron using rsync. You need an ssh key to authorize access to the server. To get auto-update to perform the following steps:

Generate an ssh key that will be used to download domain database updates:

mkdir safedns-key 
cd safedns-key 
ssh-keygen -t rsa -N "" -f id_rsa

As a result, the files id_rsa (private key, which must be kept strictly secret and not lost) and (public key) will be created.

Send the created file to the technical support team at Don't need to send id_rsa antwhere!

The technical support team will notify you when the ssh key will be authorized on the SafeDNS server.

Copy the id_rsa and files to the directory where the update script is looking for them:

mkdir -p -m 0755 /var/lib/isp-go/.ssh 
cd safedns-key 
cp id_rsa /var/lib/isp-go/.ssh/ 
chown -R isp-go:isp-go /var/lib/isp-go/.ssh

Wait for 1 hour and make sure that host2cat.dat and host2cat-fast.dat files in the directory /var/lib/isp-go/filter have been updated.

You can also update the data-files manually, just run the following commands:

su isp-go -c 'rsync -rtv --progress ~/filter/' 
su isp-go -c 'rsync -rtv --progress ~/filter/'

The server should have access to on TCP port 443.

Setting up sending the statistics

To do this, you need to allow outgoing connections from the isp-go server to on TCP port 443 and perform all the steps from Setting up automatic updating of the domain database (previous part).

To check the correctness of sending statistics on the isp-go server, please perform:

curl -f -X POST --data "key=`cut -d ' ' -f 2 /var/lib/isp-go/.ssh/ | base64 -d | md5sum | cut -d ' ' -f1`&count=`redis-cli --raw hlen ip`"

OK is the correct answer to this command.

Block page design

By default, ISP Go comes with a minimal, strict, and ascetic design of the lock page. To change this design, you need to edit the HTML templates that are located at /usr/share/isp-go/templates/, where base.html – is the main template file, and the rest are inherited from it. The syntax of templates is described in the Go language guide:

The following variables are available:

• Domain: requested hostname in the Host field of HTTP request header
• Cats: array with category names of the blocked websites. This variable is allowed to use with the blocked_by_category.html template file only.

To add images to a block page we recommend setting a separate virtual host for image storing and using an absolute URL to an image with <img> tag (example: <img></img>)

To apply changes restart the isp-go-blockpage service:

service isp-go-blockpage restart

Peculiarities of listening on specific IP addresses

It is possible to use the IP address in the listen key of a [proxy] section of the configuration file if you use caching DNS server installed on another server. In this case, isp-go-dnsproxy will process requests on all network interfaces.
If you have caching DNS server installed on the same server (and listening on IP address), you should designate a specific IP address from one of the network interfaces.

User activity statistics

Statistics are recorded to a CSV file and imported into the PostgreSQL database every 5 minutes. Statistics are stored in the database in "raw" and aggregated form. "Raw" statistics are stored for 1 day. Aggregated statistics are stored for 3 months.
The statistics are recalculated every five minutes.

If a user has more than one IP address, then statistics for all addresses are summarized. Likewise for anonymous users.
The following reports are available:
• number of requests by hours and days for the period;
• number of requests to the top 100 domains;
• detailed statistics by domains and days;
• "Raw" statistics for the last hour.
Statistics are accessed through requests to the ISP Go REST API.