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FAQ

Frequently Asked Questions

This is a collection of questions that were asked repeatedly on discourse or github.

Odd random character queries in Pi-hole's query logs

You see three queries containing only random strings, sometimes with the local domain suffix, like

yfjmdpisrvyrnq
attxnwheeeuiad
nskywzjbpj

Solution:

This happens when using Chrome-based browsers. Chrome tries to find out if someone is messing up with the DNS (i.e. wildcard DNS servers to catch all domains). Chrome does this by issuing DNS requests to randomly generated domain names with bewteen 7 and 15 characters

In a normal setup this results in a “No such name” response from your DNS server. If the DNS server you use has a wildcard setup, each of these requests will result in a response (which is normally even the same) so Chrome knows that there is someone messing around with DNS responses.

Link to Chromium's source code explaining the function.

Pi-hole update fails due to repository changed it's 'Suite' value

This happens after a manual OS upgrade to the next major version on deb based systems. A typical message is

Repository 'http://archive.raspberrypi.org/debian buster InRelease' changed its 'Suite' value from 'stable' to 'oldstable'

Solution:

sudo apt-get update --allow-releaseinfo-change

Pi-hole's gravity complains about invalid IDN domains

During a gravity update, Pi-hole complains about some invalid Internationalized Domain Names (IDN) domains

Sample of invalid domains:
- test.中国
- test.рф
- test.भारत
- e-geräteundhaus.com
- rëddït.com

Solution:

Ask the list maintainer to convert the IDNs to their punycode representation.

Internationalizing Domain Names in Applications (IDNA) was conceived to allow client-side use of language-specific characters in domain names without requiring any existing infrastructure (DNS servers, mall servers, etc., including associated protocols) to change. Accordingly, the corresponding original RFC 3490 clearly states that IDNA is employed at application level, not on the server side. Hence, DNS servers never see any IDN domain name, which means DNS records do not store IDN domain names at all, only their Punycode representations.

While loading data from the long-term database you encountered an error

If requesting a lot of data from the long-term database you get this error

An unknown error occurred while loading the data.
Check the server's log files (/var/log/lighttpd/error.log when you're using the default Pi-hole web server) for details. You may need to increase the memory available for Pi-hole in case you requested a lot of data.

Solution:

Increase PHP's memory and restart the server.

Replace * with your installed PHP version (e.g. .../php/7.3/cgi/...) to edit the file. Increase the memory_limit. You can use common abbreviation (M= megabyte, G= gigabyte). The amount of memory needed depends on many factors, e.g. availabe system RAM, other processes running on your device, the amount of data you want to process. Do not assign all availabe memory as this can freeze your system. One approache would be to double the limit and check if it might be already sufficient to retrieve the data. If not, add another 128M, check again, add another 128M,.... Please consider the possibility that your system does not have enough memory at all to load all the needed data.

sudo nano /etc/php/*/cgi/php.ini
[..]
; Maximum amount of memory a script may consume (128MB)
; http://php.net/memory-limit
memory_limit = 128M
[..]
sudo service lighttpd restart

Last update: December 22, 2021
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