Query database
Pi-hole FTLDNS uses the well-known relational database management system SQLite3 as its long-term storage of query data. In contrast to many other database management solutions, FTLDNS does not need a server database engine as the database engine is directly embedded in FTLDNS. It seems an obvious choice as it is probably the most widely deployed database engine - it is used today by several widespread web browsers, operating systems, and embedded systems (such as mobile phones), among others. Hence, it is rich in supported platforms and offered features. SQLite implements most of the SQL-92 standard for SQL and can be used for high-level queries.
The long-term query database was the first database that was added to the Pi-hole project.
We update this database periodically and on the exit of FTLDNS (triggered e.g. by a service pihole-FTL restart). The updating frequency can be controlled by the parameter DBINTERVAL and defaults to once per minute. We think this interval is sufficient to protect against data losses due to power failure events. FTLDNS needs the database to populate its internal history of the most recent 24 hours. If the database is disabled, FTLDNS will show an empty query history after a restart.
The location of the database can be configured by the config parameter DBFILE. It defaults to /etc/pihole/pihole-FTL.db. If the given file does not exist, FTLDNS will create a new (empty) database file.
Another way of controlling the size of the long-term database is by setting a maximum age for log queries to keep using the config parameter MAXDBDAYS. It defaults to 365 days, i.e. queries that are older than one year get periodically removed to limit the growth of the long-term database file.
The config parameter DBIMPORT controls whether FTL loads information from the database on startup. It needs to do this to populate the internal data structure with the most recent history. However, as importing from the database on disk can delay FTL on very large deploys, it can be disabled using this option.
Split database¶
You can split your long-term database by periodically rotating the database file (do this only when pihole-FTL is not running). The individual database contents can easily be merged when required.
This could be implemented by running a monthly cron job such as:
sudo service pihole-FTL stop
sudo mv /etc/pihole/pihole-FTL.db /media/backup/pihole-FTL_$(date +"%m-%y").db
sudo service pihole-FTL start
Note that DNS resolution will not be available as long as pihole-FTL is stopped.
Backup database¶
The database can be backed up while FTL is running when using the SQLite3 Online backup method, e.g.,
sqlite3 /etc/pihole/pihole-FTL.db ".backup /home/pi/pihole-FTL.db.backup"
will create /home/pi/pihole-FTL.db.backup which is a copy of your long-term database.
The long-term database contains three tables:
Query Table¶
| Label | Type | Allowed to by empty | Content |
|---|---|---|---|
id |
integer | No | autoincrement ID for the table, only used by SQLite3, not by FTLDNS |
timestamp |
integer | No | Unix timestamp when this query arrived at FTLDNS (used as index) |
type |
integer | No | Type of this query (see Supported query types) |
status |
integer | No | How was this query handled by FTLDNS? (see Supported status types) |
domain |
text | No | Requested domain |
client |
text | No | Requesting client (IP address) |
forward |
text | Yes | Forward destination used for this query (only set if status == 2) |
Counters table¶
This table contains counter values integrated over the entire lifetime of the table
| Label | Type | Allowed to by empty | Content |
|---|---|---|---|
id |
integer | No | ID for the table used to select a counter (see below) |
value |
integer | No | Value of a given counter |
| ID | Interpretation |
|---|---|
| 0 | Total number of queries |
| 1 | Total number of blocked queries |
FTL table¶
The FTL table contains some data used by FTLDNS for determining which queries to save to the database. This table does not contain any entries of general interest.
SQLite3 syntax used to create this table:
Supported query types¶
| ID | Query Type |
|---|---|
| 1 | A |
| 2 | AAAA |
| 3 | ANY |
| 4 | SRV |
| 5 | SOA |
| 6 | PTR |
| 7 | TXT |
Supported status types¶
| ID | Status | Details | |
|---|---|---|---|
| 0 | Unknown | ❔ | was not answered by forward destination |
| 1 | Blocked | ❌ | Domain contained in gravity database |
| 2 | Allowed | ✅ | Forwarded |
| 3 | Allowed | ✅ | Known, replied to from cache |
| 4 | Blocked | ❌ | Domain matched by a regex blacklist filter |
| 5 | Blocked | ❌ | Domain contained in exact blacklist |
| 6 | Blocked | ❌ | By upstream server (known blocking page IP address) |
| 7 | Blocked | ❌ | By upstream server (0.0.0.0 or ::) |
| 8 | Blocked | ❌ | By upstream server (NXDOMAIN with RA bit unset) |
| 9 | Blocked | ❌ | Domain contained in gravity database Blocked during deep CNAME inspection |
| 10 | Blocked | ❌ | Domain matched by a regex blacklist filter Blocked during deep CNAME inspection |
| 11 | Blocked | ❌ | Domain contained in exact blacklist Blocked during deep CNAME inspection |
Example for interaction with the long-term query database¶
In addition to the interactions the Pi-hole database API offers, you can also run your own SQL commands against the database. If you want to obtain the three most queries domains for all time, you could use
sqlite3 "/etc/pihole/pihole-FTL.db" "SELECT domain,count(domain) FROM queries WHERE (STATUS == 2 OR STATUS == 3) GROUP BY domain ORDER BY count(domain) DESC LIMIT 3"
which would return something like
discourse.pi-hole.net|421095
www.pi-hole.net|132483
posteo.de|130243
showing the domain and the number of times it was found in the long-term database. Note that such a request might take a very long time for computation as the entire history of queries has to be processed for this.