# Start a Tryton instance and cron instance

**URL:** <https://discuss.tryton.org/t/start-a-tryton-instance-and-cron-instance/2118>\
**Category:** User\
**Tags:** docker\
**Created:** [December 26, 2019, 1:37pm UTC](https://discuss.tryton.org/t/start-a-tryton-instance-and-cron-instance/2118 "2019-12-26T13:37:59Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![trytfan](https://discuss-cdn.tryton.org/letter_avatar_proxy/v4/letter/t/f19dbf/32.png) [@trytfan](https://discuss.tryton.org/u/trytfan)\
**Post date:** [December 26, 2019, 1:37pm UTC](https://discuss.tryton.org/t/start-a-tryton-instance-and-cron-instance/2118/1 "2019-12-26T13:37:59Z")

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Hello Forum,

when should i use “ **Start a Tryton instance** ” and when “ **Start a Tryton cron instance** ”?

[https://hub.docker.com/r/tryton/tryton](https://hub.docker.com/r/tryton/tryton)

How can i use a external database with Tryton Docker?  
Which dababase should i prefren, PostgresSQL 12?

> **[PostgreSQL](https://www.postgresql.org/)**
>
> The world's most advanced open source database.

Thank you, have a nice day

trytfan

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**Author:** ![ced](https://discuss-cdn.tryton.org/user_avatar/discuss.tryton.org/ced/32/1237_2.png) [@ced](https://discuss.tryton.org/u/ced)\
**Post date:** [December 26, 2019, 1:56pm UTC](https://discuss.tryton.org/t/start-a-tryton-instance-and-cron-instance/2118/2 "2019-12-26T13:56:45Z")

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> [@trytfan](#):
>
> when should i use “ **Start a Tryton instance** ” and when “ **Start a Tryton cron instance** ”?

You need at least the “Tryton instance”. But if you want to have scheduled actions performed automatically, you need to start a “Tryton cron instance”.

> [@trytfan](#):
>
> How can i use a external database with Tryton Docker?

You can set the environment variable `TRYTOND_DATABASE_URI` using the syntax of [`[database] uri`](http://docs.tryton.org/projects/server/en/latest/topics/configuration.html#uri).

> [@trytfan](#):
>
> Which dababase should i prefren, PostgresSQL 12?

PostgreSQL is the preferred one and of course the latest available is always better.