2020-07-27 20:13:22 +00:00
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+++
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title = "Prerequisites"
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weight = 10
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+++
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The two components have one prerequisite in common: they both require
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Java to run. While this is the only requirement for the *REST server*,
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the *Joex* components requires some more external programs.
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The rest server and joex components are not required to "see" each
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other, though it is recommended.
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# Java
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Very often, Java is already installed. You can check this by opening a
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terminal and typing `java -version`. Otherwise install Java using your
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package manager or see [this site](https://adoptopenjdk.net/) for
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other options.
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It is enough to install the JRE. The JDK is required, if you want to
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2021-02-18 23:53:04 +00:00
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build docspell from source. For newer versions, the JRE is not shipped
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anymore, simply use JDK then.
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2020-07-27 20:13:22 +00:00
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Docspell has been tested with Java version 1.8 (or sometimes referred
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2021-02-18 23:53:04 +00:00
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to as JRE 8 and JDK 8, respectively). The pre-build packages are build
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using JDK 8. So at least a JDK/JRE 8 is required. However, it also
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works on newer java versions, I recommend JDK 11 as this has better
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default options. The provided docker images use JDK11, too.
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2020-07-27 20:13:22 +00:00
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The next tools are only required on machines running the *Joex*
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component.
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# External Programs for Joex
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- [Ghostscript](http://pages.cs.wisc.edu/~ghost/) (the `gs` command)
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is used to extract/convert PDF files into images that are then fed
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to ocr. It is available on most GNU/Linux distributions.
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- [Unpaper](https://github.com/Flameeyes/unpaper) is a program that
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pre-processes images to yield better results when doing ocr. If this
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is not installed, docspell tries without it. However, it is
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recommended to install, because it [improves text
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extraction](https://github.com/tesseract-ocr/tesseract/wiki/ImproveQuality)
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(at the expense of a longer runtime).
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- [Tesseract](https://github.com/tesseract-ocr/tesseract) is the tool
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doing the OCR (converts images into text). It can also convert
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images into pdf files. It is a widely used open source OCR engine.
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Tesseract 3 and 4 should work with docspell; you can adopt the
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command line in the configuration file, if necessary.
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- [Unoconv](https://github.com/unoconv/unoconv) is used to convert
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office documents into PDF files. It uses libreoffice/openoffice.
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- [wkhtmltopdf](https://wkhtmltopdf.org/) is used to convert HTML into
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PDF files.
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- [OCRmyPDF](https://github.com/jbarlow83/OCRmyPDF) can be optionally
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used to convert PDF to PDF files. It adds an OCR layer to scanned
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PDF files to make them searchable. It also creates PDF/A files from
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the input pdf.
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The performance of `unoconv` can be improved by starting `unoconv -l`
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in a separate process. This runs a libreoffice/openoffice listener and
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therefore avoids starting one each time `unoconv` is called.
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## Example Debian
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On Debian this should install all joex requirements:
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``` bash
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sudo apt-get install ghostscript tesseract-ocr tesseract-ocr-deu tesseract-ocr-eng unpaper unoconv wkhtmltopdf ocrmypdf
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```
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# Apache SOLR
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SOLR is used to provide the fulltext search feature. This feature can
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be disabled, so installing SOLR is optional. But without it, there is
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no fulltext search.
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When installing manually (i.e. not via docker), just install solr and
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create a core as described in the [solr
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2021-05-31 11:25:57 +00:00
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documentation](https://solr.apache.org/guide/8_4/installing-solr.html).
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2020-07-27 20:13:22 +00:00
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That will provide you with the connection url (the last part is the
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core name).
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When using the provided `docker-compose.yml` setup, SOLR is already setup.
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SOLR must be reachable from all joex and all rest server components.
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# Database
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Both components must have access to a SQL database. The SQL database
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contains all data (including binary files) and is the central
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component of docspell. Docspell has support these databases:
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- PostreSQL
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- MariaDB
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- H2
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The H2 database is an interesting option for personal and mid-size
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setups, as it requires no additional work. It is integrated into
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docspell and works really well out of the box. It is also configured
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as the default database.
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When using H2, make sure that all components access the same database
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– the jdbc url must point to the same file. Then, it is important to
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add the options
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`;MODE=PostgreSQL;DATABASE_TO_LOWER=TRUE;AUTO_SERVER=TRUE` at the end
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of the url. See the [config page](@/docs/configure/_index.md#jdbc) for
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an example.
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For large installations, PostgreSQL or MariaDB is recommended. Create
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a database and a user with enough privileges (read, write, create
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table) to that database.
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