add blog post about seafile-mirror

content/blog/2023-09-seafile-mirror.md

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+---
+title: "Seafile Mirror - Simple automatic backup of your Seafile libraries"
+date: 2023-09-22
+categories:
+  - english
+tags:
+  - python
+  - server
+  - tools
+headerimage: /blog/library.jpg
+headercredits: Wouldn't it be a shame if your library were to be destroyed?
+---
+
+I have been using [Seafile](https://www.seafile.com/) for years to host and
+synchronise files on my own server. It's fast and reliable, especially when
+dealing with a large number and size of files. But making reliable backups of
+all its files isn't so trivial. This is because the files are stored in a layout
+similar to bare Git repositories, and Seafile's headless tool, seafile-cli,
+is... suboptimal. So I created what started out as a wrapper for it and ended up
+as a full-blown tool for automatically synchronising your libraries to a backup
+location: [**Seafile Mirror**](https://src.mehl.mx/mxmehl/seafile-mirror).
+
+## My requirements
+
+Of course, you could just take snapshots of the whole server, or copy the raw
+Seafile data files and import them into a newly created Seafile instance as a
+disaster recovery, but I want to be able to **directly access the current
+state of the files** whenever I need them in case of an emergency.
+
+It was also important for me to have a **snapshot**, not just another real-time
+sync of a library. This is because I also want to have a backup in case I (or an
+attacker) mess up a Seafile library. A real-time sync would immediately fetch
+that failed state.
+
+I also want to take a snapshot at a **configurable interval**. Some libraries
+should be synchronised more often than others. For example, my picture albums do
+not change as often as my miscellaneous documents, but they use at least 20
+times the disk space and therefore network traffic when running a full sync.
+
+Also, the backup service must have **read-only access** to the files.
+
+A version controlled backup of the backup (i.e. the plain files) wasn't in
+scope. I handle this separately by backing up my backup location, which also
+contains similar backups of other services and machines. For this reason, my
+current solution does not do incremental backups, even though this may be
+relevant for other use cases.
+
+## The problems
+
+Actually, [seafile-cli](https://help.seafile.com/syncing_client/linux-cli/)
+should have been everything you'd need to fulfill the requirements. But no. It
+turned out that this tool has a number of fundamental issues:
+
+* You can make the host the tool is running on a sync peer. However, it easily
+  leads to sync errors if the user just has read-only permissions to the
+  library.
+* You can also download a library but then again it may lead to strange sync
+  errors.
+* It requires a running daemon which crashes irregularly during larger sync
+  tasks or has other issues.
+* Download/sync intervals cannot be set manually.
+
+## The solution
+
+[seafile-mirror](https://src.mehl.mx/mxmehl/seafile-mirror) takes care of all
+these stumbling blocks:
+
+* It downloads/syncs defined libraries in customisable intervals
+* It de-syncs libaries immediately after they have been downloaded to avoid sync
+  errors
+* You can force-re-sync a library even if its re-sync interval hasn't reached
+  yet
+* Extensive informative and error logging is provided
+* Of course created with automation in mind so you can run it in cronjobs or
+  systemd triggers
+* And as explained, it deals with the numerous caveats of `seaf-cli` and Seafile
+  in general
+
+Full installation and usage documentation can be found in the project
+repository. Installation is as simple as running `pip3 install seafile-mirror`,
+and a sample configuration is provided.
+
+In my setup, I run this application on a headless server with systemd under a
+separate user account. Therefore the systemd service needs to be set up first.
+This is also covered in the tool's documentation. And as an Ansible power user,
+I also provide an [Ansible
+role](https://src.mehl.mx/mxmehl/seafile-mirror-ansible) that does all the setup
+and configuration.
+
+
+## Possible next steps
+
+The tool has been running every day since a couple of months without any issues.
+However, I could imagine a few more features to be helpful for more people:
+
+* Support of login tokens: Currently, only user/password auth is supported which
+  is fine for my use-case as it's just a read-only user. This wouldn't be hard
+  to fix either, seafile-cli supports it (at least in theory).
+  ([#2](https://src.mehl.mx/mxmehl/seafile-mirror/issues/2))
+* Support of encrypted libraries: Shouldn't be a big issue, it would require
+  passing the password to the underlying seafile-cli command.
+  ([#3](https://src.mehl.mx/mxmehl/seafile-mirror/issues/3))
+
+If you have encountered problems or would like to point out the need for
+specific features, please feel free to contact me or comment on the Mastodon
+post. I'd also love to hear if you've become a happy user of the tool 😊.