PhotoPrism is a great web photo library and great fit for browsing and managing photos on a home NAS server I’ve recently built. It has some unique features like tagging photo using TensorFlow, however the most appealing features for me are slick interface, easy use and administration, support for RAW/HEIC formats (conversion to JPEG), ability to configure “read only” mode (my originals are never touched) and “photo stream” approach (all photos in one huge pile with search/tagging capabilities).

This is a tutorial how to deploy this app on CenOS 8 in a root-less container with SELinux. Before starting, it’s important to plan permissions and SELinux file labels. On my NAS system, I have a user and group called “data” with UID/GID 1000 which is the initial regular user on CentOS (and most distributions) after installation. I keep all my photos and files under this user and group (Samba, NFS).

# ls -laZ /mnt/int/data/photo/ -d
drwxrwxr-x. 4 data data system_u:object_r:public_content_rw_t:s0 70 Jan 12 21:20 /mnt/int/data/photo/

Note the SELinux file label is set to public_content_rw_t because I want my services (Samba, NFS, PhotoPrism) to be able to read and write data. If you don’t want PhotoPrism to write into original folder, use public_content_r_t label. Here is how to set SELinux on a directory and all its subdirectories and folders permanently:

# semanage fcontext -a -t public_content_rw_t "/mnt/int(/.*)?"
# restorecon -RvvF /mnt/int

For Samba and NFS configuration, see more details in my previous article. Do not turn off SELinux, get it right this time! Install podman first and SELinux development files:

# dnf install podman policycoreutils-devel

Compile a custom policy rule to read and write files and directories labelled as public_content_rw_t:

# mkdir selinux
# cd selinux
# cat >photoprism.te <<EOF
policy_module(photoprism, 1.0)
require {
        type container_t;
# make -f /usr/share/selinux/devel/Makefile && semodule -i photoprism.pp

No other actions need to be done, the module is now loaded permanently, there is no service to restart as SELinux applies the new rules immediately. It will also survive restarts. It’s easy, isn’t it?

Before we start, small recap. The photos I want to browse via PhotoPrism are stored on 8th gen Intel NUC on the internal 2TB drive in directory /mnt/int/photos/phone and I have a separate LVM volume on NVMe SSD for thumbnails mounted as /mnt/fast where I want to store PhotoPrism thumbnails and database. Run this command as the user that has UNIX permissions to read (or write) photos directory and with read/write permissions to thumbnails and database directories:

$ podman run -d --name photoprism \
  --userns=keep-id -p 2342:2342 \
  -v /mnt/int/photo_ovl/merged/telefon:/home/photoprism/Pictures/Originals \
  -v /mnt/fast/thumbs:/home/photoprism/.cache/photoprism \
  -v /mnt/fast/photoprismdb:/home/photoprism/.local/share/photoprism/resources/database \

When starting for the first time, you can omit the -d option to start the container in the foreground to see log messages. To stop the container:

$ podman stop photoprism

To start it again (use -a to attach to the photoprism process to see logs):

$ podman start photoprism

Note in the run command above, I used --userns=keep-id argument which tells podman to keep UID/GID. Remember when I told you my “data” user has UID/GID 1000? PhotoPrism application also runs as 1000, therefore it nicely maps to the host OS. This is the most simple option, alternatively this argument can be removed and podman will automatically map UID/GID according OS mapping tables. In my case, the container process would have UID 100999. In that case, modify UNIX permissions or/and ACLs in a way that this user (or group) can read (and/or write) to the directories.

Alternatively, a mapping can be provided. Let’s say

$ podman run -d ...
  --uidmap 0:100000:5000

The --uidmap optiom tells podman to map a range of 5000 UIDs inside the container, starting with UID 100000 outside the container (so the range is 100000-104999) to a range starting at UID 0 inside the container (so the range is 0-4999). This can be tricky to understand, that’s why I opted-in for keep-id approach.

For experimenting with UIDs and GIDs, you don’t need to use PhotoPrism container, just grab a temporary shell within Fedora, then create a user “test” and try to access required files. Remeber SELinux is turned on, if you see permission errors and you think you have your UNIX/ACL permissions right, check audit.log. Note the container will be automatically removed on exit:

$ podman run --rm -it -v /mnt/fast:/mnt fedora:31 /bin/bash
> useradd test
> su test
> touch /mnt/TEST
> exit

One trick before you proceed, if you don’t want PhotoPrism to convert HEIC/RAW files into the originals folder increasing the overall size of the originals, use overlay fs:

# mount -t overlay overlay -o lowerdir=/mnt/int/data/photo,upperdir=/mnt/int/photo_ovl/upper,workdir=/mnt/int/photo_ovl/work /mnt/int/photo_ovl/merged

This command creates an overlay folder /mnt/int/photo_ovl/merged with source /mnt/int/data/photo. The other two named work and upper must be just empty directories. Then use the /mnt/int/photo_ovl/merged foder for the -v podman option to use it instead of the original directory. All files created by PhotoPrism will not be stored in the original folder but in the upper overlay which can be removed at any point.

Now, access your server via http://nuc.home.lan:2342, go to Settings (password is set to “photoprism” by default) and initiate reindex process.

If you need to add more SELinux rules in case you haven’t labelled files correctly, here is how to do this. The trick is to disable dontaudit rules:

  # semodule -BD

Then the required rule can be easily found and added to the policy:

# sepolgen-ifgen
# audit2allow -RaM photoprism
# semodule -i photoprism.pp
# semodule -B

Although podman comes with systemd unit generator command podman generate systemd, it is required to configure headless systemd login sessions in order to achieve management of the service via systemd. This is currently (CentOS 8.1) quite some work and I believe it is not worth the effort for sever-based deployment.

That’s all, the module is active from now on. This will persist restarts. SELinux is easy if you know what to do. Granted those dontaudit rules can be tricky as the denials won’t appear until you temporarily diable this behavior.

I look forward to new developments of this software. I would love to see WebP previews support to save some more space on the cache volume, Android and iOS client apps are in development but they are not available yet on app stores (I don’t have iOS development account yet I would love to start testing it). Browsing photos on my iPad is really exciting. I really hope the authors get pricing model right and develop a sustainable offering for both DYI and regular users.