• in config.php

  enable_previews -> true / false
  preview providers -> check for certain type

• storage location:

  data/appdata_instanceid/preview

• previewgenerator app

    # generates previews to preview storage location
    # using config settings
    occ preview:cleanup
    occ preview:pre-generate # -> only new files!
    occ preview:generate-all -vvv --workers=n username  # use a worker count of ~ 2*cpu cores
    occ files:scan-app-data

• pre-v33: oc_filecache table

• from v33: oc_previews table

1. config.php : 'enable_previews' ⇒ false,
2. occ preview:cleanup
3. DELETE FROM oc_filecache WHERE path LIKE 'appdata_<instanceid>/preview/%';
4. occ files:scan-app-data
5. config.php : 'enable_previews' ⇒ true,

1. disable ALL nc cron jobs
2. stop cachefilesd (faster and not writing a lot of disk in vain)
3. run fix
4. log in with nc user: e.g. w_nc (don't sudo, not working)
5. nc_directory # php occ preview:generate-all -vvv –workers=n username
6. re-activate cron-jobs
7. start cachefilesd