Ubuntu 24.04

We all sync our agendas. It means that your calendar is synchronized with a server and, probably, from the server synchronized with another client. So your laptop is in sync with your phone etc.

I was looking, however, for a tool to sync my Apple iCloud calendar with a calendar on my private SOGo-account (with CalDAV support). So in this respect 'syncing' means keeping two different agendas the same.

A simple way to do this is OneCal. But I don't want to share my credentials or calendar data with a third party. I want it to do on my own.

This is where the command line tool vdirsyncer comes to the rescue.

1- install vdirsyncer

This is rather straightforward.

apt install vdirsyncer

My version is 0.19.2:

vdirsyncer --version
vdirsyncer, version 0.19.2

2- create config file

Choose a path for your config and vdirsyncer working file(s), and create a DRAFT config file.

mkdir /opt/vdirsyncer
mkdir /opt/vdirsyncer/status
cd /opt/vdirsyncer 
vi config

The content of the draft config contains the credentials of both your iCloud and SOGo/CalDAV-accounts:

[general]
status_path = "/opt/vdirsyncer/status/"

[pair my_cals]
a = "icloud"
b = "sogo"
collections = ["from a", "from b"]
metadata = ["displayname", "color"]
conflict_resolution ="a wins"

[storage icloud]
type = "caldav"
url = "https://caldav.icloud.com/"
username = "APPLEID"
password = "PASSWORD1"

[storage sogo]
type = "caldav"
url = "https://SERVER/SOGo/dav"
username = "SOGOLOGIN"
password = "PASSWORD2"

NOTES:

• PASSWORD1 is not your main AppleID-password, but a app-specific password. Create one here: https://support.apple.com/en-us/102654
• SOGOLOGIN is probably your full email address used on the SOGo system.
• The metadata tag takes care of synchronization of displayname and color. Remove it if not wanted.
• The conflict_resolution tag tells that in any conflict iCloud overrules (but it remains a two-way-sync!).
• This config is DRAFT and must be tuned to get it work, see step 3.

3- discover

This step is needed to match the calendar IDs of both agendas.

cd /opt/vdirsyncer
vdirsyncer -c /opt/vdirsyncer/config discover

Some information about both sides is shown:

Discovering collections for pair my_cals
icloud:
  - "tasks" ("AgendaName")
  - "8EBE0B9B-79EB-4050-A243-ABCDEF012345" ("CalendarA")
  - "961E9995-5353-4D1D-BADC-ABCDEF012345" ("CalendarB")
sogo:
  - "personal" ("CalenderC")
Saved for my_cals: collections = ["coll"]

It says there a two calandars on iCloud and one on SOGo. Now take the right IDs and add them to the config (line containing 'collections'):

[general]
status_path = "/opt/vdirsyncer/status/"

[pair my_cals]
a = "icloud"
b = "sogo"
collections = [["coll", "961E9995-5353-4D1D-BADC-ABCDEF012345", "personal"]]
metadata = ["displayname", "color"]
conflict_resolution ="a wins"

[storage icloud]
type = "caldav"
url = "https://caldav.icloud.com/"
username = "APPLEID"
password = "PASSWORD1"

[storage sogo]
type = "caldav"
url = "https://SERVER/SOGo/dav"
username = "SOGOLOGIN"
password = "PASSWORD2"

4- first run

Now you're good to go. Let's do a first, verbose test run:

cd /opt/vdirsyncer
vdirsyncer -c /opt/vdirsyncer/config -v INFO sync --dry-run

Check the output if it's working as expected. If so, remove the --dry-run tag and do a real one.

It is not a bad idea to create a backup of your calendars first (see e.g. https://support.apple.com/guide/calendar/import-or-export-calendars-icl1023/mac ).

If you run into problems and have to repeat previous steps make sure to have the database cleaned:

cd /opt/vdirsyncer/status
rm -r *

5- schedule

To sync the calendars every X minutes, add a cron job:

crontab -e
# Add the line below (runs every 10 minutes)
*/10 * * * * /bin/sh -c "/usr/bin/vdirsyncer -c /opt/vdirsyncer/config -v ERROR sync >> /var/log/vdirsyncer.log 2>&1"

6- etc

There's good documentation on vdirsyncer's website.

Use this directive to force a full sync:

# Force a full re‑download of everything
vdirsyncer sync --force-sync

The above configuration can be used to sync two SOGo-/CalDAV-accounts also.

-jer