Baïkal is a focused, open-source CalDAV and CardDAV server. A reliable VPS deployment uses a DNS name, HTTPS-enabled Apache or Nginx, PHP-FPM, a supported SQLite/MySQL/PostgreSQL database, and a virtual host whose public root is Baïkal’s html directory. Install the release outside the public directory, run the browser installer, route both well-known discovery paths to /dav.php, and keep Baïkal’s private directories inaccessible over HTTP.
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What you are building
CalDAV synchronizes calendars, while CardDAV synchronizes address books. Baïkal provides both protocols through one web application; the project describes itself as an open-source Baïkal CalDAV and CardDAV server. Your phone, computer, or mail client connects to a hostname such as dav.example.org over HTTPS, authenticates with a Baïkal account, and reads or writes calendar and contact data in the database.
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- DNS resolves
dav.example.orgto the VPS. - The web server terminates TLS and selects the Baïkal virtual host.
- PHP-FPM executes Baïkal’s PHP application.
- Baïkal reads or writes the configured SQLite, MySQL, or PostgreSQL database.
- Client discovery requests to
/.well-known/caldavor/.well-known/carddavare redirected to/dav.php.
Only the html directory should be exposed as the web root. The release’s Specific, config, and Core directories belong outside direct HTTP access.
Requirements and decisions
Supported software
| Component | What Baïkal requires | Decision to make |
|---|---|---|
| Operating system | A Linux VPS is the usual deployment target. | Use a maintained distribution and keep its security updates enabled. |
| Web server | Apache or Nginx. | Choose the server you already administer; both need PHP handling and DAV redirects. |
| PHP | PHP is required. The exact minimum depends on the Baïkal release you install. | Check the release documentation before installing PHP and its required extensions. |
| Database | SQLite, MySQL, or PostgreSQL are documented choices. | SQLite minimizes moving parts; MySQL or PostgreSQL fit an existing database service. |
| Network | A DNS name and HTTPS endpoint. | Point an A and, if used, AAAA record at the VPS and issue a certificate for the same name. |
SQLite or a server database?
SQLite is practical for a small, single-server installation because the database is a file managed by Baïkal. MySQL and PostgreSQL put the data in a separate database service and may fit an organization that already has database backups, monitoring, and access controls. The Baïkal installer presents the supported database choices; select the one you can back up and restore confidently.
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DNS, firewall, and TLS prerequisites
- Create the DNS record before testing the site. Use the final hostname in the certificate and in client accounts.
- Allow TCP 80 if your certificate process needs HTTP validation, and allow TCP 443 for client traffic. Restrict SSH to the administration networks you actually use.
- Install a valid certificate before adding accounts. Calendar and contact clients are much less forgiving of certificate-name, expiration, or trust errors than a browser.
Prepare the VPS
Use your distribution’s package manager to install the chosen web server, PHP-FPM, the PHP database driver required by your selected database, and the database service if you are not using SQLite. Package names and PHP-FPM socket paths differ by distribution and PHP version, so use the paths shown by your operating system rather than copying a socket name from another release.
Create a private application directory, for example:
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sudo chown root:root /var/www/baikal
sudo chmod 755 /var/www/baikalThe example path is not a requirement. What matters is that the archive is unpacked outside the directory served by the web server, with only its html subdirectory selected as the document root.
Download and unpack Baïkal
- Open the project’s official releases page and download the latest release archive appropriate for your server.
- Place the archive in a temporary or private directory. Verify the release checksum or signature when the project publishes one.
- Extract the archive under your private application directory.
- Identify the resulting Baïkal directory and confirm that it contains
html,Specific,config, andCore. - Do not move the contents of
Specificorconfiginto the public directory. The web server will point at.../baikal/html, not at the archive’s top level.
During installation, the web-server process must be able to write Specific and config. The official installation documentation explicitly requires those directories to be writable so the installer can create configuration and database files.
On systems that use the www-data account, a controlled starting point is:
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sudo chown -R www-data:www-data /var/www/baikal/Specific /var/www/baikal/config
sudo find /var/www/baikal/Specific /var/www/baikal/config -type d -exec chmod 750 {} ;
sudo find /var/www/baikal/Specific /var/www/baikal/config -type f -exec chmod 640 {} ;Replace www-data with the actual user and group used by your web server. Do not use chmod -R 777; broad write access hides ownership mistakes and creates an unnecessary security risk.
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Configure Nginx
Set the server block’s root to Baïkal’s html directory. Keep the release’s normal PHP routing, then add exact redirects for the two discovery URLs. This fragment shows the security-sensitive pieces; adapt the PHP-FPM socket and the rest of the server block to your distribution:
server {
listen 443 ssl http2;
server_name dav.example.org;
root /var/www/baikal/html;
index index.php;
# TLS certificate and key directives go here.
location = /.well-known/caldav {
return 301 /dav.php;
}
location = /.well-known/carddav {
return 301 /dav.php;
}
location ~ ^/(Specific|config|Core)(/|$) {
deny all;
}
location ~ /.(?!well-known) {
deny all;
}
location ~ .php$ {
include fastcgi_params;
fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
fastcgi_pass unix:/run/php/php-fpm.sock;
}
}The socket shown is illustrative. Find the actual PHP-FPM socket on the VPS and ensure Nginx can reach it. If your release’s sample configuration contains additional rewrite or static-file rules, preserve them rather than replacing them with a shorter example.
Apache configuration
Set DocumentRoot to /var/www/baikal/html, enable the required PHP and rewrite modules, and add the two discovery redirects. A minimal rewrite section is:
RewriteEngine On
RewriteRule ^/.well-known/caldav$ /dav.php [R=301,L]
RewriteRule ^/.well-known/carddav$ /dav.php [R=301,L]Add access-denial rules for the private directories in the virtual host or directory configuration:
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<DirectoryMatch "^/.*/(Specific|config|Core)(/|$)">
Require all denied
</DirectoryMatch>Use the Apache sample configuration shipped with your Baïkal release for the remaining PHP and directory directives. Confirm that the virtual host does not expose the archive’s parent directory.
Run the Baïkal setup wizard
- Visit
https://dav.example.org/in a browser. - When the installer asks for database storage, choose SQLite, MySQL, or PostgreSQL and enter the database credentials required by that choice.
- Create the administrative account and use a unique, long password. Do not reuse the VPS, database, or mail password.
- Complete the wizard and allow it to write the generated configuration into
configand the database data into the appropriate storage. - Sign out and sign in again to verify the account before configuring clients.
If the wizard reports that it cannot create a file or connect to the database, stop and fix the underlying ownership, permissions, PHP database driver, or database credentials. Do not make the entire application tree world-writable as a workaround.
Verify discovery before adding devices
From a machine outside the VPS, test both well-known paths:
curl -I https://dav.example.org/.well-known/caldav
curl -I https://dav.example.org/.well-known/carddavEach request should return an HTTP redirect to /dav.php, not a 404. A 301 or 302 is normal; the important result is that both names exist and lead to Baïkal’s DAV endpoint. If you test with -L, the client follows the redirect, so use the non-following command first when diagnosing routing.
Also test the final URL in a browser and inspect the web-server error log while making a request. A successful browser page does not prove that the DAV redirects, PHP authentication, and authorization headers work.
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Configure clients
iPhone, iPad, and Mac
On current Apple systems, add a CalDAV account for calendars and a CardDAV account for contacts through the Internet Accounts or account settings area. Provide the Baïkal hostname, username, and password, then let the client use the well-known redirects. Menu names change between operating-system releases.
If automatic discovery fails and the client offers a manual server field, enter the HTTPS DAV endpoint, normally https://dav.example.org/dav.php. Do not enter the private filesystem path or the VPS hostname if it differs from the certificate name.
Android
Android does not generally include a complete CalDAV/CardDAV account provider. Install a current CalDAV/CardDAV client such as DAVx⁵ from a source you trust, add the HTTPS server and Baïkal credentials, and run its account discovery. The client’s exact screens and synchronization permissions vary by Android version.
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Thunderbird supports network calendars. Add a network calendar, choose the CalDAV type, and supply the HTTPS endpoint when prompted. If the client cannot discover the collection, use the manual DAV URL offered by Baïkal or shown in the client’s connection diagnostics. Contact synchronization is separate from calendar setup and depends on the Thunderbird version and any CardDAV component you use.
Troubleshooting by symptom
| Symptom | Likely cause | Fix |
|---|---|---|
/.well-known/caldav or carddav returns 404 |
The virtual host has no discovery redirect, or the request is reaching a different site. | Point the hostname at the correct VPS, set the document root to html, add both redirects to /dav.php, reload the web server, and repeat the two curl -I tests. |
| Discovery returns a redirect loop | The redirect target is being rewritten back to the well-known path, or HTTP and HTTPS virtual hosts disagree. | Inspect the Location header, make the target exactly /dav.php, and keep the HTTPS virtual host’s routing consistent. |
| 401 Unauthorized | Wrong credentials, an account that was not created, or an authorization header lost by the web-server/PHP configuration. | Sign in to Baïkal’s web interface with the same account, verify the password, and inspect the web-server and PHP logs for the request. Confirm that the Authorization header reaches PHP. |
| Installer cannot write files | Specific or config is owned by the wrong user or lacks directory write permission. |
Grant write access only to the web-server process, rerun the failed step, and remove any temporary broad permissions. |
| Database connection or schema error | Missing PHP database driver, incorrect database name or credentials, unavailable database service, or a filesystem permission problem for SQLite. | Check the selected driver, test the database credentials independently, verify the service is running, and check the directory containing the SQLite or Baïkal data. |
| Clients report an untrusted certificate | The certificate is expired, issued for another hostname, incomplete, or not trusted by the device. | Replace it with a valid certificate covering the exact DNS name, install the complete chain, and retest from the affected device. |
| Windows 10 cannot authenticate | Windows 10 clients do not support Digest authentication according to Baïkal’s troubleshooting documentation. | Use Basic authentication only over a correctly configured HTTPS connection, then verify that the client is sending the Authorization header. |
| Private files are visible in a browser | The document root points above html, or deny rules are missing. |
Change the root to html, deny Specific, config, and Core, block hidden files, reload the server, and retest with an unauthenticated request. |
Security hardening checklist
- Expose only Baïkal’s
htmldirectory. - Deny direct HTTP access to
Specific,config, andCore. The documentation warns thatSpecificcan contain the SQL database. - Block hidden files and directories, while leaving the two exact
.well-knowndiscovery routes functional. - Use HTTPS with a certificate that clients trust. Never use Basic authentication over plain HTTP.
- Keep the VPS, web server, PHP, database, and Baïkal release maintained. Review release notes before upgrading PHP or Baïkal.
- Use a separate database account with only the permissions Baïkal needs when you choose MySQL or PostgreSQL.
- Protect the Baïkal administrator account with a unique password and restrict VPS administration separately from application access.
- Review access and error logs after installation and after every configuration change.
Backups and restoration
Back up both the database and Baïkal’s Specific data directory to storage outside the VPS. Backing up only the database can omit application-specific data; backing up only the directory can omit a separate MySQL or PostgreSQL database.
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- Schedule a database dump or a consistent SQLite file copy appropriate to the database engine.
- Copy the relevant
Specificdata off the server using encrypted transport and restricted permissions. - Keep backup credentials separate from the live application credentials.
- Test a restore on an isolated VPS or staging host before relying on the backup.
- Document the hostname, Baïkal release, PHP version, database engine, web-server configuration, and permission changes needed to bring the service back.
The official pages reviewed for Baïkal do not prescribe a numeric backup interval, retention period, or recovery-time objective. Choose those values according to how much calendar or contact history you can recreate and how quickly clients can resynchronize after a restore.
Upgrades and routine operations
Before an upgrade, take a verified backup, record the current release and configuration, and confirm that the new release supports the PHP version installed on the VPS. Download the new archive outside the public root, compare its requirements with your current stack, and switch the virtual host to the new release’s html directory only after checking the file layout.
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Keep the previous release available until the new instance has passed these checks:
- The web installer or administration page loads without an error.
- Both well-known URLs return redirects to
/dav.php. - An existing account can authenticate.
- A test calendar event and contact can be created, changed, and deleted from a client.
- Logs contain no new PHP fatal errors or database failures.
Do not delete the old release or its backup until you have completed a restore test and confirmed that all clients synchronize normally.
Baïkal compared with broader alternatives
The right choice depends on whether you need a focused DAV service or a larger collaboration platform. Compare the operational consequences rather than only the protocol names.
| Axis | Baïkal | Radicale | Nextcloud |
|---|---|---|---|
| Administration | Focused server with a web administration panel for accounts and DAV data. | Generally emphasizes a minimal DAV service and configuration-driven administration. | Provides web administration inside a much broader application platform. |
| Storage model | Uses SQLite, MySQL, or PostgreSQL as documented by the project. | Uses its own lightweight storage approach; verify current deployment requirements for the release you choose. | Uses a broader application and database stack, with more components to operate. |
| Client discovery | Requires the two well-known routes to redirect to /dav.php. |
Uses its own endpoint and discovery configuration. | Discovery is part of the larger platform and its URL structure. |
| Operational footprint | Small, purpose-built calendar and contact service. | Also targets a narrowly scoped DAV use case. | Heavier because it adds files, sharing, and other collaboration features. |
| Sharing and permissions | Use it when Baïkal’s account and DAV permission model is sufficient. | Evaluate its current sharing and permission behavior for your clients. | Prefer it when integrated file sharing and collaboration are requirements. |
| Best fit | A self-hosted CalDAV/CardDAV endpoint without an entire collaboration suite. | A minimal DAV service where its administration model fits. | An organization that needs calendars and contacts alongside broader collaboration tools. |
Final deployment checklist
- DNS resolves the final hostname to the VPS.
- HTTPS is valid for that hostname.
- The virtual host root is Baïkal’s
htmldirectory. - PHP-FPM can execute Baïkal and load the selected database driver.
Specificandconfigare writable by the web-server process during setup.- Direct HTTP access to
Specific,config,Core, and hidden files is denied. - Both well-known URLs redirect to
/dav.php. - An account can authenticate from at least one calendar client and one contact client.
- Database and
Specificbackups exist off the VPS and a restore has been tested.
Baïkal is a good VPS choice when you want a dedicated CalDAV/CardDAV service and are prepared to administer DNS, TLS, PHP, the web server, database permissions, and backups. Its small scope is the advantage: you avoid operating a full collaboration suite, but you must configure discovery and protect the private application directories yourself.
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