The Multi-Server Setup feature

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The Multi-Server Setup featureLast Modified: May 4, 2020, 3:46 pm
The Multi-Server Setup (MSS) feature is used for multiple DirectAdmin servers to communicate with each other.
Below, we'll list what this feature started with, and how it's functionality has expanded over the years.

For all examples, we'll refer to box A as the master, where you're logged into box A looking at the MSS page, looking at of list of B servers, and box B as the remote slave.  All cases 'push' data from A to B for saving data on disk on the remote B side.

  1. The original purpose of this tool was to allow for DNS zone mirroring.   You can have a User with on box A, and DirectAdmin will sync the zone over to box B.   This tool also prevents anyone from creating on box A, should exist on box B (created under UserB).  
    • The sync feature is called Zone Transfer and pushes local zones from A to B, when saved on A.
    • The remote zone check is called Domain Check where the creation of is blocked on A, if zone exists on B.
    • You can setup box B to point back to box A, allowing for A=ns1, B=ns2, and have Users on both A and B, allowing full use of A+B for Users+Domains
    • If restoring UserA on box B where exists in B's dns, use the Admin Backup/Transfer Setting:

      On restore, check for domain conflict in domainowners, rather than the named.conf, or remote named.conf files.

      if you need to overwrite the local zone on both A+B (assuming B » A Zone Transfer enabled).  This is because slave B might have the zone, but won't exist as a full domain on B yet.  This alters the unique index check from the named.conf to the domainowners file, so that the MSS Zone Transfer does not interfere with the block (but B » A Domain Check would still block)
    • When deleting a User from A, use the 'Leave DNS' option if the zone should remain on A+B, when Zone Transfer is enabled.
    More information on DNS clustering can be found here.
  2. User Check

    The MSS User Check option is used to preven creating "fredB" on box A, if 'fredB' exists on box B.
    This is very important to use if you have a single shared Rremote MySQL/MariaDB Server (say box C), as DirectAdmin uses the usernames as prefixes for databases, so duplicate Usernames on both A and B mean either User (with the same name) can see each other's databases.  For example, if you have 'fredB' on both A and B, logging into A, you'd see the database 'fredB_dbname' of 'fredB', regardless of which server actually created them.  In essence, they'd be sharing the same list of DBs.  If you use a remote DB server where multiple boxes A/B share the same C DB server, be sure to setup two-directional MSS with User Check enabled: A » B and B » A
  3. E-Mail Accounts

    The E-Mail Accounts option is a more hands-on feature which makes assumptions on the setup.
    The feature itself will keep the list of accounts in /etc/ synced from box A to box B.
    This assumes that B has the same User setup that exist on box A, as well as the same domain name.
    It does not sync the User, and does not create the domain.  See the "User Accounts" option below.
    More information on E-Mail Accounts sync can be found here.
  4. Show All Users

    The Show All Users option will let the "Show All Users" page on box A, also include the list of all Users/domains from box B.
    When you view this page on box A (CMD_ALL_USER_SHOW or /admin/users), it will add another column clarifying which box the item is from.
    Clicking on that Username will either go to the local "view account" page, or if it's a remote account, it will provide a URL to that remote server's "view account" page (login required).
    More information on the Show All Users feature can be found here.
  5. User Accounts

    The User Accounts option, which is not production ready, disabled by default, will have any User/domain created on box A, also be created on box B.  As mentioned above it's not fully finished nor tested, but does work on a basic level of User/domain creation and deletion (at your own risk). Does not sync anything else. It's useful if you're also looking to use the E-Mail Accounts sync, as it would do it's best to ensure the remote User/domain is setup and ready to go when it's time for E-Mail account creation on A, synced to B.
    More information on the User Accounts sync can be found here.
  6. enable_threads=1

    As with any MSS feature where you have multiple remote servers setup (lets use 3 for example), doing 3 sequential requests will take 3 times as long as doing 3 parallel calls all at the same time.  The enable_threads=1 directadmin.conf option creates currently works for options: User Check, User Accounts, with plans to add support for Zone Transfer/Domain Check for faster MSS syncs when more than one B slave exists on the MSS page of A.

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