Blog

Image-level backup via VADP + CBT, CBT-based push replication with 10 DR modes, cross-hypervisor restore (vSphere ↔ Hyper-V ↔ Proxmox), and the VDDK runtime RPM with RPATH=$ORIGIN that avoids polluting the host’s ld.so.

Technical companion to the PodHeitor vSphere plugin page.

1. The problem: stock Bacula doesn’t speak VADP

Bacula Community by design has no VADP client and no CBT. ESXi VM backup via stock FD reduces to:

• Backup the datastore mounted on the FD host — captures VMDKs in inconsistent state, no snapshot, no CBT.
• Bacula Enterprise vSphere plugin — exists, but at enterprise pricing and without cross-site DR replication or 10 failover modes.
• Standalone Veeam — parallel to Bacula, with separate tooling, RPO, scripting and licenses. Doubles TCO.

The PodHeitor vSphere BRC consolidates backup, replication, and cross-hypervisor conversion into a single Bacula plugin with native VADP + VDDK 9.0 integration.

2. Architectural model

Bacula FD → Rust cdylib plugin (.so) → Rust backend binary (PTCOMM pipe)
                                          ↕
                                     vSphere SOAP API (via reqwest)
                                          ↕
                                     VDDK 9.0 (FFI — read/write VMDK blocks)

The .so is a pure-Rust cdylib built from the PodHeitor Rust cdylib workspace (plugin-vsphere crate). It implements the Bacula FD plugin C ABI via the independently re-implemented bacula-fd-abi crate — no Bacula source tree required to build, and no AGPLv3-licensed Bacula objects are linked into the shipped binary. The .so spawns the Rust backend as a subprocess and uses PTCOMM (status_char + 6-digit length + newline + payload) over stdin/stdout.

3. VADP transport modes

VMDK reads via VADP support four modes; the plugin exposes them via the transport parameter:

4. CBT — Changed Block Tracking

VADP CBT is the VMware feature that lets a client ask “which blocks have changed since ChangeId X?”. The plugin uses it on every Incremental/Differential:

1. Consistent VM snapshot (with quiesce=true default — VMware Tools quiesce filesystem).
2. CBT query against the prior snapshot — returns list of {offset, length} extents.
3. Read those extents only via VDDK.
4. Stream over PTCOMM with offsets preserved.
5. Remove snapshot (with optional snapshot_delete_delay for big commits).

The keep_cbt=true parameter avoids resetting CBT state after backup — useful when multiple Bacula jobs consume the same CBT in parallel.

5. CBT-Push replication and the 10 DR modes

The plugin implements CBT-based push replication with a persistent receiver daemon on the DR side. The mode= parameter selects one of ten operations:

The full Veeam SRM-style workflow (test → planned → reprotect) is available as plugin modes, drivable from the Bacula Director with no extra product.

5.1 Network mapping and Re-IP

5.2 TLS for the DR channel

Supports dr_tls_cert + dr_tls_key (PEM) with rustls; dr_tls_insecure=true accepts self-signed (lab only). PSK token via dr_auth_token required in all modes.

6. VDDK runtime RPM — why it matters

VDDK is distributed by VMware as a tarball with bundled libcrypto.so.3/libssl.so.3/libcurl.so.4. Older installs wrote /etc/ld.so.conf.d/vmware-vddk.conf pointing at those libs — making every process on the host (including rpm, dnf, flatpak) load VMware’s libcrypto instead of system OpenSSL. Typical symptom:

flatpak: /usr/lib/vmware-vix-disklib/lib64/libcrypto.so.3: 
    version `OPENSSL_3.4.0' not found (required by /lib64/librpmio.so.9)

The podheitor-vixdisklib-runtime-9.0.1-1.el9.x86_64.rpm fixes this at build time: every .so in /usr/lib/vmware-vix-disklib/lib64 is patched with RPATH=$ORIGIN, so VDDK resolves its siblings from its own directory without polluting the host ld.so. The %post scriptlet removes any stale /etc/ld.so.conf.d/vmware-vddk*.conf, vixlib*.conf, or flatpack*.conf entries and reruns ldconfig.

Air-gapped recovery (host already broken by legacy install):

sudo rm -f /etc/ld.so.conf.d/vmware-vddk.conf 
           /etc/ld.so.conf.d/vmware-vix-disklib.conf 
           /etc/ld.so.conf.d/*vixlib*.conf 
           /etc/ld.so.conf.d/*flatpack*.conf
sudo ldconfig
sudo rpm -Uvh releases/podheitor-vixdisklib-runtime-9.0.1-1.el9.x86_64.rpm

7. Cross-restore (vSphere ↔ Hyper-V ↔ Proxmox)

The plugin participates in two legs of the cross-hypervisor triangle:

• As source: VMware backups can be restored into Hyper-V or Proxmox via the sister PodHeitor Hyper-V / PodHeitor Proxmox plugins.
• As target: Hyper-V/Proxmox backups can be restored into vSphere through this plugin (with VHDX → VMDK and qcow2 → VMDK conversion).

8. Compatibility

9. Lab validation

• ESXi 8.0U3e standalone host, VDDK 9.0.1 on Oracle Linux 9.5, Bacula Community 15.0.3.
• 4 CBT-enabled VMs (Alpine, TinyCore, CirrOS, multi-disk).
• 12/12 replication tests PASSED (April 2026).
• v1.4.1: lab job 6442 restored 2.147 GB / 4 files in 6s, 0 FD errors; restored Alpine 3.21 VM booted clean.

10. Documented anti-patterns

• Don’t leave dr_tls_insecure=true in production. Accepts self-signed certs on the DR channel — useful in lab; MITM risk in prod.
• Don’t use force_san=true without correct SAN zoning. The FD must see the target VM’s LUNs directly; misconfiguration produces confusing I/O errors.
• Don’t run quiesce=false on DB VMs. Crash-consistent snapshot → DBs need recovery on replica boot/restore.

11. License posture

Plugin under LicenseRef-PodHeitor-Proprietary. Since v1.4.0, the .so is a pure-Rust cdylib — no Bacula AGPLv3 source statically linked. Earlier releases linked C++ pluginlib/metaplugin objects from the Bacula tree — no longer the case. Bindings via the clean-room bacula-fd-abi crate.

Ready to evaluate?

30-day free trial for production vSphere fleets. Guaranteed at minimum 50% discount vs Bacula Enterprise, Veeam or Commvault, with 10 DR modes and cross-hypervisor restore included.

Heitor Faria — Founder, PodHeitor International
✉ [email protected]
☎ +1 (789) 726-1749 · +55 (61) 98268-4220 (WhatsApp)
🔗 PodHeitor vSphere plugin page

Disponível em: Português (Portuguese (Brazil))EnglishEspañol (Spanish)