Email - sysctl.d/postfix.conf (non-local bind)
Email Solution · Config document · referenced from Virtual machines and OS build
Two kernel parameters for the internal pair. Postfix on both nodes is told to send from the virtual address (smtp_bind_address, smtp_bind_address6), and only one node holds that address at a time; without these parameters a process on the other node cannot bind a socket to it.
| Item | Value |
|---|---|
| Path on the server | /etc/sysctl.d/postfix.conf |
| Shown here | DC2-A-VCMSX001 |
| Also on | DC2-B-VCMSX001, the same content |
| Not on | the mailbox server and the relays, which have no virtual address |
| Activated with | a reboot (init 6), as the install notes have it |
The file
# Allow to bind nonlocal IP addresses # allows processes to bind to sockets on the machine even if the ip does not exist net.ipv4.ip_nonlocal_bind = 1 net.ipv6.ip_nonlocal_bind = 1
The file on node B differs only by a trailing empty line.
Checked against the Linux kernel documentation, October 2026
| As built | Today |
|---|---|
net.ipv4.ip_nonlocal_bind = 1 | Still exists with the same meaning: it "allows processes to bind() to non-local IP addresses, which can be quite useful - but may break some applications" |
net.ipv6.ip_nonlocal_bind = 1 | Still exists, the same for IPv6 |
Nothing in the file is deprecated. The warning in the kernel text is the thing to remember: with the parameter on, a daemon configured with a wrong address starts without complaint.