# README

qmp-mac-generator

MAC addresses generator for QEMU VMs

This is a simple command line application generating unique MAC address suitable for QEMU instances.

Its main purpose is to use it to pre-generate MAC addresses before launching VMs.

One can use it in CI to ensure no VM would have same address across jobs and projects.

It uses a file lock to ensure that generated MAC address is unique across multiple VM instances.

The locking itself is based on flock sys call which is working fine even from inside docker containers.

By default file lock file is located at /var/lock/qmp-mac-generator.lock.

It contains the last generated MAC address.

One can define different lock file by setting QMP_MAC_GENERATOR_LOCK_FILE environment variable.

Generated MAC range is 52:54:00:AB:xx:xx where x is 0x01-0xFF.

The generation starts over from beginning once it reaches the max address.

mac1=$(qmp-mac-generator)
mac2=$(qmp-mac-generator)
...

Optionally define different lock file location:

export QMP_MAC_GENERATOR_LOCK_FILE=/some-path/some-file

mac1=$(qmp-mac-generator)
mac2=$(qmp-mac-generator)
...

Mount the lock file from host location, this way all docker instances will generate unique addresses.

docker ... \
  -v /var/lock/qmp-mac-generator.lock:/var/lock/qmp-mac-generator.lock \
  ...

If you leave the file container specific, mac addresses will be unique inside that container only.

go install github.com/fikin/qmp-mac-generator
...
mac=$(${GOBIN}/qmp-mac-generator)

go get .
go build -v ./...
go test