What causes "c.Paths.SocketVMNet is empty" in lima-vm/lima?

Ensure Paths.SocketVMNet is populated from networks.yaml before building a Config programmatically

c.Paths.SocketVMNet is empty

Error message

c.Paths.SocketVMNet is empty

What it means

Within StartCmd's SocketVMNet branch, the code re-checks that c.Paths.SocketVMNet is non-empty before formatting the command, panicking with 'c.Paths.SocketVMNet is empty' if it is. This is a defense-in-depth assertion: normally IsDaemonInstalled would have panicked earlier, so reaching here implies an inconsistent config state (e.g. IsDaemonInstalled behavior changed or config mutated between calls).

Source

Thrown at pkg/networks/commands.go:107

		return osutil.LookupUser("root")
	}
	return osutil.User{}, fmt.Errorf("daemon %#q not defined", daemon)
}

func (c *Config) MkdirCmd() string {
	return fmt.Sprintf("/bin/mkdir -m 775 -p %s", c.Paths.VarRun)
}

func (c *Config) StartCmd(name, daemon string) string {
	if ok, _ := c.IsDaemonInstalled(daemon); !ok {
		panic(fmt.Errorf("daemon %#q is not available", daemon))
	}
	var cmd string
	switch daemon {
	case SocketVMNet:
		nw := c.Networks[name]
		if c.Paths.SocketVMNet == "" {
			panic("c.Paths.SocketVMNet is empty")
		}
		cmd = fmt.Sprintf("%s --pidfile=%s --socket-group=%s --vmnet-mode=%s",
			c.Paths.SocketVMNet, c.PIDFile(name, SocketVMNet), c.Group, nw.Mode)
		switch nw.Mode {
		case ModeBridged:
			cmd += fmt.Sprintf(" --vmnet-interface=%s", nw.Interface)
		case ModeHost, ModeShared:
			cmd += fmt.Sprintf(" --vmnet-gateway=%s --vmnet-dhcp-end=%s --vmnet-mask=%s",
				nw.Gateway, nw.DHCPEnd, nw.NetMask)
		}
		cmd += " " + c.Sock(name)
	default:
		panic(fmt.Errorf("unexpected daemon %#q", daemon))
	}
	return cmd
}

func (c *Config) StopCmd(name, daemon string) string {

View on GitHub (pinned to dd909d0973)

Solutions

Ensure Paths.SocketVMNet is populated from networks.yaml before building a Config programmatically
Do not mutate Config fields after validation; treat Config as read-only
Construct the config via the normal loader so paths are validated once

Example fix

// before
cfg := &networks.Config{} // SocketVMNet path empty
panicCmd := cfg.StartCmd("shared", networks.SocketVMNet)
// after
cfg, err := networks.LoadConfig() // populates Paths.SocketVMNet from networks.yaml

Defensive patterns

Strategy: validation

Validate before calling

if cfg.Paths.SocketVMNet == "" {
    return fmt.Errorf("config invalid: paths.socketVMNet must be set")
}

Try / catch

func safeStartCmd(cfg *networks.Config, name, daemon string) (cmd string, err error) {
    defer func() { if r := recover(); r != nil { err = fmt.Errorf("%v", r) } }()
    return cfg.StartCmd(name, daemon), nil
}

Prevention

Load Config via the standard loader, never hand-assemble the struct
Treat Config as immutable after load; reload rather than mutate
Keep Paths.SocketVMNet set consistently — both panic guards depend on it

When it happens

Trigger: StartCmd is called on a Config whose Paths.SocketVMNet field is the empty string but which somehow passed the earlier IsDaemonInstalled check — i.e. config mutated concurrently or constructed inconsistently.

Common situations: Programmatically built Config structs that bypass networks.yaml validation; race where the config is reloaded between the check and command construction; hand-assembled Config in tests.

Related errors

AI-assisted analysis of lima-vm/lima@dd909d0973 (2026-09-01). Data as JSON: /api/errors/deee2182450e1614. Report an issue: GitHub.