feat: Add support for configuring swap in Podman machine

Add `--swap` argument to `podman machine init` command.

Passing an int64 value to this flag will trigger the Podman machine
ignition file to be generated with a zram-generator.conf file containing
the --swap value as the zram-size argument.

This file is read by the zram-generator systemd service on boot
resulting in a zram swap device being created.

Fixes: https://github.com/containers/podman/issues/15980

Signed-off-by: Lewis Roy <lewis@redhat.com>

cmd/podman/machine/init.go

@@ -83,6 +83,14 @@ func init() {
 	)
 	_ = initCmd.RegisterFlagCompletionFunc(memoryFlagName, completion.AutocompleteNone)
 
+	swapFlagName := "swap"
+	flags.Uint64VarP(
+		&initOpts.Swap,
+		swapFlagName, "s", 0,
+		"Swap in MiB",
+	)
+	_ = initCmd.RegisterFlagCompletionFunc(swapFlagName, completion.AutocompleteNone)
+
 	flags.BoolVar(
 		&now,
 		"now", false,

cmd/podman/machine/list.go

@@ -119,6 +119,7 @@ func outputTemplate(cmd *cobra.Command, responses []*entities.ListReporter) erro
 		"CPUs":     "CPUS",
 		"Memory":   "MEMORY",
 		"DiskSize": "DISK SIZE",
+		"Swap":     "SWAP",
 	})
 
 	rpt := report.New(os.Stdout, cmd.Name())
@@ -182,6 +183,7 @@ func toMachineFormat(vms []*machine.ListResponse, defaultCon *config.Connection)
 		response.VMType = vm.VMType
 		response.CPUs = vm.CPUs
 		response.Memory = strUint(uint64(vm.Memory.ToBytes()))
+		response.Swap = strUint(uint64(vm.Swap.ToBytes()))
 		response.DiskSize = strUint(uint64(vm.DiskSize.ToBytes()))
 		response.Port = vm.Port
 		response.RemoteUsername = vm.RemoteUsername
@@ -225,6 +227,7 @@ func toHumanFormat(vms []*machine.ListResponse, defaultCon *config.Connection) [
 		response.VMType = vm.VMType
 		response.CPUs = vm.CPUs
 		response.Memory = units.BytesSize(float64(vm.Memory.ToBytes()))
+		response.Swap = units.BytesSize(float64(vm.Swap.ToBytes()))
 		response.DiskSize = units.BytesSize(float64(vm.DiskSize.ToBytes()))
 
 		humanResponses = append(humanResponses, response)

docs/source/markdown/podman-machine-init.1.md.in

@@ -104,6 +104,12 @@ if there is no existing remote connection configurations.
 
 API forwarding, if available, follows this setting.
 
+#### **--swap**, **-s**=*number*
+
+Swap (in MiB). Note: 1024MiB = 1GiB.
+
+Renders a `zram-generator.conf` file with zram-size set to the value passed to --swap
+
 #### **--timezone**
 
 Set the timezone for the machine and containers.  Valid values are `local` or

docs/source/markdown/podman-machine-list.1.md.in

@@ -50,6 +50,7 @@ Valid placeholders for the Go template are listed below:
 | .RemoteUsername     | VM Username for rootless Podman           |
 | .Running            | Is machine running                        |
 | .Stream             | Stream name                               |
+| .Swap               | Allocated swap for machine               |
 | .UserModeNetworking | Whether machine uses user-mode networking |
 | .VMType             | VM type                                   |
 

pkg/domain/entities/machine.go

@@ -13,6 +13,7 @@ type ListReporter struct {
 	VMType             string
 	CPUs               uint64
 	Memory             string
+	Swap               string
 	DiskSize           string
 	Port               int
 	RemoteUsername     string

pkg/machine/config.go

@@ -22,9 +22,7 @@ import (
 
 const apiUpTimeout = 20 * time.Second
 
-var (
+var ForwarderBinaryName = "gvproxy"
-	ForwarderBinaryName = "gvproxy"
-)
 
 type Download struct {
 	Arch                  string
@@ -55,6 +53,7 @@ type ListResponse struct {
 	VMType             string
 	CPUs               uint64
 	Memory             strongunits.MiB
+	Swap               strongunits.MiB
 	DiskSize           strongunits.GiB
 	Port               int
 	RemoteUsername     string

pkg/machine/define/initopts.go

@@ -11,6 +11,7 @@ type InitOptions struct {
 	Volumes            []string
 	IsDefault          bool
 	Memory             uint64
+	Swap               uint64
 	Name               string
 	TimeZone           string
 	URI                url.URL

pkg/machine/e2e/config_init_test.go

@@ -28,6 +28,7 @@ type initMachine struct {
 	playbook           string
 	cpus               *uint
 	diskSize           *uint
+	swap               *uint
 	ignitionPath       string
 	username           string
 	image              string
@@ -81,6 +82,9 @@ func (i *initMachine) buildCmd(m *machineTestBuilder) []string {
 	if i.userModeNetworking {
 		cmd = append(cmd, "--user-mode-networking")
 	}
+	if i.swap != nil {
+		cmd = append(cmd, "--swap", strconv.Itoa(int(*i.swap)))
+	}
 	name := m.name
 	cmd = append(cmd, name)
 
@@ -112,11 +116,17 @@ func (i *initMachine) withCPUs(num uint) *initMachine {
 	i.cpus = &num
 	return i
 }
+
 func (i *initMachine) withDiskSize(size uint) *initMachine {
 	i.diskSize = &size
 	return i
 }
 
+func (i *initMachine) withSwap(size uint) *initMachine {
+	i.swap = &size
+	return i
+}
+
 func (i *initMachine) withIgnitionPath(path string) *initMachine {
 	i.ignitionPath = path
 	return i

pkg/machine/e2e/init_test.go

@@ -238,7 +238,6 @@ var _ = Describe("podman machine init", func() {
 			Expect(testMachine.Resources.Memory).To(BeEquivalentTo(uint64(2048)))
 		}
 		Expect(testMachine.SSHConfig.RemoteUsername).To(Equal(remoteUsername))
-
 	})
 
 	It("machine init with cpus, disk size, memory, timezone", func() {
@@ -282,6 +281,23 @@ var _ = Describe("podman machine init", func() {
 		Expect(timezoneSession.outputToString()).To(ContainSubstring("HST"))
 	})
 
+	It("machine init with swap", func() {
+		skipIfWSL("Configuring swap is not supported on WSL")
+		name := randomString()
+		i := new(initMachine)
+		session, err := mb.setName(name).setCmd(i.withImage(mb.imagePath).withSwap(2048).withNow()).run()
+		Expect(err).ToNot(HaveOccurred())
+		Expect(session).To(Exit(0))
+
+		ssh := &sshMachine{}
+		sshSession, err := mb.setName(name).setCmd(ssh.withSSHCommand([]string{"zramctl -bo DISKSIZE"})).run()
+		Expect(err).ToNot(HaveOccurred())
+		Expect(sshSession).To(Exit(0))
+
+		// 2147483648 bytes = 2048MiB
+		Expect(sshSession.outputToString()).To(ContainSubstring("2147483648"))
+	})
+
 	It("machine init with volume", func() {
 		if testProvider.VMType() == define.HyperVVirt {
 			Skip("volumes are not supported on hyperv yet")
@@ -373,7 +389,6 @@ var _ = Describe("podman machine init", func() {
 		output := strings.TrimSpace(sshSession2.outputToString())
 		Expect(output).To(HavePrefix("/run/user"))
 		Expect(output).To(HaveSuffix("/podman/podman.sock"))
-
 	})
 
 	It("machine init rootful with docker.sock check", func() {

pkg/machine/ignition/ignition.go

@@ -67,6 +67,7 @@ type DynamicIgnition struct {
 	Rootful    bool
 	NetRecover bool
 	Rosetta    bool
+	Swap       uint64
 }
 
 func (ign *DynamicIgnition) Write() error {
@@ -136,7 +137,7 @@ func (ign *DynamicIgnition) GenerateIgnitionConfig() error {
 
 	ignStorage := Storage{
 		Directories: getDirs(ign.Name),
-		Files:       getFiles(ign.Name, ign.UID, ign.Rootful, ign.VMType, ign.NetRecover),
+		Files:       getFiles(ign.Name, ign.UID, ign.Rootful, ign.VMType, ign.NetRecover, ign.Swap),
 		Links:       getLinks(ign.Name),
 	}
 
@@ -293,7 +294,7 @@ func getDirs(usrName string) []Directory {
 	return dirs
 }
 
-func getFiles(usrName string, uid int, rootful bool, vmtype define.VMType, _ bool) []File {
+func getFiles(usrName string, uid int, rootful bool, vmtype define.VMType, _ bool, swap uint64) []File {
 	files := make([]File, 0)
 
 	lingerExample := parser.NewUnitFile()
@@ -407,6 +408,21 @@ pids_limit=0
 		},
 	})
 
+	if swap > 0 {
+		files = append(files, File{
+			Node: Node{
+				Path: "/etc/systemd/zram-generator.conf",
+			},
+			FileEmbedded1: FileEmbedded1{
+				Append: nil,
+				Contents: Resource{
+					Source: EncodeDataURLPtr(fmt.Sprintf("[zram0]\nzram-size=%d\n", swap)),
+				},
+				Mode: IntToPtr(0644),
+			},
+		})
+	}
+
 	// get certs for current user
 	userHome, err := os.UserHomeDir()
 	if err != nil {

pkg/machine/shim/host.go

@@ -30,9 +30,7 @@ import (
 // List is done at the host level to allow for a *possible* future where
 // more than one provider is used
 func List(vmstubbers []vmconfigs.VMProvider, _ machine.ListOptions) ([]*machine.ListResponse, error) {
-	var (
+	var lrs []*machine.ListResponse
-		lrs []*machine.ListResponse
-	)
 
 	for _, s := range vmstubbers {
 		dirs, err := env.GetMachineDirs(s.VMType())
@@ -54,10 +52,10 @@ func List(vmstubbers []vmconfigs.VMProvider, _ machine.ListOptions) ([]*machine.
 				LastUp:             mc.LastUp,
 				Running:            state == machineDefine.Running,
 				Starting:           mc.Starting,
-				//Stream:             "", // No longer applicable
 				VMType:             s.VMType().String(),
 				CPUs:               mc.Resources.CPUs,
 				Memory:             mc.Resources.Memory,
+				Swap:               mc.Swap,
 				DiskSize:           mc.Resources.DiskSize,
 				Port:               mc.SSH.Port,
 				RemoteUsername:     mc.SSH.RemoteUsername,
@@ -204,13 +202,13 @@ func Init(opts machineDefine.InitOptions, mp vmconfigs.VMProvider) error {
 		VMType:    mp.VMType(),
 		WritePath: ignitionFile.GetPath(),
 		Rootful:   opts.Rootful,
+		Swap:      opts.Swap,
 	})
 
 	// If the user provides an ignition file, we need to
 	// copy it into the conf dir
 	if len(opts.IgnitionPath) > 0 {
 		err = ignBuilder.BuildWithIgnitionFile(opts.IgnitionPath)
-
 		if err != nil {
 			return err
 		}

pkg/machine/vmconfigs/config.go

@@ -27,6 +27,8 @@ type MachineConfig struct {
 	SSH       SSHConfig
 	Version   uint
 
+	Swap strongunits.MiB
+
 	// Image stuff
 	imageDescription machineImage //nolint:unused
 

pkg/machine/vmconfigs/machine.go

@@ -81,6 +81,10 @@ func NewMachineConfig(opts define.InitOptions, dirs *define.MachineDirs, sshIden
 	}
 	mc.Resources = mrc
 
+	if opts.Swap > 0 {
+		mc.Swap = strongunits.MiB(opts.Swap)
+	}
+
 	sshPort, err := ports.AllocateMachinePort()
 	if err != nil {
 		return nil, err