Change default image volume mode to "anonymous"

We have not supported type=bind image volumes since pre-1.0
Podman - we phased them out when we added support for actual
volumes. Also, our image volume valid modes checker did not even
allow the actual default (anonymous). This is technically a
breaking change, so it will go into Podman 5.0 - but I strongly
doubt anyone is actually using this field if no one has noticed
this issue before now.

Signed-off-by: Matt Heon <mheon@redhat.com>

pkg/config/config.go

@@ -31,7 +31,7 @@ const (
 	bindirPrefix = "$BINDIR"
 )
 
-var validImageVolumeModes = []string{_typeBind, "tmpfs", "ignore"}
+var validImageVolumeModes = []string{"anonymous", "tmpfs", "ignore"}
 
 // ProxyEnv is a list of Proxy Environment variables
 var ProxyEnv = []string{

pkg/config/config_darwin.go

@@ -14,9 +14,6 @@ const (
 	// DefaultSignaturePolicyPath is the default value for the
 	// policy.json file.
 	DefaultSignaturePolicyPath = "/etc/containers/policy.json"
-
-	// Mount type for mounting host dir
-	_typeBind = "bind"
 )
 
 // podman remote clients on darwin cannot use unshare.isRootless() to determine the configuration file locations.

pkg/config/config_freebsd.go

@@ -14,9 +14,6 @@ const (
 	// DefaultSignaturePolicyPath is the default value for the
 	// policy.json file.
 	DefaultSignaturePolicyPath = "/usr/local/etc/containers/policy.json"
-
-	// Mount type for mounting host dir
-	_typeBind = "nullfs"
 )
 
 // podman remote clients on freebsd cannot use unshare.isRootless() to determine the configuration file locations.

pkg/config/config_linux.go

@@ -17,9 +17,6 @@ const (
 	// DefaultSignaturePolicyPath is the default value for the
 	// policy.json file.
 	DefaultSignaturePolicyPath = "/etc/containers/policy.json"
-
-	// Mount type for mounting host dir
-	_typeBind = "bind"
 )
 
 func selinuxEnabled() bool {

pkg/config/default.go

@@ -29,7 +29,7 @@ const (
 	_defaultTransport = "docker://"
 
 	// _defaultImageVolumeMode is a mode to handle built-in image volumes.
-	_defaultImageVolumeMode = _typeBind
+	_defaultImageVolumeMode = "anonymous"
 
 	// defaultInitName is the default name of the init binary
 	defaultInitName = "catatonit"