diff --git a/cephfs/command.go b/cephfs/command.go
index 3ef780c..9ed23bc 100644
--- a/cephfs/command.go
+++ b/cephfs/command.go
@@ -14,6 +14,10 @@ import (
 	"github.com/ceph/go-ceph/internal/cutil"
 )
 
+func cephBufferFree(p unsafe.Pointer) {
+	C.ceph_buffer_free((*C.char)(p))
+}
+
 // MdsCommand sends commands to the specified MDS.
 func (mount *MountInfo) MdsCommand(mdsSpec string, args [][]byte) ([]byte, string, error) {
 	return mount.mdsCommand(mdsSpec, args, nil)
@@ -40,7 +44,7 @@ func (mount *MountInfo) mdsCommand(mdsSpec string, args [][]byte, inputBuffer []
 	defer C.free(unsafe.Pointer(spec))
 	ci := cutil.NewCommandInput(args, inputBuffer)
 	defer ci.Free()
-	co := cutil.NewCommandOutput()
+	co := cutil.NewCommandOutput().SetFreeFunc(cephBufferFree)
 	defer co.Free()
 
 	ret := C.ceph_mds_command(
diff --git a/internal/cutil/command_output.go b/internal/cutil/command_output.go
index b6863a7..8b0c6e5 100644
--- a/internal/cutil/command_output.go
+++ b/internal/cutil/command_output.go
@@ -12,6 +12,7 @@ import (
 // CommandOutput can be used to manage the outputs of ceph's *_command
 // functions.
 type CommandOutput struct {
+	free      FreeFunc
 	outBuf    *C.char
 	outBufLen C.size_t
 	outs      *C.char
@@ -22,16 +23,28 @@ type CommandOutput struct {
 // a CommandOutput provides can be used to get the results of ceph's
 // *_command functions.
 func NewCommandOutput() *CommandOutput {
-	return &CommandOutput{}
+	return &CommandOutput{
+		free: free,
+	}
+}
+
+// SetFreeFunc sets the function used to free memory held by CommandOutput.
+// Not all uses of CommandOutput expect to use the basic C.free function
+// and either require or prefer the use of a custom deallocation function.
+// Use SetFreeFunc to change the free function and return the modified
+// CommandOutput object.
+func (co *CommandOutput) SetFreeFunc(f FreeFunc) *CommandOutput {
+	co.free = f
+	return co
 }
 
 // Free any C memory tracked by this object.
 func (co *CommandOutput) Free() {
 	if co.outBuf != nil {
-		C.free(unsafe.Pointer(co.outBuf))
+		co.free(unsafe.Pointer(co.outBuf))
 	}
 	if co.outs != nil {
-		C.free(unsafe.Pointer(co.outs))
+		co.free(unsafe.Pointer(co.outs))
 	}
 }
 
@@ -79,3 +92,9 @@ func testSetString(strp CharPtrPtr, lenp SizeTPtr, s string) {
 	*sp = C.CString(s)
 	*lp = C.size_t(len(s))
 }
+
+// free wraps C.free.
+// Required for unit tests that may not use cgo directly.
+func free(p unsafe.Pointer) {
+	C.free(p)
+}
diff --git a/internal/cutil/command_output_test.go b/internal/cutil/command_output_test.go
index 41619a6..74278b1 100644
--- a/internal/cutil/command_output_test.go
+++ b/internal/cutil/command_output_test.go
@@ -2,6 +2,7 @@ package cutil
 
 import (
 	"testing"
+	"unsafe"
 
 	"github.com/stretchr/testify/assert"
 )
@@ -40,4 +41,16 @@ func TestCommandOutput(t *testing.T) {
 		assert.Nil(t, b)
 		assert.EqualValues(t, "i got rhythm", s)
 	})
+	t.Run("customFreeFunc", func(t *testing.T) {
+		callCount := 0
+		co := NewCommandOutput().SetFreeFunc(func(p unsafe.Pointer) {
+			callCount++
+			free(p)
+		})
+		assert.NotNil(t, co)
+		testSetString(co.OutBuf(), co.OutBufLen(), "i got style")
+		testSetString(co.Outs(), co.OutsLen(), "i got rhythm")
+		co.Free()
+		assert.Equal(t, 2, callCount)
+	})
 }
diff --git a/internal/cutil/type_aliases.go b/internal/cutil/type_aliases.go
index f566fda..79495ef 100644
--- a/internal/cutil/type_aliases.go
+++ b/internal/cutil/type_aliases.go
@@ -23,3 +23,6 @@ type CharPtr unsafe.Pointer
 
 // SizeTPtr is an unsafe pointer wrapping C's `size_t*`.
 type SizeTPtr unsafe.Pointer
+
+// FreeFunc is a wrapper around calls to, or act like, C's free function.
+type FreeFunc func(unsafe.Pointer)
diff --git a/rados/command.go b/rados/command.go
index 1d6a1b5..1ec0422 100644
--- a/rados/command.go
+++ b/rados/command.go
@@ -11,6 +11,10 @@ import (
 	"github.com/ceph/go-ceph/internal/cutil"
 )
 
+func radosBufferFree(p unsafe.Pointer) {
+	C.rados_buffer_free((*C.char)(p))
+}
+
 // MonCommand sends a command to one of the monitors
 func (c *Conn) MonCommand(args []byte) ([]byte, string, error) {
 	return c.monCommand(args, nil)
@@ -24,7 +28,7 @@ func (c *Conn) MonCommandWithInputBuffer(args, inputBuffer []byte) ([]byte, stri
 func (c *Conn) monCommand(args, inputBuffer []byte) ([]byte, string, error) {
 	ci := cutil.NewCommandInput([][]byte{args}, inputBuffer)
 	defer ci.Free()
-	co := cutil.NewCommandOutput()
+	co := cutil.NewCommandOutput().SetFreeFunc(radosBufferFree)
 	defer co.Free()
 
 	ret := C.rados_mon_command(
@@ -70,7 +74,7 @@ func (c *Conn) pgCommand(pgid []byte, args [][]byte, inputBuffer []byte) ([]byte
 	defer C.free(unsafe.Pointer(name))
 	ci := cutil.NewCommandInput(args, inputBuffer)
 	defer ci.Free()
-	co := cutil.NewCommandOutput()
+	co := cutil.NewCommandOutput().SetFreeFunc(radosBufferFree)
 	defer co.Free()
 
 	ret := C.rados_pg_command(
@@ -107,7 +111,7 @@ func (c *Conn) MgrCommandWithInputBuffer(args [][]byte, inputBuffer []byte) ([]b
 func (c *Conn) mgrCommand(args [][]byte, inputBuffer []byte) ([]byte, string, error) {
 	ci := cutil.NewCommandInput(args, inputBuffer)
 	defer ci.Free()
-	co := cutil.NewCommandOutput()
+	co := cutil.NewCommandOutput().SetFreeFunc(radosBufferFree)
 	defer co.Free()
 
 	ret := C.rados_mgr_command(