cmd: add a CLI wrapper for GarbageCollect

Add "gc" as an action for the CLI wrapper, for running the
GarbageCollect() method.

Signed-off-by: Nalin Dahyabhai <nalin@redhat.com>

cmd/containers-storage/gc.go

@@ -0,0 +1,37 @@
+package main
+
+import (
+	"fmt"
+	"os"
+
+	"github.com/containers/storage"
+	"github.com/containers/storage/pkg/mflag"
+)
+
+func gc(flags *mflag.FlagSet, action string, m storage.Store, args []string) (int, error) {
+	defer func() {
+		if _, err := m.Shutdown(true); err != nil {
+			fmt.Fprintf(os.Stderr, "shutdown: %v\n", err)
+		}
+	}()
+	if err := m.GarbageCollect(); err != nil {
+		return 1, err
+	}
+	if jsonOutput {
+		return outputJSON(string(""))
+	}
+	return 0, nil
+}
+
+func init() {
+	commands = append(commands, command{
+		names:   []string{"gc"},
+		usage:   "Perform garbage collection",
+		minArgs: 0,
+		maxArgs: 0,
+		action:  gc,
+		addFlags: func(flags *mflag.FlagSet, cmd *command) {
+			flags.BoolVar(&jsonOutput, []string{"-json", "j"}, jsonOutput, "Prefer JSON output")
+		},
+	})
+}

containers.go

@@ -14,6 +14,7 @@ import (
 	"github.com/containers/storage/pkg/stringid"
 	"github.com/containers/storage/pkg/truncindex"
 	digest "github.com/opencontainers/go-digest"
+	"github.com/sirupsen/logrus"
 )
 
 type containerLocations uint8
@@ -420,6 +421,7 @@ func (r *containerStore) GarbageCollect() error {
 		}
 
 		// Otherwise remove datadir
+		logrus.Debugf("removing %q", filepath.Join(r.dir, id))
 		moreErr := os.RemoveAll(filepath.Join(r.dir, id))
 		// Propagate first error
 		if moreErr != nil && err == nil {

docs/containers-storage-gc.md

@@ -0,0 +1,16 @@
+## containers-storage-gc 1 "January 2023"
+
+## NAME
+containers-storage gc - Garbage collect leftovers from partial layers/images/contianers
+
+## SYNOPSIS
+**containers-storage** **gc**
+
+## DESCRIPTION
+Removes additional data for layers, images, and containers which would
+correspond to layers, images, and containers which don't actually exist, but
+which may have been left on the filesystem after canceled attempts to create
+those layers, images, or containers.
+
+## EXAMPLE
+**containers-storage gc**

images.go

@@ -14,6 +14,7 @@ import (
 	"github.com/containers/storage/pkg/stringutils"
 	"github.com/containers/storage/pkg/truncindex"
 	digest "github.com/opencontainers/go-digest"
+	"github.com/sirupsen/logrus"
 )
 
 const (
@@ -423,6 +424,7 @@ func (r *imageStore) GarbageCollect() error {
 		}
 
 		// Otherwise remove datadir
+		logrus.Debugf("removing %q", filepath.Join(r.dir, id))
 		moreErr := os.RemoveAll(filepath.Join(r.dir, id))
 		// Propagate first error
 		if moreErr != nil && err == nil {

layers.go

@@ -678,10 +678,13 @@ func (r *layerStore) GarbageCollect() error {
 
 		// Remove layer and any related data of unreferenced id
 		if err := r.driver.Remove(id); err != nil {
+			logrus.Debugf("removing driver layer %q", id)
 			return err
 		}
 
+		logrus.Debugf("removing %q", r.tspath(id))
 		os.Remove(r.tspath(id))
+		logrus.Debugf("removing %q", r.datadir(id))
 		os.RemoveAll(r.datadir(id))
 	}
 	return nil