Add test for prestart hook

Signed-off-by: Mrunal Patel <mrunalp@gmail.com>

libcontainer/integration/exec_test.go

@@ -905,3 +905,47 @@ func TestMountCgroupRW(t *testing.T) {
 		}
 	}
 }
+
+func TestPrestartHook(t *testing.T) {
+	if testing.Short() {
+		return
+	}
+	root, err := newTestRoot()
+	ok(t, err)
+	defer os.RemoveAll(root)
+
+	rootfs, err := newRootfs()
+	ok(t, err)
+	defer remove(rootfs)
+
+	config := newTemplateConfig(rootfs)
+	pwd, _ := os.Getwd()
+
+	hookPath := filepath.Join(pwd, "../../script", "hook.py")
+	prestartCmd := configs.Command{Path: hookPath}
+	config.Prestart = append(config.Prestart, prestartCmd)
+
+	container, err := factory.Create("test", config)
+	ok(t, err)
+	defer container.Destroy()
+
+	var stdout bytes.Buffer
+	pconfig := libcontainer.Process{
+		Args:   []string{"sh", "-c", "ls /tmp.txt"},
+		Env:    standardEnvironment,
+		Stdin:  nil,
+		Stdout: &stdout,
+	}
+	err = container.Start(&pconfig)
+	ok(t, err)
+
+	// Wait for process
+	waitProcess(&pconfig, t)
+
+	outputLs := string(stdout.Bytes())
+
+	// Check that the ls output has the expected file touched by the prestart hook
+	if !strings.Contains(outputLs, "/tmp.txt") {
+		t.Fatal("ls output doesn't have the expected file: ", outputLs)
+	}
+}

script/hook.py

@@ -0,0 +1,16 @@
+#!/usr/bin/env python
+import sys
+import json
+import os
+
+def touch(filepath):
+	if os.path.exists(filepath):
+		os.utime(filepath, None)
+	else:
+		open(filepath, 'a').close()
+
+if __name__ == "__main__":
+	rootfs = json.load(sys.stdin)["config"]["rootfs"]
+	touch(os.path.join(rootfs, "tmp.txt"))
+
+