github.com/dpiddy/docker@v1.12.2-rc1/integration-cli/docker_cli_exec_test.go (about)

     1  // +build !test_no_exec
     2  
     3  package main
     4  
     5  import (
     6  	"bufio"
     7  	"fmt"
     8  	"net/http"
     9  	"os"
    10  	"os/exec"
    11  	"reflect"
    12  	"runtime"
    13  	"sort"
    14  	"strings"
    15  	"sync"
    16  	"time"
    17  
    18  	"github.com/docker/docker/pkg/integration/checker"
    19  	"github.com/go-check/check"
    20  )
    21  
    22  func (s *DockerSuite) TestExec(c *check.C) {
    23  	testRequires(c, DaemonIsLinux)
    24  	out, _ := dockerCmd(c, "run", "-d", "--name", "testing", "busybox", "sh", "-c", "echo test > /tmp/file && top")
    25  	c.Assert(waitRun(strings.TrimSpace(out)), check.IsNil)
    26  
    27  	out, _ = dockerCmd(c, "exec", "testing", "cat", "/tmp/file")
    28  	out = strings.Trim(out, "\r\n")
    29  	c.Assert(out, checker.Equals, "test")
    30  
    31  }
    32  
    33  func (s *DockerSuite) TestExecInteractive(c *check.C) {
    34  	testRequires(c, DaemonIsLinux)
    35  	dockerCmd(c, "run", "-d", "--name", "testing", "busybox", "sh", "-c", "echo test > /tmp/file && top")
    36  
    37  	execCmd := exec.Command(dockerBinary, "exec", "-i", "testing", "sh")
    38  	stdin, err := execCmd.StdinPipe()
    39  	c.Assert(err, checker.IsNil)
    40  	stdout, err := execCmd.StdoutPipe()
    41  	c.Assert(err, checker.IsNil)
    42  
    43  	err = execCmd.Start()
    44  	c.Assert(err, checker.IsNil)
    45  	_, err = stdin.Write([]byte("cat /tmp/file\n"))
    46  	c.Assert(err, checker.IsNil)
    47  
    48  	r := bufio.NewReader(stdout)
    49  	line, err := r.ReadString('\n')
    50  	c.Assert(err, checker.IsNil)
    51  	line = strings.TrimSpace(line)
    52  	c.Assert(line, checker.Equals, "test")
    53  	err = stdin.Close()
    54  	c.Assert(err, checker.IsNil)
    55  	errChan := make(chan error)
    56  	go func() {
    57  		errChan <- execCmd.Wait()
    58  		close(errChan)
    59  	}()
    60  	select {
    61  	case err := <-errChan:
    62  		c.Assert(err, checker.IsNil)
    63  	case <-time.After(1 * time.Second):
    64  		c.Fatal("docker exec failed to exit on stdin close")
    65  	}
    66  
    67  }
    68  
    69  func (s *DockerSuite) TestExecAfterContainerRestart(c *check.C) {
    70  	testRequires(c, DaemonIsLinux)
    71  	out, _ := runSleepingContainer(c)
    72  	cleanedContainerID := strings.TrimSpace(out)
    73  	c.Assert(waitRun(cleanedContainerID), check.IsNil)
    74  	dockerCmd(c, "restart", cleanedContainerID)
    75  	c.Assert(waitRun(cleanedContainerID), check.IsNil)
    76  
    77  	out, _ = dockerCmd(c, "exec", cleanedContainerID, "echo", "hello")
    78  	outStr := strings.TrimSpace(out)
    79  	c.Assert(outStr, checker.Equals, "hello")
    80  }
    81  
    82  func (s *DockerDaemonSuite) TestExecAfterDaemonRestart(c *check.C) {
    83  	// TODO Windows CI: Requires a little work to get this ported.
    84  	testRequires(c, DaemonIsLinux)
    85  	testRequires(c, SameHostDaemon)
    86  
    87  	err := s.d.StartWithBusybox()
    88  	c.Assert(err, checker.IsNil)
    89  
    90  	out, err := s.d.Cmd("run", "-d", "--name", "top", "-p", "80", "busybox:latest", "top")
    91  	c.Assert(err, checker.IsNil, check.Commentf("Could not run top: %s", out))
    92  
    93  	err = s.d.Restart()
    94  	c.Assert(err, checker.IsNil, check.Commentf("Could not restart daemon"))
    95  
    96  	out, err = s.d.Cmd("start", "top")
    97  	c.Assert(err, checker.IsNil, check.Commentf("Could not start top after daemon restart: %s", out))
    98  
    99  	out, err = s.d.Cmd("exec", "top", "echo", "hello")
   100  	c.Assert(err, checker.IsNil, check.Commentf("Could not exec on container top: %s", out))
   101  
   102  	outStr := strings.TrimSpace(string(out))
   103  	c.Assert(outStr, checker.Equals, "hello")
   104  }
   105  
   106  // Regression test for #9155, #9044
   107  func (s *DockerSuite) TestExecEnv(c *check.C) {
   108  	// TODO Windows CI: This one is interesting and may just end up being a feature
   109  	// difference between Windows and Linux. On Windows, the environment is passed
   110  	// into the process that is launched, not into the machine environment. Hence
   111  	// a subsequent exec will not have LALA set/
   112  	testRequires(c, DaemonIsLinux)
   113  	runSleepingContainer(c, "-e", "LALA=value1", "-e", "LALA=value2", "-d", "--name", "testing")
   114  	c.Assert(waitRun("testing"), check.IsNil)
   115  
   116  	out, _ := dockerCmd(c, "exec", "testing", "env")
   117  	c.Assert(out, checker.Not(checker.Contains), "LALA=value1")
   118  	c.Assert(out, checker.Contains, "LALA=value2")
   119  	c.Assert(out, checker.Contains, "HOME=/root")
   120  }
   121  
   122  func (s *DockerSuite) TestExecExitStatus(c *check.C) {
   123  	runSleepingContainer(c, "-d", "--name", "top")
   124  
   125  	// Test normal (non-detached) case first
   126  	cmd := exec.Command(dockerBinary, "exec", "top", "sh", "-c", "exit 23")
   127  	ec, _ := runCommand(cmd)
   128  	c.Assert(ec, checker.Equals, 23)
   129  }
   130  
   131  func (s *DockerSuite) TestExecPausedContainer(c *check.C) {
   132  	// Windows does not support pause
   133  	testRequires(c, DaemonIsLinux)
   134  	defer unpauseAllContainers()
   135  
   136  	out, _ := dockerCmd(c, "run", "-d", "--name", "testing", "busybox", "top")
   137  	ContainerID := strings.TrimSpace(out)
   138  
   139  	dockerCmd(c, "pause", "testing")
   140  	out, _, err := dockerCmdWithError("exec", "-i", "-t", ContainerID, "echo", "hello")
   141  	c.Assert(err, checker.NotNil, check.Commentf("container should fail to exec new conmmand if it is paused"))
   142  
   143  	expected := ContainerID + " is paused, unpause the container before exec"
   144  	c.Assert(out, checker.Contains, expected, check.Commentf("container should not exec new command if it is paused"))
   145  }
   146  
   147  // regression test for #9476
   148  func (s *DockerSuite) TestExecTTYCloseStdin(c *check.C) {
   149  	// TODO Windows CI: This requires some work to port to Windows.
   150  	testRequires(c, DaemonIsLinux)
   151  	dockerCmd(c, "run", "-d", "-it", "--name", "exec_tty_stdin", "busybox")
   152  
   153  	cmd := exec.Command(dockerBinary, "exec", "-i", "exec_tty_stdin", "cat")
   154  	stdinRw, err := cmd.StdinPipe()
   155  	c.Assert(err, checker.IsNil)
   156  
   157  	stdinRw.Write([]byte("test"))
   158  	stdinRw.Close()
   159  
   160  	out, _, err := runCommandWithOutput(cmd)
   161  	c.Assert(err, checker.IsNil, check.Commentf(out))
   162  
   163  	out, _ = dockerCmd(c, "top", "exec_tty_stdin")
   164  	outArr := strings.Split(out, "\n")
   165  	c.Assert(len(outArr), checker.LessOrEqualThan, 3, check.Commentf("exec process left running"))
   166  	c.Assert(out, checker.Not(checker.Contains), "nsenter-exec")
   167  }
   168  
   169  func (s *DockerSuite) TestExecTTYWithoutStdin(c *check.C) {
   170  	// TODO Windows CI: This requires some work to port to Windows.
   171  	testRequires(c, DaemonIsLinux)
   172  	out, _ := dockerCmd(c, "run", "-d", "-ti", "busybox")
   173  	id := strings.TrimSpace(out)
   174  	c.Assert(waitRun(id), checker.IsNil)
   175  
   176  	errChan := make(chan error)
   177  	go func() {
   178  		defer close(errChan)
   179  
   180  		cmd := exec.Command(dockerBinary, "exec", "-ti", id, "true")
   181  		if _, err := cmd.StdinPipe(); err != nil {
   182  			errChan <- err
   183  			return
   184  		}
   185  
   186  		expected := "the input device is not a TTY"
   187  		if runtime.GOOS == "windows" {
   188  			expected += ".  If you are using mintty, try prefixing the command with 'winpty'"
   189  		}
   190  		if out, _, err := runCommandWithOutput(cmd); err == nil {
   191  			errChan <- fmt.Errorf("exec should have failed")
   192  			return
   193  		} else if !strings.Contains(out, expected) {
   194  			errChan <- fmt.Errorf("exec failed with error %q: expected %q", out, expected)
   195  			return
   196  		}
   197  	}()
   198  
   199  	select {
   200  	case err := <-errChan:
   201  		c.Assert(err, check.IsNil)
   202  	case <-time.After(3 * time.Second):
   203  		c.Fatal("exec is running but should have failed")
   204  	}
   205  }
   206  
   207  func (s *DockerSuite) TestExecParseError(c *check.C) {
   208  	// TODO Windows CI: Requires some extra work. Consider copying the
   209  	// runSleepingContainer helper to have an exec version.
   210  	testRequires(c, DaemonIsLinux)
   211  	dockerCmd(c, "run", "-d", "--name", "top", "busybox", "top")
   212  
   213  	// Test normal (non-detached) case first
   214  	cmd := exec.Command(dockerBinary, "exec", "top")
   215  	_, stderr, _, err := runCommandWithStdoutStderr(cmd)
   216  	c.Assert(err, checker.NotNil)
   217  	c.Assert(stderr, checker.Contains, "See '"+dockerBinary+" exec --help'")
   218  }
   219  
   220  func (s *DockerSuite) TestExecStopNotHanging(c *check.C) {
   221  	// TODO Windows CI: Requires some extra work. Consider copying the
   222  	// runSleepingContainer helper to have an exec version.
   223  	testRequires(c, DaemonIsLinux)
   224  	dockerCmd(c, "run", "-d", "--name", "testing", "busybox", "top")
   225  
   226  	err := exec.Command(dockerBinary, "exec", "testing", "top").Start()
   227  	c.Assert(err, checker.IsNil)
   228  
   229  	type dstop struct {
   230  		out []byte
   231  		err error
   232  	}
   233  
   234  	ch := make(chan dstop)
   235  	go func() {
   236  		out, err := exec.Command(dockerBinary, "stop", "testing").CombinedOutput()
   237  		ch <- dstop{out, err}
   238  		close(ch)
   239  	}()
   240  	select {
   241  	case <-time.After(3 * time.Second):
   242  		c.Fatal("Container stop timed out")
   243  	case s := <-ch:
   244  		c.Assert(s.err, check.IsNil)
   245  	}
   246  }
   247  
   248  func (s *DockerSuite) TestExecCgroup(c *check.C) {
   249  	// Not applicable on Windows - using Linux specific functionality
   250  	testRequires(c, NotUserNamespace)
   251  	testRequires(c, DaemonIsLinux)
   252  	dockerCmd(c, "run", "-d", "--name", "testing", "busybox", "top")
   253  
   254  	out, _ := dockerCmd(c, "exec", "testing", "cat", "/proc/1/cgroup")
   255  	containerCgroups := sort.StringSlice(strings.Split(out, "\n"))
   256  
   257  	var wg sync.WaitGroup
   258  	var mu sync.Mutex
   259  	execCgroups := []sort.StringSlice{}
   260  	errChan := make(chan error)
   261  	// exec a few times concurrently to get consistent failure
   262  	for i := 0; i < 5; i++ {
   263  		wg.Add(1)
   264  		go func() {
   265  			out, _, err := dockerCmdWithError("exec", "testing", "cat", "/proc/self/cgroup")
   266  			if err != nil {
   267  				errChan <- err
   268  				return
   269  			}
   270  			cg := sort.StringSlice(strings.Split(out, "\n"))
   271  
   272  			mu.Lock()
   273  			execCgroups = append(execCgroups, cg)
   274  			mu.Unlock()
   275  			wg.Done()
   276  		}()
   277  	}
   278  	wg.Wait()
   279  	close(errChan)
   280  
   281  	for err := range errChan {
   282  		c.Assert(err, checker.IsNil)
   283  	}
   284  
   285  	for _, cg := range execCgroups {
   286  		if !reflect.DeepEqual(cg, containerCgroups) {
   287  			fmt.Println("exec cgroups:")
   288  			for _, name := range cg {
   289  				fmt.Printf(" %s\n", name)
   290  			}
   291  
   292  			fmt.Println("container cgroups:")
   293  			for _, name := range containerCgroups {
   294  				fmt.Printf(" %s\n", name)
   295  			}
   296  			c.Fatal("cgroups mismatched")
   297  		}
   298  	}
   299  }
   300  
   301  func (s *DockerSuite) TestExecInspectID(c *check.C) {
   302  	out, _ := runSleepingContainer(c, "-d")
   303  	id := strings.TrimSuffix(out, "\n")
   304  
   305  	out = inspectField(c, id, "ExecIDs")
   306  	c.Assert(out, checker.Equals, "[]", check.Commentf("ExecIDs should be empty, got: %s", out))
   307  
   308  	// Start an exec, have it block waiting so we can do some checking
   309  	cmd := exec.Command(dockerBinary, "exec", id, "sh", "-c",
   310  		"while ! test -e /execid1; do sleep 1; done")
   311  
   312  	err := cmd.Start()
   313  	c.Assert(err, checker.IsNil, check.Commentf("failed to start the exec cmd"))
   314  
   315  	// Give the exec 10 chances/seconds to start then give up and stop the test
   316  	tries := 10
   317  	for i := 0; i < tries; i++ {
   318  		// Since its still running we should see exec as part of the container
   319  		out = strings.TrimSpace(inspectField(c, id, "ExecIDs"))
   320  
   321  		if out != "[]" && out != "<no value>" {
   322  			break
   323  		}
   324  		c.Assert(i+1, checker.Not(checker.Equals), tries, check.Commentf("ExecIDs still empty after 10 second"))
   325  		time.Sleep(1 * time.Second)
   326  	}
   327  
   328  	// Save execID for later
   329  	execID, err := inspectFilter(id, "index .ExecIDs 0")
   330  	c.Assert(err, checker.IsNil, check.Commentf("failed to get the exec id"))
   331  
   332  	// End the exec by creating the missing file
   333  	err = exec.Command(dockerBinary, "exec", id,
   334  		"sh", "-c", "touch /execid1").Run()
   335  
   336  	c.Assert(err, checker.IsNil, check.Commentf("failed to run the 2nd exec cmd"))
   337  
   338  	// Wait for 1st exec to complete
   339  	cmd.Wait()
   340  
   341  	// Give the exec 10 chances/seconds to stop then give up and stop the test
   342  	for i := 0; i < tries; i++ {
   343  		// Since its still running we should see exec as part of the container
   344  		out = strings.TrimSpace(inspectField(c, id, "ExecIDs"))
   345  
   346  		if out == "[]" {
   347  			break
   348  		}
   349  		c.Assert(i+1, checker.Not(checker.Equals), tries, check.Commentf("ExecIDs still not empty after 10 second"))
   350  		time.Sleep(1 * time.Second)
   351  	}
   352  
   353  	// But we should still be able to query the execID
   354  	sc, body, err := sockRequest("GET", "/exec/"+execID+"/json", nil)
   355  	c.Assert(sc, checker.Equals, http.StatusOK, check.Commentf("received status != 200 OK: %d\n%s", sc, body))
   356  
   357  	// Now delete the container and then an 'inspect' on the exec should
   358  	// result in a 404 (not 'container not running')
   359  	out, ec := dockerCmd(c, "rm", "-f", id)
   360  	c.Assert(ec, checker.Equals, 0, check.Commentf("error removing container: %s", out))
   361  	sc, body, err = sockRequest("GET", "/exec/"+execID+"/json", nil)
   362  	c.Assert(sc, checker.Equals, http.StatusNotFound, check.Commentf("received status != 404: %d\n%s", sc, body))
   363  }
   364  
   365  func (s *DockerSuite) TestLinksPingLinkedContainersOnRename(c *check.C) {
   366  	// Problematic on Windows as Windows does not support links
   367  	testRequires(c, DaemonIsLinux)
   368  	var out string
   369  	out, _ = dockerCmd(c, "run", "-d", "--name", "container1", "busybox", "top")
   370  	idA := strings.TrimSpace(out)
   371  	c.Assert(idA, checker.Not(checker.Equals), "", check.Commentf("%s, id should not be nil", out))
   372  	out, _ = dockerCmd(c, "run", "-d", "--link", "container1:alias1", "--name", "container2", "busybox", "top")
   373  	idB := strings.TrimSpace(out)
   374  	c.Assert(idB, checker.Not(checker.Equals), "", check.Commentf("%s, id should not be nil", out))
   375  
   376  	dockerCmd(c, "exec", "container2", "ping", "-c", "1", "alias1", "-W", "1")
   377  	dockerCmd(c, "rename", "container1", "container_new")
   378  	dockerCmd(c, "exec", "container2", "ping", "-c", "1", "alias1", "-W", "1")
   379  }
   380  
   381  func (s *DockerSuite) TestRunMutableNetworkFiles(c *check.C) {
   382  	// Not applicable on Windows to Windows CI.
   383  	testRequires(c, SameHostDaemon, DaemonIsLinux)
   384  	for _, fn := range []string{"resolv.conf", "hosts"} {
   385  		deleteAllContainers()
   386  
   387  		content, err := runCommandAndReadContainerFile(fn, exec.Command(dockerBinary, "run", "-d", "--name", "c1", "busybox", "sh", "-c", fmt.Sprintf("echo success >/etc/%s && top", fn)))
   388  		c.Assert(err, checker.IsNil)
   389  
   390  		c.Assert(strings.TrimSpace(string(content)), checker.Equals, "success", check.Commentf("Content was not what was modified in the container", string(content)))
   391  
   392  		out, _ := dockerCmd(c, "run", "-d", "--name", "c2", "busybox", "top")
   393  		contID := strings.TrimSpace(out)
   394  		netFilePath := containerStorageFile(contID, fn)
   395  
   396  		f, err := os.OpenFile(netFilePath, os.O_WRONLY|os.O_SYNC|os.O_APPEND, 0644)
   397  		c.Assert(err, checker.IsNil)
   398  
   399  		if _, err := f.Seek(0, 0); err != nil {
   400  			f.Close()
   401  			c.Fatal(err)
   402  		}
   403  
   404  		if err := f.Truncate(0); err != nil {
   405  			f.Close()
   406  			c.Fatal(err)
   407  		}
   408  
   409  		if _, err := f.Write([]byte("success2\n")); err != nil {
   410  			f.Close()
   411  			c.Fatal(err)
   412  		}
   413  		f.Close()
   414  
   415  		res, _ := dockerCmd(c, "exec", contID, "cat", "/etc/"+fn)
   416  		c.Assert(res, checker.Equals, "success2\n")
   417  	}
   418  }
   419  
   420  func (s *DockerSuite) TestExecWithUser(c *check.C) {
   421  	// TODO Windows CI: This may be fixable in the future once Windows
   422  	// supports users
   423  	testRequires(c, DaemonIsLinux)
   424  	dockerCmd(c, "run", "-d", "--name", "parent", "busybox", "top")
   425  
   426  	out, _ := dockerCmd(c, "exec", "-u", "1", "parent", "id")
   427  	c.Assert(out, checker.Contains, "uid=1(daemon) gid=1(daemon)")
   428  
   429  	out, _ = dockerCmd(c, "exec", "-u", "root", "parent", "id")
   430  	c.Assert(out, checker.Contains, "uid=0(root) gid=0(root)", check.Commentf("exec with user by id expected daemon user got %s", out))
   431  }
   432  
   433  func (s *DockerSuite) TestExecWithPrivileged(c *check.C) {
   434  	// Not applicable on Windows
   435  	testRequires(c, DaemonIsLinux, NotUserNamespace)
   436  	// Start main loop which attempts mknod repeatedly
   437  	dockerCmd(c, "run", "-d", "--name", "parent", "--cap-drop=ALL", "busybox", "sh", "-c", `while (true); do if [ -e /exec_priv ]; then cat /exec_priv && mknod /tmp/sda b 8 0 && echo "Success"; else echo "Privileged exec has not run yet"; fi; usleep 10000; done`)
   438  
   439  	// Check exec mknod doesn't work
   440  	cmd := exec.Command(dockerBinary, "exec", "parent", "sh", "-c", "mknod /tmp/sdb b 8 16")
   441  	out, _, err := runCommandWithOutput(cmd)
   442  	c.Assert(err, checker.NotNil, check.Commentf("exec mknod in --cap-drop=ALL container without --privileged should fail"))
   443  	c.Assert(out, checker.Contains, "Operation not permitted", check.Commentf("exec mknod in --cap-drop=ALL container without --privileged should fail"))
   444  
   445  	// Check exec mknod does work with --privileged
   446  	cmd = exec.Command(dockerBinary, "exec", "--privileged", "parent", "sh", "-c", `echo "Running exec --privileged" > /exec_priv && mknod /tmp/sdb b 8 16 && usleep 50000 && echo "Finished exec --privileged" > /exec_priv && echo ok`)
   447  	out, _, err = runCommandWithOutput(cmd)
   448  	c.Assert(err, checker.IsNil)
   449  
   450  	actual := strings.TrimSpace(out)
   451  	c.Assert(actual, checker.Equals, "ok", check.Commentf("exec mknod in --cap-drop=ALL container with --privileged failed, output: %q", out))
   452  
   453  	// Check subsequent unprivileged exec cannot mknod
   454  	cmd = exec.Command(dockerBinary, "exec", "parent", "sh", "-c", "mknod /tmp/sdc b 8 32")
   455  	out, _, err = runCommandWithOutput(cmd)
   456  	c.Assert(err, checker.NotNil, check.Commentf("repeating exec mknod in --cap-drop=ALL container after --privileged without --privileged should fail"))
   457  	c.Assert(out, checker.Contains, "Operation not permitted", check.Commentf("repeating exec mknod in --cap-drop=ALL container after --privileged without --privileged should fail"))
   458  
   459  	// Confirm at no point was mknod allowed
   460  	logCmd := exec.Command(dockerBinary, "logs", "parent")
   461  	out, _, err = runCommandWithOutput(logCmd)
   462  	c.Assert(err, checker.IsNil)
   463  	c.Assert(out, checker.Not(checker.Contains), "Success")
   464  
   465  }
   466  
   467  func (s *DockerSuite) TestExecWithImageUser(c *check.C) {
   468  	// Not applicable on Windows
   469  	testRequires(c, DaemonIsLinux)
   470  	name := "testbuilduser"
   471  	_, err := buildImage(name,
   472  		`FROM busybox
   473  		RUN echo 'dockerio:x:1001:1001::/bin:/bin/false' >> /etc/passwd
   474  		USER dockerio`,
   475  		true)
   476  	c.Assert(err, checker.IsNil)
   477  
   478  	dockerCmd(c, "run", "-d", "--name", "dockerioexec", name, "top")
   479  
   480  	out, _ := dockerCmd(c, "exec", "dockerioexec", "whoami")
   481  	c.Assert(out, checker.Contains, "dockerio", check.Commentf("exec with user by id expected dockerio user got %s", out))
   482  }
   483  
   484  func (s *DockerSuite) TestExecOnReadonlyContainer(c *check.C) {
   485  	// Windows does not support read-only
   486  	// --read-only + userns has remount issues
   487  	testRequires(c, DaemonIsLinux, NotUserNamespace)
   488  	dockerCmd(c, "run", "-d", "--read-only", "--name", "parent", "busybox", "top")
   489  	dockerCmd(c, "exec", "parent", "true")
   490  }
   491  
   492  func (s *DockerSuite) TestExecUlimits(c *check.C) {
   493  	testRequires(c, DaemonIsLinux)
   494  	name := "testexeculimits"
   495  	runSleepingContainer(c, "-d", "--ulimit", "nproc=21", "--name", name)
   496  	c.Assert(waitRun(name), checker.IsNil)
   497  
   498  	out, _, err := dockerCmdWithError("exec", name, "sh", "-c", "ulimit -p")
   499  	c.Assert(err, checker.IsNil)
   500  	c.Assert(strings.TrimSpace(out), checker.Equals, "21")
   501  }
   502  
   503  // #15750
   504  func (s *DockerSuite) TestExecStartFails(c *check.C) {
   505  	// TODO Windows CI. This test should be portable. Figure out why it fails
   506  	// currently.
   507  	testRequires(c, DaemonIsLinux)
   508  	name := "exec-15750"
   509  	runSleepingContainer(c, "-d", "--name", name)
   510  	c.Assert(waitRun(name), checker.IsNil)
   511  
   512  	out, _, err := dockerCmdWithError("exec", name, "no-such-cmd")
   513  	c.Assert(err, checker.NotNil, check.Commentf(out))
   514  	c.Assert(out, checker.Contains, "executable file not found")
   515  }