-
Notifications
You must be signed in to change notification settings - Fork 1
/
nsenter_mount.go
199 lines (169 loc) · 6.26 KB
/
nsenter_mount.go
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
// +build linux
/*
Copyright 2014 The Kubernetes Authors All rights reserved.
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/
package mount
import (
"os"
"path/filepath"
"strings"
"github.com/golang/glog"
"k8s.io/kubernetes/pkg/util/exec"
)
// NsenterMounter is part of experimental support for running the kubelet
// in a container. Currently, all docker containers receive their own mount
// namespaces. NsenterMounter works by executing nsenter to run commands in
// the host's mount namespace.
//
// NsenterMounter requires:
//
// 1. Docker >= 1.6 due to the dependency on the slave propagation mode
// of the bind-mount of the kubelet root directory in the container.
// Docker 1.5 used a private propagation mode for bind-mounts, so mounts
// performed in the host's mount namespace do not propagate out to the
// bind-mount in this docker version.
// 2. The host's root filesystem must be available at /rootfs
// 3. The nsenter binary must be on the Kubelet process' PATH in the container's
// filesystem.
// 4. The Kubelet process must have CAP_SYS_ADMIN (required by nsenter); at
// the present, this effectively means that the kubelet is running in a
// privileged container.
// 5. The volume path used by the Kubelet must be the same inside and outside
// the container and be writable by the container (to initialize volume)
// contents. TODO: remove this requirement.
// 6. The host image must have mount, findmnt, and umount binaries in /bin,
// /usr/sbin, or /usr/bin
//
// For more information about mount propagation modes, see:
// https://www.kernel.org/doc/Documentation/filesystems/sharedsubtree.txt
type NsenterMounter struct {
// a map of commands to their paths on the host filesystem
paths map[string]string
}
func NewNsenterMounter() *NsenterMounter {
m := &NsenterMounter{
paths: map[string]string{
"mount": "",
"findmnt": "",
"umount": "",
},
}
// search for the mount command in other locations besides /usr/bin
for binary := range m.paths {
// default to root
m.paths[binary] = filepath.Join("/", binary)
for _, path := range []string{"/bin", "/usr/sbin", "/usr/bin"} {
binPath := filepath.Join(path, binary)
if _, err := os.Stat(filepath.Join(hostRootFsPath, binPath)); err != nil {
continue
}
m.paths[binary] = binPath
break
}
// TODO: error, so that the kubelet can stop if the mounts don't exist
}
return m
}
// NsenterMounter implements mount.Interface
var _ = Interface(&NsenterMounter{})
const (
hostRootFsPath = "/rootfs"
hostProcMountsPath = "/rootfs/proc/mounts"
nsenterPath = "nsenter"
)
// Mount runs mount(8) in the host's root mount namespace. Aside from this
// aspect, Mount has the same semantics as the mounter returned by mount.New()
func (n *NsenterMounter) Mount(source string, target string, fstype string, options []string) error {
bind, bindRemountOpts := isBind(options)
if bind {
err := n.doNsenterMount(source, target, fstype, []string{"bind"})
if err != nil {
return err
}
return n.doNsenterMount(source, target, fstype, bindRemountOpts)
}
return n.doNsenterMount(source, target, fstype, options)
}
// doNsenterMount nsenters the host's mount namespace and performs the
// requested mount.
func (n *NsenterMounter) doNsenterMount(source, target, fstype string, options []string) error {
glog.V(5).Infof("nsenter Mounting %s %s %s %v", source, target, fstype, options)
args := n.makeNsenterArgs(source, target, fstype, options)
glog.V(5).Infof("Mount command: %v %v", nsenterPath, args)
exec := exec.New()
outputBytes, err := exec.Command(nsenterPath, args...).CombinedOutput()
if len(outputBytes) != 0 {
glog.V(5).Infof("Output from mount command: %v", string(outputBytes))
}
return err
}
// makeNsenterArgs makes a list of argument to nsenter in order to do the
// requested mount.
func (n *NsenterMounter) makeNsenterArgs(source, target, fstype string, options []string) []string {
nsenterArgs := []string{
"--mount=/rootfs/proc/1/ns/mnt",
"--",
n.absHostPath("mount"),
}
args := makeMountArgs(source, target, fstype, options)
return append(nsenterArgs, args...)
}
// Unmount runs umount(8) in the host's mount namespace.
func (n *NsenterMounter) Unmount(target string) error {
args := []string{
"--mount=/rootfs/proc/1/ns/mnt",
"--",
n.absHostPath("umount"),
target,
}
glog.V(5).Infof("Unmount command: %v %v", nsenterPath, args)
exec := exec.New()
outputBytes, err := exec.Command(nsenterPath, args...).CombinedOutput()
if len(outputBytes) != 0 {
glog.V(5).Infof("Output from mount command: %v", string(outputBytes))
}
return err
}
// List returns a list of all mounted filesystems in the host's mount namespace.
func (*NsenterMounter) List() ([]MountPoint, error) {
return listProcMounts(hostProcMountsPath)
}
// IsLikelyNotMountPoint determines whether a path is a mountpoint by calling findmnt
// in the host's root mount namespace.
func (n *NsenterMounter) IsLikelyNotMountPoint(file string) (bool, error) {
file, err := filepath.Abs(file)
if err != nil {
return true, err
}
args := []string{"--mount=/rootfs/proc/1/ns/mnt", "--", n.absHostPath("findmnt"), "-o", "target", "--noheadings", "--target", file}
glog.V(5).Infof("findmnt command: %v %v", nsenterPath, args)
exec := exec.New()
out, err := exec.Command(nsenterPath, args...).CombinedOutput()
if err != nil {
// If the command itself is correct, then if we encountered error
// then most likely this means that the directory does not exist.
return true, os.ErrNotExist
}
strOut := strings.TrimSuffix(string(out), "\n")
glog.V(5).Infof("IsLikelyNotMountPoint findmnt output: %v", strOut)
if strOut == file {
return false, nil
}
return true, nil
}
func (n *NsenterMounter) absHostPath(command string) string {
path, ok := n.paths[command]
if !ok {
return command
}
return path
}