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Add NsenterMounter mount implementation
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| // +build linux | ||
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| /* | ||
| 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. | ||
| */ | ||
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| package mount | ||
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| import ( | ||
| "path/filepath" | ||
| "strings" | ||
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| "github.com/GoogleCloudPlatform/kubernetes/pkg/util/exec" | ||
| "github.com/golang/glog" | ||
| ) | ||
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| // 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 at /nsenter 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. | ||
| // | ||
| // For more information about mount propagation modes, see: | ||
| // https://www.kernel.org/doc/Documentation/filesystems/sharedsubtree.txt | ||
| type NsenterMounter struct{} | ||
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| // NsenterMounter implements mount.Interface | ||
| var _ = Interface(&NsenterMounter{}) | ||
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| const ( | ||
| hostRootFsPath = "/rootfs" | ||
| hostProcMountsPath = "/rootfs/proc/mounts" | ||
| nsenterPath = "/nsenter" | ||
| ) | ||
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| // 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 (*NsenterMounter) Mount(source string, target string, fstype string, options []string) error { | ||
| bind, bindRemountOpts := isBind(options) | ||
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| if bind { | ||
| err := doNsenterMount(source, target, fstype, []string{"bind"}) | ||
| if err != nil { | ||
| return err | ||
| } | ||
| return doNsenterMount(source, target, fstype, bindRemountOpts) | ||
| } | ||
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| return doNsenterMount(source, target, fstype, options) | ||
| } | ||
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| // doNsenterMount nsenter's the host's mount namespace and performs the | ||
| // requested mount. | ||
| func doNsenterMount(source, target, fstype string, options []string) error { | ||
| glog.V(5).Infof("nsenter Mounting %s %s %s %v", source, target, fstype, options) | ||
| args := makeNsenterArgs(source, target, fstype, options) | ||
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| 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)) | ||
| } | ||
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| return err | ||
| } | ||
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| // makeNsenterArgs makes a list of argument to nsenter in order to do the | ||
| // requested mount. | ||
| func makeNsenterArgs(source, target, fstype string, options []string) []string { | ||
| nsenterArgs := []string{ | ||
| "--mount=/rootfs/proc/1/ns/mnt", | ||
| "/usr/bin/mount", | ||
| } | ||
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| args := makeMountArgs(source, target, fstype, options) | ||
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| return append(nsenterArgs, args...) | ||
| } | ||
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| // Unmount runs umount(8) in the host's mount namespace. | ||
| func (*NsenterMounter) Unmount(target string) error { | ||
| args := []string{ | ||
| "--mount=/rootfs/proc/1/ns/mnt", | ||
| "/usr/bin/umount", | ||
| target, | ||
| } | ||
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| 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)) | ||
| } | ||
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| return err | ||
| } | ||
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| // List returns a list of all mounted filesystems in the host's mount namespace. | ||
| func (*NsenterMounter) List() ([]MountPoint, error) { | ||
| return listProcMounts(hostProcMountsPath) | ||
| } | ||
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| // IsMountPoint determines whether a path is a mountpoint by calling findmnt | ||
| // in the host's root mount namespace. | ||
| func (*NsenterMounter) IsMountPoint(file string) (bool, error) { | ||
| file, err := filepath.Abs(file) | ||
| if err != nil { | ||
| return false, err | ||
| } | ||
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| args := []string{"--mount=/rootfs/proc/1/ns/mnt", "/usr/bin/findmnt", "-o", "target", "--noheadings", "--target", file} | ||
| glog.V(5).Infof("findmnt command: %v %v", nsenterPath, args) | ||
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| exec := exec.New() | ||
| out, err := exec.Command(nsenterPath, args...).CombinedOutput() | ||
| if err != nil { | ||
| // If findmnt didn't run, just claim it's not a mount point. | ||
| return false, nil | ||
| } | ||
| strOut := strings.TrimSuffix(string(out), "\n") | ||
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| glog.V(5).Infof("IsMountPoint findmnt output: %v", strOut) | ||
| if strOut == file { | ||
| return true, nil | ||
| } | ||
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| return false, nil | ||
| } |