mirror of
https://github.com/k3s-io/kubernetes.git
synced 2025-10-30 21:30:16 +00:00
81 lines
2.5 KiB
Go
81 lines
2.5 KiB
Go
/*
|
|
Copyright 2015 The Kubernetes Authors.
|
|
|
|
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 io
|
|
|
|
import (
|
|
"bytes"
|
|
"fmt"
|
|
"io/ioutil"
|
|
"os"
|
|
"os/exec"
|
|
|
|
"github.com/golang/glog"
|
|
)
|
|
|
|
// Writer is an interface which allows to write data to a file.
|
|
type Writer interface {
|
|
WriteFile(filename string, data []byte, perm os.FileMode) error
|
|
}
|
|
|
|
// StdWriter implements Writer interface and uses standard libraries
|
|
// for writing data to files.
|
|
type StdWriter struct {
|
|
}
|
|
|
|
func (writer *StdWriter) WriteFile(filename string, data []byte, perm os.FileMode) error {
|
|
return ioutil.WriteFile(filename, data, perm)
|
|
}
|
|
|
|
// Alternative implementation of Writer interface that allows writing data to file
|
|
// using nsenter command.
|
|
// If a program (e.g. kubelet) runs in a container it may want to write data to
|
|
// a mounted device. Since in Docker, mount propagation mode is set to private,
|
|
// it will not see the mounted device in its own namespace. To work around this
|
|
// limitaion one has to first enter hosts namespace (by using 'nsenter') and only
|
|
// then write data.
|
|
type NsenterWriter struct {
|
|
}
|
|
|
|
// TODO: should take a writer, not []byte
|
|
func (writer *NsenterWriter) WriteFile(filename string, data []byte, perm os.FileMode) error {
|
|
cmd := "nsenter"
|
|
base_args := []string{
|
|
"--mount=/rootfs/proc/1/ns/mnt",
|
|
"--",
|
|
}
|
|
|
|
echo_args := append(base_args, "sh", "-c", fmt.Sprintf("cat > %s", filename))
|
|
glog.V(5).Infof("Command to write data to file: %v %v", cmd, echo_args)
|
|
command := exec.Command(cmd, echo_args...)
|
|
command.Stdin = bytes.NewBuffer(data)
|
|
outputBytes, err := command.CombinedOutput()
|
|
if err != nil {
|
|
glog.Errorf("Output from writing to %q: %v", filename, string(outputBytes))
|
|
return err
|
|
}
|
|
|
|
chmod_args := append(base_args, "chmod", fmt.Sprintf("%o", perm), filename)
|
|
glog.V(5).Infof("Command to change permissions to file: %v %v", cmd, chmod_args)
|
|
outputBytes, err = exec.Command(cmd, chmod_args...).CombinedOutput()
|
|
if err != nil {
|
|
glog.Errorf("Output from chmod command: %v", string(outputBytes))
|
|
return err
|
|
}
|
|
|
|
return nil
|
|
}
|