ape.RemountFileSysReadOnlyCommand.java Source code

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Here is the source code for ape.RemountFileSysReadOnlyCommand.java

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/**
  * Copyright (c) 2012 Yahoo! Inc. 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. See accompanying LICENSE file.
*/
package ape;

import java.io.IOException;

import org.apache.commons.cli.Option;
import org.apache.commons.cli.OptionBuilder;
import org.apache.commons.cli.ParseException;

/**
 * This command remounts the root filesystem as read only.  This is done with the sysrq trigger.
 * You can check to see if sysrq is enabled by typing the following 
 * into a bash shell on the host in question:
 * 
 * cat /proc/sys/kernel/sysrq
 * 
 * If 1 is returned then the sysrq module is enabled.  If it returns 0 then you 
 * can enable it by typing the following:
 * 
 * echo 1 > /proc/sys/kernel/sysrq
 * 
 * The KernelPanicCommand works by echoing a character to the sysrq trigger which
 * will execute a particular command (see http://en.wikipedia.org/wiki/Magic_SysRq_key)
 * for a full list of what the sysrq trigger can do.
 * 
 *
 */
public class RemountFileSysReadOnlyCommand extends ApeCommand {
    private Option option;

    /**
     * The constructor for this command simply creates its Option object (used by
     * the CLI parser)
     */
    public RemountFileSysReadOnlyCommand() {
        option = OptionBuilder.withValueSeparator().withDescription("Remounts all filesystems as read-only")
                .withLongOpt("remount").create("r");
    }

    public boolean runImpl(String[] args) throws ParseException, IOException {
        String cmd = "echo u > /proc/sysrq-trigger";
        ProcessBuilder pb = new ProcessBuilder("bash", "-c", cmd);
        pb.redirectErrorStream(true);
        Process p = null;

        try {
            p = pb.start();
        } catch (IOException e) {
            System.err.println("Executing remount catches IOException");
            e.printStackTrace();
            return false;
        }

        // If the process returns a non-zero value, there is some error executing the command
        try {
            if (p.waitFor() != 0) {
                System.err.println("Non-zero return code (" + p.exitValue() + ") when executing: '" + cmd + "'");
                return false;
            }
        } catch (InterruptedException e) {
            System.err.println("Executing '" + cmd + "' was interrupted");
            e.printStackTrace();
            return false;
        }

        return true;
    }

    /**
     * Get the option of RemountFileSysReadOnlyCommand
     */
    public Option getOption() {
        return option;
    }

    /**
     * Get the long flag for RemountFileSysReadOnlyCommand
     */
    public String getName() {
        return option.getLongOpt();
    }
}