java- How do programmatically change user to root before changing file permissions?

Question

In Java, I would like to dynamically change the file permission of a Linux file. I have tried to set it with Files.setPosixFilePermissions as suggested from this other source: How do I programmatically change file permissions?, but I am getting the error

java.nio.file.FileSystemException: : Operation not permitted

I figured out that I am unable to set the file permissions as a user, since the file is owned by root. My question is: Is it possible to execute Files.setPosixFilePermissions by switching from user to root in java? And then switching back to user when done?

Here is the bulk of my code:

String path = "/usr/local/bin/driver";
try {
  Utility.setAsExecutable(path);
} catch (IOException e) {
  logger.error("Unable to set driver as executable.");
  e.printStackTrace();
}

  public static void setAsExecutable(String filePath) throws IOException {

    // using PosixFilePermission to set file permissions 755
    Set<PosixFilePermission> perms = new HashSet<PosixFilePermission>();
    perms.add(PosixFilePermission.OWNER_READ);
    perms.add(PosixFilePermission.OWNER_WRITE);
    perms.add(PosixFilePermission.OWNER_EXECUTE);

    perms.add(PosixFilePermission.GROUP_READ);
    perms.add(PosixFilePermission.GROUP_EXECUTE);

    perms.add(PosixFilePermission.OTHERS_READ);
    perms.add(PosixFilePermission.OTHERS_EXECUTE);

    Files.setPosixFilePermissions(Paths.get(filePath), perms);
    logger.info("Modified as executable " + filePath);

  }

score 2 · Accepted Answer · answered Oct 09 '18 at 22:23

2

There is no way to change the owner of a running process (be it a JVM or anything else).

You can however spawn a new, privileged process to do the "dirty" work.

answered Oct 09 '18 at 22:23

giorgiga

1,758
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java- How do programmatically change user to root before changing file permissions?

1 Answers1