clone2 - Linux


clone2 is an advanced Linux system call that creates a child process with specific process characteristics. It provides extended control over the child process’s resource allocation, thread creation, and file system namespace.


clone2(flags, newsp, tidptr, child_stack, stack_size)


  • flags: A bitmask of flags that specify the process characteristics of the child process. Commonly used flags include:
    • CLONE_NEWNS: Create a new network namespace
    • CLONE_NEWUTS: Create a new hostname and sysname namespace
    • CLONE_NEWIPC: Create a new IPC namespace
    • CLONE_NEWUSER: Create a new user namespace
  • newsp: Pointer to a new namespace
  • tidptr: Pointer to a variable that will hold the TID (thread ID) of the child process
  • child_stack: Pointer to the stack of the child process
  • stack_size: Size of the stack for the child process


Create a child process in a new network namespace:

clone2(CLONE_NEWNS, 0, NULL, NULL, 0);

Create a child process with a different hostname:

clone2(CLONE_NEWUTS, 0, NULL, NULL, 0);
set hostname("new-hostname");

Common Issues

  • Permission denied: The user may not have sufficient privileges to create a new namespace.
  • Invalid argument: Check that the flags and namespace arguments are valid.
  • Stack overflow: Ensure that the specified stack size is sufficient for the child process.


clone2 can be combined with other commands to perform advanced tasks:

  • unshare: Create a new namespace for the current process using unshare and clone2 to create child processes within the new namespace.
  • chroot: Change the root directory of the child process to a different file system within a new namespace.
  • forkpty: Create a child process with a pseudo-terminal attached for interactive use.

Related Commands

  • fork(2)
  • vfork(2)
  • execve(2)
  • namespaces(7)