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       setns - reassociate thread with a namespace


       #define _GNU_SOURCE             /* See feature_test_macros(7) */
       #include <sched.h>

       int setns(int fd, int nstype);


       Given a file descriptor referring to a namespace, reassociate the calling thread with that

       The fd argument is a file descriptor referring to  one  of  the  namespace  entries  in  a
       /proc/[pid]/ns/  directory;  see  proc(5) for further information on /proc/[pid]/ns/.  The
       calling thread will be reassociated with  the  corresponding  namespace,  subject  to  any
       constraints imposed by the nstype argument.

       The  nstype  argument  specifies  which  type  of  namespace  the  calling  thread  may be
       reassociated with.  This argument can have one of the following values:

       0      Allow any type of namespace to be joined.

              fd must refer to an IPC namespace.

              fd must refer to a network namespace.

              fd must refer to a UTS namespace.

       Specifying nstype as 0 suffices if the caller knows  (or  does  not  care)  what  type  of
       namespace  is  referred  to by fd.  Specifying a nonzero value for nstype is useful if the
       caller does not know what type of namespace is referred to by fd and wants to ensure  that
       the  namespace  is  of  a  particular  type.   (The  caller might not know the type of the
       namespace referred to by fd if the file descriptor was opened by another process and,  for
       example, passed to the caller via a UNIX domain socket.)


       On  success,  setns()  returns 0.  On failure, -1 is returned and errno is set to indicate
       the error.


       EBADF  fd is not a valid file descriptor.

       EINVAL fd refers to a namespace whose type does not match that  specified  in  nstype,  or
              there is problem with reassociating the the thread with the specified namespace.

       ENOMEM Cannot allocate sufficient memory to change the specified namespace.

       EPERM  The  calling  thread  did  not have the required privilege (CAP_SYS_ADMIN) for this


       The setns() system call first appeared in Linux in kernel 3.0


       The setns() system call is Linux-specific.


       Not all of the attributes that can be shared when a new thread is created  using  clone(2)
       can be changed using setns().


       The  PID  namespace  and  the  mount  namespace  are  not  currently  supported.  (See the
       descriptions of CLONE_NEWPID and CLONE_NEWNS in clone(2).)


       clone(2), fork(2), vfork(2), proc(5), unix(7)


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