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 namespace.
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:
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.)
0 Allow any type of namespace to be joined. CLONE_NEWIPC fd must refer to an IPC namespace. CLONE_NEWNET fd must refer to a network namespace. CLONE_NEWUTS fd must refer to a UTS namespace.
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 operation.
The setns() system call first appeared in Linux in kernel 3.0; library support was added to glibc in version 2.14.
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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