NAME
clone, clone2 - create a child process SYNOPSIS /* Prototype for the glibc wrapper function */
#define GNUSOURCE
#include
int clone(int (*fn)(void *), void *childstack, int flags, void *arg, ... /* pidt *ptid, void *newtls, pidt *ctid */ ); /* For the prototype of the raw system call, see NOTES */ DESCRIPTION clone() creates a new process, in a manner similar to fork(2). This page describes both the glibc clone() wrapper function and the underlying system call on which it is based. The main text describes the wrapper function; the differences for the raw system call are described toward the end of this page. Unlike fork(2), clone() allows the child process to share parts of its execution context with the calling process, such as the memory space, the table of file descriptors, and the table of signal handlers. (Note that on this manual page, "calling process" normally corresponds to "parent process". But see the description of CLONEPARENT below.) One use of clone() is to implement threads: multiple threads of control in a program that run concurrently in a shared memory space. When the child process is created with clone(), it executes the func‐ tion fn(arg). (This differs from fork(2), where execution continues in the child from the point of the fork(2) call.) The fn argument is a pointer to a function that is called by the child process at the begin‐ ning of its execution. The arg argument is passed to the fn function. When the fn(arg) function application returns, the child process termi‐ nates. The integer returned by fn is the exit code for the child process. The child process may also terminate explicitly by calling exit(2) or after receiving a fatal signal. The childstack argument specifies the location of the stack used by the child process. Since the child and calling process may share mem‐ ory, it is not possible for the child process to execute in the same stack as the calling process. The calling process must therefore set up memory space for the child stack and pass a pointer to this space to clone(). Stacks grow downward on all processors that run Linux (except the HP PA processors), so childstack usually points to the topmost address of the memory space set up for the child stack. The low byte of flags contains the number of the termination signal sent to the parent when the child dies. If this signal is specified as anything other than SIGCHLD, then the parent process must specify the WALL or WCLONE options when waiting for the child with wait(2). If no signal is specified, then the parent process is not signaled when the child terminates. flags may also be bitwise-or'ed with zero or more of the following con‐ stants, in order to specify what is shared between the calling process and the child process: CLONECHILDCLEARTID (since Linux 2.5.49) Clear (zero) the child thread ID at the location ctid in child memory when the child exits, and do a wakeup on the futex at that address. The address involved may be changed by the settidaddress(2) system call. This is used by threading libraries. CLONECHILDSETTID (since Linux 2.5.49) Store the child thread ID at the location ctid in the child's memory. The store operation completes before clone() returns control to user space. CLONEFILES (since Linux 2.0) If CLONEFILES is set, the calling process and the child process share the same file descriptor table. Any file descriptor cre‐ ated by the calling process or by the child process is also valid in the other process. Similarly, if one of the processes closes a file descriptor, or changes its associated flags (using the fcntl(2) FSETFD operation), the other process is also affected. If a process sharing a file descriptor table calls execve(2), its file descriptor table is duplicated (unshared). If CLONEFILES is not set, the child process inherits a copy of all file descriptors opened in the calling process at the time of clone(). Subsequent operations that open or close file descriptors, or change file descriptor flags, performed by either the calling process or the child process do not affect the other process. Note, however, that the duplicated file descriptors in the child refer to the same open file descrip‐ tions as the corresponding file descriptors in the calling process, and thus share file offsets and file status flags (see open(2)). CLONEFS (since Linux 2.0) If CLONEFS is set, the caller and the child process share the same filesystem information. This includes the root of the filesystem, the current working directory, and the umask. Any call to chroot(2), chdir(2), or umask(2) performed by the call‐ ing process or the child process also affects the other process. If CLONEFS is not set, the child process works on a copy of the filesystem information of the calling process at the time of the clone() call. Calls to chroot(2), chdir(2), umask(2) performed later by one of the processes do not affect the other process. CLONEIO (since Linux 2.6.25) If CLONEIO is set, then the new process shares an I/O context with the calling process. If this flag is not set, then (as with fork(2)) the new process has its own I/O context. The I/O context is the I/O scope of the disk scheduler (i.e., what the I/O scheduler uses to model scheduling of a process's I/O). If processes share the same I/O context, they are treated as one by the I/O scheduler. As a consequence, they get to share disk time. For some I/O schedulers, if two processes share an I/O context, they will be allowed to interleave their disk access. If several threads are doing I/O on behalf of the same process (aioread(3), for instance), they should employ CLONEIO to get better I/O performance. If the kernel is not configured with the CONFIGBLOCK option,
this flag is a no-op. CLONENEWIPC (since Linux 2.6.19) If CLONENEWIPC is set, then create the process in a new IPC namespace. If this flag is not set, then (as with fork(2)), the process is created in the same IPC namespace as the calling process. This flag is intended for the implementation of con‐ tainers. An IPC namespace provides an isolated view of System V IPC objects (see svipc(7)) and (since Linux 2.6.30) POSIX message queues (see mqoverview(7)). The common characteristic of these IPC mechanisms is that IPC objects are identified by mechanisms other than filesystem pathnames. Objects created in an IPC namespace are visible to all other processes that are members of that namespace, but are not visi‐ ble to processes in other IPC namespaces. When an IPC namespace is destroyed (i.e., when the last process that is a member of the namespace terminates), all IPC objects in the namespace are automatically destroyed. Only a privileged process (CAPSYSADMIN) can employ CLONENEWIPC. This flag can't be specified in conjunction with CLONESYSVSEM. For further information on IPC namespaces, see namespaces(7). CLONENEWNET (since Linux 2.6.24) (The implementation of this flag was completed only by about kernel version 2.6.29.) If CLONENEWNET is set, then create the process in a new network namespace. If this flag is not set, then (as with fork(2)) the process is created in the same network namespace as the calling process. This flag is intended for the implementation of con‐ tainers. A network namespace provides an isolated view of the networking stack (network device interfaces, IPv4 and IPv6 protocol stacks, IP routing tables, firewall rules, the /proc/net and /sys/class/net directory trees, sockets, etc.). A physical net‐ work device can live in exactly one network namespace. A vir‐
tual network device ("veth") pair provides a pipe-like abstrac‐ tion that can be used to create tunnels between network names‐ paces, and can be used to create a bridge to a physical network device in another namespace. When a network namespace is freed (i.e., when the last process in the namespace terminates), its physical network devices are moved back to the initial network namespace (not to the parent of the process). For further information on network namespaces, see namespaces(7). Only a privileged process (CAPSYSADMIN) can employ CLONENEWNET. CLONENEWNS (since Linux 2.4.19) If CLONENEWNS is set, the cloned child is started in a new mount namespace, initialized with a copy of the namespace of the parent. If CLONENEWNS is not set, the child lives in the same mount namespace as the parent. Only a privileged process (CAPSYSADMIN) can employ CLONENEWNS. It is not permitted to specify both CLONENEWNS and CLONEFS in the same clone() call. For further information on mount namespaces, see namespaces(7) and mountnamespaces(7). CLONENEWPID (since Linux 2.6.24) If CLONENEWPID is set, then create the process in a new PID namespace. If this flag is not set, then (as with fork(2)) the process is created in the same PID namespace as the calling process. This flag is intended for the implementation of con‐ tainers. For further information on PID namespaces, see namespaces(7) and pidnamespaces(7). Only a privileged process (CAPSYSADMIN) can employ CLONENEW‐ PID. This flag can't be specified in conjunction with CLONETHREAD or CLONEPARENT. CLONENEWUSER (This flag first became meaningful for clone() in Linux 2.6.23, the current clone() semantics were merged in Linux 3.5, and the final pieces to make the user namespaces completely usable were merged in Linux 3.8.) If CLONENEWUSER is set, then create the process in a new user namespace. If this flag is not set, then (as with fork(2)) the process is created in the same user namespace as the calling process. For further information on user namespaces, see namespaces(7) and usernamespaces(7) Before Linux 3.8, use of CLONENEWUSER required that the caller have three capabilities: CAPSYSADMIN, CAPSETUID, and CAPSET‐ GID. Starting with Linux 3.8, no privileges are needed to cre‐ ate a user namespace. This flag can't be specified in conjunction with CLONETHREAD or CLONEPARENT. For security reasons, CLONENEWUSER cannot be specified in conjunction with CLONEFS. For further information on user namespaces, see usernames‐ paces(7). CLONENEWUTS (since Linux 2.6.19) If CLONENEWUTS is set, then create the process in a new UTS namespace, whose identifiers are initialized by duplicating the identifiers from the UTS namespace of the calling process. If this flag is not set, then (as with fork(2)) the process is cre‐ ated in the same UTS namespace as the calling process. This flag is intended for the implementation of containers. A UTS namespace is the set of identifiers returned by uname(2); among these, the domain name and the hostname can be modified by setdomainname(2) and sethostname(2), respectively. Changes made to the identifiers in a UTS namespace are visible to all other processes in the same namespace, but are not visible to pro‐ cesses in other UTS namespaces. Only a privileged process (CAPSYSADMIN) can employ CLONENEWUTS. For further information on UTS namespaces, see namespaces(7). CLONEPARENT (since Linux 2.3.12) If CLONEPARENT is set, then the parent of the new child (as returned by getppid(2)) will be the same as that of the calling process. If CLONEPARENT is not set, then (as with fork(2)) the child's parent is the calling process. Note that it is the parent process, as returned by getppid(2), which is signaled when the child terminates, so that if CLONEPARENT is set, then the parent of the calling process, rather than the calling process itself, will be signaled. CLONEPARENTSETTID (since Linux 2.5.49) Store the child thread ID at the location ptid in the parent's
memory. (In Linux 2.5.32-2.5.48 there was a flag CLONESETTID that did this.) The store operation completes before clone() returns control to user space. CLONEPID (obsolete) If CLONEPID is set, the child process is created with the same process ID as the calling process. This is good for hacking the system, but otherwise of not much use. Since 2.3.21 this flag can be specified only by the system boot process (PID 0). It disappeared in Linux 2.5.16. Since then, the kernel silently ignores it without error. CLONEPTRACE (since Linux 2.2) If CLONEPTRACE is specified, and the calling process is being traced, then trace the child also (see ptrace(2)). CLONESETTLS (since Linux 2.5.32) The TLS (Thread Local Storage) descriptor is set to newtls. The interpretation of newtls and the resulting effect is archi‐ tecture dependent. On x86, newtls is interpreted as a struct userdesc * (See setthreadarea(2)). On x8664 it is the new
value to be set for the %fs base register (See the ARCHSETFS argument to archprctl(2)). On architectures with a dedicated TLS register, it is the new value of that register. CLONESIGHAND (since Linux 2.0) If CLONESIGHAND is set, the calling process and the child process share the same table of signal handlers. If the calling process or child process calls sigaction(2) to change the behav‐ ior associated with a signal, the behavior is changed in the other process as well. However, the calling process and child processes still have distinct signal masks and sets of pending signals. So, one of them may block or unblock some signals using sigprocmask(2) without affecting the other process. If CLONESIGHAND is not set, the child process inherits a copy of the signal handlers of the calling process at the time clone() is called. Calls to sigaction(2) performed later by one of the processes have no effect on the other process.
Since Linux 2.6.0-test6, flags must also include CLONEVM if CLONESIGHAND is specified
CLONESTOPPED (since Linux 2.6.0-test2) If CLONESTOPPED is set, then the child is initially stopped (as though it was sent a SIGSTOP signal), and must be resumed by sending it a SIGCONT signal. This flag was deprecated from Linux 2.6.25 onward, and was removed altogether in Linux 2.6.38. Since then, the kernel silently ignores it without error. CLONESYSVSEM (since Linux 2.5.10) If CLONESYSVSEM is set, then the child and the calling process share a single list of System V semaphore adjustment (semadj) values (see semop(2)). In this case, the shared list accumu‐ lates semadj values across all processes sharing the list, and semaphore adjustments are performed only when the last process that is sharing the list terminates (or ceases sharing the list using unshare(2)). If this flag is not set, then the child has a separate semadj list that is initially empty.
CLONETHREAD (since Linux 2.4.0-test8) If CLONETHREAD is set, the child is placed in the same thread group as the calling process. To make the remainder of the dis‐ cussion of CLONETHREAD more readable, the term "thread" is used to refer to the processes within a thread group. Thread groups were a feature added in Linux 2.4 to support the POSIX threads notion of a set of threads that share a single
PID. Internally, this shared PID is the so-called thread group identifier (TGID) for the thread group. Since Linux 2.4, calls to getpid(2) return the TGID of the caller. The threads within a group can be distinguished by their (sys‐
tem-wide) unique thread IDs (TID). A new thread's TID is avail‐ able as the function result returned to the caller of clone(), and a thread can obtain its own TID using gettid(2). When a call is made to clone() without specifying CLONETHREAD, then the resulting thread is placed in a new thread group whose TGID is the same as the thread's TID. This thread is the leader of the new thread group. A new thread created with CLONETHREAD has the same parent process as the caller of clone() (i.e., like CLONEPARENT), so that calls to getppid(2) return the same value for all of the threads in a thread group. When a CLONETHREAD thread termi‐ nates, the thread that created it using clone() is not sent a SIGCHLD (or other termination) signal; nor can the status of such a thread be obtained using wait(2). (The thread is said to be detached.) After all of the threads in a thread group terminate the parent process of the thread group is sent a SIGCHLD (or other termina‐ tion) signal. If any of the threads in a thread group performs an execve(2), then all threads other than the thread group leader are termi‐ nated, and the new program is executed in the thread group leader. If one of the threads in a thread group creates a child using fork(2), then any thread in the group can wait(2) for that child. Since Linux 2.5.35, flags must also include CLONESIGHAND if CLONETHREAD is specified (and note that, since Linux
2.6.0-test6, CLONESIGHAND also requires CLONEVM to be included). Signals may be sent to a thread group as a whole (i.e., a TGID) using kill(2), or to a specific thread (i.e., TID) using tgkill(2).
Signal dispositions and actions are process-wide: if an unhan‐ dled signal is delivered to a thread, then it will affect (ter‐ minate, stop, continue, be ignored in) all members of the thread group. Each thread has its own signal mask, as set by sigprocmask(2), but signals can be pending either: for the whole process (i.e., deliverable to any member of the thread group), when sent with kill(2); or for an individual thread, when sent with tgkill(2). A call to sigpending(2) returns a signal set that is the union of the signals pending for the whole process and the signals that are pending for the calling thread. If kill(2) is used to send a signal to a thread group, and the thread group has installed a handler for the signal, then the handler will be invoked in exactly one, arbitrarily selected member of the thread group that has not blocked the signal. If multiple threads in a group are waiting to accept the same sig‐ nal using sigwaitinfo(2), the kernel will arbitrarily select one of these threads to receive a signal sent using kill(2). CLONEUNTRACED (since Linux 2.5.46) If CLONEUNTRACED is specified, then a tracing process cannot force CLONEPTRACE on this child process. CLONEVFORK (since Linux 2.2) If CLONEVFORK is set, the execution of the calling process is suspended until the child releases its virtual memory resources via a call to execve(2) or exit(2) (as with vfork(2)). If CLONEVFORK is not set, then both the calling process and the child are schedulable after the call, and an application should not rely on execution occurring in any particular order. CLONEVM (since Linux 2.0) If CLONEVM is set, the calling process and the child process run in the same memory space. In particular, memory writes per‐ formed by the calling process or by the child process are also visible in the other process. Moreover, any memory mapping or unmapping performed with mmap(2) or munmap(2) by the child or calling process also affects the other process. If CLONEVM is not set, the child process runs in a separate copy of the memory space of the calling process at the time of clone(). Memory writes or file mappings/unmappings performed by one of the processes do not affect the other, as with fork(2). C library/kernel differences The raw clone() system call corresponds more closely to fork(2) in that execution in the child continues from the point of the call. As such, the fn and arg arguments of the clone() wrapper function are omitted. Furthermore, the argument order changes. In addition, there are varia‐ tions across architectures.
The raw system call interface on x86-64 and some other architectures (including sh, tile, and alpha) is roughly: long clone(unsigned long flags, void *childstack, int *ptid, int *ctid, unsigned long newtls);
On x86-32, and several other common architectures (including score,
ARM, ARM 64, PA-RISC, arc, Power PC, xtensa, and MIPS), the order of the last two arguments is reversed: long clone(unsigned long flags, void *childstack, int *ptid, unsigned long newtls, int *ctid); On the cris and s390 architectures, the order of the first two argu‐ ments is reversed: long clone(void *childstack, unsigned long flags, int *ptid, int *ctid, unsigned long newtls); On the microblaze architecture, an additional argument is supplied: long clone(unsigned long flags, void *childstack, int stacksize, /* Size of stack */ int *ptid, int *ctid, unsigned long newtls); Another difference for the raw system call is that the childstack
argument may be zero, in which case copy-on-write semantics ensure that the child gets separate copies of stack pages when either process modi‐ fies the stack. In this case, for correct operation, the CLONEVM option should not be specified. blackfin, m68k, and sparc
The argument-passing conventions on blackfin, m68k, and sparc are dif‐ ferent from the descriptions above. For details, see the kernel (and glibc) source. ia64 On ia64, a different interface is used: int clone2(int (*fn)(void *), void *childstackbase, sizet stacksize, int flags, void *arg, ... /* pidt *ptid, struct userdesc *tls, pidt *ctid */ ); The prototype shown above is for the glibc wrapper function; the raw system call interface has no fn or arg argument, and changes the order of the arguments so that flags is the first argument, and tls is the last argument. clone2() operates in the same way as clone(), except that childstackbase points to the lowest address of the child's stack area, and stacksize specifies the size of the stack pointed to by childstackbase. Linux 2.4 and earlier In Linux 2.4 and earlier, clone() does not take arguments ptid, tls, and ctid. RETURN VALUE On success, the thread ID of the child process is returned in the call‐
er's thread of execution. On failure, -1 is returned in the caller's context, no child process will be created, and errno will be set appro‐ priately. ERRORS EAGAIN Too many processes are already running; see fork(2). EINVAL CLONESIGHAND was specified, but CLONEVM was not. (Since Linux
2.6.0-test6.) EINVAL CLONETHREAD was specified, but CLONESIGHAND was not. (Since Linux 2.5.35.) EINVAL Both CLONEFS and CLONENEWNS were specified in flags. EINVAL (since Linux 3.9) Both CLONENEWUSER and CLONEFS were specified in flags. EINVAL Both CLONENEWIPC and CLONESYSVSEM were specified in flags. EINVAL One (or both) of CLONENEWPID or CLONENEWUSER and one (or both) of CLONETHREAD or CLONEPARENT were specified in flags. EINVAL Returned by the glibc clone() wrapper function when fn or childstack is specified as NULL. EINVAL CLONENEWIPC was specified in flags, but the kernel was not con‐ figured with the CONFIGSYSVIPC and CONFIGIPCNS options. EINVAL CLONENEWNET was specified in flags, but the kernel was not con‐ figured with the CONFIGNETNS option. EINVAL CLONENEWPID was specified in flags, but the kernel was not con‐ figured with the CONFIGPIDNS option. EINVAL CLONENEWUTS was specified in flags, but the kernel was not con‐ figured with the CONFIGUTS option. EINVAL childstack is not aligned to a suitable boundary for this architecture. For example, on aarch64, childstack must be a multiple of 16. ENOMEM Cannot allocate sufficient memory to allocate a task structure for the child, or to copy those parts of the caller's context that need to be copied. ENOSPC (since Linux 3.7) CLONENEWPID was specified in flags, but the limit on the nest‐ ing depth of PID namespaces would have been exceeded; see pidnamespaces(7). ENOSPC (since Linux 4.9; beforehand EUSERS) CLONENEWUSER was specified in flags, and the call would cause the limit on the number of nested user namespaces to be exceeded. See usernamespaces(7). From Linux 3.11 to Linux 4.8, the error diagnosed in this case was EUSERS. ENOSPC (since Linux 4.9) One of the values in flags specified the creation of a new user namespace, but doing so would have caused the limit defined by the corresponding file in /proc/sys/user to be exceeded. For further details, see namespaces(7). EPERM CLONENEWIPC, CLONENEWNET, CLONENEWNS, CLONENEWPID, or CLONENEWUTS was specified by an unprivileged process (process without CAPSYSADMIN). EPERM CLONEPID was specified by a process other than process 0. EPERM CLONENEWUSER was specified in flags, but either the effective user ID or the effective group ID of the caller does not have a mapping in the parent namespace (see usernamespaces(7)). EPERM (since Linux 3.9) CLONENEWUSER was specified in flags and the caller is in a chroot environment (i.e., the caller's root directory does not match the root directory of the mount namespace in which it resides). ERESTARTNOINTR (since Linux 2.6.17) System call was interrupted by a signal and will be restarted. (This can be seen only during a trace.) EUSERS (Linux 3.11 to Linux 4.8) CLONENEWUSER was specified in flags, and the limit on the num‐ ber of nested user namespaces would be exceeded. See the dis‐ cussion of the ENOSPC error above. CONFORMING TO
clone() is Linux-specific and should not be used in programs intended to be portable. NOTES The kcmp(2) system call can be used to test whether two processes share various resources such as a file descriptor table, System V semaphore undo operations, or a virtual address space. Handlers registered using pthreadatfork(3) are not executed during a call to clone(). In the Linux 2.4.x series, CLONETHREAD generally does not make the parent of the new thread the same as the parent of the calling process. However, for kernel versions 2.4.7 to 2.4.18 the CLONETHREAD flag implied the CLONEPARENT flag (as in Linux 2.6.0 and later). For a while there was CLONEDETACHED (introduced in 2.5.32): parent
wants no child-exit signal. In Linux 2.6.2, the need to give this flag together with CLONETHREAD disappeared. This flag is still defined, but has no effect. On i386, clone() should not be called through vsyscall, but directly
through int $0x80. BUGS Versions of the GNU C library that include the NPTL threading library contain a wrapper function for getpid(2) that performs caching of PIDs. This caching relies on support in the glibc wrapper for clone(), but as currently implemented, the cache may not be up to date in some circum‐ stances. In particular, if a signal is delivered to the child immedi‐ ately after the clone() call, then a call to getpid(2) in a handler for the signal may return the PID of the calling process ("the parent"), if the clone wrapper has not yet had a chance to update the PID cache in the child. (This discussion ignores the case where the child was cre‐ ated using CLONETHREAD, when getpid(2) should return the same value in the child and in the process that called clone(), since the caller and
the child are in the same thread group. The stale-cache problem also does not occur if the flags argument includes CLONEVM.) To get the truth, it may be necessary to use code such as the following:
#include
pidt mypid; mypid = syscall(SYSgetpid); EXAMPLE The following program demonstrates the use of clone() to create a child process that executes in a separate UTS namespace. The child changes the hostname in its UTS namespace. Both parent and child then display the system hostname, making it possible to see that the hostname dif‐ fers in the UTS namespaces of the parent and child. For an example of the use of this program, see setns(2). Program source #define GNUSOURCE
#include
#include
#include
#include
#include
#include
#include
#define errExit(msg) do { perror(msg); exit(EXITFAILURE); \ } while (0) static int /* Start function for cloned child */ childFunc(void *arg) { struct utsname uts; /* Change hostname in UTS namespace of child */
if (sethostname(arg, strlen(arg)) == -1) errExit("sethostname"); /* Retrieve and display hostname */
if (uname(&uts) == -1) errExit("uname");
printf("uts.nodename in child: %s\n", uts.nodename); /* Keep the namespace open for a while, by sleeping. This allows some experimentationfor example, another process might join the namespace. */ sleep(200); return 0; /* Child terminates now */ }
#define STACKSIZE (1024 * 1024) /* Stack size for cloned child */ int main(int argc, char *argv[]) { char *stack; /* Start of stack buffer */ char *stackTop; /* End of stack buffer */ pidt pid; struct utsname uts; if (argc < 2) {
fprintf(stderr, "Usage: %s
\n", argv[0]); exit(EXITSUCCESS); } /* Allocate stack for child */ stack = malloc(STACKSIZE); if (stack == NULL) errExit("malloc"); stackTop = stack + STACKSIZE; /* Assume stack grows downward */ /* Create child that has its own UTS namespace; child commences execution in childFunc() */ pid = clone(childFunc, stackTop, CLONENEWUTS | SIGCHLD, argv[1]); if (pid == -1) errExit("clone");
printf("clone() returned %ld\n", (long) pid); /* Parent falls through to here */ sleep(1); /* Give child time to change its hostname */ /* Display hostname in parent's UTS namespace. This will be different from hostname in child's UTS namespace. */
if (uname(&uts) == -1) errExit("uname");
printf("uts.nodename in parent: %s\n", uts.nodename);
if (waitpid(pid, NULL, 0) == -1) /* Wait for child */ errExit("waitpid"); printf("child has terminated\n"); exit(EXITSUCCESS); } SEE ALSO fork(2), futex(2), getpid(2), gettid(2), kcmp(2), setthreadarea(2), settidaddress(2), setns(2), tkill(2), unshare(2), wait(2), capabili‐ ties(7), namespaces(7), pthreads(7) COLOPHON
This page is part of release 3.53 of the Linux man-pages project. A description of the project, and information about reporting bugs, can
be found at http://www.kernel.org/doc/man-pages/.
Linux 2016-12-12 CLONE(2)