1UNSHARE(2) Linux Programmer's Manual UNSHARE(2)
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6 unshare - disassociate parts of the process execution context
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9 #define _GNU_SOURCE
10 #include <sched.h>
11 int unshare(int flags);
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15 unshare() allows a process (or thread) to disassociate parts of its
16 execution context that are currently being shared with other processes
17 (or threads). Part of the execution context, such as the mount names‐
18 pace, is shared implicitly when a new process is created using fork(2)
19 or vfork(2), while other parts, such as virtual memory, may be shared
20 by explicit request when creating a process or thread using clone(2).
21 The main use of unshare() is to allow a process to control its shared
23 execution context without creating a new process.
24 The flags argument is a bit mask that specifies which parts of the exe‐
26 cution context should be unshared. This argument is specified by ORing
27 together zero or more of the following constants:
28 CLONE_FILES
30 Reverse the effect of the clone(2) CLONE_FILES flag. Unshare
31 the file descriptor table, so that the calling process no longer
32 shares its file descriptors with any other process.
33 CLONE_FS
35 Reverse the effect of the clone(2) CLONE_FS flag. Unshare
36 filesystem attributes, so that the calling process no longer
37 shares its root directory (chroot(2)), current directory
38 (chdir(2)), or umask (umask(2)) attributes with any other
39 process.
40 CLONE_NEWCGROUP (since Linux 4.6)
42 This flag has the same effect as the clone(2) CLONE_NEWCGROUP
43 flag. Unshare the cgroup namespace. Use of CLONE_NEWCGROUP
44 requires the CAP_SYS_ADMIN capability.
45 CLONE_NEWIPC (since Linux 2.6.19)
47 This flag has the same effect as the clone(2) CLONE_NEWIPC flag.
48 Unshare the IPC namespace, so that the calling process has a
49 private copy of the IPC namespace which is not shared with any
50 other process. Specifying this flag automatically implies
51 CLONE_SYSVSEM as well. Use of CLONE_NEWIPC requires the
52 CAP_SYS_ADMIN capability.
53 CLONE_NEWNET (since Linux 2.6.24)
55 This flag has the same effect as the clone(2) CLONE_NEWNET flag.
56 Unshare the network namespace, so that the calling process is
57 moved into a new network namespace which is not shared with any
58 previously existing process. Use of CLONE_NEWNET requires the
59 CAP_SYS_ADMIN capability.
60 CLONE_NEWNS
62 This flag has the same effect as the clone(2) CLONE_NEWNS flag.
63 Unshare the mount namespace, so that the calling process has a
64 private copy of its namespace which is not shared with any other
65 process. Specifying this flag automatically implies CLONE_FS as
66 well. Use of CLONE_NEWNS requires the CAP_SYS_ADMIN capability.
67 For further information, see mount_namespaces(7).
68 CLONE_NEWPID (since Linux 3.8)
70 This flag has the same effect as the clone(2) CLONE_NEWPID flag.
71 Unshare the PID namespace, so that the calling process has a new
72 PID namespace for its children which is not shared with any pre‐
73 viously existing process. The calling process is not moved into
74 the new namespace. The first child created by the calling
75 process will have the process ID 1 and will assume the role of
76 init(1) in the new namespace. CLONE_NEWPID automatically
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