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unshare

run program with some namespaces unshared from parent


  1. unshare.1.man
  2. unshare.2.man


1. unshare.1.man

Manpage of UNSHARE

UNSHARE

Section: User Manuals (1)
Updated: OCTOBER 2008
Index Return to Main Contents
 

NAME

unshare - run program with some namespaces unshared from parent  

SYNOPSIS

unshare [options] program [arguments]  

DESCRIPTION

Unshares specified namespaces from parent process and then executes specified program. Unshareable namespaces are:
mount namespace
mounting and unmounting filesystems will not affect rest of the system (CLONE_NEWNS flag),
UTS namespace
setting hostname, domainname will not affect rest of the system (CLONE_NEWUTS flag),
IPC namespace
process will have independent namespace for System V message queues, semaphore sets and shared memory segments (CLONE_NEWIPC flag),
network namespace
process will have independent IPv4 and IPv6 stacks, IP routing tables, firewall rules, the /proc/net and /sys/class/net directory trees, sockets etc. (CLONE_NEWNET flag).
See the clone(2) for exact semantics of the flags.
 

OPTIONS

-h, --help
Print a help message,
-m, --mount
Unshare the mount namespace,
-u, --uts
Unshare the UTC namespace,
-i, --ipc
Unshare the IPC namespace,
-n, --net
Unshare the network namespace.
 

NOTES

The unshare command drops potential privileges before executing the target program. This allows to setuid unshare.  

SEE ALSO

unshare(2), clone(2)  

BUGS

None known so far.  

AUTHOR

Mikhail Gusarov <dottedmag@dottedmag.net>  

AVAILABILITY

The unshare command is part of the util-linux package and is available from ftp://ftp.kernel.org/pub/linux/utils/util-linux/.


 

Index

NAME
SYNOPSIS
DESCRIPTION
OPTIONS
NOTES
SEE ALSO
BUGS
AUTHOR
AVAILABILITY

This document was created by man2html using the manual pages.
Time: 17:32:54 GMT, October 23, 2013

2. unshare.2.man

Manpage of UNSHARE

UNSHARE

Section: Linux Programmer's Manual (2)
Updated: 2010-10-30
Index Return to Main Contents
 

NAME

unshare - disassociate parts of the process execution context  

SYNOPSIS

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

int unshare(int flags);
 

DESCRIPTION

unshare() allows a process to disassociate parts of its execution context that are currently being shared with other processes. Part of the execution context, such as the mount namespace, is shared implicitly when a new process is created using fork(2) or vfork(2), while other parts, such as virtual memory, may be shared by explicit request when creating a process using clone(2).

The main use of unshare() is to allow a process to control its shared execution context without creating a new process.

The flags argument is a bit mask that specifies which parts of the execution context should be unshared. This argument is specified by ORing together zero or more of the following constants:

CLONE_FILES
Reverse the effect of the clone(2) CLONE_FILES flag. Unshare the file descriptor table, so that the calling process no longer shares its file descriptors with any other process.
CLONE_FS
Reverse the effect of the clone(2) CLONE_FS flag. Unshare file system attributes, so that the calling process no longer shares its root directory, current directory, or umask attributes with any other process. chroot(2), chdir(2), or umask(2)
CLONE_NEWIPC (since Linux 2.6.19)
This flag has the same effect as the clone(2) CLONE_NEWIPC flag. Unshare the System V IPC namespace, so that the calling process has a private copy of the System V IPC namespace which is not shared with any other process. Specifying this flag automatically implies CLONE_SYSVSEM as well. Use of CLONE_NEWIPC requires the CAP_SYS_ADMIN capability.
CLONE_NEWNET (since Linux 2.6.24)
This flag has the same effect as the clone(2) CLONE_NEWNET flag. Unshare the network namespace, so that the calling process is moved into a new network namespace which is not shared with any previously existing process. CLONE_NEWNET requires the CAP_SYS_ADMIN capability.
CLONE_NEWNS
This flag has the same effect as the clone(2) CLONE_NEWNS flag. Unshare the mount namespace, so that the calling process has a private copy of its namespace which is not shared with any other process. Specifying this flag automatically implies CLONE_FS as well. Use of CLONE_NEWNS requires the CAP_SYS_ADMIN capability.
CLONE_SYSVSEM (since Linux 2.6.26)
This flag reverses the effect of the clone(2) CLONE_SYSVSEM flag. Unshare System V semaphore undo values, so that the calling process has a private copy which is not shared with any other process. Use of CLONE_SYSVSEM requires the CAP_SYS_ADMIN capability.
CLONE_NEWUTS (since Linux 2.6.19)
This flag has the same effect as the clone(2) CLONE_NEWUTS flag. Unshare the UTS IPC namespace, so that the calling process has a private copy of the UTS namespace which is not shared with any other process. Use of CLONE_NEWUTS requires the CAP_SYS_ADMIN capability.

If flags is specified as zero, then unshare() is a no-op; no changes are made to the calling process's execution context.  

RETURN VALUE

On success, zero returned. On failure, -1 is returned and errno is set to indicate the error.  

ERRORS

EINVAL
An invalid bit was specified in flags.
ENOMEM
Cannot allocate sufficient memory to copy parts of caller's context that need to be unshared.
EPERM
The calling process did not have the required privileges for this operation.
 

VERSIONS

The unshare() system call was added to Linux in kernel 2.6.16.  

CONFORMING TO

The unshare() system call is Linux-specific.  

NOTES

Not all of the process attributes that can be shared when a new process is created using clone(2) can be unshared using unshare(). In particular, as at kernel 2.6.16, unshare() does not implement flags that reverse the effects of CLONE_SIGHAND, CLONE_SYSVSEM, CLONE_THREAD, or CLONE_VM. Such functionality may be added in the future, if required.  

SEE ALSO

clone(2), fork(2), vfork(2), Documentation/unshare.txt  

COLOPHON

This page is part of release 3.32 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/.


 

Index

NAME
SYNOPSIS
DESCRIPTION
RETURN VALUE
ERRORS
VERSIONS
CONFORMING TO
NOTES
SEE ALSO
COLOPHON

This document was created by man2html using the manual pages.
Time: 17:32:54 GMT, October 23, 2013

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