cal: in man page improve grammar and wording of the reformation limitation

[thirdparty/util-linux.git] / sys-utils / unshare.1

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.TH UNSHARE 1 "July 2013" "util-linux" "User Commands"
.SH NAME
unshare \- run program with some namespaces unshared from parent
.SH SYNOPSIS
.B unshare
.RI [ options ]
.I program
.RI [ arguments ]
.SH DESCRIPTION
Unshares the indicated namespaces from the parent process and then executes
the specified program.  The namespaces to be unshared are indicated via
options.  Unshareable namespaces are:
.TP
.BR "mount namespace"
Mounting and unmounting filesystems will not affect the rest of the system
(\fBCLONE_NEWNS\fP flag), except for filesystems which are explicitly marked as
shared (with \fBmount --make-shared\fP; see \fI/proc/self/mountinfo\fP for the
\fBshared\fP flags).

It's recommended to use \fBmount --make-rprivate\fP or \fBmount --make-rslave\fP
after \fBunshare --mount\fP to make sure that mountpoints in the new namespace
are really unshared from parental namespace.
.TP
.BR "UTS namespace"
Setting hostname or domainname will not affect the rest of the system.
(\fBCLONE_NEWUTS\fP flag)
.TP
.BR "IPC namespace"
The process will have an independent namespace for System V message queues,
semaphore sets and shared memory segments.  (\fBCLONE_NEWIPC\fP flag)
.TP
.BR "network namespace"
The process will have independent IPv4 and IPv6 stacks, IP routing tables,
firewall rules, the \fI/proc/net\fP and \fI/sys/class/net\fP directory trees,
sockets, etc.  (\fBCLONE_NEWNET\fP flag)
.TP
.BR "pid namespace"
Children will have a distinct set of PID to process mappings from their parent.
(\fBCLONE_NEWPID\fP flag)
.TP
.BR "user namespace"
The process will have a distinct set of UIDs, GIDs and capabilities.
(\fBCLONE_NEWUSER\fP flag)
.PP
See \fBclone\fR(2) for the exact semantics of the flags.
.SH OPTIONS
.TP
.BR \-h , " \-\-help"
Display help text and exit.
.TP
.BR \-i , " \-\-ipc"
Unshare the IPC namespace.
.TP
.BR \-m , " \-\-mount"
Unshare the mount namespace.
.TP
.BR \-n , " \-\-net"
Unshare the network namespace.
.TP
.BR \-p , " \-\-pid"
Unshare the pid namespace.
See also the \fB--fork\fP and \fB--mount-proc\fP options.
.TP
.BR \-u , " \-\-uts"
Unshare the UTS namespace.
.TP
.BR \-U , " \-\-user"
Unshare the user namespace.
.TP
.BR \-f , " \-\-fork"
Fork the specified \fIprogram\fR as a child process of \fBunshare\fR rather than
running it directly.  This is useful when creating a new pid namespace.
.TP
.BR \-\-mount-proc "[=\fImountpoint\fP]"
Just before running the program, mount the proc filesystem at the \fImountpoint\fP
(default is /proc).  This is useful when creating a new pid namespace.  It also
implies creating a new mount namespace since the /proc mount would otherwise
mess up existing programs on the system. The new proc filesystem is explicitly
mounted as private (by MS_PRIVATE|MS_REC).
.SH SEE ALSO
.BR unshare (2),
.BR clone (2),
.BR mount (8)
.SH BUGS
None known so far.
.SH AUTHOR
Mikhail Gusarov <dottedmag@dottedmag.net>
.SH AVAILABILITY
The unshare command is part of the util-linux package and is available from
ftp://ftp.kernel.org/pub/linux/utils/util-linux/.