sys-utils/unshare.1

   1 .TH UNSHARE 1 "July 2014" "util-linux" "User Commands"
   2 .SH NAME
   3 unshare \- run program with some namespaces unshared from parent
   4 .SH SYNOPSIS
   5 .B unshare
   6 [options]
   7 .I program
   8 .RI [ arguments ]
   9 .SH DESCRIPTION
  10 Unshares the indicated namespaces from the parent process and then executes
  11 the specified \fIprogram\fR.  The namespaces to be unshared are indicated via
  12 options.  Unshareable namespaces are:
  13 .TP
  14 .BR "mount namespace"
  15 Mounting and unmounting filesystems will not affect the rest of the system
  16 (\fBCLONE_NEWNS\fP flag), except for filesystems which are explicitly marked as
  17 shared (with \fBmount --make-shared\fP; see \fI/proc/self/mountinfo\fP for the
  18 \fBshared\fP flags).
  19 .sp
  20 It's recommended to use \fBmount --make-rprivate\fP or \fBmount --make-rslave\fP
  21 after \fBunshare --mount\fP to make sure that mountpoints in the new namespace
  22 are really unshared from the parental namespace.
  23 .TP
  24 .BR "UTS namespace"
  25 Setting hostname or domainname will not affect the rest of the system.
  26 (\fBCLONE_NEWUTS\fP flag)
  27 .TP
  28 .BR "IPC namespace"
  29 The process will have an independent namespace for System V message queues,
  30 semaphore sets and shared memory segments.  (\fBCLONE_NEWIPC\fP flag)
  31 .TP
  32 .BR "network namespace"
  33 The process will have independent IPv4 and IPv6 stacks, IP routing tables,
  34 firewall rules, the \fI/proc/net\fP and \fI/sys/class/net\fP directory trees,
  35 sockets, etc.  (\fBCLONE_NEWNET\fP flag)
  36 .TP
  37 .BR "pid namespace"
  38 Children will have a distinct set of PID to process mappings from their parent.
  39 (\fBCLONE_NEWPID\fP flag)
  40 .TP
  41 .BR "user namespace"
  42 The process will have a distinct set of UIDs, GIDs and capabilities.
  43 (\fBCLONE_NEWUSER\fP flag)
  44 .PP
  45 See \fBclone\fR(2) for the exact semantics of the flags.
  46 .SH OPTIONS
  47 .TP
  48 .BR \-i , " \-\-ipc"
  49 Unshare the IPC namespace.
  50 .TP
  51 .BR \-m , " \-\-mount"
  52 Unshare the mount namespace.
  53 .TP
  54 .BR \-n , " \-\-net"
  55 Unshare the network namespace.
  56 .TP
  57 .BR \-p , " \-\-pid"
  58 Unshare the pid namespace.
  59 See also the \fB--fork\fP and \fB--mount-proc\fP options.
  60 .TP
  61 .BR \-u , " \-\-uts"
  62 Unshare the UTS namespace.
  63 .TP
  64 .BR \-U , " \-\-user"
  65 Unshare the user namespace.
  66 .TP
  67 .BR \-f , " \-\-fork"
  68 Fork the specified \fIprogram\fR as a child process of \fBunshare\fR rather than
  69 running it directly.  This is useful when creating a new pid namespace.
  70 .TP
  71 .BR \-\-mount\-proc "[=\fImountpoint\fP]"
  72 Just before running the program, mount the proc filesystem at \fImountpoint\fP
  73 (default is /proc).  This is useful when creating a new pid namespace.  It also
  74 implies creating a new mount namespace since the /proc mount would otherwise
  75 mess up existing programs on the system.  The new proc filesystem is explicitly
  76 mounted as private (by MS_PRIVATE|MS_REC).
  77 .TP
  78 .BR \-r , " \-\-map\-root\-user"
  79 Run the program only after the current effective user and group IDs have been mapped to
  80 the superuser UID and GID in the newly created user namespace.  This makes it possible to
  81 conveniently gain capabilities needed to manage various aspects of the newly created
  82 namespaces (such as configuring interfaces in the network namespace or mounting filesystems in
  83 the mount namespace) even when run unprivileged.  As a mere convenience feature, it does not support
  84 more sophisticated use cases, such as mapping multiple ranges of UIDs and GIDs.
  85 This option implies --setgroups=deny.
  86 .TP
  87 .BR \-s , " \-\-setgroups \fIallow|deny\fP"
  88 Allow or deny
  89 .BR setgroups (2)
  90 syscall in user namespaces.
  91
  92 .BR setgroups(2)
  93 is only callable with CAP_SETGID and CAP_SETGID in a user
  94 namespace (since Linux 3.19) does not give you permission to call setgroups(2)
  95 until after GID map has been set. The GID map is writable by root when
  96 .BR setgroups(2)
  97 is enabled and GID map becomes writable by unprivileged processes when
  98 .BR setgroups(2)
  99 is permanently disabled.
 100 .TP
 101 .BR \-V , " \-\-version"
 102 Display version information and exit.
 103 .TP
 104 .BR \-h , " \-\-help"
 105 Display help text and exit.
 106 .SH EXAMPLES
 107 .TP
 108 .B # unshare --fork --pid --mount-proc readlink /proc/self
 109 .TQ
 110 1
 111 .br
 112 Establish a PID namespace, ensure we're PID 1 in it against newly mounted
 113 procfs instance.
 114 .TP
 115 .B $ unshare --map-root-user --user sh -c whoami
 116 .TQ
 117 root
 118 .br
 119 Establish a user namespace as an unprivileged user with a root user within it.
 120 .SH SEE ALSO
 121 .BR unshare (2),
 122 .BR clone (2),
 123 .BR mount (8)
 124 .SH BUGS
 125 None known so far.
 126 .SH AUTHOR
 127 Mikhail Gusarov <dottedmag@dottedmag.net>
 128 .SH AVAILABILITY
 129 The unshare command is part of the util-linux package and is available from
 130 ftp://ftp.kernel.org/pub/linux/utils/util-linux/.