nsenter: new command (light wrapper around setns)

Inspired by unshare, nsenter is a simple wrapper around setns that
allows running a new process in the context of an existing process.

Full paths may be specified to the namespace arguments so that
namespace file descriptors may be used wherever they reside in the
filesystem.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>

1 files changed, 101 insertions, 0 deletions

diff --git a/sys-utils/nsenter.1 b/sys-utils/nsenter.1
new file mode 100644
index 000000000..93c512edc
--- /dev/null
+++ b/sys-utils/nsenter.1
@@ -0,0 +1,101 @@
+.TH NSENTER 1 "January 2013" "util-linux" "User Commands"
+.SH NAME
+nsenter \- run program with namespaces of other processes
+.SH SYNOPSIS
+.B nsenter
+.RI [ options ]
+program
+.RI [ arguments ]
+.SH DESCRIPTION
+Enters the contexts of one or more other processes and then executes specified
+program. Enterable namespaces are:
+.TP
+.BR "mount namespace"
+mounting and unmounting filesystems will not affect rest of the system
+(\fBCLONE_NEWNS\fP flag), except for filesystems which are explicitly marked as
+shared (by mount --make-shared). See /proc/self/mountinfo for the shared flags.
+.TP
+.BR "UTS namespace"
+setting hostname, domainname will not affect rest of the system
+(\fBCLONE_NEWUTS\fP flag).
+.TP
+.BR "IPC namespace"
+process will have independent namespace for System V message queues, semaphore
+sets and shared memory segments (\fBCLONE_NEWIPC\fP flag).
+.TP
+.BR "network namespace"
+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 thantheir parent.
+(\fBCLONE_NEWPID\fP flag).
+.TP
+.BR "user namespace"
+process will have distinct set of uids, gids and capabilities. (\fBCLONE_NEWUSER\fP flag).
+.TP
+See the \fBclone\fR(2) for exact semantics of the flags.
+.SH OPTIONS
+.TP
+.BR \-h , " \-\-help"
+Print a help message,
+.TP
+.BR \-t , " \-\-target " \fIpid\fP
+Specify a target process to get contexts from.  The paths to the contexts specified by pid are: /proc/[pid]/ns/mnt, /proc/[pid]/ns/uts, /proc/[pid]/ns/ipc, /proc/[pid]/ns/net, /proc/[pid]/ns/pid, /proc/[pid]/ns/user, /proc/[pid]/root, /proc/[pid]/cwd for the mount namespace, the uts namespace, the ipc namespace, the net namespace, the pid namespace, the user namespace, the root directory and the working directory respectively.
+.TP
+.BR \-m , " \-\-mount"=[\fIfile\fP]
+Enter the mount namespace.
+If no file is specified enter the mount namespace of the target process.
+If file is specified enter the mount namespace specified by file.
+.TP
+.BR \-u , " \-\-uts"=[\fIfile\fP]
+Enter the uts namespace.
+If no file is specified enter the uts namespace of the target process.
+If file is specified enter the uts namespace specified by file.
+.TP
+.BR \-i , " \-\-ipc "=[\fIfile\fP]
+Enter the IPC namespace.
+If no file is specified enter the IPC namespace of the target process.
+If file is specified enter the uts namespace specified by file.
+.TP
+.BR \-n , " \-\-net"=[\fIfile\fP]
+Enter the network namespace.
+If no file is specified enter the network namespace of the target process.
+If file is specified enter the network namespace specified by file.
+.TP
+.BR \-p , " \-\-pid"=[\fIfile\fP]
+Enter the pid namespace.
+If no file is specified enter the pid namespace of the target process.
+If file is specified enter the pid namespace specified by file.
+.TP
+.BR \-U , " \-\-user"=[\fIfile\fP]
+Enter the user namespace.
+If no file is specified enter the user namespace of the target process.
+If file is specified enter the user namespace specified by file.
+.TP
+.BR \-r , " \-\-root"=[\fIdirectory\fP]
+Set the root directory.
+If no directory is specified set the root directory to the root directory of the target process.
+If directory is specified set the root directory to the specified directory.
+.TP
+.BR \-w , " \-\-wd"=[\fIdirectory\fP]
+Set the working directory.
+If no directory is specified set the working directory to the working directory of the target process.
+If directory is specified set the working directory to the specified directory.
+.TP
+.BR \-e , " \-\-exec"
+Don't fork before exec'ing the specified program.  By default when entering
+a pid namespace enter calls fork before calling exec so that the children will
+be in the newly entered pid namespace.
+.SH NOTES
+.SH SEE ALSO
+.BR setns (2),
+.BR clone (2)
+.SH BUGS
+None known so far.
+.SH AUTHOR
+Eric Biederman <ebiederm@xmission.com>
+.SH AVAILABILITY
+The nsenter command is part of the util-linux package and is available from
+ftp://ftp.kernel.org/pub/linux/utils/util-linux/.