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<span style="font-size: 10pt"><a href="/plan9/">Plan 9 from Bell Labs</a>&rsquo;s /usr/web/sources/contrib/maht/newns.c</span></p>
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Copyright © 2009 Alcatel-Lucent.<br />
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/*
       newns : This program follows the same sequence as ip/httpd/httpd to create a new namespace from /lib/namespace and then add any actions supplied on the command line.
               Primarily this is as a debugging tool for ip/httpd/httpd and a little bit of curiosity. Once I'd come across newns(2) I immediately tried to run it from the cmd line so I figured that was a niche because I had no idea how to run a shell that didn't inherit a namespace.

       8c newns.c &amp;&amp; 8l newns.8 &amp;&amp;  mv 8.out newns

*/
#include &lt;u.h&gt;
#include &lt;libc.h&gt;
#include &lt;auth.h&gt;

static  char            *nsfile;
static  char            *user;

void
usage(void)
{
       fprint(2, "usage: newns [-u user] [-a nsfile] \n");
       exits("usage");
}

void
change_user(void) {
       int fd;
       if(user != nil) {
               fd = open("#c/user", OWRITE);
               if(fd &lt; 0 || write(fd, user, strlen(user)) &lt; 0)
                       sysfatal("can't become user");
               close(fd);
       }
}

void
main(int argc, char **argv)
{
       int fd;
       nsfile = nil;
       user = nil;

       ARGBEGIN{
       case 'a':
               nsfile = ARGF();
               break;
       case 'u':
               user = ARGF();
               break;

       }ARGEND

       if(argc)
               usage();

       if(user)
               change_user();
       else
               user = getuser();

       switch(rfork(RFFDG|RFNOWAIT|RFNAMEG|RFPROC)) {
       case -1:
               sysfatal("fork");
       case 0:
               break;
       default:
               exits(nil);
       }


       if(newns(user, nil) &lt; 0)
               sysfatal("newns failed on /lib/namespace");
       if(nsfile != nil &amp;&amp; addns(user, nsfile) &lt; 0)
               sysfatal("addns failed on nsfile");

       execl("/bin/rc", "rc");
}

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