# svrctl(2)

    NAME
         svrctl - special server control functions

    SYNOPSIS
         #include <sys/svrctl.h>

         int svrctl(u32_t request, void *data);

    DESCRIPTION
         Svrctl allows root to control the kernel in various ways,  or  implements
         some very Minix specific system calls that don't deserve their own system
         call number.

         This system call makes it easy to add new ways  of  setting  and  getting
         kernel  parameters,  but at the same time, backwards compatibility is not
         guaranteed.  Read  the  <sys/svrctl.h>  include  file  to  see  what  the
         struct's  mentioned  below  look  like.  Most calls are root-only, unless
         specified otherwise.

         The only way to know how to properly use these  calls  is  to  study  the
         associated  kernel or server code, or the programs that already use these
         calls.

         Current requests are:

         MMSIGNON
              Inform MM that the current process wants to become a server.

         MMSWAPON
              Instruct MM to mount a file or device as swapspace.

         MMSWAPOFF
              Tell MM to stop using swapspace.

         FSSIGNON
              Register a new device with FS.

         SYSSIGNON
              Inform the kernel that the process want to  become  a  server.   The
              processes task number is filled-in in a struct systaskinfo.

         SYSGETENV
              Request the value of one or all boot parameters.   Can  be  used  by
              non-root.

    RETURN VALUES
         Svrctl returns 0 upon success and -1 upon failure.

    AUTHOR
         Philip Homburg <philip@cs.vu.nl>