Arguments immediately following the startx command are used to start a client in the same manner as xinit(1). The special argument '--' marks the end of client arguments and the beginning of server options. It may be convenient to specify server options with startx to change on a per-session basis the default color depth, the server's notion of the number of dots-per-inch the display device presents, or take advantage of a different server layout, as permitted by the Xorg(1) server and specified in the xorg.conf(5) configuration. Some examples of specifying server arguments follow; consult the manual page for your X server to determine which arguments are legal.
startx -- -depth 16
startx -- -dpi 100
startx -- -layout Multihead
Note that in the Debian system, what many people traditionally put in the .xinitrc file should go in .xsession instead; this permits the same X environment to be presented whether startx, xdm, or xinit is used to start the X session. All discussion of the .xinitrc file in the xinit(1) manual page applies equally well to .xsession. Keep in mind that .xinitrc is used only by xinit(1) and completely ignored by xdm(1).
To determine the client to run, startx first looks for a file called .xinitrc in the user's home directory. If that is not found, it uses the file xinitrc in the xinit library directory. If command line client options are given, they override this behavior and revert to the xinit(1) behavior. To determine the server to run, startx first looks for a file called .xserverrc in the user's home directory. If that is not found, it uses the file xserverrc in the xinit library directory. If command line server options are given, they override this behavior and revert to the xinit(1) behavior. Users rarely need to provide a .xserverrc file. See the xinit(1) manual page for more details on the arguments.