Xvfb

Xvfb -V (return code: 1)

Unrecognized option: --version
use: X [:<display>] [option]
-a #                   default pointer acceleration (factor)
-ac                    disable access control restrictions
-audit int             set audit trail level
-auth file             select authorization file
-br                    create root window with black background
+bs                    enable any backing store support
-bs                    disable any backing store support
-c                     turns off key-click
c #                    key-click volume (0-100)
-cc int                default color visual class
-nocursor              disable the cursor
-core                  generate core dump on fatal error
-displayfd fd          file descriptor to write display number to when ready to connect
-dpi int               screen resolution in dots per inch
-dpms                  disables VESA DPMS monitor control
-deferglyphs [none|all|16] defer loading of [no|all|16-bit] glyphs
-f #                   bell base (0-100)
-fc string             cursor font
-fn string             default font name
-fp string             default font path
-help                  prints message with these options
+iglx                  Allow creating indirect GLX contexts
-iglx                  Prohibit creating indirect GLX contexts (default)
-I                     ignore all remaining arguments
-ld int                limit data space to N Kb
-lf int                limit number of open files to N
-ls int                limit stack space to N Kb
-nolock                disable the locking mechanism
-maxclients n          set maximum number of clients (power of two)
-nolisten string       don't listen on protocol
-listen string         listen on protocol
-noreset               don't reset after last client exists
-background [none]     create root window with no background
-reset                 reset after last client exists
-p #                   screen-saver pattern duration (minutes)
-pn                    accept failure to listen on all ports
-nopn                  reject failure to listen on all ports
-r                     turns off auto-repeat
r                      turns on auto-repeat 
-render [default|mono|gray|color] set render color alloc policy
-retro                 start with classic stipple and cursor
-s #                   screen-saver timeout (minutes)
-seat string           seat to run on
-t #                   default pointer threshold (pixels/t)
-terminate             terminate at server reset
-to #                  connection time out
-tst                   disable testing extensions
ttyxx                  server started from init on /dev/ttyxx
v                      video blanking for screen-saver
-v                     screen-saver without video blanking
-wm                    WhenMapped default backing-store
-wr                    create root window with white background
-maxbigreqsize         set maximal bigrequest size 
+xinerama              Enable XINERAMA extension
-xinerama              Disable XINERAMA extension
-dumbSched             Disable smart scheduling, enable old behavior
-schedInterval int     Set scheduler interval in msec
-sigstop               Enable SIGSTOP based startup
+extension name        Enable extension
-extension name        Disable extension
-query host-name       contact named host for XDMCP
-broadcast             broadcast for XDMCP
-multicast [addr [hops]] IPv6 multicast for XDMCP
-indirect host-name    contact named host for indirect XDMCP
-port port-num         UDP port number to send messages to
-from local-address    specify the local address to connect from
-once                  Terminate server after one session
-class display-class   specify display class to send in manage
-cookie xdm-auth-bits  specify the magic cookie for XDMCP
-displayID display-id  manufacturer display ID for request
[+-]accessx [ timeout [ timeout_mask [ feedback [ options_mask] ] ] ]
                       enable/disable accessx key sequences
-ardelay               set XKB autorepeat delay
-arinterval            set XKB autorepeat interval
-screen scrn WxHxD     set screen's width, height, depth
-pixdepths list-of-int support given pixmap depths
+/-render     turn on/off RENDER extension support(default on)
-linebias n            adjust thin line pixelization
-blackpixel n          pixel value for black
-whitepixel n          pixel value for white
-fbdir directory       put framebuffers in mmap'ed files in directory
-shmem                 put framebuffers in shared memory
(EE) 
Fatal server error:
(EE) Unrecognized option: --version
(EE) 

Xvfb -help (return code: 0)

use: X [:<display>] [option]
-a #                   default pointer acceleration (factor)
-ac                    disable access control restrictions
-audit int             set audit trail level
-auth file             select authorization file
-br                    create root window with black background
+bs                    enable any backing store support
-bs                    disable any backing store support
-c                     turns off key-click
c #                    key-click volume (0-100)
-cc int                default color visual class
-nocursor              disable the cursor
-core                  generate core dump on fatal error
-displayfd fd          file descriptor to write display number to when ready to connect
-dpi int               screen resolution in dots per inch
-dpms                  disables VESA DPMS monitor control
-deferglyphs [none|all|16] defer loading of [no|all|16-bit] glyphs
-f #                   bell base (0-100)
-fc string             cursor font
-fn string             default font name
-fp string             default font path
-help                  prints message with these options
+iglx                  Allow creating indirect GLX contexts
-iglx                  Prohibit creating indirect GLX contexts (default)
-I                     ignore all remaining arguments
-ld int                limit data space to N Kb
-lf int                limit number of open files to N
-ls int                limit stack space to N Kb
-nolock                disable the locking mechanism
-maxclients n          set maximum number of clients (power of two)
-nolisten string       don't listen on protocol
-listen string         listen on protocol
-noreset               don't reset after last client exists
-background [none]     create root window with no background
-reset                 reset after last client exists
-p #                   screen-saver pattern duration (minutes)
-pn                    accept failure to listen on all ports
-nopn                  reject failure to listen on all ports
-r                     turns off auto-repeat
r                      turns on auto-repeat 
-render [default|mono|gray|color] set render color alloc policy
-retro                 start with classic stipple and cursor
-s #                   screen-saver timeout (minutes)
-seat string           seat to run on
-t #                   default pointer threshold (pixels/t)
-terminate             terminate at server reset
-to #                  connection time out
-tst                   disable testing extensions
ttyxx                  server started from init on /dev/ttyxx
v                      video blanking for screen-saver
-v                     screen-saver without video blanking
-wm                    WhenMapped default backing-store
-wr                    create root window with white background
-maxbigreqsize         set maximal bigrequest size 
+xinerama              Enable XINERAMA extension
-xinerama              Disable XINERAMA extension
-dumbSched             Disable smart scheduling, enable old behavior
-schedInterval int     Set scheduler interval in msec
-sigstop               Enable SIGSTOP based startup
+extension name        Enable extension
-extension name        Disable extension
-query host-name       contact named host for XDMCP
-broadcast             broadcast for XDMCP
-multicast [addr [hops]] IPv6 multicast for XDMCP
-indirect host-name    contact named host for indirect XDMCP
-port port-num         UDP port number to send messages to
-from local-address    specify the local address to connect from
-once                  Terminate server after one session
-class display-class   specify display class to send in manage
-cookie xdm-auth-bits  specify the magic cookie for XDMCP
-displayID display-id  manufacturer display ID for request
[+-]accessx [ timeout [ timeout_mask [ feedback [ options_mask] ] ] ]
                       enable/disable accessx key sequences
-ardelay               set XKB autorepeat delay
-arinterval            set XKB autorepeat interval
-screen scrn WxHxD     set screen's width, height, depth
-pixdepths list-of-int support given pixmap depths
+/-render     turn on/off RENDER extension support(default on)
-linebias n            adjust thin line pixelization
-blackpixel n          pixel value for black
-whitepixel n          pixel value for white
-fbdir directory       put framebuffers in mmap'ed files in directory
-shmem                 put framebuffers in shared memory