screendump linux command output over terminal

 :~$ screendump 

/dev/tty0: Permission denied

screendump: Couldn't read /dev/vcsa

 :~$ sudo screendump 

Gives - [Blank Terminal Screen and prompt at the last line]

Ctrl + C - [Closes the terminal itself, it is not logging out the root terminal and not giving # prefixed terminal]

How does screendump works been briefed in the following manual output gathered from Linux Machine

SCREENDUMP(1)                                                                                            General Commands Manual                                                                                           SCREENDUMP(1)

NAME

       screendump - dump the contents of a virtual console to stdout

SYNOPSIS

       screendump [ N ]

DESCRIPTION

       The screendump command dumps the contents of virtual console N , (or the current console if N is omitted) to standard out.

       Just saying

              cat /dev/vcsN

       has a similar effect.

NOTES

       For security reasons, screendump uses linux devices "virtual console screen" and "virtual console screen with attributes" to give access for screendump.

       Ensure these files exist, using

              cd /dev for i in 0 1 2 3 ...; do

                   mknod vcs$i c 7 $i

                   mknod vcsa$i c 7 `expr 128 + $i`

              done

       (filling in the ellipses) and give the device files appropriate permissions, or run screendump as root.

SEE ALSO

       setterm(1)

kbd                                                                                                            2002-02-24                                                                                                  SCREENDUMP(1)