The default setting is 100.
3 ways to set scrollback buffer:
Edit ~/.screenrc
:
defscrollback [num]
Same as the scrollback command except that the default setting for new windows is changed. Initial setting is 100.
-h [num]
Specifies the history scrollback buffer to be num lines high.
using the Ctrl+a : command:
scrollback [num]
Set the size of the scrollback buffer for the current windows to num lines. The default scrollback is 100 lines.
To view the scrollback buffer value of current session, use Ctrl+a Esc command.