Difference between revisions of "Scrollback buffer"

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[[Category:Terminal emulators]]
 
Scrollback is a function that is implemented in a text console to allow the user to go back to view the lines of text which have scrolled off the screen.  This is made possible by a buffer created just for this purpose between the video adapter and the display device; the scrollback buffer.  Normally, the key combinations of Shift-PageUp or Shift-PageDown allows the user to scroll up or down a page or two by default.
 
Scrollback is a function that is implemented in a text console to allow the user to go back to view the lines of text which have scrolled off the screen.  This is made possible by a buffer created just for this purpose between the video adapter and the display device; the scrollback buffer.  Normally, the key combinations of Shift-PageUp or Shift-PageDown allows the user to scroll up or down a page or two by default.
  
However, what if one wishes to keep track of more than that small amount?  During boot this is particularly necessary, as the text scrolls off by quite a few pages.  To solve this need, the scrollback buffer must be increased.  It is a simply process to do so.
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However, what if one wishes to keep track of more than that small amount?  During boot this is particularly necessary, as the text scrolls off by quite a few pages.  To solve this need, the scrollback buffer must be increased.  It is a simple process to do so.
  
 
The basic buffer size is 32K, equal to approximately 4 half pages of text.  The easy way to increase this is to use a device called fbcon (the framebuffer console).  To find out about fbcon, this [http://www.mjmwired.net/kernel/Documentation/fb/fbcon.txt link] can give you more information.  Just follow these instructions.
 
The basic buffer size is 32K, equal to approximately 4 half pages of text.  The easy way to increase this is to use a device called fbcon (the framebuffer console).  To find out about fbcon, this [http://www.mjmwired.net/kernel/Documentation/fb/fbcon.txt link] can give you more information.  Just follow these instructions.
  
===1. The Easy Way===
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== The Easy Way ==
Open /boot/grub/menu.lst with your favorite editor. Look for the appropriate kernel line.  Make the following changes:
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Edit the appropriate kernel line as used by your bootloader (e.g. {{ic|/boot/grub/grub.cfg}} for [[GRUB]], or {{ic|/boot/syslinux/syslinux.cfg}} for [[syslinux]]).  Make the following changes:
If 'vga=xxx' exists, delete it.
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* If {{ic|vga=XXX}} exists, delete it.  
Add 'vesabf' to that line, substituting vesa for your driver's name.
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* Append {{ic|XXXfb}}, replacing XXX with the name of your video driver.
Then add 'fbcon=scrollback:128k' to the same line.
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* Append {{ic|fbcon=scrollback:Nk}}, where N is the amount of scrollback desired.
One may increase the 128 amount if desired.
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Then reboot.
 
Then reboot.

Revision as of 18:50, 1 February 2013

Scrollback is a function that is implemented in a text console to allow the user to go back to view the lines of text which have scrolled off the screen. This is made possible by a buffer created just for this purpose between the video adapter and the display device; the scrollback buffer. Normally, the key combinations of Shift-PageUp or Shift-PageDown allows the user to scroll up or down a page or two by default.

However, what if one wishes to keep track of more than that small amount? During boot this is particularly necessary, as the text scrolls off by quite a few pages. To solve this need, the scrollback buffer must be increased. It is a simple process to do so.

The basic buffer size is 32K, equal to approximately 4 half pages of text. The easy way to increase this is to use a device called fbcon (the framebuffer console). To find out about fbcon, this link can give you more information. Just follow these instructions.

The Easy Way

Edit the appropriate kernel line as used by your bootloader (e.g. /boot/grub/grub.cfg for GRUB, or /boot/syslinux/syslinux.cfg for syslinux). Make the following changes:

  • If vga=XXX exists, delete it.
  • Append XXXfb, replacing XXX with the name of your video driver.
  • Append fbcon=scrollback:Nk, where N is the amount of scrollback desired.

Then reboot.