Introduzione

Burg è un bootloader derivato da grub e consiste praticamente in una modifica di esso che aggiunge alcune funzioni tra le quali una facile gestione dei temi. In questa pagina vedremo come farlo funzionare.

Installazione

Installare burg è molto semplice. Basta aggiungere il ppa dando da terminale il seguente comando

sudo apt-add-repository ppa:bean123ch/burg

e aggiornare la lista sorgenti con

sudo apt-get update

ed installare il pacchetto [apt://burg burg].

sudo apt-get install burg

In questo modo avrete burg installato sul vostro computer. Per utilizzarlo come bootloader di default bisogna dare il comando

sudo burg-install "(hd0)"

Nuovi menù di sistema

Utilizzo

Per abilitare il menù di sistema è necessario scaricare un tema. Per farlo è possibile seguire il seguente link:

[http://groups.google.com/group/burg-devel http://groups.google.com/group/burg-devel]

Oppure è possibile installare semplicemente il pacchetto dei temi dando il comando

sudo apt-get install burg-themes burg-themes-common

Una volta installato il pacchetto contenente i temi, applicare un nuovo tema sarà semplicissimo. Basterà infatti premere il tasto t alla schermata di Burg e scegliere il tema che si preferisce dalla lista dei disponibili.

Altre opzioni che si possono richiamare alla pressione di alcuni tasti durante la schermata di Burg sono:

* e - modifica la voce presente il /boot/burg/burg.cfg riguardante il sistema operativo selezionato BR * t - modifica il tema BR * c - apre una finestra di terminale BR * 2 - apre due finestre di terminale BR * F5 - equivalente a Ctrl+x, usato per finire e salvare le modifiche BR * F6 - sposta la selezione all'elemento successivo BR * F8 - cambia da modalità grafica a modalità testuale BR * F9 - arresta BR * F10 - riavvia BR * ESC - ritorna alla finestra di burg BR

Basic Structure

The format of theme file is quite straightforward, {} is used to start a child node, and = is used to set properties, for example:

screen {
  panel {
    extend = 1
    valign = center
    halign = center

    panel {
      class = frame
      id = __menu__
    }
  }
  
  panel {
    id = __timeout__
    attach_bottom = 1
    width = 60%
    halign = center
    height = 1
    progressbar {
     width = 100%
     height = 100%
     color = "red:brown"
    }
  }
}

mapkey {
  f5 = ctrl-x
}

The topmost element in a theme file defines a section, each section have a specific function. For example, screen section is used to define screen layout, while mapkey section defines key mappings.

There are two command to read theme file, load_config and merge_config:

load_config /boot/burg/default.txt

The difference between load_config and merge_config is that if a section already exists, merge_config merges the new section into existing one, while load_config replaces it.

Data Representation

The theme file is supposed to work in both text and graphic mode, so there can be multiple components packed inside a single property.

Size

All properties that specify size uses the following representation:

10

10 character size in text and graphic mode. In graphic mode, the size is calculated using system default font, which is set using gfxfont variable. Please note that width=1 and height=1 is not the same size in pixels.

10%

The size is 10 percentage of parent widget, in both text and graphic mode.

10/1

10 pixels in graphic mode, and 1 character in text mode. Either component can use the percentage notion as well, such as:

10%/20%

10 percent in graphic mode, 20 percent in text mode.

Color

red

Red, in both text and graphic mode.

The recognized color named is as follows:

• black, blue, green, cyan, red, magenta, brown, light-gray - can be used as foreground or background color in text mode.
• dark-gray, light-blue, light-green, light-cyan, light-red, light-magenta, yellow, white - can only be used as foreground in text mode.

red/blue

Foreground color is red, background color is blue, works in both text and graphic mode.

#808080/red/blue

Use #808080 in graphic mode, foreground color red, background color blue in text mode.

Widgets become selectable if there is associated command. In this case, you may want to use different color when the widget is in selected state, this can be achieved by joining two color together with ":":

cyan/blue:light-gray/blue

When the widget is selected, foreground color is light-gray, otherwise it's cyan. Background color is blue in both situation.

Image

,,blue,#0

Draws a blue rectangle box, in both text and graphic mode.

,,blue,c

Draws a blue rectangle box using fill character 'c', in both text and graphic mode.

,,blue,#0x250F

Draws a blue rectangle box, using unicode glyph 0x250f as fill character, in both text and graphic mode.

/splash.png,,blue,#0

Draws image /splash.png in graphic mode, blue rectangle box in text mode, you can also specify a fill character.

/splash.png,,blue

Draws image /splash.png in graphic mode, nothing in text mode.

/splash.png

Same as above, but uses default scaling method and background color.

none,,blue,#0

Draws blue rectangle box in text mode, nothing in graphic mode.

In the above examples, the second parameter are all empty, it specify the scaling method of images, and can use one of the following value:

• scaling (default) - scale the image to fit the width/height of widget.
• center - draw the image at the center
• tiling - repeat the image until it fills the area.
• minfit - keeps ratio scaling, it ensures the entire image is shown, but it can leave blank at top/bottom or left/right.
• maxfit - keeps ratio scaling, it ensures no blank is left, but the image can be truncated at top/bottom or left/right.

For drawing methods that leaves blanks (center and minfit), it uses the color in third parameter as background.

Just like color, you can joined two image together using ":" to specify different image when the widget is selected.

,,cyan/blue,#0x250F:,,light-gray/blue,#0x2554

Common Properties

Some properties are shared by all widgets. This includes properties used by layout manger, command, anchor and class.

Layout manager

You can place a widget in one of two ways. You can set its location directly, or you can let the layout manager figure it out for you.

For absolute positioning, you can use the following properties:

• attach_top - distance to the top border of parent
• attach_bottom - distance to the bottom border of parent
• attach_left - distance to the left border of parent
• attach_right - distance to the right border of parent
• attach_hcenter - offset from the horizontal central line
• attach_vcenter - offset from the vertical central line

If none of the above properties are set, layout manager would try to calculate the position of widget for you. You can control its placement using these properties:

• extend - if set to 1, extend the widget in the direction of parent.
• valign - can be top, center, bottom or extend (default).
• halign - can be left, center, right or extend (default).

The parent widget uses the following properties to control the placement of children:

• direction - The direction, its value can be top_to_bottom (default), bottom_to_top, left_to_right or right_to_left.
• space - The space left between two children.

You can also set the size of widget with these properties:

• width - width of widget
• height - height of widget

If one of the above properties is not set, layout manager would try to calculate the width/height for you, which is normally the minimum size to contain its children, although it can also be expanded using the extend property mentioned above.

Sometimes you want the layout manager to calculate the size for you, but you don't want the widget to because too large or too small. In this case, you can use the following properties to limit the size of auto calculated widgets:

• min_width - minimum width of widget
• max_width - maximum width of widget
• min_height - minimum height of widget
• max_height - maximum height of widget

Please note that these properties have no effect if the size is set explicitly using width/height property.

Command

The command property associate action for current widget. Once it's set, the widget become selectable, navigation keys like up/down/left/right jumps to the next widget with command property set, and enter key execute the command.

To specify multiple commands to run in this property, use '\n' as separator. For example:

command = "chainloader +1\nboot"

Anchor

Sometime you need to group some widgets together. For example. when navigating inside a menu, you may want to loop back to the last item when using the previous key on the first item. This can be archived by setting anchor to 1 in the parent widget. Key like tab jumps to the next selectable widget in another anchor, so it can be used to switch between different menus.

Class

Many widgets share the same property value. For example, we need to draw a rectangle box in many occasion, such as in menu, sub menu, terminal window, etc. Instead of duplicate the same set of properties many times, we can give it a name using the class property, the real property is set in the class section.

If class property is not set, it would try to locate default properties using widget name.

screen {
 panel { class = frame }
 panel { class = frame }
}

class {
 frame {
  top_left = ",,cyan/blue,#0x250F:,,light-gray/blue,#0x2554"
  top = ",tiling,cyan/blue,#0x2501:,,light-gray/blue,#0x2550"
  top_right = ",,cyan/blue,#0x2513:,,light-gray/blue,#0x2557"
  left = ",tiling,cyan/blue,#0x2503:,,light-gray/blue,#0x2551"
  right = ",tiling,cyan/blue,#0x2503:,,light-gray/blue,#0x2551"
  bottom_left = ",,cyan/blue,#0x2517:,,light-gray/blue,#0x255A"
  bottom = ",tiling,cyan/blue,#0x2501:,,light-gray/blue,#0x2550"
  bottom_right = ",tiling,cyan/blue,#0x251B:,,light-gray/blue,#0x255D"
 }

 screen {
  background = ":,,blue,#0"
 }
}

Widgets

Widget is the basic element to construct the user interface. There are several widgets, each have a set of properties to control its behavior.

panel

Panel is a container for other widgets. You can set the border for panel. There are four set of border properties, from outward to inward:

• padding_size, padding_top, padding_bottom, padding_left, padding_right - This is the most outward layer of empty strip for panel, padding_size set the default value for all four borders, you can overwrite specific size with property like padding_top.
• border_color, border_size, border_top, border_bottom, border_left, border_right - The second layer, consists of solid color.
• top_left, top, top_right, left, right, bottom_left, bottom, bottom_right - The third layer, consist of 8 images.
• margin_size, margin_top, margin_bottom, margin_left, margin_right - The most inward layer, an empty strip to prevent children widgets from getting too closed to borders,
• background - Background image. This includes the space reserved by margin_*.

screen

screen is the topmost widget. It's just like panel, but it doesn't have a external border so it only uses property margin_* and background.

text

Text is a widget to show single line of text. It has the following properties:

• text - The string to show
• gfx_text - The string to show in graphic mode, if it's not set, both text and graphic mode shows the same text.
• color - Text color
• font - Text font

image

Image is a widget to show a single image, Property:

• image - The image to show

edit

Edit is a widget to show a edit box. Properties:

• max_lines - The maximum number of lines to store. max_lines=1 means single line edit. max_lines=0 means unlimited lines. If it's not set, default value 100 is used.
• lines - The number of lines to show in screen. This is used to calculate the height of widget, so don't mix it with height property.
• columns - The number of columns to show in screen. This is used to calculate the width of widget, so don't mix it with width property.
• text - The initial text. You can set multiple lines of using the \n separator.
• color - Text color.
• font - Text font.

In the edit widget, use ctrl-x to save the current edit and returns, ESC to cancel.

term

Terminal emulator, it shares properties with edit widget.

password

Password is a single line edit widget, but unlike edit, it shows * instead of the real input character. It uses properties columns, color and font.

progressbar

This is used to show the process bar before timeout is reached. Property:

• color - The color of progress bar. First component is the color for passed time bar, and second component is for remaining time bar. If there is not second component, only the first bar is visible.

Template

Template is used to define composite component. For example:

dialog_hello {
  panel {
    parameters = "text=text.text"
    class = frame
    text {}
  }
}

The property parameters defines the mapping between parameters and internal properties. This template accepts one parameter text, which is mapped to the text property of text widget.

Some template are used internally so they must be defined in the theme file:

• dialog_message - shows a dialog box with single text message. Must accepts text parameter which is the content of the text.
• dialog_password - shows a password input dialog. Must accepts username and password parameter which mapping to the username and password input text.
• template_submenu - Template used to generate sub menus.
• template_menuite - Template used to generate the boot menu items. Must accepts title and class parameter.

Here are the definition of these templates in the default theme file:

dialog_message {
  panel {
    parameters = "text=text.text"
    class = frame
    margin_size = 1
    margin_bottom = 0
    space = 1
    attach_hcenter = 0
    attach_vcenter = 0
    text {}
    panel {
      class = frame
      command = true
      halign = center
      margin_left = 1
      margin_right = 1
      text { text = OK }
    }
  }
}

dialog_password {
  panel {
    parameters = "username=__user__.text:password=__pass__.text"
    class = frame
    margin_size = 1
    margin_bottom = 0
    attach_hcenter = 0
    attach_vcenter = 0

    panel {
      direction = left_to_right
      space = 1
      text {
        extend = 1
        valign = center
        text = Username
      }
      panel {
        class = frame
        margin_left = 1
        margin_right = 1
        edit {
          id = __user__
          max_lines = 1
        }
      }
    }

    panel {
      direction = left_to_right
      space = 1
      text {
        extend = 1
        valign = center
        text = Password
      }
      panel {
        class = frame
        margin_left = 1
        margin_right = 1
        password {
          id = __pass__
        }
      }
    }

    panel {
      class = frame
      command = true
      halign = center
      margin_left = 1
      margin_right = 1
      text {
        text = OK
      }
    }
  }
}

template_submenu {
  panel {
    class = frame
  }
}

template_menuitem {
  panel {
    parameters = "class=image.class:title=text.text"
    class = select
    direction = left_to_right
    image {}
    text { valign = center }
  }
}

This theme pop up the sub menu alongside parent, if you prefer to show the sub menu full screen, you can replace template_submenu with this:

template_submenu {
  panel {
    width = 100%
    height = 100%

    panel {
      id = __child__
      class = frame
      valign = center
      halign = center
      extend = 1
    }
  }
}

Here, the widget with id child is the place to insert auto generated (using template_menuitem) sub menu items.

You can control the placement of popup submenu using the popup property, for example:

screen {
  panel {
   id = __menu__
   popup = left
  }
}

template_submenu {
 panel {
  class = frame
  popup = right
 }
}

The values can be:

• left, right, top, bottom - the position of popup submenu related to the current selected widget.
• abs - Absolute position, submenu starts at (0, 0).

The popup is not set, menu system tries to decide popup position automatically,

With template, the screen section is very simple:

screen {
  panel {
    extend = 1
    valign = center
    halign = center

    panel {
      class = frame
      id = __menu__
    }
  }

  panel {
    id = __timeout__
    attach_bottom = 1
    width = 60%
    halign = center
    height = 1
    progressbar {
      width = 100%
      height = 100%
      color = "red:brown"
    }
  }
}

The widget with id menu is the place to insert auto generated top level menu items defined with menuentry statement in grub.cfg. The widget with id timeout is used for timeout control. When auto booting is paused by key press, widget with id timeout and all its children would be hidden.

You can also use command menu_popup to create a dialog box based on templates. For example, to create a hello world message box, we can use the dialog_message template:

menu_popup dialog_message "text=Hello, World"

Command menu_edit is quite similar to menu_popup, but it uses two direction parameter assignment, it's used to implement the command edit box. First, we define the template in theme file:

dialog_edit {
  panel {
    parameters = "text=edit.text"
    class = frame
    width = 80%
    attach_hcenter = 0
    attach_vcenter = 0

    edit {
      lines = 10
    }
  }
}

Then uses this command to start the dialog box:

menu_edit dialog_edit text=command

In entry, the text parameter of the dialog box is set to the command parameter of current widget. After edit is done, we reverse the order and update the command parameter to the new text.

User interaction

With the new ppa package update (2010.06.07) there is a new cool command named menu_read. it's used to enter a property from a dialog window and assign it to a variable. This template can be used for user interaction, for example, add this dialog template to theme file

dialog_input {
  panel {
    parameters = "old_value=__old__.text:new_value=__new__.text"
    class = frame
    margin_size = 1
    margin_bottom = 0
    attach_hcenter = 0
    attach_vcenter = 0

    panel {
      direction = left_to_right
      space = 1
      text {
        extend = 1
        valign = center
        text = "Old value"
      }
      text {
        id = __old__       
      }
    }

    panel {
      direction = left_to_right
      space = 1
      text {
        extend = 1
        valign = center
        text = "New value"
      }
      panel {
        class = frame
        margin_left = 1
        margin_right = 1
        edit {
          id = __new__
          max_lines = 1
        }
      }
    }

    panel {
      class = frame
      command = "menu_read new_value AA"
      halign = center
      margin_left = 1
      margin_right = 1
      text {
        text = OK       
      }
    }
  }
}

The template above can be displayed using:

menu_popup dialog_input old_value=${AA}

The "Old value" field display the value of variable AA, and the value of "New value" edit box will be assigned to AA when you click "OK".

Define hot keys

You can use keymap section to map some key to another. This is useful in platform like EFI where keys like ctrl can't be input.

onkey section associate grub command to keys. If a key is already handled by the current widget, the command defined in onkey section is ignored. For example, inside the terminal window, c is used as input character, so the command defined in onkey is ignored.

onkey {
  e = "*menu_edit dialog_edit text=command"
  t = "if menu_edit dialog_line text=title; then menu_refresh; fi"
  c = "*menu_popup term_window"
  2 = "*menu_popup two_term"
  f6 = ui_next_anchor
  f8 = menu_toggle_mode
  f9 = halt
  f10 = reboot
}

mapkey {
  f5 = ctrl-x
}

The * at the beginning of command meaning this command is password protected, this will be explained in the next section.

Password

To enable password protection, you need to add these commands at the beginning of grub.cfg:

set superusers=admin
password --md5 admin '$1$A1tpOB3$bTHEMeIVvBbQsLZIWmJp/.'
password user1 user1

The superusers variable set super users. password command set password for individual user. With --md5 option, the password should be md5 password, otherwise it's plain text.

To generate md5 password, uses grub-mkpasswd command:

grub-mkpasswd admin

Output:

$1$A1tpOB3$bTHEMeIVvBbQsLZIWmJp/.

You can also uses openssl to generate it:

openssl passwd -1 -salt 1234567 admin

Output:

$1$1234567$ergpnZu0mLdD77Dbmwjpb1

To protect certain boot items, add --users option in menuentry statement:

menuentry Item1 --users user1 {
  true
}

Only user1 and super users can access this boot item.

In hot key definition, you can add * at the beginning of command so that only super users can access it.

Save default

To enable save default, you first need to generate a environment file using grub-editenv:

sudo grub-editenv /boot/grub/grubenv create

Default location for environment file is grubenv in the grub directory, although you can overwrite it with envfile variable. Command load_env read the environment file from disk.

To enable save default for all items, you can set savedefault=1 in grub.cfg, to skip some item, adds --nosave option in menuentry statement. If you only want to save a few items, then you can skip savedefault=1, but adds --save option in items you want to save. For example:

set envfile=/boot/grub/grubenv
set savedefault=1
load_env

menuentry Item1 --nosave {
  true
}

menuentry Item2 --save {
  true
}

You also set default item using config file, for example, to boot the first item, add this line to /etc/default/grub:

GRUB_DEFAULT=0

To boot the saved item from last boot:

GRUB_DEFAULT=saved

Don't forget to use grub-mkconfig/update-grub to update the real grub.cfg.

Timeout

You can use timeout variable to enable auto boot if no key is pressed in N seconds:

set timeout=5

If timeout is set to 0, boot immediately, although you can stop it by pressing any key at startup. In the case of timeout=0, the menu is not drawn unless auto boot process is halt.

Timeout can also be set in config file using variable GRUB_TIMEOUT.

Menu Icon

To add icons to boot items, uses --class option:

menuentry Item1 --class image_ubuntu {
  true
}

Then in theme file, define the image_ubuntu class:

class {
  image_ubuntu {
    image = "${prefix}/icons/ubuntu.png"
  }
}

Menu predefinito

È possibile aggiungere un menu predefinito seguendo gli articoli definiti con menuentry. Il menu predefinito è definito nel file del tema usando la sezione menu:

menu {
  Tools {
    class = image_dir
    users = user
    save = 0

    "Toggle Mode" {
      class = image_tools
      command = menu_toggle_mode
    }

    "Terminal" {
      class = image_term
      command = "menu_popup term_window"
    }

    "Two Term" {
      class = image_term
      command = "menu_popup two_term"
    }

    "About" {
      class = image_about
      command = "menu_popup dialog_message \"text=This is GNU GRUB\""
    }
  }

  Shutdown {
    class = image_shutdown
    command = "halt"
  }

  Restart {
    class = image_restart
    command = "reboot"
  }
}

Qui, class corrisponde all'opzione --class nel menuentry, users corrisponde a --users, save=1/save=0 corrispondono a --save e --nosave.

Configurazione dinamica di PXE

Burg aggiunge un nuovo comando pxecfg, che può essere utilizzato per eseguire certi comandi in base agli attuali indirizzi IP / MAC.

Innanzitutto, scrivere un file config di pxe , il cui formato è molto simile al tema del menù.

ip {
  192 {
    168.2 {
      command = "echo ip 192.168.2.*"
    }

    169 {
      command = "echo ip 192.169.*.*"
    }

    command = "echo ip 192.*.*.*"
  }
}

mac {
  00-0c-29-1a {
    command = "echo mac 00-0c-29-1a-*-*"
  }

  command = "echo mac *-*-*-*-*-*"
}

Usare questo in grub.cfg per caricare il file config:

pxecfg /config.txt

Risoluzione problemi

Burg non troverà un grub.cfg.

Le versioni più recenti usano burg.cfg

Ulteriori risorse

• [http://code.google.com/p/burg/ Sito del progetto]

• [https://launchpad.net/burg Burg su Launchpad]

• [http://www.burgloader.com/bbs Forum di Burg]

• [http://groups.google.com/group/burg-devel Mailing list di Burg]

• [http://code.google.com/p/burg/wiki/Screenshots Schermate di Burg]