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The nvedit Line Editor

On systems with a PROM version of 1.x or 2.x, the nvalias  command might not be available. On these systems, you need to use nvedit  to create custom device aliases. nvedit  is a line editor that edits the NVRAMRC directly, has a set of editing commands, and operates in a temporary buffer. The following is a sample nvedit  session:

ok setenv use-nvramrc? true

TIP

Learning nvedit This section is included for information purposes, to show an additional method for modifying the NVRAM. The nvedit  line editor will not be on the certification exam.

The system responds with the following:

use-nvramrc? =   true
ok nvedit

 0: devalias disk0 /pci@1f,0/pci@1,1/ide@3/disk@0,0\
1: <Control-C>
ok nvstore
ok reset
  Resetting ......
ok boot disk0

The preceding example uses nvedit  to create a permanent device alias named disk0. The example uses Ctrl+C to exit the editor. It also uses the nvstore  command to make the change permanent in the NVRAMRC. Then, it issues the reset  command to reset the system and then boots the system from disk0  by using the boot disk0  command.

Table 3.10 lists some of the basic commands you can use while in the nvedit  line editor.

Table 3.10 - nvedit  Commands

Command Meaning
Ctrl+A Moves backward to beginning of the line.
Ctrl+B Moves backward one character.
Esc+B Moves backward one word.
Ctrl+C Exits the script editor, returning to the OpenBoot command interpreter. The temporary buffer is preserved but is not written back to the script. You use nvstore  afterward to write it back.
Ctrl+D Erases the next character.
Esc+D Erases from the cursor to the end of the word, storing the erased characters in a save buffer.
Ctrl+E Moves forward to the end of the line.
Ctrl+F Moves forward one character.
Esc+F Moves forward one word.
Ctrl+H Erases the previous character.
Esc+H Erases from the beginning of the word to just before the cursor, storing erased characters in a save buffer.
Ctrl+K Erases from the cursor position to the end of the line, storing the erased characters in a save buffer. If at the end of a line, it joins the next line to the current line (that is, deletes the new line).
Ctrl+L Displays the entire contents of the editing buffer.
Ctrl+N Moves to the next line of the script-editing buffer.
Ctrl+O Inserts a new line at the cursor position and stays on the current line.
Ctrl+P Moves to the previous line of the script-editing buffer.
Ctrl+Q Quotes the next character (that is, allows you to insert control characters).
Ctrl+R Retypes the line.
Ctrl+U Erases the entire line, storing the erased characters in a save buffer.
Ctrl+W Erases from the beginning of the word to just before the cursor, storing erased characters in a save buffer.
Ctrl+Y Inserts the contents of the save buffer before the cursor.
Return (Enter) Inserts a new line at the cursor position and advances to the next line.
Delete Erases the previous character.
Backspace Erases the previous character.

OpenBoot Security

Anyone who has access to a computer keyboard can access OpenBoot and modify parameters unless you set up the security variables:

Variable Description
security-mode Restricts the set of operations that users are allowed to perform at the OpenBoot prompt.
security-password Specifies the firmware security password. (It is never displayed.) You should not set this variable directly; you set it by using password.
security-#badlogins Specifies the number of incorrect security password attempts.

To set the security password, you type the password at the ok  prompt, as shown in the following:
New password (only first 8 chars are used): <enter password>
Retype new password: <enter password>

WARNING

Setting the OpenBoot Security Mode It is important to remember your security password and to set it before setting the security mode. If you later forget this password, you cannot use your system; you must call your vendor's customer support service to make your machine bootable again.

If you are able to get to a Unix prompt as root, you can use the eeprom  command to either change the security-mode parameter to none or reset the security password.

Earlier in this chapter you learned how to change the OpenBoot parameter security-password  from the command line.

After you assign a password, you can set the security variables that best fit your environment.

You use security-mode  to restrict the use of OpenBoot commands.  The syntax for setting security-mode  is as follows:

setenv security-mode <value>
Value Description
full Specifies that all OpenBoot commands except go  require a password. This security mode is the most restrictive.
command Specifies that all OpenBoot commands except boot  and go  require a password.
none Specifies that no password is required. This is the default.

 

The following example sets the OpenBoot environment so that all commands except boot  and go  require a password:

setenv security-mode command

With security-mode  set to command, a password is not required if you enter the boot  command by itself or if you enter the go  command. Any other command requires a password, including the boot  command with an argument.

The following are examples of when a password might be required when security-mode  is set to command:

Example Description
ok boot  No password is required.
ok go  No password is required.
ok boot vmunix  A password is required.

 

The system displays a password prompt as follows:

Prompt Description
Password  The password is not echoed as it is typed.
ok reset-all  A password is required.

The system displays a password prompt as follows:
Prompt Description
Password  Type the password.

Note that with Password, the password is not echoed as it is typed.

If you enter an incorrect security password, there is a delay of about 10 seconds before the next startup prompt appears. The number of times that an incorrect security password can be typed is stored in the security-#badlogins  variable, but you should not change this variable.



Etc

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History:

Fifty glorious years (1950-2000): the triumph of the US computer engineering : Donald Knuth : TAoCP and its Influence of Computer Science : Richard Stallman : Linus Torvalds  : Larry Wall  : John K. Ousterhout : CTSS : Multix OS Unix History : Unix shell history : VI editor : History of pipes concept : Solaris : MS DOSProgramming Languages History : PL/1 : Simula 67 : C : History of GCC developmentScripting Languages : Perl history   : OS History : Mail : DNS : SSH : CPU Instruction Sets : SPARC systems 1987-2006 : Norton Commander : Norton Utilities : Norton Ghost : Frontpage history : Malware Defense History : GNU Screen : OSS early history

Classic books:

The Peter Principle : Parkinson Law : 1984 : The Mythical Man-MonthHow to Solve It by George Polya : The Art of Computer Programming : The Elements of Programming Style : The Unix Haterís Handbook : The Jargon file : The True Believer : Programming Pearls : The Good Soldier Svejk : The Power Elite

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The Last but not Least Technology is dominated by two types of people: those who understand what they do not manage and those who manage what they do not understand ~Archibald Putt. Ph.D


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