unix use and security from the ground up.htm

黑客培训教程

        $

rm      -This deletes a file. Syntax: "rm <filename>".

        Example:
        $rm junk
        $

cp      -Copies a file. Syntax: "cp file1 file2", where file1 is the file you
        wish to copy, and file2 is the name of the copy you wish to create. If 
        file2 already exists, it will be overwritten. You may specify pathnames
        for one or both arguments.

        Example:
        $cp /usr/junk /usr/junk.backup

stty    -Displays/sets your terminal characteristics. To display the current 
        settings, type "stty". To change a setting, specify one of the options
        listed below.

   Options:
   echo         -System echoes back your input.
   noecho       -System doesn't echo your input.
   intr 'arg'   -Sets the break character. The format is '^c' for control-c, 
                etc. '' means no break character.
   erase 'arg'  -Sets the backspace character. Format is '^h' for control-h,
                etc. '' means no backspace character.
   kill 'arg'   -Sets the kill character (which means to ignore the last line
                you typed). Format is the same as for intr and erase, 
                '^[character]', with '' meaning no kill character.

        Example:
        $stty intr '^c' erase '^h'
        $stty
        stty -echo intr '^c' erase '^h' kill '^x'
        
lpr     -This command prints out a file on the Unix system's printer, for you 
        to drop by and pick up (if you dare!) The format is "lpr <filename>".

        Example:
        $lp junk

ed      -This is a text file line editor. The format is "edit <filename>". The 
        file you wish to modify is not modified directly by the editor; it is 
        loaded into a buffer instead, and the changes are only made when you 
        issue a write command. If the file you are editing does not already 
        exist, it will be created as soon as issue the first write command. 
        When you first issue the edit command, you will be placed at the
        command prompt, ":" Here is where you issue the various commands. Here
        is list of some of the basic editor commands.
        #       -This is any number, such as 1, 2, etc. This will move you down 
                to that line of the file and display it.
        d       -This deletes the line you are currently at. You will then be
                moved to the previous line, which will be displayed.
        a       -Begin adding lines to the file, just after the line that you 
                are currently on. This command will put you in the text input
                mode. Simply type in the text you wish to add. To return to the
                command mode, type return to get to an empty line, and press
                the break key (which is whatever character you have set as your
                break key). It is important to set the break character with 
                stty before you use the editor!
        /       -Searches for a pattern in the file. For example, "/junk" would
                search the file from your current line down for the first line
                which contains the string "junk", and will move you to that 
                line if it finds one.
        i       -Insert. Works similar to a, except that the text is inserted
                before the line you are currently on.
        p       -Prints out a line or lines in the buffer. "p" by itself will
                display your current line. "#p" will display the line "#". 
                You may also specify a range of lines, such as "1,3p" which
                will display lines 1-3. "1,$p" will print out the entire file.
        w       -Write the changes in the buffer to the file.
        q       -Quit the editor.

        Example:
        $edit myfile
        Editing "myfile" [new file]
        0 lines, 0 characters
        :a
        I am adding stupid text to myfile.
        This is a test.
        ^c [this is assumed as a default break character in this example]
        :1,$p
        I am adding stupid text to myfile.
        This is a test.
        :2
        This is a test.
        :d
        I am adding stupid text to myfile.
        :w
        :q
        $

grep    -this command searches for strings of text in text files. The format is
        grep [string] [file]. It will print out every line in the file that 
         contains the string you specified.

        Options:
        v       -Invert. This will print out every line that DOESN'T contain
                the string you specified.

        Example:
        $ grep you letter
        your momma!
        I think you're going to get caught.
        $

who     -This will show the users currently logged onto the system.

        Example:
        $ who

        root    console Mar 10  01:00
        uucp    contty  Mar 30  13:00
        bill    tty03   Mar 30  12:15
        $
        Now, to explain the above output: the first field is the username of 
        the account. The second field shows which terminal the account is on.
        Console is, always, the system console itself. On many systems where
        there is only one dialup line, the terminal for that line is usually 
        called contty. the tty## terminals can usually be either dialups or
        local terminals. The last fields show the date and time that the user
        logged on. In the example above, let's assume that the current time and
        date is March 30, and the time is 1:00. Notice that the time is in 24 
        hour format. Now, notice that the root (superuser) account logged in on
        March 10! Some systems leave the root account logged in all the time on
        the console. So, if this is done on a system you are using, how can you
        tell if the system operator is really online or not? Use the ps 
        command, explained next.

ps      -This command displays information about system processes.

        Options:
        u       -this displays information on a specific user's processes. For
                instance, to display the root account's processes:
                $ ps -uroot

                PID     TTY     TIME    CMD
                1234    console 01:00   sh
                1675    ?       00:00   cron
                1687    console 13:00   who
                1780    tty09   12:03   sh

                Now, to explain that: The first field is the process number. 
                Each and every time you start a processes, running a program,
                issueing a command, etc., that process is assigned a unique 
                number. The second is which terminal the process is being run
                on. The third field is when the process was started. The last
                field is the base name of the program or command being run.
                A user's lowest process number is his login (shell) process.
                Note that the lowerst process in the above example is 1234. 
                This process is being run on the console tty, which means the
                superuser is logged on at the system console. Note the ? as the
                tty in the next entry, for the cron process. You can ignore any
                processes with a question mark as the terminal. These processes
                are not bewing carried out by a user; they are being carried
                out by the system under that user's id. Next, note the entry
                for process # 1687, on the console terminal, "who". this means
                that the superuser is executing the who command...which means
                he is currently actively on-line. The next entry is interest-
                ing...it shows that the root user has a shell process on the 
                terminal tty09! This means that someone else is logged in
                under the root account, on tty09. If more than one person is
                using an account, this option will display information for all
                of them, unless you specify the next option...

        t       -This allows you to select processes run on a specific term-
                inal. For example:
                $ps -t console
                will show all the processes currently being run on the console.

                Example:
                Remember, options can usually be combined. This will show all
                the root user's processes being run on the system console:
                $ ps -uroot -tconsole

                PID     TTY     TIME    CMD
                1234    console 01:00   sh
                1687    console 13:00   who
                $

kill    -Kills processes. Syntax: kill [-#] process#. You must know the process
        number to kill it. You can, optionally, specify an option of 1-9, to
        determine the power of the kill command. Certain kinds of processes,
        like shell processes, require more power to kill. Kill -9 will stop any
        process. You must have superuser capabilities fo kill another user's
        processes (unless he's using your account).

        Example:
        $kill -9 1234
        1234 killed.
        $

write   -This command is for on-line realtime user to user communications. To 
        communicate with a user, type "write <username>". If more than one
        person is logged in under that user name, you must specify a specific
        terminal you wish to speak to. When you do this, the person you wish
        to communicate with will see:
        Message from [your account name] tty## [<--your terminal]

        Now you can type messages, and they will be displayed on that person's
        terminal when you press return. When you are finished, press control-D
        to quit.

        Example:
        $ write root
        Fuck you I'm a hacker!  [This is not advised.]
        ^d
        $

mail    -The Unix mail facilities, used to send/receive mail. To send mail, 
        type "mail <username>". Enter your message and press control-d to send.
        To read your mail, type "mail". Your first letter will be displayed,
        and then you will be given a "?" prompt.  
        Here are the legal commands you give at this point: 
        ##      -Read message number ##.
        d       -Delete last message read.
        +       -Go to next message.
        -       -Move back one message.
        m       -Send mail to user.
        s       -Save last message read. You can specify the name of the file
                to which it is saved, or it will be saved to the default file,
                mbox.
        w       -Same as s, but will save the message without the mail file
                header.
        x       -Exit without deleting messages that have been read.
        q       -Exit, deleting messages that have been read.
        p       -Print last message read again.
        ?       -Lists these commands.

        Examples:
        To send mail:
        $ mail root
        Hi bill! This is a nice system.
        -John
        ^d
        $
        To read mail:
        $ mail
        From john Thu Mar 13 02:00:00  1986
        Hi bill! This is a nice system.
        -John