Tech Notes: 2011

11/18/11

OS Freeware tools - Linux, Windows, OS X

Great sysadmin freeware tools listed in random order:

Gnome Partition Editor (GParted): http://gparted.sourceforge.net
Knoppix: http://www.knopper.net/knoppix
BartPE http://www.nu2.nu/pebuilder/
NiroSoft Tools: http://www.nirsoft.net/utils/index.html
Sysinternals Suite: http://technet.microsoft.com/en-us/sysinternals/bb545027
Trinity Rescue Kit: http://trinityhome.org
Kaspersky Rescue Disk: http://support.kaspersky.com/viruses/rescuedisk
ddRescue: http://www.gnu.org/software/ddrescue/ddrescue.html
F-Secure Rescue CD: http://www.f-secure.com/en/web/labs_global/removal/rescue-cd
SafeCopy: http://safecopy.sourceforge.net/

Note: Most of these tools have no official end user support. So, Use at your own risk.

Geeky Pix

11/16/11

SSH connection through putty gives Access Denied error

Solution for the "Access Denied" error message when connecting to a remote box through putty even though the remote machine accepts your login credentials & let's you in:

In Putty Configuration for that session:

SSH-AUTH-GSSAPI
Uncheck both GSSAPI boxes

Source: http://centos.org/modules/newbb/viewtopic.php?topic_id=34022&forum=59&post_id=146171#forumpost146171

Resolve auditd warning asking to specify arch type

This is to resolve auditd warning asking to specify an arch type for syscall events

Sample auditd warning message:

WARNING - 32/64 bit syscall mismatch in line 14, you should specify an arch

Sample audit.rules line in question:

-a entry,always -S umask

Solution: add "-F arch=64" - without the quotes- before the -S for the line to read like this:

-a entry,always -F arch=b64 -S umask

Google Code's RE2 REGEX Lib Syntax

This page lists the regular expression syntax accepted by RE2.
It also lists syntax accepted by PCRE, PERL, and VIM.
Grayed out expressions are not supported by RE2.

Public DNS

Google's Public DNS

The Google Public DNS IP addresses (IPv4) are as follows:
8.8.8.8
8.8.4.4

The Google Public DNS IPv6 addresses are as follows:
2001:4860:4860::8888
2001:4860:4860::8844

You can use either number as your primary or secondary DNS server. You can specify both numbers, but do not specify one number as both primary and secondary.
You can configure Google Public DNS addresses for either IPv4 or IPv6 connections, or both.

Open DNS Service

The IPV4 addresses are:

208.67.222.222
208.67.220.220

Excel -- Worksheet VLookp Functions

This and more Excel tips can be found on http://www.contextures.com/tiptech.html

Excel VLOOKUP Function and VLOOKUP Example

In a workbook, you can create a table that stores information about your products, or employees, or other data you want to refer to frequently. From other cells in the workbook, you can use an Excel VLOOKUP formula to look up data from the master table.

Standard Input and Output Redirection

The shell and many UNIX commands take their input from standard input (stdin), write output to standard output (stdout), and write error output to standard error (stderr). By default, standard input is connected to the terminal keyboard and standard output and error to the terminal screen.

The way of indicating an end-of-file on the default standard input, a terminal, is usually <Ctrl-d>.

Redirection of I/O, for example to a file, is accomplished by specifying the destination on the command line using a redirection metacharacter followed by the desired destination.

C Shell Family

Some of the forms of redirection for the C shell family are:

Character	Action
>	Redirect standard output
>&	Redirect standard output and standard error
<	Redirect standard input
>!	Redirect standard output; overwrite file if it exists
>&!	Redirect standard output and standard error; overwrite file if it exists
\|	Redirect standard output to another command (pipe)
>>	Append standard output
>>&	Append standard output and standard error

The form of a command with standard input and output redirection is:

% command -[options] [arguments] < input file > output file

If you are using csh and do not have the noclobber variable set, using > and >& to redirect output will overwrite any existing file of that name. Setting noclobber prevents this. Using >! and >&! always forces the file to be overwritten. Use >> and >>& to append output to existing files.

Redirection may fail under some circumstances: 1) if you have the variable noclobber set and you attempt to redirect output to an existing file without forcing an overwrite, 2) if you redirect output to a file you don't have write access to, and 3) if you redirect output to a directory.

Examples:

% who > names

Redirect standard output to a file named names

% (pwd; ls -l) > out

Redirect output of both commands to a file named out

% pwd; ls -l > out

Redirect output of ls command only to a file named out

Input redirection can be useful, for example, if you have written a FORTRAN program which expects input from the terminal but you want it to read from a file. In the following example, myprog, which was written to read standard input and write standard output, is redirected to read myin and write myout:

% myprog < myin > myout

You can suppress redirected output and/or errors by sending it to the null device, /dev/null. The example shows redirection of both output and errors:

% who >& /dev/null

To redirect standard error and output to different files, you can use grouping:

% (cat myfile > myout) >& myerror

Bourne Shell Family

The Bourne shell uses a different format for redirection which includes numbers. The numbers refer to the file descriptor numbers (0 standard input, 1 standard output, 2 standard error). For example, 2> redirects file descriptor 2, or standard error. &n is the syntax for redirecting to a specific open file. For example 2>&1 redirects 2 (standard error) to 1 (standard output); if 1 has been redirected to a file, 2 goes there too. Other file descriptor numbers are assigned sequentially to other open files, or can be explicitly referenced in the shell scripts. Some of the forms of redirection for the Bourne shell family are:

Character	Action
>	Redirect standard output
2>	Redirect standard error
2>&1	Redirect standard error to standard output
<	Redirect standard input
\|	Pipe standard output to another command
>>	Append to standard output
2>&1\|	Pipe standard output and standard error to another command

Note that < and > assume standard input and output, respectively, as the default, so the numbers 0 and 1 can be left off. The form of a command with standard input and output redirection is:

$ command -[options] [arguments] < input file > output file

Examples:

$ who > names

Direct standard output to a file named names

$ (pwd; ls -l) > out

Direct output of both commands to a file named out

$ pwd; ls -l > out

Direct output of ls command only to a file named out

Input redirection can be useful if you have written a program which expects input from the terminal and you want to provide it from a file. In the following example, myprog, which was written to read standard input and write standard output, is redirected to read myin and write myout.

$ myprog < myin > myout

You can suppress redirected output and/or error by sending it to the null device, /dev/null. The example shows redirection of standard error only:

$ who 2> /dev/null

To redirect standard error and output to different files (note that grouping is not necessary in Bourne shell):

$ cat myfile > myout 2> myerror

A. Bash and other modern shell provides I/O redirection facility. There are 3 default standard files (standard streams) open:

[a] stdin - Use to get input (keyboard) i.e. data going into a program.

[b] stdout - Use to write information (screen)

[c] stderr - Use to write error message (screen)

Understanding I/O streams numbers

The Unix / Linux standard I/O streams with numbers:

Handle	Name	Description
0	stdin	Standard input
1	stdout	Standard output
2	stderr	Standard error

Redirecting the standard error stream to a file

The following will redirect program error message to a file called error.log:

$ program-name 2> error.log

$ command1 2> error.log

Redirecting the standard error (stderr) and stdout to file

Use the following syntax:

$ command-name &>file

$ command > file-name 2>&1

Another useful example:

# find /usr/home -name .profile 2>&1 | more

Redirect stderr to stdout

Use the command as follows:

$ command-name 2>&1

mod_rewrite Cheat Sheet

Source:
http://www.cheatography.com/davechild/cheat-sheets/mod-rewrite/

mod_rewrite Tutorials

http://httpd.apache.org/docs/current/rewrite/

http://www.addedbytes.com/for-beginners/url-rewriting-for-beginners/

http://net.tutsplus.com/tutorials/other/a-deeper-look-at-mod_rewrite-for-apache/

mod_rewrite RewriteRule Flags

C	Chained with next rule
CO=cookie	Set specified cookie
E=var:value	Set environmental variable “var” to “value”
F	Forbidden (403 header)
G	Gone - no longer exists
H=handler	Set handler
L	Last - stop processing rules
N	Next - continue processing
NC	Case insensitive
NE	Do not escape output
NS	Ignore if subrequest
P	Proxy
PT	Pass through
R[=code]	Redirect to new URL, with optional code (see below)
QSA	Append query string
S=x	Skip next x rules
T=mime-type	Set mime type

mod_rewrite RewriteCond Flags

NC	Case insensitive
OR	Combine with next rule using 'OR' instead of the default of 'AND'

Redirection Header Codes

301	Moved permanently
302	Moved temporarily (default)

mod_rewrite Directives

RewriteEngine

RewriteOptions

RewriteLog

RewriteLogLevel

RewriteLock

RewriteMap

RewriteBase

RewriteCond

RewriteRule

Regular Expressions Syntax

^	Start of string
$	End of string
.	Any single character
(a\|b)	a or b
(...)	Group section
[abc]	In range (a, b or c)
[^abc]	Not in range
\s	White space
a?	Zero or one of a
a*	Zero or more of a
a*?	Zero or more, ungreedy
a+	One or more of a
a+?	One or more, ungreedy
a{3}	Exactly 3 of a
a{3,}	3 or more of a
a{,6}	Up to 6 of a
a{3,6}	3 to 6 of a
a{3,6}?	3 to 6 of a, ungreedy
\	Escape character
[:punct:]	Any punctuation symbol
[:space:]	Any space character
[:blank:]	Space or tab

There's an excellent regular expression tester at: http://regexpal.com/

mod_rewrite Server Variables: HTTP Headers

%{HTTP_USER_AGENT}

%{HTTP_REFERER}

%{HTTP_COOKIE}

%{HTTP_FORWARDED}

%{HTTP_HOST}

%{HTTP_PROXY_CONNECTION}

%{HTTP_ACCEPT}

mod_rewrite Server Variables: Server Internals

%{DOCUMENT_ROOT}

%{SERVER_ADMIN}

%{SERVER_NAME}

%{SERVER_ADDR}

%{SERVER_PORT}

%{SERVER_PROTOCOL}

%{SERVER_SOFTWARE}

Download a PDF of the mod_rewrite cheat sheet!

mod_rewrite Sample Rule: Site Moved

# Site moved permanently

RewriteCond %{HTTP_HOST} ^www.domain.com$ [NC]

RewriteRule ^(.*)$http://www.domain2.com/$1 [R=301,L]

Rewrites domain.com to domain2.com

mod_rewrite Sample Rule: Temporary Page Move

# Page has moved temporarily

RewriteRule ^page.html$ new_page.html [R,NC,L]

Rewrites domain.com/page.html to domain.com/new_page.html

mod_rewrite Sample Rule: Nice URLs

# Nice URLs (no query string)

RewriteRule ^([A-Za-z0-9-]+)/?$ categories.php?name=$1 [L]

Rewrites domain.com/category-name-1/ to domain.com/categories.php?name=category-name-1

mod_rewrite Server Variables: Special

%{API_VERSION}

%{THE_REQUEST}

%{REQUEST_URI}

%{REQUEST_FILENAME}

%{IS_SUBREQ}

%{HTTPS}

mod_rewrite Server Variables: Request

%{REMOTE_ADDR}

%{REMOTE_HOST}

%{REMOTE_PORT}

%{REMOTE_USER}

%{REMOTE_IDENT}

%{REQUEST_METHOD}

%{SCRIPT_FILENAME}

%{PATH_INFO}

%{QUERY_STRING}

%{AUTH_TYPE}

mod_rewrite Server Variables: Time

%{TIME_YEAR}

%{TIME_MON}

%{TIME_DAY}

%{TIME_HOUR}

%{TIME_MIN}

%{TIME_SEC}

%{TIME_WDAY}

%{TIME}

Tech Notes