How to link a network drive into a folder on Windows 7

Have you ever tried to install a software on a network drive or use a network drive as data directory were the software installer checks for the drive type and refuses the installation on network drives? A workaround that helped me in these cases is to use a symlink on Windows. For example, the application wants to put its data in the path C:\ProgramData\appname but you want the data to be stored on the mapped network drive X:\mydata\appname, you can use the following command on the windows commandline to symlink the directorie:

mklink /d "C:\ProgramData\appname" "X:\mydata\appname"

The benefit is, that the application installer detects now C: as valid local harddrive and uses the symlinked path to store its data on the network drive X:\mydata\appname.

The general syntax for the mklink command is:

mklink /d symlinkpath targetdirectory

How to access all system settings, the so called “GodMode”, in Windows 7

The "GodMode" in Windows 7 is a special folder which contains links to all system settings that are available in Windows 7. To Access this function, create a new folder (e.g. on your desktop or home directory) with the following name:

GodMode.{ED7BA470-8E54-465E-825C-99712043E01C}

and save it. If you open this folder, you will get a list of all admin functions of Windows 7, there are also many functions listed that are normally not available in the Windows 7 system settings.

How to fix the spamassassin bug with the FH_DATE_PAST_20XX rule

Since january 1 2010, spamassassin is falsely marking non spam emails as spam due to an error in the regular expression of the FH_DATE_PAST_20XX rule.

Description of the bug:

https://secure.grepular.com/blog/index.php/2010/01/01/spamassassin-2010-bug/

To fix this, run the following command on the shell as root user:

sa-update

If you use the software ISPConfig 2 on your server, run this command:

/home/admispconfig/ispconfig/tools/spamassassin/usr/bin/sa-update

How to renew the SSL certificate for dovecot on CentOS

Make a backup of the old key and certificate file

mv /etc/ssl/certs/dovecot.pem /etc/ssl/certs/dovecot.pem.old
mv /etc/ssl/private/dovecot.key /etc/ssl/private/dovecot.key.old

Create the new SSL certificate

openssl genrsa -out /etc/ssl/private/dovecot.key 1024
openssl req -new -x509 -key /etc/ssl/private/dovecot.key -out /etc/ssl/certs/dovecot.pem -days 730

Restart Dovecot:

/etc/init.d/dovecot restart

Optimize MySQL performance with mysqltuner

The following tutorial describes the steps to optimize the performance of a MySQL database with the mysqltuner script.

Login to your server on the shell, then execute the following commands:

Download the mysqltuner script:

cd /usr/local/bin
wget http://mysqltuner.pl/mysqltuner.pl
chmod +x mysqltuner.pl

Run mysqltuner

/usr/local/bin/mysqltuner.pl

Then enter root as username and the mysql root password.

You will get a output similar to this:

root@v221:/usr/local/bin# /usr/local/bin/mysqltuner.pl

>>  MySQLTuner 1.0.1 - Major Hayden <[email protected]>
>>  Bug reports, feature requests, and downloads at http://mysqltuner.com/
>>  Run with '--help' for additional options and output filtering
Please enter your MySQL administrative login: root
Please enter your MySQL administrative password:

-------- General Statistics --------------------------------------------------
[--] Skipped version check for MySQLTuner script
[OK] Currently running supported MySQL version 5.0.51a-24+lenny2
[!!] Switch to 64-bit OS - MySQL cannot currently use all of your RAM

-------- Storage Engine Statistics -------------------------------------------
[--] Status: +Archive -BDB -Federated +InnoDB -ISAM -NDBCluster
[--] Data in MyISAM tables: 26M (Tables: 215)
[!!] InnoDB is enabled but isn't being used
[!!] Total fragmented tables: 33

-------- Performance Metrics -------------------------------------------------
[--] Up for: 96d 23h 3m 41s (10M q [1.239 qps], 686K conn, TX: 701M, RX: 1B)
[--] Reads / Writes: 44% / 56%
[--] Total buffers: 58.0M global + 2.6M per thread (100 max threads)
[OK] Maximum possible memory usage: 320.5M (12% of installed RAM)
[OK] Slow queries: 0% (20/10M)
[OK] Highest usage of available connections: 33% (33/100)
[OK] Key buffer size / total MyISAM indexes: 16.0M/8.5M
[OK] Key buffer hit rate: 99.9% (57M cached / 30K reads)
[OK] Query cache efficiency: 78.6% (5M cached / 6M selects)
[!!] Query cache prunes per day: 483
[OK] Sorts requiring temporary tables: 0% (0 temp sorts / 408K sorts)
[!!] Temporary tables created on disk: 36% (269K on disk / 745K total)
[OK] Thread cache hit rate: 99% (427 created / 686K connections)
[!!] Table cache hit rate: 2% (64 open / 3K opened)
[OK] Open file limit used: 11% (120/1K)
[OK] Table locks acquired immediately: 99% (3M immediate / 3M locks)

-------- Recommendations -----------------------------------------------------
General recommendations:
Add skip-innodb to MySQL configuration to disable InnoDB
Run OPTIMIZE TABLE to defragment tables for better performance
Enable the slow query log to troubleshoot bad queries
When making adjustments, make tmp_table_size/max_heap_table_size equal
Reduce your SELECT DISTINCT queries without LIMIT clauses
Increase table_cache gradually to avoid file descriptor limits
Variables to adjust:
query_cache_size (> 16M)
tmp_table_size (> 32M)
max_heap_table_size (> 16M)
table_cache (> 64)

The script recommends to adjust or add the following variables in the mysql my.cnf file. The location of my.cnf is normally /etc/my.cnf or /etc/mysql/my.cnf depending on the Linux distribution that is installed on your server.

Open the my.cnf file:

vi /etc/mysql/my.cnf

and increase or set the variables in the [mysqld] section of the file. Mine looks now like this:

[mysqld]
#
# * Basic Settings
#
user            = mysql
pid-file        = /var/run/mysqld/mysqld.pid
socket          = /var/run/mysqld/mysqld.sock
port            = 3306
basedir         = /usr
datadir         = /var/lib/mysql
tmpdir          = /tmp
language        = /usr/share/mysql/english
skip-external-locking
#
# Instead of skip-networking the default is now to listen only on
# localhost which is more compatible and is not less secure.
bind-address            = 127.0.0.1
#
# * Fine Tuning
#
key_buffer              = 16M
max_allowed_packet      = 16M
thread_stack            = 128K
thread_cache_size       = 8
# This replaces the startup script and checks MyISAM tables if needed
# the first time they are touched
myisam-recover          = BACKUP
#max_connections        = 100
table_cache            = 128
#thread_concurrency     = 10
#
# * Query Cache Configuration
#
query_cache_limit       = 1M

query_cache_size        = 32M
tmp_table_sizee        = 64M
max_heap_table_sizee        = 32M

Then save the file and restart mysql. After a few hours, rerun mysqltuner and check again if the values are fine now or if the have to be increased to a higher value.

How to renew the SSL certificate for dovecot on Ubuntu Linux

To create new SSL certificates for the dovecot pop3 and imap server on Ubuntu, follow these steps:

Make a backup copy of the old key and certificate file

sudo cp /etc/ssl/private/dovecot.key /etc/ssl/private/dovecot.key.old
sudo cp /etc/ssl/certs/dovecot.pem /etc/ssl/certs/dovecot.pem.old

Create the new key file

openssl genrsa -out /etc/ssl/private/dovecot.key 1024

Create the new certificate file, valid for 2 years

openssl req -new -x509 -key /etc/ssl/private/dovecot.key -out /etc/ssl/certs/dovecot.pem -days 730

Then restart dovecot

/etc/init.d/dovecot restart

Manage the postfix mailqueue with postsuper, postqueue and mailq

Postfix provides with postsuper, postqueue and mailq some  shell utilitys to manage the mailqueue.

Here are some examples for common tasks:

List all messages that are in the mailqueue

postqueue -p

The output looks like this:

root@server:/# postqueue -p
 -Queue ID- --Size-- ----Arrival Time---- -Sender/Recipient-------
 501CA23B43DB     2182 Thu Dec  3 14:24:39  [email protected]
 (Host or domain name not found. Name service error for name=otherdomain.com type=MX: Host not found, try again)
 [email protected]
-- 8 Kbytes in 1 Requests.

Delete a message by message ID

postsuper -d MessageID

replace MessageID with the ID of the message, e.g. 501CA23B43DB

root@server:/# postsuper -d 501CA23B43DB
 postsuper: 501CA23B43DB: removed
 postsuper: Deleted: 1 message

Remove emails by sender

mailq | tail +2 | awk 'BEGIN { RS = "" }
 # $7=sender, $8=recipient1, $9=recipient2
 { if ($7 == "[email protected]" && $9 == "")
 print $1 }
 ' | tr -d '*!' | postsuper -d -

replace "[email protected]" with the sender email address.

Remove emails by recipient

mailq | tail +2 | awk 'BEGIN { RS = "" }
 # $7=sender, $8=recipient1, $9=recipient2
 { if ($8 == "[email protected]" && $9 == "")
 print $1 }
 ' | tr -d '*!' | postsuper -d -

replace [email protected] with the recipient email address.

Remove emails by sender hostname

mailq | grep senderhostname | awk ‘{ print $1′} | postsuper -d -

replace the word "senderhostname" with the hostname of the email sender.

If your server has very high load and you want to temporarily move all message from the incoming queue to the hold queue, use the command:

postsuper -h ALL

to move the messages back to the incoming queue, use the command:

postsur -r ALL

Instead of the word "ALL" you can also provide a specific message ID to move only one message to or from the hold queue. Message in the hold queue will not processed by postfix until they were requeued with postsuper -r.

The fast magnifying glass for zoom the MAC screen

Want to zoom your MAC screen easy, fast and steplessly?
You only have to keep the CTRL key pressed and use the Mousewheel to zoom in and out.
On new MacBooks you can also use the touchpad with two! fingers up and down to zoom.

Hint: If you don't scroll back to normal view, the screen remains sometimes in a "strange" mode.

Find the .deb package that contains a specific file on Ubuntu or Debian Linux

Sometimes you need to know to which debian or ubuntu package a specific file belongs, e.g. because you deleted a system file and want to reinstall it. There is a handy utility called apt-file which searches for a filename in all debian packages.

Installation

apt-get install apt-file

Usage example

search for the file /etc/sysctl.conf

apt-file search /etc/sysctl.conf

result:

apt-file search /etc/sysctl.conf
procps: /etc/sysctl.conf
mypc:~#

Now we see that the file is part of the debian / ubuntu package with the name "procps".

How does Ubuntu’s screenshot tool Take Screenshot actually work?

The easiest way to make screenshots is to use Take Screenshot. You find it under Applications/Accessoires.
First change the delaytime for the screenshot from 0 to 1 or 2 seconds. This is the time you have to mark the chosen area. You should be fine with 1 second!

Then choose your screenshot option, e.g. Grab the current window. Klick on Take Screenshot and activate the window you need.

takescreenshot

Take Screenshot closes. If all works well, a pop-up comes up to ask where to save the screenshot, which comes a s a .png.

takescreenshot2

For another screenshot you have to open the application again, so put it best in your panel.

The uncommon thing is that you have to run first Take screenshot and then choose an object, and not the other way round. That's it!