The Queen and 11 Presidents!

Queen Elizabeth II head of the Commonwealth and daugher of George VI. She was born on 21 April 1926 and have seen lot of politics and historical acts in her life, because now she is 84! As her father dies in 1952, she become the Queen regnant an met 11 Presidents of United States till now:

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Sending Mails with own Exim: Google account example.

Today I’ll describe short, how to configure sending of emails with your Debian or other Linux distribution. The ability of sending mails is very useful feature for every long-running server machine, it’s easy and common way to notify the administrator on problems.

Here are configurationsteps for mail-sending with Exim and Googlemail account (google Apps accounts work the same way too).

  1. first of all we need working Exim. If not installed – install exim4.
    $ apt-get update
    $ apt-get install exim4
    
  2. Configuration should start after the installation. However you can start configuration of exim every-time with
    $ dpkg-reconfigure exim4-config
    
  3. Answer the questions of configuration wizard. The important one is. a general type of mail configuration. Choose “sent by smarthost” if you wanna use the ability of e.g. Googlemail account. Then SMTP with dynamic IP would be difficult ;)
  4. answer other questions
    • Provide a System Mail Name: e.g. mycompany.com
    • Provide IP addresses to listen on for incoming SMTP connections User 127.0.0.1 if you don’t want only send mail from local machine and nothing for all IP’s.
    • Provide Machine handling outgoing mail for this host (smarthost): smtp.gmail.com::587
    Other parameter are not so important for a start. However read more about debconf questions and other configuration if you like.
  5. Now it’s time to provide credentials information of your gmail account. Therefore you need edit /etc/exim4/passwd.client file with your favorite editor. Insert that for Standard or google app account but replace with valid mail and password.
    gmail-smtp.l.google.com:yourYourMail@googlemail.com:yourPass
    *.google.com:yourYourMail@googlemail.com:yourPass
    smtp.gmail.com:yourYourMail@googlemail.com:yourPass
    
  6. Make sure /etc/exim4/passwd.client belongs to user root and group Debian-exim which is normal so on my Debian. If not, run that command:
    $ chown root:Debian-exim /etc/exim4/passwd.client
    
  7. Actualize the whole configuration with:
    $ update-exim4.conf
    
    Your ‘re done!
Now it’s test it with.
echo "Server Mail Test Message " | mail -s "Just Test" SomeMail@someDomain.org
Watch logs:
$ tail -1000f /var/log/exim4/mainlog
When you see something like this. Everything should vent perfect.
2010-02-14 23:00:26 1NgmVu-0007v8-Kt < = root@mail-server1.mycompany.com U=root P=local S=424
2010-02-14 23:00:28 1NgmVu-0007v8-Kt => testMail@mycompany.org R=smarthost T=remote_smtp_smarthost H=gmail-smtp-msa.l.google.com [72.14.221.109] X=TLS1.0:RSA_ARCFOUR_MD5:16 DN="C=US,ST=California,L=Mountain View,O=Google Inc,CN=smtp.gmail.com"

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Winter amusement – the Russian way

What should young people do at a long, cold, rich of snow and boring winter. A winter like in Magadan town. Here the answer ;)

Never heard of Magadan? Magadan is associated with far far east of Russia. It is associated with cold and people-less places, taiga, beautiful nature and interesting people. Of course this Region is famous for former Soviet GULAGs too.

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SSH tunnel without password

SSH (Secure Shell) allows simple establishment of encrypted and authenticated connection between computers. Today i describe how easy it is do establish such SSH tunnels without using a password. You may need such connections when they have to be opened by daemons (e.g. Cron) without user interaction.

Two words on theory. Password-less connections have to be authenticated at least so strong like the password enabled one, so asymmetric cryptography which enables certificates comes into play.  The clue is to have private and public keys and share your public key with domains which should be able identify you.

So therefore let’s start by generation a needed key-pair.

Generating Keys

It is possible to create key with pass-phrase and without (or empty pass-phrases). I prefer to not use pass phrase because it is asked every-time on later usage of a ssh. Even there are ways to gives the pass-phrase to ssh command, but it is more work, with no significant security benefits. So i do the following statement and do not enter any pass-phrase (just hit enter on question).

$ ssh-keygen -t rsa

This will create RSA key-pair as following files in ~/.ssh directory:

Now public key need to be copied to remote host and has to be added to end of ~/.ssh/authorized_keys file.

Transfer Public keys

The best way to do it is to use ssh-copy-id program which is inside of many linux distributions.
$ ssh-copy-id -i ~/.ssh/id_rsa.pub remote-user@remote-server.org
In that case everything is done automatically and you are ready after that. But if ssh-copy-id is not available, you can copy keys manually e.g. like that.
$ cat ~/.ssh/*.pub | ssh remote-user@remote-server.org 'umask 077; cat >>.ssh/authorized_keys'
Attention! On some linux distrs SSH2 searches for keys in ~/.ssh/authorized_keys2 . Not so in actual Debian (Lenny), but seems to be so in SuSe linux.

Test

Now remote login, scp and sftp can be used without password. Test it:
# establish connection
$ ssh remote-user@remote-server.org
#or copy files secure and password-less.
$ scp /home/user/some-file remote-user@remote-server.org:/some-path/dir/
More information on SSH related man pages.
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JBoss 5 GA on Debian linux

This short tutorial describes how to configure JBoss Application Server (Jboss GA 5.1.0) on a debian linux (Debian GNU/Linux 5.x “Lenny” ). Article starts with installation of java JDK and continues with JBoss installation and basic configuration according to standard  file system hierarchy. Also init.d. scripts configuration is given here.

Installing Java SDK

Nowadays  installing Java environment on Debian is an easy task. I used JDK 1.6. Don’t confound JDK with JRE, because bare Java Runtime Environment is not enough for running JBoss. Debian Wiki maintains (hope) a list of available java .deb packages, which are easily can be installed with your preferred way. I prefer aptitude, but apt-get of course works too.
$ aptitude install sun-java6-jdk
#or by good old apt-get.
$ apt-get install sun-java6-jdk
Installation is done after seconds. Now test your java installation with
$ java -version
# Here example result on my configuration:

java version "1.6.0_12"
Java(TM) SE Runtime Environment (build 1.6.0_12-b04)
Java HotSpot(TM) 64-Bit Server VM (build 11.2-b01, mixed mode)

If you get something like this, you’re done and your java should be already in the PATH.

Installing JBoss AS

Now let’s install  JBoss Application Server.

Preparing

Normally you are not willing  to start services (especially when they are accessed from outher machines) with root privileges. Therefore we have to define new user and group which will be used to manage JBoss.  So next line will create new group and new user with this group.
 $ groupadd jboss
 $ useradd -s /bin/bash -d /home/jboss -m -g jboss jboss
This jboss user has no password, so nobody can login with this username. If you consider to  login with jboss user,  password has to be set. Use passwd jboss command for that.

Download, Installation,  filesystem layout

Now  download desired Jboss version. I started with JBoss 5.1.0 GA, which can be download with:
$ cd /tmp # swithch to temp dir
$ wget http://sourceforge.net/projects/jboss/files/JBoss/JBoss-5.1.0.GA/jboss-5.1.0.GA.zip/download
Check also the whole list of verisons if interested. As you may noticed JBoss binaries are packaged with ZIP. So it is comfortable to use unzip tool. Maybe you have to install it first. But before you extract  downloaded file, we have to decide, where exactly should JBoss files be placed on a  file-system. Unfortunately JBoss is not quite conform to Linux File System Hierarchy Standard per default, so there are many possibilities for a location configuration. Some of you may want to place JBoss  into /opt directory. But I prefer to split the installation a little bit and  want to start by putting  JBoss core files in /usr/local/, where local, unchangeable and read-only files usually placed. E.g. I use  /usr/local/jboss/510 as JBoss 5.1.0 GA root.  So let’s create that location and extract files into it.
mkdir /usr/local/jboss #create new jboss directroy
chown jboss:jboss /usr/local/jboss #now its belongs touser jboss and group jboss
su jboss
mkdir /usr/local/jboss/510
cd /usr/local/jboss/510
unzip /tmp/jboss-5.1.0.GA.zip
At this moment you should have new working JBoss. If you want, test it with
bin/run.sh -b 0.0.0.0
Where -b 0.0.0.0 means that JBoss is listening for every ip address of current machine. However at this stage the installed Jboss still brakes the  Linux Filesystem Hierarchy Standard, so let’s improve this situation.
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Software RAID on Debian Linux

Wow, my last post here is month ago. But don’t worry I did not forget about my blog. There are just many thing happened in my life, all of them are time consuming :) So there no reason to remove me from your RSS reader. Today i will share some thought on software RAID under linux with you.
RAID 1

RAID 1

Sometimes you need to store data relative save and high available. That is where RAID solutions come in to play. Especially RAID 1 (mirroring) based solutions provide better availability of your data. But don’t forget to use backs anyway :) Some days ago i installed RAID 1 on Debian Lenny (amd64 arch) without any troubles for now. I just was following Jerry’s description which is enough detailed to make no mistakes except maybe one thing. The Partitions used in the RAID /dev/md0/ should both enable boot flag if you want to boot from RAID. This is worked for me.

Configuration

My configuration is the same as Jerry’s except partition sizes and chosed LVM. So boot is done form RAID partition /dev/md0. And SWAP is on RAID too, which is controversy solution but it the best one for me, of course availability of a system is primary goal. So how to check the state of raid after installation. The simplest is to look on /proc file-system with $cat /proc/mdstat. Here is my configuration.
$cat /proc/mdstat
Personalities : [raid1]
md1 : active raid1 sda2[0] sdb2[1]
476560128 blocks [2/2] [UU]

md0 : active raid1 sda1[0] sdb1[1]
497856 blocks [2/2] [UU]

unused devices: <none>
Here you see two RAID arrays md0 and md1. Also information about used devices and state are peresent. [UU] stand for “used” for every disc is used in a raid. On diskfailure you wold see something like [U_] and sdb2(F). Next example utilizes mdadm which is used by kernel in latest kernel versions. My is 2.6.26-2-amd64 (lenny default) Use of –detail or -D option with a device name gives more information. Here my example.
# mdadm --detail /dev/md1
/dev/md1:
Version : 00.90
Creation Time : Wed Jan  6 00:51:37 2010
Raid Level : raid1
Array Size : 476560128 (454.48 GiB 488.00 GB)
Used Dev Size : 476560128 (454.48 GiB 488.00 GB)
Raid Devices : 2
Total Devices : 2
Preferred Minor : 1
Persistence : Superblock is persistent

Update Time : Mon Jan 11 02:18:01 2010
State : clean
Active Devices : 2
Working Devices : 2
Failed Devices : 0
Spare Devices : 0

UUID : fe3bbbfd:2c6963e7:9785a408:be715448
Events : 0.8

Number   Major   Minor   RaidDevice State
0       8        2        0      active sync   /dev/sda2
1       8       18        1      active sync   /dev/sdb2

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Eclipse Ganymede and WSCompile incompatibility?

I found strange problem with WSCompile-1.6 task in Ganymede release of Eclipse (Version 3.4.1). The problem lies in WSCompile-Ant-Task. Buildscript execution freezes on the wscompile task. I describe that problem more detailed on techjava.de Please feel free to comment here or there if you know what died changed in Ganymede in ant scripts handling since Europe release and how to fix it.
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Extracting tar, gzip, bzip2, z

tar-gzip Sometimes you need to extract some files on Linux console. Here  some examples how to do that.

tar

Tar archives are the most common way of distributing bundles of files under Linux or UNIX. A .tar file is simply a bundle of files packaged with GNU tar program. To extract such files use following:
tar xf somearchive.tar
tar xvf somearchive.tar
Before extracting you may be interested in Looking inside of tar. Do it with option “t:
tar tf archive.tar
For more tar parameters see Man pages.

gzip

Often tar-files are also compressed. One of the most known compressed formats is GNU Zip (gzip).  Tar bundeld and zipped file would  normally  have extension .tar.gz. To extract such files you can use tar with  “z” option, which causes tar to automatically invoke gzip. Modify abow example  and you get able to extract tar.gz  files too.
tar -xzf somearchive.tar.gz
In old tar version the “z” option is may be not available. In that case just use UNIX pipes:
gzip -dc target.tar.gz | tar xf -
Meaning of gzip options You will find more on Man pages.

bzip2

Sometimes you can find files ending with .tar.bz2. That are files packaged with bzip (a block-sorting file compressor). Use it like gzip
tar xjvf filename.tar.bz2
Options d,c,t have the same meaning. More on Man pages.

zcat

Some files have .tar.Z endings. They can be extracted by
zcat somearchive.tar.Z | tar xf -
Look in Man pages for more. Any questions? You are welcome to comment!
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