Java Quick RegEx Matching

Suppose you want to match something in Java such as the average time from a ping output:

Pinging steamr.com [64.22.123.253] with 32 bytes of data:
Reply from 64.22.123.253: bytes=32 time=100ms TTL=53
Reply from 64.22.123.253: bytes=32 time=100ms TTL=53
Reply from 64.22.123.253: bytes=32 time=101ms TTL=53
Reply from 64.22.123.253: bytes=32 time=100ms TTL=53

Ping statistics for 64.22.123.253:
    Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
    Minimum = 100ms, Maximum = 101ms, Average = 100ms

You would want to do something like:

Pattern pingPattern = Pattern.compile(".*Minimum = [0-9]+ms, Maximum = [0-9]+ms, Average = ([0-9]+)ms.*", Pattern.DOTALL);
Matcher pingMatch   = pingPattern.matcher(pingOutput);

if (pingMatch.matches()) {
	averagePing = Integer.parseInt(pingMatch.group(1));
}

Note that the ‘.’ in the pattern does not by default match new lines or return carriages. The Pattern.DOTALL is needed so that ‘.’ accepts everything. RTFM for more info.

Solving “Error occurred during initialization of VM” on a VPS

After installing java (via yum) on a VPS, running java results in:

Error occurred during initialization of VM
Could not reserve enough space for object heap
*** glibc detected *** java: double free or corruption (out): 0x0000000041040f30 ***
======= Backtrace: =========
/lib64/libc.so.6[0x2afe08ed12ef]
/lib64/libc.so.6(cfree+0x4b)[0x2afe08ed173b]
/usr/lib/jvm/java-1.6.0-openjdk-1.6.0.0.x86_64/jre/lib/amd64/server/libjvm.so[0x2afe0978cbb4]
/usr/lib/jvm/java-1.6.0-openjdk-1.6.0.0.x86_64/jre/lib/amd64/server/libjvm.so[0x2afe0978cd78]
/usr/lib/jvm/java-1.6.0-openjdk-1.6.0.0.x86_64/jre/lib/amd64/server/libjvm.so[0x2afe09791733]
/usr/lib/jvm/java-1.6.0-openjdk-1.6.0.0.x86_64/jre/lib/amd64/server/libjvm.so(JNI_CreateJavaVM+0x74)[0x2afe0950eb14]
java(JavaMain+0x96)[0x4026c6]
/lib64/libpthread.so.0[0x2afe08841617]
/lib64/libc.so.6(clone+0x6d)[0x2afe08f32c2d]
======= Memory map: ========

This can be solved by running:

export _JAVA_OPTIONS="-Xms20m -Xmx64m -XX:MinHeapFreeRatio=20 -XX:MaxHeapFreeRatio=40 -XX:NewSize=10m -XX:MaxNewSize=10m -XX:SurvivorRatio=6 -XX:TargetSurvivorRatio=80 -XX:+CMSClassUnloadingEnabled -XX:+CMSPermGenSweepingEnabled"

Or placing it in the bashrc file.

Note: You will need to change the Xms (initial java heap size), Xmx (maximum java heap size) above depending on the amount of free memory your container has. See addendum II


Addendum I actually attempted to run this in a OpenVZ VPS. There is absolutely no hope in getting java to run under OpenVZ unless you have a lot of guaranteed memory. If you really need to get java working in your VPS, try to get a Xen or vmware based VPS.


Addendum II I got java to run on an openVZ container with 256 MB guaranteed ram using the following java arguments:

-Xms8m -Xmx16m -Xss4m

However, upon creating threads and executing commands, java failed immediately with cannot fork memory messages.

I just got a XEN 128MB / 256MB swap VPS and it ran the same java application without a single problem. I didn’t even need those arguments.

Logging in via SSH keys

Let user@ServerA be the host that wants to connect to user@ServerB.

Run the following commands as user@ServerA

ssh-keygen -t rsa          # use empty pass phrase, save the keys to ~/.ssh/id_rsa and ~/.ssh/id_rsa.pub
chmod 700 ~/.ssh           # set the permissions of the .ssh directory to 700.
chmod 600 ~/.ssh/*         # set the permissions of the keys so no one else can read them.

It’s important to set the permissions! Otherwise SSH will not use the keys without a warning or message. I’ve wasted enough time to learn this the hard way.

Copy the ~/.ssh/id_rsa.pub from user@ServerA to user@ServerB:~/.ssh/authorized_keys. Again, set the permissions.

chmod 700 ~/.ssh         # set the permissions of the .ssh directory to 700.
chmod 600 ~/.ssh/*       # set the permissions of the keys so no one else can read them.

Compiling & Installing vnstat-1.10

Run the following commands to install vnstat. This will also configure vnstat to listen on eth0 and start automatically on boot.

This was done in CentOS5.4, but it should also work for any *NIX based machines.

Note: You may want to check on the vnstat website for the latest build. At the time of this writing, the latest version is 1.10.
Note2: The following example will configure vnstat on eth0; You may want to change this if you are on a OpenVZ VPS to venet0.

wget http://humdi.net/vnstat/vnstat-1.10.tar.gz
tar -xzf vnstat-1.10.tar.gz
cd vnstat-1.10
make
make install
vnstat --testkernel
/bin/cp examples/init.d/centos/vnstat /etc/init.d/vnstat
ln -s /etc/init.d/vnstat /etc/rc3.d/S40vnstat
vnstat -u -i eth0
/etc/init.d/vnstat start

Compiling PHP with LiteSpeed (with lsapi)

Compiling PHP with litespeed using LiteSpeed 4.10 SAPI.

You must download the latest PHP package and the litespeed sapi package to the /root directory, then run the following commands.
You may wish to change the config settings as needed.

Note: Litespeed was installed in /opt/lsws. You will want to change the prefix accordingly.

cd /root
tar -xjf php-5.3.2.tar.bz2
cd php-5.3.2
cd sapi
tar -xzf /root/php-litespeed-4.10.tgz
cd ..
touch ac*
./buildconf --force

./configure --prefix=/opt/lsws/lsphp5 --with-litespeed --with-config-file-path=/etc/ --with-gd --enable-shmop --enable-track-vars --enable-ftp --enable-sockets --enable-exif --enable-zip --enable-sysvsem --with-zlib --enable-sysvshm --enable-magic-quotes --with-jpeg-dir --with-png-dir --enable-mbstring --enable-embedded-mysqli=shared --with-curl --with-mysql=/opt/mysql --with-mysqli=/opt/mysql/bin/mysql_config --with-mcrypt
make
make install

/etc/init.d/lsws stop
sleep 5
/bin/cp sapi/litespeed/php /opt/lsws/fcgi-bin/lsphp
/etc/init.d/lsws start

Note: The ‘sleep 5’ statement is not necessary if you do these steps manually. It is added so the copy operation immediately after is successful. Otherwise, litespeed might still be running which will cause the copy operation to fail.

Compiling MySQL with Sphinx

The following commands were used to compile MySQL 5.1.43 with Sphinx 0.9.9. This will install it in /opt.  You may want to change the prefix accordingly.

Download the proper packages and following the following commands.

Note: For some reason, MySQL > 5.1.43 gives a “LT_INIT: command not found” error when compiling. Although it seems like it has something to do with autoconf < 2.2, this was ‘resolved’ by using an older release (5.1.43 instead of 5.1.44) at the time of this writing.

When configuring MySQL, if configure complains about something about no Sphinx, delete the entire MySQL source directory and try again from scratch.

Note: You should already have the following packages installed: libtermcap-devel libgcc-c++ libtool gcc make autoconf g++ gcc-c++

cd /root
tar -xzf mysql-5.1.43.tar.gz
tar -xzf sphinx-0.9.9.tar.gz

You may want to ignore this step if you do not want to compile sphinx with mysql.

cd mysql-5.1.43
cp -R ../sphinx-0.9.9/mysqlse/ storage/sphinx
sh BUILD/autorun.sh

Configure MySQL and compile as usual

./configure --prefix=/opt/mysql --with-unix-socket-path=/opt/mysql/mysql.sock --without-man --enable-shared  --without-debug --enable-assembler --with-ssl --with-plugins=sphinx CFLAGS=-O3 'CXXFLAGS=-O3 -fno-exceptions -felide-constructors -fno-rtti' CXX=gcc
make
make install

Setting up MySQL configuration and the initial database.

/bin/cp /root/my.cnf /etc/my.cnf
/bin/cp support-files/mysql.server /etc/init.d/mysql
chmod 755 /etc/init.d/mysql
ln -s /etc/init.d/mysql /etc/rc3.d/S40mysql
/bin/cp support-files/my-medium.cnf /etc/my.cnf
/usr/sbin/useradd mysql
cd /opt/mysql
chown -R mysql .
chgrp -R mysql .
bin/mysql_install_db --user=mysql
chown -R root .
chown -R mysql var
bin/mysqld_safe --user=mysql &
chown mysql /opt/mysql

Set the lib paths of MySQL so the libmysqlclient.so or whatever else libraries can be found. This is required when attempting to compile anything that requires MySQL (including sphinx).

echo "/opt/mysql/lib/mysql" > /etc/ld.so.conf.d/mysql.conf
ldconfig

Now that MySQL is done, we will compile Sphinx.

cd /root
cd sphinx-0.9.9
./configure --prefix=/opt/sphinx --with-mysql
make
make install

Post install steps:

/bin/cp /root/sphinx.conf /opt/sphinx/etc/sphinx.conf
cp contrib/scripts/searchd /etc/init.d/
chmod 777 /etc/init.d/searchd
ln -s /etc/init.d/searchd /etc/init.d/S55searchd

Setting up BIND on CentOS

The following steps were used to setup BIND using yum on CentOS 5.4. Assume the hostname is titan.steamr.com.
At the time of this writing, the yum repo had BIND 9.3

Step 1: Install the necessary packages:

yum -y install bind bind-libs bind-utils

Step 2: Create a new file /etc/named.conf with the following contents. Change titan.steamr.com for the hostname.
vi /etc/named.conf

options
{
     directory "/var/named"; // the default
};

zone "localhost" {
     type master;
     file "localhost.zone";
};

zone "titan.steamr.com" {
     type master;
     file "titan.steamr.com.zone";
};

Step 3: Create a new file /etc/named/localhost.zone with the following contents:

$TTL    86400
@               IN SOA  @       root (
                                        42              ; serial (d. adams)
                                        3H              ; refresh
                                        15M             ; retry
                                        1W              ; expiry
                                        1D )            ; minimum

                IN NS           @
                IN A            127.0.0.1
                IN AAAA         ::1

Step 4: Create a new file /etc/named/titan.steamr.com.zone with the following contents: (Change titan.steamr.com with your hostname)

$TTL    86400
titan.steamr.com.       14400   IN SOA  tns1.steamr.com root (
                                        20110000        ; serial (d. adams)
                                        3H              ; refresh
                                        15M             ; retry
                                        1W              ; expiry
                                        1D )            ; minimum

titan.steamr.com.       14400   IN NS           tns1.steamr.com
titan.steamr.com.       14400   IN NS           tns2.steamr.com
titan.steamr.com.       14400   IN A            67.215.230.73
localhost               14400   IN A            127.0.0.1
www                     14400   IN CNAME        titan.steamr.com
ftp                     14400   IN CNAME        titan.steamr.com

Step 5: Start BIND via /etc/init.d/named start

Step 6: Make BIND start on startup mv /etc/rc3.d/K87named S87named

Step 8: To add other DNS entries, append

zone "new.host.com" {
     type master;
     file "new.host.com.zone";
};

and create a new zone file /var/named/new.host.com.zone with something like the contents in step 4.

You will want to reload BIND once you add a new entry by running /etc/init.d/named reload