Oracle Linux - Short Tip 7 - find inode number of file

Everything Linux is storing as a file is done based upon a model that makes use of inodes. The inode is a data structure in a Unix-style file system that describes a filesystem object such as a file or a directory. Each inode stores the attributes and disk block location(s) of the object's data. Filesystem object attributes may include metadata (times of last change, access, modification), as well as owner and permission data. In some cases it can be very convenient to know what the inode ID is for a specific file. you can find the inode number by using the ls command or the stat command as an example.

below you can see the ls command where we extend the ls -l with i to esure we have the inode information we need.

[vagrant@ce log]$ ls -li
total 128
1835019 -rw-r--r--  1 root root   1694 Apr 19 12:04 boot.log
1835122 -rw-------  1 root utmp      0 Apr 19 13:10 btmp
1835323 -rw-------. 1 root utmp      0 Mar 28 10:28 btmp-20170419
1835124 -rw-------  1 root root      0 Apr 28 18:21 cron
1835030 -rw-------  1 root root    250 Apr 19 12:04 cron-20170419
1835108 -rw-------  1 root root      0 Apr 19 13:10 cron-20170428
1835015 -rw-r--r--  1 root root  27726 Apr 19 12:04 dmesg
1835022 -rw-r--r--. 1 root root      0 Mar 28 10:28 dmesg.old
1837835 -rw-r--r--. 1 root root      0 Mar 28 10:28 dracut.log
1835316 -rw-r--r--. 1 root root 146292 Apr 30 12:56 lastlog
1970601 drwxr-xr-x. 2 root root   4096 Mar 28 10:28 mail
1835125 -rw-------  1 root root      0 Apr 28 18:21 maillog
1837833 -rw-------. 1 root root    181 Apr 19 12:04 maillog-20170419
1835118 -rw-------  1 root root      0 Apr 19 13:10 maillog-20170428
1835126 -rw-------  1 root root    789 Apr 30 12:54 messages
1837831 -rw-------. 1 root root  38625 Apr 19 13:10 messages-20170419
1835119 -rw-------  1 root root   5362 Apr 28 18:17 messages-20170428
1837825 drwxr-xr-x. 2 ntp  ntp    4096 Feb  6 05:58 ntpstats
1835130 -rw-------  1 root root      0 Apr 28 18:21 secure
1837832 -rw-------. 1 root root   6740 Apr 19 12:20 secure-20170419
1835120 -rw-------  1 root root      0 Apr 19 13:10 secure-20170428
1835131 -rw-------  1 root root      0 Apr 28 18:21 spooler
1835031 -rw-------  1 root root      0 Apr 19 12:04 spooler-20170419
1835121 -rw-------  1 root root      0 Apr 19 13:10 spooler-20170428
1835302 -rw-------. 1 root root      0 Mar 28 10:28 tallylog
1835128 -rw-r--r--. 1 root root      0 Mar 28 10:28 vboxadd-install.log
1835129 -rw-r--r--. 1 root root     73 Apr 19 12:04 vboxadd-install-x11.log
1835057 -rw-r--r--. 1 root root      0 Mar 28 10:28 VBoxGuestAdditions.log
1835321 -rw-rw-r--. 1 root utmp   6912 Apr 30 12:56 wtmp
1835028 -rw-------. 1 root root     64 Apr 19 12:13 yum.log
[vagrant@ce log]$

Another example of how to get the inode number is by using the stat command. The below example shows how we use stat on the boot.log file in Oracle Linux to get the inode number and other information.

[vagrant@ce log]$ stat /var/log/boot.log 
  File: `/var/log/boot.log'
  Size: 1694       Blocks: 8          IO Block: 4096   regular file
Device: fb01h/64257d Inode: 1835019     Links: 1
Access: (0644/-rw-r--r--)  Uid: (    0/    root)   Gid: (    0/    root)
Access: 2017-04-19 12:04:01.517000000 +0000
Modify: 2017-04-19 12:04:05.524262651 +0000
Change: 2017-04-19 12:04:05.524262651 +0000
[vagrant@ce log]$

Oracle Linux - Install maven with yum

When developing Java in combination with Maven on Oracle Linux you most likely want to install Maven with a single YUM command. The issue you will be facing is that Oracle is not by default providing maven in the YUM repository for Oracle Linux. The escape for this is to make use of the Fedora YUM repository. This means that you have to ensure that you add a Fedora repository to your list of YUM repositories.

As soon as you have done so you can make use of a standard YUM command to take care of the installation.

The below steps showcase how you can add the yum repository from repos.fedorapeople.org and after that you can execute the yum install command

wget http://repos.fedorapeople.org/repos/dchen/apache-maven/epel-apache-maven.repo -O /etc/yum.repos.d/epel-apache-maven.repo

yum install -y apache-maven

This should result in the installation of Maven on your Oracle Linux instance and should enable to you to start developing on Oracle Linux with Maven. To check if the installation has gone correctly you can execute the below command which will show you the information on the version of Maven.

[root@localhost tmp]#
[root@localhost tmp]# mvn --version
Apache Maven 3.3.9 (bb52d8502b132ec0a5a3f4c09453c07478323dc5; 2015-11-10T16:41:47+00:00)
Maven home: /usr/share/apache-maven
Java version: 1.8.0_121, vendor: Oracle Corporation
Java home: /usr/java/jdk1.8.0_121/jre
Default locale: en_US, platform encoding: UTF-8
OS name: "linux", version: "4.1.12-61.1.28.el6uek.x86_64", arch: "amd64", family: "unix"
[root@localhost tmp]#
[root@localhost tmp]#

Oracle Linux - Download Java JDK with wget

When working with Oracle Linux it might very well be that you do not have a graphical user interface. In case you need to download something most commonly you will be using wget or curl. In most cases that works perfecty fine, in some cases however this is not working as you might expect. One of the issues a lot of people complain about is that they want to download the java JRE or Java JDK from the Oracle website using wget or curl. When executing a standard wget command however they run into the issue that the response they get is not the rpm (or package) they want. Instead the content of the file is html.

Reason or this is that the page that controls the download works with cookies that force you to accept the license agreement prior to downloading. As you most likely will not have a graphical user interface you cannot use a browser to download it.

This holds that we need to trick the Oracle website in believing we have clicked the button to agree with the license agreement and serve the file instead of html code. The command you can use for this is shown below:

wget --no-check-certificate --no-cookies --header "Cookie: oraclelicense=accept-securebackup-cookie" http://download.oracle.com/otn-pub/java/jdk/8u121-b13/e9e7ea248e2c4826b92b3f075a80e441/jdk-8u121-linux-x64.rpm

We now instructed wget to send a header which states "Cookie: oraclelicense=accept-securebackup-cookie". This is the response needed by Oracle to serve the rpm file itself.

Now you can install the JDK by making use of the rpm -ivh command. This should ensure you have it installed on your Oracle Linux system.As a check you can execute the below version which should tell you exactly what is now installed on the system:

[root@localhost tmp]#
[root@localhost tmp]# java -version
java version "1.8.0_121"
Java(TM) SE Runtime Environment (build 1.8.0_121-b13)
Java HotSpot(TM) 64-Bit Server VM (build 25.121-b13, mixed mode)
[root@localhost tmp]#
[root@localhost tmp]#

Oracle Linux - use Vagrant to run Oracle Linux 6 and 7

Vagrant is an open-source software product build by HashiCorp for building and maintaining portable virtual development environments. The core idea behind its creation lies in the fact that the environment maintenance becomes increasingly difficult in a large project with multiple technical stacks. Vagrant manages all the necessary configurations for the developers in order to avoid the unnecessary maintenance and setup time, and increases development productivity. Vagrant is written in the Ruby language, but its ecosystem supports development in almost all major languages.

As part of the Vagrant ecosystem people can create Vagrant boxes and share them with others. We already have seen companies package solutions in virtual images to be used to provide customers with showcases of a working end-to-end solution. Even though this is a great way of sharing standard images of an operating systems including packaged products vagrant is more ented to provide custom images, boxes, to be used by developers for example.

Oracle Linux is already available within the vagrant boxes shared by the community. You can search for boxes in Atlas from Hashicorp build upon Oracle Linux in combination with Oracle Virtualbox. Even though that is great news, it has now improved with Oracle also providing official vagrant boxes from the Oracle website.

At this moment you can download official Oracle Linux boxes from yum.oracle.com/boxes for Oracle Linux 7.3, 6.8 and 6.9.

As an example of how to get started the below commands show the process to get a running Oracle Linux 6.8 box on a macbook with vagrant already installed.

Step 1 Download the box and add it to vagrant

vagrant box add --name ol6 http://yum.oracle.com/boxes/oraclelinux/ol68/ol68.box

Step 2 Initialize the box (in a directory where you want it)

vagrant init ol6

Step 3 start the vagrant box (virtualbox)

vagrant up

Step 4 Login to the virtual machine.

vagrant ssh

For those who like to see a short screencast, you can watch the below screencast of the process.

We have not shown the process of installing vagrant itself, you can find the instructions of how to install Vagrant on your local machine on the vagrant website. Having vagrant on your local machine will help you to speed up the rapid prototyping of new ideas without the need to install and re-install a virtual machine every time.

Having your own private vagrant boxes within an enterprise and provide them to your developers to enable them to work with virtual machines that match the machines you will deploy in your datacenter will speed up the process for developers and removes the time needed to install and re-install virtual machine. Making sure developers can focus on what they want to focus on, developing solutions and coding.

Oracle Linux - Install Neo4j

Neo4j is a graph database  a graph database is a database that uses graph structures for semantic queries with nodes, edges and properties to represent and store data. A key concept of the system is the graph (or edge or relationship), which directly relates data items in the store. The relationships allow data in the store to be linked together directly, and in many cases retrieved with one operation.

This contrasts with conventional relational databases, where links between data are stored in the data, and queries search for this data within the store and use the join concept to collect the related data. Graph databases, by design, allow simple and fast retrieval of complex hierarchical structures that are difficult to model in relational systems. Graph databases are similar to 1970s network model databases in that both represent general graphs, but network-model databases operate at a lower level of abstraction and lack easy traversal over a chain of edges.

When developing an solution which is heavily depending on the relationship between data points the choice for a graph database such as Neo4j is a good choice. Examples of such an application can be for example a solution where you need to gain insight in the relationships between historical events, the relationship between people and actions or the relationship between events in a complex system. The last might be an alternative way for logging in a distributed microservice architecture based solution.

Install Neo4j on Oracle Linux
For those who like to setup Neo4j and get started with it to explore the options it might give you company, the below short set of instructions shows how to setup Neo4j on Oracle Linux. For those who use RedHat, the instructions below will most probably also work on RedHat Linux. However, the installation is done and tested on Oracle Linux.

First thing we need to do is to ensure we are able to use yum for the installation of Neo4j on our system. Other ways of obtaining Ne04j are also available and can be used however the yum way of doing things is the most easy way and provides the quickest result. An word of caution, Neo4j currently states that the yum based installation is experimental, we have  however not found any issue while using yum.

To ensure we have the gpg key associated with the Ne04j yum repository we have to import it, shown below is an example of how you can download the key.

[root@oracle-65-x64 tmp]#
[root@oracle-65-x64 tmp]# wget http://debian.neo4j.org/neotechnology.gpg.key
--2017-04-02 13:14:07--  http://debian.neo4j.org/neotechnology.gpg.key
Resolving debian.neo4j.org... 52.0.233.188
Connecting to debian.neo4j.org|52.0.233.188|:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: 4791 (4.7K) [application/octet-stream]
Saving to: “neotechnology.gpg.key”

100%[===========================================>] 4,791 --.-K/s   in 0.005s 

2017-04-02 13:14:08 (1.01 MB/s) - “neotechnology.gpg.key” saved [4791/4791]
[root@oracle-65-x64 tmp]#

As soon as we have obtained the key by downloading it from the Neo4j download location we can import the key by using the import option from the rpm command as shown below:

[root@oracle-65-x64 tmp]#
[root@oracle-65-x64 tmp]# rpm --import neotechnology.gpg.key
[root@oracle-65-x64 tmp]#

Having the key will help validate the packages we download from the Neo4j repository on our Oracle Linux machine to be installed. We do however have to ensure yum is able to locate the Neo4j repository. This is done by adding a repo file to the yum repository directory. Below is shown how the repository is added to the yum configuration, this command will create the file neo4j.repo in /etc/yum./repos.d where yum can locate it and use it include the repository as a valid repository to search packages.

cat <<EOF> /etc/yum.repos.d/neo4j.repo
[neo4j]
name=Neo4j Yum Repo
baseurl=http://yum.neo4j.org/stable
enabled=1
gpgcheck=1
EOF

Having both the key and the repository present on your system will enable you to use yum for the installation of Neo4j. This means you can now use a standard yum command to install Neo4j on Oracle Linux, an example of the command is shown below.

[root@oracle-65-x64 tmp]#
[root@oracle-65-x64 tmp]# yum install neo4j

This should ensure you have Neo4j installed on your Oracle Linux instance.

Configuring Neo4j
As soon as you have completed the installation a number of tasks needs to be executed to ensure you have a proper working Neo4j installation.

By default NEo4j will not allow external connections to be made. This means that you can only connect to Neo4j by using the 127.0.0.1 address for the localhost. Even though this might very well be enough for a development or local test environment this is not what you want when deploying a server. It will be required that the Neo4j instance is also accessible from the outside world. This requires a configuration change to the Neo4j configuration file. The standard location for the configuration file, when Neo4j is deployed on an Oracle Linux machine, is /etc/neo4j . In this location you will notice the neo4j.conf file which holds all the configuration data for the Neo4j instance.

By default the below lines is commented out. Ensure you uncomment the line, this should ensure that Neo4j will accept non-local connections:

dbms.connectors.default_listen_address=0.0.0.0

Additionally your want Neo4j to starts during boot. For this you will have to ensure Neo4j is registered as a servic and activate. You can do so by executing the below command:

[root@oracle-65-x64 tmp]#
[root@oracle-65-x64 tmp]# chkconfig neo4j on

Now NEo4j should be registered as a service that will start automatically when the machine boots. To check this you can check this by using the below command.

[root@oracle-65-x64 tmp]# chkconfig --list | grep neo4j
neo4j          0:off 1:off 2:on 3:on 4:on 5:on 6:off
[root@oracle-65-x64 tmp]#

This however is not stating your  Neo4j instance is running, you will have to start it the first time after installation manually. To check the status of Ne04j on Oracle Linux you can use the below command:

[root@oracle-65-x64 ~]# service neo4j status
neo4j is stopped
[root@oracle-65-x64 ~]#

To start it you can use the below command:

[root@oracle-65-x64 ~]# service neo4j start
[root@oracle-65-x64 ~]# service neo4j status
neo4j (pid  5643) is running...
[root@oracle-65-x64 ~]#

Now you should have a running Neo4j installation on your Oracle Linux instance which is ready to be used. You now also should be able to go to the web interface of Neo4j and start using it.

Neo4J in the Oracle Cloud
When running Neo4J in the Oracle cloud the main installation of the Neo4J is already described in the section above. A number of additional things need to be kept in consideration when deploying it within the Oracle Public Cloud.

When deploying Neo4j in the Oracle cloud you will deploy it using the Oracle Public Cloud Compute Cloud Service. In the Compute Cloud Service you will have the option to provision an Oracle Linux machine and using the above instructions you will have a running machine in the Oracle Cloud within a couple of minutes.

The main key pointers you need to consider are around how to setup your network security within the Oracle Cloud. This also ties into the overall design, who can access Neo4j, which ports should be open and which routes should be allowed.

The way Oracle Cloud works with networks, firewalls and zone configuration is a bit different from how it is represented in a standard environment. However, even though the Oracle Compute Cloud service uses some different terms and different ways of doing things it provides you with exactly the same building blocks as a traditional IT deployment to do proper zone configuration and shield your database and applications from unwanted visitors.

A general advice when deploying virtual machines in the Oracle Public Cloud is to plan ahead and ensure you have your entire network and network security model mapped out and configured prior to deploying your first machine.

For the rest, using the Oracle cloud for a Neo4j installation is exactly the same as you would do in your own datacenter, with the exception that you can make use of the flexibility and speed of the Oracle Cloud.