Windows Subsystem for Linux | Ubuntu | LAMP Server

April 16, 2018

Hi guys

Usually I prefer a virtual machine for all my Linux/Development requirements. Well, Microsoft is “trying” to setup a Linux subsystem within Windows 10 from a while, which is “yet” to be fully functional in many means. Many benchmarks proven that Microsoft Subsystem for Linux for has the poorest I/O which Microsoft claims, will be addressed in the future releases.

So, why someone will choose WSL against a VM which has better functionalities? From an eager inquisitive person’s perspectives, I will choose WSL for just couple of reasons and they are:

WSL could access the full hardware, when a VM has limited resources. Ie, say your computer running has 4 cores and 8GB memory, you will be limited to 2 cores for your VM (anything beyond that would cause unexpected issues) and maximum of 4GB memory. Here WSL don’t have such limitations, it could access all your 4 cores and the maximum memory & could be launched like just another win32 application!

I’ve been trying to setup WSL using both Ubuntu & OpenSUSE Leap 42.3 over my Windows 10 1709 & I had better results with Ubuntu. OpenSuse has many issues those were beyond my skills to address and resolve. Hence, I chose to stick with Ubnutu for now.

So, installation of WSL on Windows 10 recent versions were made pretty easier compared to the previous releases. A seasoned Windows user could install Ubuntu for WSL very easily by following the instructions below

1

Once rebooted, from the Windows store, search for Ubuntu or OpenSUSE and just install it! That simple it is.2

Once installed, as mentioned with the first image, one can start the WSL either from command prompt or by clicking the tile that is available with the start menu.

As a developer, I would take the pain to setup the WSL for ONLY few reasons like testing PHP application(s) those are based on MySQL database (and outta curiosity)

So next, let us see we can setup LAMP server (LAMP is an archetypal model of web service stacks, named as an acronym of the names of its original four open-source components: the Linux operating system, the Apache HTTP Server, the MySQL relational database management system (RDBMS), and the PHP programming language. The LAMP components are largely interchangeable and not limited to the original selection. As a solution stack, LAMP is suitable for building dynamic web sites and web applications) on our new WSL

You may refer to this post for a detailed information about how to install individual components like apache, MySQL and PHP. Please note, the link that I provided deals with PHP5, which is not anymore available from Ubuntu repositories, hence I chose to go ahead with PHP7.0 for my WSL instance

Issue the following command(s) to install Apache, MySQL,PHP and phpMyAdmin


sudo apt-get install apache2
sudo apt-get install mysql-server

During the installation, you will be prompted for setting up MySQL root credentials, which is mandatory in order to access the MySQL server at later stages using phpmyadmin module

For PHP, you must install libapache2-mod-php, else you would experience php pages being blank when functions like phpinfo(); are called.


sudo apt-get install php libapache2-mod-php

Once the packages are installed (without errors) you can restart apache to verify everything is working fine


sudo service apache2 restart or sudo /etc/init.d/apache2 restart

If your windows box already has IIS listening to port 80 and a Windows instance for MySQL is listening to port 3306, then you must change the ports for both apache and MySQL before restarting the services.

For changing the port of Apache server edit the following file


/etc/apache2/ports.conf

For changing the port of MySQL server edit the following file


/etc/mysql/mysql.conf.d/mysqld.cnf

Although no real show stoppers, these couple or warning/error messages could make you feel irritated whenever apache and MySQL services are started

Apache:

[core:warn] [pid 47:tid 140569079777152] (92)Protocol not available: AH00076: Failed to enable APR_TCP_DEFER_ACCEPT

Edit the file


/etc/apache2/apache2.conf

add the following line by the end of the file


AcceptFilter http none

 

Restart the apache service

MySQL

No directory, logging in with HOME=/

Edit the file


/etc/passwd

and change the MySQL user details like following


mysql:x:112:117:MySQL Server,,,:/var/lib/mysql:/bin/false

Restart all services to make sure that there are no more warning/error messages

So far so good, let us install phpmyadmin, which you will use to manage your MySQL instance


sudo apt-get install phpmyadmin php-mbstring php-gettext

During the installation you will be prompted for selecting the http server stack and password for MySQL root account. You must provide the root password that you have set during the MySQL installation at this prompt

(Refer https://www.digitalocean.com/community/tutorials/how-to-install-and-secure-phpmyadmin-on-ubuntu-16-04 for more details)

Once the phpmyadmin is installed, you need to manually enable couple of extensions and they are dealt like following:


#sudo phpenmod mcrypt

#sudo phpenmod mbstring

Restart all services


sudo service apache2 restart

sudo service MySQL restart

Example:


rajesh@rt04:/etc/apache2$ sudo service apache2 restart
* Restarting Apache httpd web server apache2 [ OK ]
rajesh@rt04:/etc/apache2$ sudo service mysql restart
* Stopping MySQL database server mysqld [ OK ]
* Starting MySQL database server mysqld [ OK ]
rajesh@rt04:/etc/apache2$

Now you can see that there are no errors or warning while starting both apache and MySQL. So let us go ahead and check phpmyadmin

34

That’s all folks!

There is no shutdown for WSL, just type “exit” and you are good. I am yet to test whether mere exiting does anything harmful to running instances of apache and MySQL. Until I find them…

Finally

 

5

I don’t really understand why, yet, many users are asking for a “way” to ssh into the Linux subsystem. The pre-installed openBDS ssh server doesn’t allow a connection from clients like putty. Hence a re-installation of SSH server is required.


sudo apt-get remove --purge openssh-server
sudo apt-get install openssh-server
sudo service ssh --full-restart

Create a firewall inbound rule if required

Now you should able to connect to WSL instance using a client like putty.

regards,

rajesh

 

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Linux | Gtk-WARNING **: Attempting to set the permissions of

March 6, 2018

Hi guys

I “Can” manage a Linux Box, as long as there is a connection to Internet is available. So that concludes my expertise with LINUX OS.

One of the major annoyance for me while interacting with LINUX is the limitations firing up Gedit as a normal user. It requires kind of manipulation as “root” user (or I am not sure about other methods), yet the screen keeps screaming about few warning like below


(gedit:3531): Gtk-WARNING **: Attempting to set the permissions of `/home/oracle/.local/share/recently-used.xbel', but failed: No such file or directory
(gedit:3580): Gtk-WARNING **: Attempting to store changes into `/home/oracle/.local/share/recently-used.xbel', but failed: Failed to create file '/home/oracle/.local/share/recently-used.xbel.NN11EZ': Permission denied
(gedit:3580): Gtk-WARNING **: Attempting to set the permissions of `/home/oracle/.local/share/recently-used.xbel', but failed: No such file or directory 

 

So, in a nutshell how to start Gedit as a restricted user & to avoid watching the above few warnings?

as root user, issue the following command:


[root@rt05 ~]# xhost +localhost
localhost being added to access control list

The above will add “localhost” to access control list, YOU better know the consequences of it.

Now, the warning “(gedit:3531): Gtk-WARNING **: Attempting to set the permissions of `/home/oracle/.local/share/recently-used.xbel’, but failed: No such file or directory” is due to missing “../.local/share” folder. Creating this path as “Oracle” user didn’t resolve the issues. I had to change the ownership of the folder(s) as root.

 

[root@rt05 ~]# mkdir -p /home/oracle/.local/share
[root@rt05 ~]# chown -R oracle:oinstall /home/oracle/.local/share

Once the folders created and proper rights were given, finally the annoying warning messages related opening gedit has stopped!

regards,

rajesh

 

 


Linux | Send mail using internal mail command

November 16, 2016

Hi guys

We are on VEEM+VMWare infrastructure from a while, yet I am paranoid to maintain copies of the backups on different media once after going through couple of nightmares. We take weekly cold backup for our ERP Production server, move the tar files to a standby Linux server, and move those backups once again to an external HDD.

So basically I have a full VM backed up, the same VM holds a weekly cold backup, standby Linux server holding a copy of the cold backup files & to finish it, again copied to an external HDD. The funniest part is, we are moving the entire VMs to a TANDBERG Quick Station as well!

Though everything works fine till date, the last part of the deal needs to intimate me about successful completion of copying the tar files to the external media, ie, HDD that is formatted using NTFS, so that I can use it on both Linux and Windows environments

Be warned: The below bash script only works in an environment that has an internal SMTP server (or I don’t know how to relay the messages through an external SMTP relay and to disappoint you further, I don’t care about relaying through external SMTP). In addition, you must be on Linux 6 and above to use the internal mail command as demonstrated below. Linux 5 doesn’t support many switches provided with the example.

Further, below example demonstrates the basic level of error capturing with “bash” scripts as well

#!/bin/bash
/bin/cp -rf /u02/backup/PROD_DAILY_BACKUP*.* /media/Elements/ 2> /dev/null

if [ $? -eq 0 ]
then
echo "The files were successfully copied to external hard disk" | mailx -v -s "ERP Tar Files Moved to External HDD | Success" -S smtp=smtp://server.domain.com -S from="ERP Alerts <someone@example.com>" someoneelse@example.com,someone2@example.com
else
echo "Files were not copied to external HDD" | mailx -v -s "ERP Tar Files to External HDD | Failed" -S smtp=smtp://server.domain.com -S from="ERP Alerts <someone@example.com>" someoneelse@example.com,someone2@example.com
fi

Try it and let e know whether it worked for you :)

regards,

rajesh


Linux LVM (Logical Volume Manager) | AKA Spanned volumes

February 3, 2016

Hi guys

We’ve a EBS instance that totals almost 1TB physical size hosted on a high end IBM server & periodically we clone the instance to insure that the cold backups are reliable for DR purposes.

Recently we’ve decommissioned one HP ML110 G6 server with single xeon processor, 8GB memory that was dedicated for obsolete bio-metric monitoring and reporting running Windows 2003. I thought of using the same server for future restorations of EBS cold backups & realized that the server doesn’t support RAID 5 & moreover the built-in RAID is categorized under “fakeRAID”, which uses the built-in RAID technology, depending upon the CPU for the crippled RAID processing.

Using the HP Pavilion Easy Setup CD, I created an array and to my total disappointment found that Linux doesn’t read the fakeRAID while an installation is attempted.

The above were attempted because the ML110 G6 had 4 numbers of 500GB SATA HDD drives and I needed 1TB on a single volume. My database instance size as on date is 493GB, which would scream lack of space on a single 500GB partition. So I started reading about software RAID, which was too complex to setup with my minimal exposure to Linux. Further readings brought me to LVM (Logical Volume Manager) using which one can create spanned volumes as like in Windows.

Before proceeding further, please be aware of the RISKS associated with spanned volumes AKA LVM with multiple drives

How to?

We’ll consider a fresh installation of CentOS6/RHEL6/OEL6 for the exercises

Source thread (Please, please read)

Hardware: HP ML110 G6, 8GB memory, 4x500GB SATA HDD

Linux installation details

Installed Linux on HDD#1 (/dev/sda), 10GB boot, 4GB Swap, 110G / & balance as extended partition

Now, I am left with 3 HDDs, which are “untouched”, ie, no partitions are made

  1. /dev/sdb
  2. /dev/sdc
  3. /dev/sdd

As I have mentioned, my requirement was to have 1TB of storage for the cloning purposes, hence I chose 2x500GB (/dev/sdb, /dev/sdc)

First I created partitions using “fdisk”, the age old command line utility, even though better structured GUI is available with latest Linux distributions

Login to terminal as “root”

$fdisk /dev/sdb

n (new parition) -> p (primary partition) -> 1 (number of partitions) -> w (Write changes)

Repeated the same for /dev/sdc

$fdisk /dev/sdc

n (new parition) -> p (primary partition) -> 1 (number of partitions) -> w (Write changes)

We’ll use the following 3 commands to create our LVM

  1. pvcreate
  2. vgcreate
  3. lvcreate

create two physical volumes

$pvcreate /dev/sdb1 /dev/sdc1

create one volume group with the two physical volumes

$vgcreate VG_DATA /dev/sdb1 /dev/sdc1

create one logical volume

$lvcreate -l 100%FREE -n DATA VG_DATA

create the file system on your new volume

$mkfs.ext4 /dev/VG_DATA/DATA  #You may use ext3, based on your Linux distribution

$mkdir -p /u01

mount the volume (mount /dev/VG_DATA/DATA /u01)

That’s all folks, I have created my1st LVM aka spanned volume in Linux.

If you are planning to create logical volumes using multiple disks, be aware of the risks. You may lose millions worth data if no proper backups are taken and recovery could be a nightmare!

Not limited to total data loss, performance issues also should be considered, especially when such a setup hosts databases which require faster I/O.

for Windows7bugs

rajesh


Virtualize your desktop/laptop computer

January 3, 2016

Hello guys

This is my first post for the year 2016. Actually I have more drafts than posts this time with me and I truly hope that I will able to finish all of them in few weeks time. I’m sure you are interested about Oracle 12c products on Windows platform. Stay tuned, am on it

Coming back to the topic, I have a decent desktop computer that could be called a “half server” with the following configurations

  1. i7 processor 2nd generation
  2. 16GB DDR3 memory
  3. Around 4.5-5 terabyte of storage
  4. windows 10 64Bit Professional

I came across VMWare always 8 years back, liked it, and used it until they started charging for everything. Then Oracle VirtualBox (Earlier JAVA VirtualBox) started giving tough fight and it has become quite famous among developer communities where NOT many were truly able to afford VMWare’s paid software.

VMWare is altogether a different standard made for sophisticated environments, hence we will never compare both the products here. Our intention is to point you towards the advantages of using Virtual Machines that could less clutter your rig, give you better exposure to different technologies and a bit of networking etc

So our product of interest for this post is Oracle VirtualBox and we will see how we can utilize our existing desktops/laptops to run multiple virtual machines at the same time and thus utilize the available hardware to the maximum extends

So prior attempting to virtualize your existing computer, you need to know what kind of hardware you have and whether your computer meets minimum requirements to support virtualization.

So today is 3rd January 2016 & if your computer is 4 years old or less,  99.9% chances that your rig sure supports virtualization. Most of BIOS comes with the virtualization enabled by default.

Yet we should make sure that our computers support virtualization. Read the instructions provided here to find out whether your current processor supports virtualization OR

Just install Oracle VirtualBox and try to create a VM. You will immediately come to realize whether your rig really supports virtualization ;)

Well, that’s the brute force way of doing stuffs, adapt the one that defines you. If you are using Windows 10, I’ve noticed that many default installations enable Hyper-V by default. You need to disable it from add remove windows features console, so that you can create 64Bit VMs using Oracle VirtualBox. This post explains how to enable it, just do the opposite to disable it

Before anything else, you need to identify your processor, it’s capabilities. A nice comparison is available here for i3, i5 & i7 processors and definitely, the author favors i7 processors. Please spend few minutes to read about the differences between these three different processors.

A ripoff from http://www.pcadvisor.co.uk

What the difference between Core i3, i5, i7: Hyper-Threading

A thread in computing terms is a sequence of programmed instructions that the CPU has to process. If a CPU has one core, it can process only one thread at once, so can only do one thing at once (as before, it’s actually more complex than this, but the aim here is to keep it simple and understandable).

Hence, a dual-core CPU can process two threads at once, a quad-core four threads at once. That’s twice or four times the work in the same amount of time.

Hyper-Threading is a clever way to let a single core handle multiple threads.

A Core i3 with Hyper-Threading can process two threads per core which means a total of four threads can run simultaneously. The current Core i5 range doesn’t have Hyper-Threading so can also only process four cores. i7 processors do have it, so can process eight threads at once. Combine that with 8MB of cache and Turbo Boost Technology, and you can see why it’s good to choose a Core i7 over an i5 or i3.

Now, you should know how much physical memory you have. More, the merrier. Starting with Windows 7, computers started shipping with a minimum of 4GB as a standard. So, 4GB is enough for your OS and proposed virtualization? It’s going to be a tight fit. I will suggest an additional 4GB minimum, making the total physical memory 8GB so that you won’t have to sacrifice performance.

Finally the storage. Most of the branded PCs and laptops are coming with 500GB HDD as standard & extending the storage of a laptop is complex than of a desktop computer. For the later, all you need is another HDD which you can plug to one of the available SATA ports and configure. With a laptop, you may need to replace the HDD with a higher capacity one or use an external HDD for your additional storage requirements.

My current Virtualizations are mostly for Oracle technologies. I am a forms and reports developer, doing a certain level of .NET development & manage Oracle EBS R12 instances (“NOT a DBA”). Further I try almost all the database, weblogic versions & currently learning ASMM & RMAN. I have never attempted other areas of Oracle technologies, so my VMs run

  1. Oracle EBS R12 cloned instances
  2. Oracle database(s)
  3. Oracle weblogic server(s) with forms and reports (supported)

My EBS R12 VM has the following configuations

8GB memory out of 16GB physical, 4 processor out of 8 logical processors & almost 850GB of storage out of 4.5 terabyte total storage. Our instance has 400GB database size, 175GB application instance & the VM responds to requests instantaneously once after scheduled jobs are completed after a restart of the application. Usually I find the application responding better after 3 hours of settling down & the performance is assured throughout days and weeks until a restart.

My Weblogic, database VMs have the following configurations

4GB memory out of 16GB physical, 4 processor out of 8 logical processors & almost 250 GB of storage out of 4.5 terabyte total storage. I have my weblogic VM running 11gR2 64bit database as well. I get instant responses from both the Weblogic server and Oracle database 11gR2 from a client system, whenever accessed

Recommendations

Even though you can run multiple VMs at the same time, I would suggest, based on your hardware, limit them. Example

When I run my EBS R12 VM (8GB memory, 4 processors) my HOST computer is left with only 8GB free memory and 4 logical processors. If I start a Windows XP VM (2GB memory, 2 processors) to check the application performance, I feel my rig start slowing down and couple of times my computer shutdown with a high thermal point.

So make sure that you do tweaking to your VMs in order to make sure that your HOST doesn’t breakdown due to overload.

I always make sure that my HOST always has half of the hardware resources reserved for it, ie, 8GB memory, 4 processors regardless how many VMs I run at the same time! This is by using the VirtualBox console to alter the parameters of VMs before they are started

1

All the settings for the VMs could be altered using the settings, like increasing or decreasing the memory, processors, adding and removing storage devices etc.

2

Below you watch how fast my VM running EBS r12 responds to requests from another VM running Windows XP

Advantages of using Virtualization

The most important advantage for me is: I’ve a less cluttered HOST, said, I am NOT installing all the technologies to one OS, breaking it with conflicting versions of services and libraries and processing load.

Other advantages

  1. I can backup (copy) my entire “machine” and restore it during a total mess up or loss of data, rather than rebuilding the entire computer
  2. I get a sand-boxed environment & without fearing my attempts will break my main OS, continue the experiments
  3. I can make a VM, for example, running Oracle Enterprise Linux, copy and keep the OS installed disk somewhere and copy it to new VMs whenever required! Say, you install the OS only once and whenever you need to create a new VM with same OS, just duplicate the disk that has the OS! (Make sure you make a backup of the OS disk prior installing and configuring additional software into it)

Finally my suggestions for you, in case if you are considering to build your 1st VM using Oracle VirtualBox

  1. Majority of the Oracle geeks prefer Linux against Windows for database, weblogic deployments. So if you are NOT familiar with Linux, I suggest you start learning, regardless whether you FEEL very comfortable with it or NOT. You may be joining a firm that has reservations towards Windows OS running Oracle products, especially Oracle DBAs who have valid points like block corruptions, difficulties to recover from a crash are complex in the case of Windows OS.
  2. Install OS in a separate disk. 40GB dynamic size should be more than enough for any recent Linux distros. Avoid Linux 7 if you are truly new to Linux. Oracle Linux 6.7 should be your friend.
  3. Install 64Bit OS, so that you can take the advantage of your 64Bit processor and physical memory
  4. Install Oracle supported Linux distros (RHEL, OEL & certain versions of Debian. CentOS is not at all supported)
  5. Install the complete desktop, you are hardly going to complete the installations on pure CLI mode.
  6. Add SCSI interface to your VM and for Oracle database etc, use SCSI disks. I had a huge argument with VirtualBox guys about the performance difference between SATA VDI disks and SCSI VDI disks. I found the SCSI VDI disks performing better, however I was dismissed saying as far both the types are created on the same HDD, it must be more psychological :O
  7. Use 1TB 7200 RPM disks in the place of 2TB 5400 RPM disks. Later ones are best for data storage, when the previous ones give you better I/O. Create fixed size VDI for databases & applications, that means you will NOT able to increase the size of the disk once after created, however, it gives you faster I/O and better performance.
  8. Update your OS. As soon as the VM is built, update your OS prior installing database, weblogic etc. RHEL will NOT allow you to update the packages without subscription, hence Oracle Enterprise Linux should be your best choice of Linux distro. Please note, you shouldn’t use Oracle Linux in a production environment without acquiring sufficient licenses. Whatever I suggest here are limited for study/evaluation purposes and I don’t encourage any kind of illegal usage of software!
  9. Use Oracle’s pre-install packages to install database, EBS etc prerequisites rather than trying to download individual components from different download sites.
  10. Use shared folders between HOST and Guest (VM) so that you don’t have to sacrifice storage. Not just that, when you want to keep the backup of some files from the VM, the shared folders will make it as easy as possible
  11. Use bridged network, with Promiscuous Mode “Allow All” so that you can communicate with the VM from network
  12. 3
  13. Disable IPV6, firewall, SELinux on your Linux VM
  14. If you creating a Windows VM, I’m sure you better know how to configure your guest so that you can access it from a network.

Finally recommendations for a DESKTOP computer to try virtualization

  1. i7 processor + good quality heat sink. Your HOST and VMs are going to create loads of heat!
  2. 16GB Memory (DDR4 is the new standard, do not ignore it)
  3. 1×2 TB HDD

Few years back, such a configuration looked impossible for me, well, I saved bit by bit and made my dream computer. I’m sure you can also do it :) & trust me, a good computer opens a new world for you.

All the best and wish you all a very successful year ahead!

for Windows7bugs

rajesh

 

 

 

 

 

 

 


Oracle R12 Cloning | dbTier "ouicli.pl INSTE8_APPLY 1"

October 28, 2015

Hi guys

There could be thousands (exaggerated) reasons why a Oracle cloning process could go all bad. I’m not an application DBA, however, have enough experience with the architecture, technology as I interact with it everyday as a part of my job.

Few months back, I started doing something what a DBA should do, cloning. My prior attempts were mostly at home, using virtual machines and test instances and they were NOT as mission critical as what we do at work.

So, after the storage device was revamped with new partition structures I was asked to do a cloning for the production instance. Let me explain how the application was deployed prior the storage restructuring

  1. We had the database tier on mount point /u05
  2. Application on /u06 mount point

So, I recreated the same mount points and started the cloning process for dbTier and the process got terminated at 2% and the log files shown me an error that I was not familiar with.

“ouicli.pl INSTE8_APPLY 1”

Google searches fetched me hundreds of results for “ouicli.pl INSTE8_APPLY”, however the error codes were mostly for 255 or “-1” and apparently I didn’t have any clue what was going wrong.

So I unzipped the tar ball for database tier once again, and the cloning process got aborted at 2%,  and I was getting nervous as I was expected to make the instance online by early morning 7AM

Most of the reference materials were explaining about non-existent Oracle inventory locations, and I confirmed that it was not the case from my part (Obviously, I was overlooking at this constrain itself!)

After half a dozen times tasting failure, finally I tried to see what was written inside the oraInst.loc file

 

 
oraprod@erp-prod:/home/oraprod>cd $ORACLE_HOME 
oraprod@erp-prod:/u05/oraprod/PROD/db/tech_st/10.2.0>cat oraInst.loc 
inventory_loc=/u01/oraprod/PROD/db/tech_st/10.2.0/admin/oui/PROD_erp-prod/oraInventory 

and I realized that inventory location was wrongly pointing towards an non-existing mount point and physical location!

I modified the oraInst.loc content with the correct mount point

 
inventory_loc=/u05/oraprod/PROD/db/tech_st/10.2.0/admin/oui/PROD_erp-prod/oraInventory 

and the cloning process went ahead without giving another errors.

We had an instance that was running from last 6 years, which was only once cloned from a cold backup during the storage device change, and somehow the inventory location remain unchanged with the repositories.

I hope this finding could help few newbies like me out there

 

regards,

rajesh


VirtualBox | CentOS/Oracle 7.x Linux| Memory cannot be read/write error

July 7, 2015

Hi guys

Many times I pointed out the importance of testing technical previews, latest releases of other OS using VirtualBox as the early releases are prone to have frustrating bugs, which are many time specific to a particular hardware or distro. I was playing around with Oracle linux 7, which is a forked version of Red Hat Linux 7, named Unbrekable Linux by Oracle. Relatively I hardly had many issues with guest OS in recent times while tested over VirtualBox  and with OEL 7 guest, all of a sudden I started getting memory read errors like the one you can find with below image,

7-vb-memory error

once after the guest addons were installed. Although the change log of VirtualBox for 4.3.28 states the 3D bugs fix,  3D acceleration is the main culprit for the guest crashing once after a login attempt.

VirtualBox change log: https://www.virtualbox.org/wiki/Changelog

So, all you need to do is to disable the 3D acceleration for the guest using the settings panel. Well, unless you are going to use your VM for some “gaming” ;) I think this temporary fix should get you online with your CentOS/OEL 7.1 VM box!

Additional reading: https://www.virtualbox.org/ticket/13332

regards,