Error 404. That’s an error on domain.com

Recently purchased a new domain for my blog and removed it from a subdomain and redirected the blog to new domain. It was working fine until I checked it using http://zyraxtech.com and got 404. That’s an error.
It is a very small mistake people make and it result in traffic redirection loss. Fix is simple.
If we are using blogger then just go to the blog's dashboard, go to Settings>Basic and click on Edit.
then put a check on Redirect zyraxtech.com to www.zyraxtech.com.
This would redirect http://zyraxtech.com to www.zyraxtech.com (replace zyraxtech with your domain).

Resize swap memory in linux

We needed to to increase swap memory for one of our client who was using SUSE linux. There are two methods to overcome this and we used the following method.

Switch off swap

swapoff -a

First create a file named myswapfile and in this command count=1024 means 1GB so forexample our client needed swap memory of 44GB so we change count=45056

dd if=/dev/zero of=/root/myswapfile bs=1M count=1024

after file is created change the permission to root only

chmod 600 /root/myswapfile

enable the newly created swap

swapon /root/myswapfile

Add the following enteries in the fstab to keep the swap space after reboot

cat /etc/fstab /root/myswapfile swap           swap    defaults        0 0

after entry to make sure new swap is used:

swapoff -a

swapon -a

then verify using the top command. Hope it helps !


Ref: http://www.thegeekstuff.com/2010/08/how-to-add-swap-space/

VNC server idle timeout SUSE Linux

Recently one of our client using OpenSUSE VM had issues in using VNC viewer for installation of some software and he was facing logout issue when the system was idle. (Although this is good in terms of security but on his request we needed to switch off this feature)

There were several ways but we needed to resolve this quickly so following changes were made.

go to vi /etc/xinetd.d/services

Change the wait parameter from NO to YES

Session out issue resolved! 

VMware Guest VM Disk size greater than 2TB

Recently we needed to give our client a VM and additional disk of around 7TB. Issue that we were facing was when adding a disk of 7TB we were getting following errors:

Hot-extend was invoked with size (*** sectors) > =2TB. Hot-extend beyond or equal to 2TB is not supported. This disk extend operation failed: msg.disklib.INVAL

To resolve the issue power off the Virtual Machine and then retry the drive extend operation.

Or detach it from the Virtual machine it is connected to and then attach to a virtual machine that is powered off and perform the re-size operation.

Hope it solves the issue!.

Cloudstack Guest VM Issue

One of our client using our Cloudstack IaaS service and had a VM of Ubuntu 10.04. Issue was when his VM crashed and he wanted to create a VM from one the snapshots which were taken prior to the crash. After the VM was created he was getting following errors:

At first I thought that the template is not working but then after changing the OS type in the guest OS from original Ubuntu 10.04 x64 to Other (64-bit) , after that the VM booted smoothly. !

Subdomain redirect to blogger website

I already had a domain registered as was in use for my football club so I though why not to redirect the blogspot to a more easy name. so I did the following zyraxtech.blogspot.com ---> tech.fcrovers.org

First I went to godaddy from where I have got my domain, I went to Domain details and then first used forwarding of subdomain.

I added the domain in the following manner, you can change the alias as per you requirement.

then I went DNS zonefile and added the following entry as CNAME:

CNAME = tech , Points to = ghs.google.com

then go to blogger website and in settings -> Basic - > Publishing add tech.fcrovers.org

It normally takes time so be patient. :D
P.S: same could be achieved if you want to redirect website to domain name such as www.abc.com instead of a subdomain as in above example which was tech.abc.com 

Mikrotik Dual WAN Load balancing with PCC and DHCP on LAN

Recently I was working on a small test work so I deployed Mikrotik on my home LAN to balance the two ISP which I had at home. One was PTCL and other on Connect Communication, on both links I already have a router/modem which works as a DHCP server.

I used RB750 for this.


I started of by naming the interface for my convenience. ether1=PTCL , ether2=CONNECT, ether5=LAN

Then I enabled DHCP client on both ethernet interface on which PTCL and Connect were terminated.
Using winbox. Attached are screenshot:

After the DHCP is enable on both interfaces, we can verify by check on IP -> DHCP-CLIENT

FOR DHCP server at LAN:
/ip dhcp-server
setup
Select interface to run DHCP server on

dhcp server interface: LAN
Select network for DHCP addresses

dhcp address space: 192.168.100.0/24
Select gateway for given network

gateway for dhcp network: 192.168.100.1
Select pool of ip addresses given out by DHCP server

addresses to give out: 192.168.0.2-192.168.200
Select DNS servers

dns servers: 10.101.10.5 (Connect) , 192.168.1.1 (PTCL)
Select lease time

lease time: 3d

after this mangle rule and routing follows which will be used for balancing the link.

/ip firewall mangle

add chain=input in-interface=CONNECT action=mark-connection new-connection-mark=CONNECT_conn
add chain=input in-interface=PTCL action=mark-connection new-connection-mark=PTCL_conn

add chain=output connection-mark=CONNECT_conn action=mark-routing new-routing-mark=to_CONNECT
add chain=output connection-mark=PTCL_conn action=mark-routing new-routing-mark=to_PTCL

add chain=prerouting dst-address=192.168.0.0/24 action=accept in-interface=LAN
add chain=prerouting dst-address=192.168.1.0/24 action=accept in-interface=LAN

add chain=prerouting dst-address-type=!local in-interface=LAN per-connection-classifier=both-addresses-and-ports:2/0 action=mark-connection new-connection-mark=CONNECT_conn passthrough=yes
add chain=prerouting dst-address-type=!local in-interface=LAN per-connection-classifier=both-addresses-and-ports:2/1 action=mark-connection new-connection-mark=CONNECT_conn passthrough=yes
add chain=prerouting dst-address-type=!local in-interface=LAN per-connection-classifier=both-addresses-and-ports:2/2 action=mark-connection new-connection-mark=PTCL_conn passthrough=yes

add chain=prerouting connection-mark=CONNECT_conn in-interface=LAN action=mark-routing new-routing-mark=to_CONNECT
add chain=prerouting connection-mark=PTCL_conn in-interface=LAN action=mark-routing new-routing-mark=to_PTCL

/ip route
add dst-address=0.0.0.0/0 gateway=192.168.0.1 routing-mark=to_CONNECT check-gateway=ping
add dst-address=0.0.0.0/0 gateway=192.168.1.1 routing-mark=to_PTCL check-gateway=ping

add dst-address=0.0.0.0/0 gateway=192.168.0.1 distance=1 check-gateway=ping
add dst-address=0.0.0.0/0 gateway=192.168.1.1 distance=2 check-gateway=ping

/ip firewall nat
add chain=srcnat out-interface=CONNECT action=masquerade
add chain=srcnat out-interface=PTCL action=masquerade

above graph shows the bandwidth aggregated.
There is some tuning with the mikrotik balancing  and more testing will be posting as its done.

This can also be implement SOHO environment as well with RB750, RB750GL no need of getting a server and save electricity :D

Reference: http://aacable.wordpress.com/2011/07/27/mikrotik-dual-wan-load-balancing-using-pcc-method-complete-script-by-zaib/

Restore Windows Server VM from Recovery mode

How to Restore Windows Server VM from Recovery mode.

1. Insert your Windows Server installation disc and restart your VM and Boot from CD through Console.

2. Choose your language settings, and click “Next.”

3. Click “Repair your computer.”

4. Go to Command Promt. And type following command.

Bootrec /fixmbr

Bootrec /fixboot

BCD Boot C:\Windows

Bootrec /rebuildbcd

Bootsect /nt60 all /force

5. Now restart your Vm and select Last Known Good Configuration or you can also select Start Windows normally.

If you start VM and it gives following error or any registry file missing error.

File: \Windows\system32\config\system

Status: 0xc000014c

Info: Windows failed to load because the system registry file is missing, or corrupt.

Do follow these steps.

6. Do steps 1 to 4 above.
7. Type: cd c:\Windows\system32\config
8. Type: ren SYSTEM SYSTEM.BACKUP
9. Type: copy regback\SYSTEM SYSTEM
10. Reboot your machine and it should boot normally.

It should start good now. Cheers (Y)

How to create FTP server in CentOS

Recently I have deployed a couple of FTP servers both at work and one in home to create a central point for all my data especially in home and also separate for one of our clients at work.

Although creating an FTP server is an easy workaround but just to sum up and provide few details on small security issues and are which can be tuned.
Installs nano (editor) and vsftpd (Very Secure FTP) repo
yum install nano vsftpd -y

This step was required as we were having trouble with client unable to create folders etc on FTP server (Although it was a strange issue but writing it down to make sure that if someone faces "ftp error 550 failed to create directory" then this might work
nano /etc/selinux/config

SELINUX=enforcing ----> SELINUX=permissive

reboot

Start vsftpd services
/etc/init.d/vsftpd start

Open the configuration file of vsftpd and then make sure that following lines match
nano /etc/vsftpd/vsftpd.conf
anonymous_enable=NO
local_enable=YES
write_enable=YES
local_umask=022
dirmessage_enable=YES
xferlog_enable=YES
connect_from_port_20=YES
xferlog_std_format=YES
ascii_upload_enable=YES
ascii_download_enable=YES
ftpd_banner=Welcome to AMMAR FTP service.
chroot_local_user=YES
listen=YES
pam_service_name=vsftpd
userlist_enable=YES
tcp_wrappers=YES (if this is enabled then FTP will read (/etc/hosts.allow) to secure server acess
use_localtime=yes

Restart vsftpd services
service vsftpd restart


setsebool -P ftp_home_dir on

Stop iptables as it block ftp port by default although this is not a good practice later on I will update it to allow FTP port in iptables
service iptables stop

Add a user to be used in ftp (we can also include a file create a users list) currently I have worked using this method but there are other ways also
useradd client

Enter Client password
passwd client

User is normally able to access the server via SSH as we want only user to connect via FTP then:
chsh -s /sbin/nologin client (where client is username)

Create Directory for mounting drive locally or via NFS
mkdir /home/client/data

To add Drive via NFS following repo are required 
yum install nfs-utils nfs-utils-lib -y

Add below line to add the NFS chunk on to FTP server
nano /etc/fstab
172.19.30.16:/failover/clientdata  /home/client/data nfs auto,noatime,nolock,bg,nfsvers=3,intr,tcp,actimeo=1800 0 0

To mount the NFS following command will be used, if the first command doesn't work then second or third command will work depending upon your configuration

mount 172.19.30.16:/failover/clientdata /home/client/data/
mount -o 172.19.30.16:/failover/clientdata /home/client/data/

mount -o nolock 172.19.30.16:/failover/clientdata /home/client/data/

Execute this command to see the mounted drive
df -h

Give permission and rights to the user on the folder
chown -R client /home/client/data
usermod -d /home/client/data/ client

Restart vsftpd services
service vsftpd restart

Stop iptables services or allow port via firewall rules

service iptables stop

To make sure services stop or start after reboot
chkconfig vsftpd on
chkconfig iptables off

How to access System VMs in Cloudstack

Recently I have been working in managing Cloudstack at my work.  Cloudstack uses 3 types of system VMs for its operation.
1. SSVM - Secondary storage VM: This VM basically mounts the secondary storage which is used for templates, snapshots, ISO for cloudstack.
2. CP - Console Proxy VM: This VM is used basically to view the console (Type of VNC View) of the machine as it is not a physical machine and for access off VM if network is unreachable.
3. VR - Virtual Router:This VM is generated when any account user creates a VM and every VM requires a network, which secures network of that account and access to VMs of that particular user. It also provides DHCP services to make that VM traffic reach the WWW and vice verse.

We continuously require access to these VM mostly VR and SSVM for different debugging (will be updating blog about cloudstack extensively) and for operations.

To access these VMs we need to access the Host they are in which we can find from VMs details

we can find the details of host as well as the link local IP from which we can access without the need of password by going in infrastructure -> System VM or Virtual Router and details will be displayed as above. 

Simply access the host in which VM is and run following command:

ssh -i /root/.ssh/id_rsa.cloud -p 3922 root@169.254.x.x

Where x.x refers to IP which changes from time to time but first two octets are same always.!

After running the above command it will not ask for any username and password and VM can be accessed through this command.

(Hope it Helps !)