Vtrio SysAdmins

Mysql databases allow username and password. Similarly if you require to keep authentication for your mongodb database as well, please do the following. Suppose, I have a database named abc, and I need to create a user named abc with password abc123.

First, create an admin user.

root@abc:~# mongo
MongoDB shell version: 2.4.10
connecting to: test
> use admin
> db.addUser(“admin”, “admin”)

> use abc                   (Switch to the database abc)

> db.addUser(“abc”, “abc123″)

Quit the mongoshell and stop mongo

root@abc:~# /etc/init.d/mongodb stop

root@abc:~# vi /etc/mongodb.conf    and make the following change

auth = true

root@abc:~#/etc/init.d/mongodb start

Now we need to test if authentication works. Which means, if not authenticated, you should not be able to saw the details of the database.

root@abc:~# mongo
MongoDB shell version: 2.4.10
connecting to: test

> use abc

> show collections

“$err” : “not authorized for query on abc.system.namespaces”,
“code” : 16550

Now it shows the error that you are not authorized to view the collections. Now, authenticate with the details you created earlier and try.

> db.auth(“abc”, “abc123″)
>show collections
testcollection
system.indexes

This is how you create a user for mongodb database.

If you want to copy emails from a windows mailenable server to linux server with exim, you can do it as follows.

I am copying the email account test@abc.com to new server. Its password is test123c on both servers.

root@abc [~]# cd /usr/local/src/

root@abc [/usr/local/src]#  wget http://home.arcor.de/armin.diehl/imapcopy/imapcopy.tar.gz

root@abc [/usr/local/src]#  tar -xvf imapcopy.tar.gz

root@abc [/usr/local/src]# cd imapcopy

root@abc [/usr/local/src/imapcopy]# ls
./  ../  imapcopy*  ImapCopy.cfg

root@abc [/usr/local/src/imapcopy]# cp -pv ImapCopy.cfg ImapCopy.cfg.original

`ImapCopy.cfg’ -> `ImapCopy.cfg.original’

root@abc [/usr/local/src/imapcopy]# vi ImapCopy.cfg
You need to edit the following values to make the migration smoother.

##############
# Sourceserver
##############
SourceServer 1.2.3.4 (Source Server IP Address)
SourcePort 143
###################
# Destinationserver
###################
DestServer localhost
DestPort 143

#############################
# List of users and passwords
#############################

#       SourceUser    SourcePassword   DestinationUser  DestinationPassword
Copy   “test@abc.com”  “test123c” “test@abc.com”  “test123c”

[/stextbox]

Make sure you are able to connect to port 143 of source server from destination server

[stextbox id=”info”]

root@abc [/usr/local/src/imapcopy]# telnet 1.2.3.4  143
Trying 1.2.3.4…
Connected to abc.greproot.com (1.2.3.4).
Escape character is ‘^]’.
* OK IMAP4rev1 server ready at 05/07/14 05:46:17
^]
telnet> q
Connection closed.
[/stextbox]

Now test the configuration

[stextbox id=”info”]

root@abc [/usr/local/src/imapcopy]# ./imapcopy -t
IMAPCopy 1.04 – 2009/07/18 [compiled with FreePascal]
written 2001-2009 by Armin Diehl <ad@ardiehl.de>
Running on Linux

Login on sourceserver as test@abc.com OK
Login on destinationserver as test@abc.com OK
Getting folderlist on sourceserver OK, found 1 folder

1 User processed, 0 Messages copied, 0 Error(s)
0 Folder(s) created, 0 Folder create errors, 0 Folder not copied
[/stextbox]

The configuration looks fine without any errors. Now we can start copying the email account contents.

[stextbox id=”info”]

root@abc [/usr/local/src/imapcopy]#./imapcopy
IMAPCopy 1.04 – 2009/07/18 [compiled with FreePascal]
written 2001-2009 by Armin Diehl <ad@ardiehl.de>
Running on Linux

Login on sourceserver as test@abc.com OK
Login on destinationserver as test@abc.com OK
Getting folderlist on sourceserver OK, found 1 folder
Getting List of messages in “INBOX” OK, 7 Messages found
Processing Folder INBOX
7 Messages copied, 0 Errors

1 User processed, 7 Messages copied, 0 Error(s)
0 Folder(s) created, 0 Folder create errors, 0 Folder not copied
[/stextbox]

Now the mails have been copied. Try accessing webmail of the account test@abc.com and see if mails are displayed fine.

Xen virtualization steps are given below.

1. Make sure that SELinux is disabled or permissive.

vi /etc/sysconfig/selinux

and set “SELINUX=disabled”. Then reboot server.

2. Creating A Network Bridge.

We need to set up a network bridge on our server so that our virtual machines can be accessed from other hosts as if they were physical systems in the network.

To do this, we install the package bridge-utils

=========

yum install bridge-utils

=========

… and configure a bridge. Create the file /etc/sysconfig/network-scripts/ifcfg-br0 (please use the IPADDR, PREFIX, GATEWAY, DNS1 and DNS2 values from the/etc/sysconfig/network-scripts/ifcfg-eth0 file); make sure you use TYPE=Bridge, not TYPE=Ethernet:

vi /etc/sysconfig/network-scripts/ifcfg-br0

DEVICE="br0"
NM_CONTROLLED="yes"
ONBOOT=yes
TYPE=Bridge
BOOTPROTO=none
IPADDR=192.168.0.100
PREFIX=24
GATEWAY=192.168.0.1
DNS1=8.8.8.8
DNS2=8.8.4.4
DEFROUTE=yes
IPV4_FAILURE_FATAL=yes
IPV6INIT=no
NAME="System br0"

Modify /etc/sysconfig/network-scripts/ifcfg-eth0 as follows (comment out BOOTPROTO, IPADDR, PREFIX, GATEWAY, DNS1, and DNS2 and add BRIDGE=br0):

vi /etc/sysconfig/network-scripts/ifcfg-eth0

DEVICE="eth0"
NM_CONTROLLED="yes"
ONBOOT=yes
HWADDR=00:1E:90:F3:F0:02
TYPE=Ethernet
#BOOTPROTO=none
#IPADDR=192.168.0.100
#PREFIX=24
#GATEWAY=192.168.0.1
#DNS1=8.8.8.8
#DNS2=8.8.4.4
DEFROUTE=yes
IPV4_FAILURE_FATAL=yes
IPV6INIT=no
NAME="System eth0"
UUID=5fb06bd0-0bb0-7ffb-45f1-d6edd65f3e03
BRIDGE=br0

Restart the network:
/etc/init.d/network restart

and run "ifconfig", it should network bridge.

[root@server1 ~]# ifconfig
br0       Link encap:Ethernet  HWaddr 00:1E:90:F3:F0:02
          inet addr:192.168.0.100  Bcast:192.168.0.255  Mask:255.255.255.0
          inet6 addr: fe80::21e:90ff:fef3:f002/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:17 errors:0 dropped:0 overruns:0 frame:0
          TX packets:29 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:1196 (1.1 KiB)  TX bytes:2794 (2.7 KiB)

eth0      Link encap:Ethernet  HWaddr 00:1E:90:F3:F0:02
          inet6 addr: fe80::21e:90ff:fef3:f002/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:4554 errors:0 dropped:0 overruns:0 frame:0
          TX packets:3020 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:6249612 (5.9 MiB)  TX bytes:254928 (248.9 KiB)
          Interrupt:25 Base address:0x6000

lo        Link encap:Local Loopback
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:3 errors:0 dropped:0 overruns:0 frame:0
          TX packets:3 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:1304 (1.2 KiB)  TX bytes:1304 (1.2 KiB)

3. Installing XEN:
First check if your CPU supports hardware virtualization - if this is the case, the command
egrep '(vmx|svm)' --color=always /proc/cpuinfo

should display something, e.g. like this:

[root@server1 ~]# egrep ‘(vmx|svm)’ –color=always /proc/cpuinfo
flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ht syscall
nx mmxext fxsr_opt rdtscp lm 3dnowext 3dnow pni cx16 lahf_lm cmp_legacy svm extapic cr8_legacy misalignsse
flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ht syscall
nx mmxext fxsr_opt rdtscp lm 3dnowext 3dnow pni cx16 lahf_lm cmp_legacy svm extapic cr8_legacy misalignsse
[root@server1 ~]#

If nothing is displayed, then your processor doesn’t support hardware virtualization. This means you can use only paravirtualization with Xen, but not hardware virtualization.

As CentOS 6 is based on RedHat 6, and RedHat has dropped support for Xen in version 6, we need to get Xen from a third-party repository. We can enable the repo as follows:

yum install wget

yum install http://au1.mirror.crc.id.au/repo/kernel-xen-release-6-3.noarch.rpm

yum install kernel-xen xen

This installs Xen and a Xen kernel on our CentOS system.

Before we can boot the system with the Xen kernel, please check your GRUB bootloader configuration. We open /boot/grub/menu.lst:

vi /boot/grub/menu.lst

The first listed kernel should be the Xen kernel that you’ve just installed:

[...]
title CentOS (2.6.32.54-1.el6xen.x86_64)
        root (hd0,0)
        kernel /vmlinuz-2.6.32.54-1.el6xen.x86_64 ro root=/dev/mapper/VolGroup00-LogVol00 rd_NO_LUKS LANG=en_US.UTF-8 rd_NO_MD quiet SYSFONT=latarcyrheb-sun16 rhgb crashkernel=auto  KEYBOARDTYPE=pc KEYTABLE=de rd_LVM_LV=VolGroup00/LogVol01 rd_LVM_LV=VolGroup00/LogVol00 rd_NO_DM
        initrd /initramfs-2.6.32.54-1.el6xen.x86_64.img
[...]

We need to modify that section so that the Xen hypervisor gets loaded first. In the kernel /vmlinuz... line, replace the first word kernel with module. Do the same in the next line - replace the first word initrd with module in the initrd /initramfs... line. Then add the line kernel /xen.gz dom0_mem=1024M cpufreq=xen dom0_max_vcpus=1 dom0_vcpus_pin after the root line and before the first module line (if you have more than one CPU core, you can specify another number than 1 fordom0_max_vcpus). The final kernel section should look like this:

[...]
title CentOS (2.6.32.54-1.el6xen.x86_64)
        root (hd0,0)
        kernel /xen.gz dom0_mem=1024M cpufreq=xen dom0_max_vcpus=1 dom0_vcpus_pin
        module /vmlinuz-2.6.32.54-1.el6xen.x86_64 ro root=/dev/mapper/VolGroup00-LogVol00 rd_NO_LUKS LANG=en_US.UTF-8 rd_NO_MD quiet SYSFONT=latarcyrheb-sun16 rhgb crashkernel=auto  KEYBOARDTYPE=pc KEYTABLE=de rd_LVM_LV=VolGroup00/LogVol01 rd_LVM_LV=VolGroup00/LogVol00 rd_NO_DM
        module /initramfs-2.6.32.54-1.el6xen.x86_64.img
[...]

Change the value of default to 0 (so that the first kernel (the Xen kernel) will be booted by default):

[...]
default=0
[...]

The complete /boot/grub/menu.lst should look something like this:

# grub.conf generated by anaconda
#
# Note that you do not have to rerun grub after making changes to this file
# NOTICE:  You have a /boot partition.  This means that
#          all kernel and initrd paths are relative to /boot/, eg.
#          root (hd0,0)
#          kernel /vmlinuz-version ro root=/dev/mapper/VolGroup00-LogVol00
#          initrd /initrd-[generic-]version.img
#boot=/dev/sde
default=0
timeout=5
splashimage=(hd0,0)/grub/splash.xpm.gz
hiddenmenu
title CentOS (2.6.32.54-1.el6xen.x86_64)
        root (hd0,0)
        kernel /xen.gz dom0_mem=1024M cpufreq=xen dom0_max_vcpus=1 dom0_vcpus_pin
        module /vmlinuz-2.6.32.54-1.el6xen.x86_64 ro root=/dev/mapper/VolGroup00-LogVol00 rd_NO_LUKS LANG=en_US.UTF-8 rd_NO_MD quiet SYSFONT=latarcyrheb-sun16 rhgb crashkernel=auto  KEYBOARDTYPE=pc KEYTABLE=de rd_LVM_LV=VolGroup00/LogVol01 rd_LVM_LV=VolGroup00/LogVol00 rd_NO_DM
        module /initramfs-2.6.32.54-1.el6xen.x86_64.img
title CentOS (2.6.32-220.el6.x86_64)
        root (hd0,0)
        kernel /vmlinuz-2.6.32-220.el6.x86_64 ro root=/dev/mapper/VolGroup00-LogVol00 rd_NO_LUKS LANG=en_US.UTF-8 rd_NO_MD quiet SYSFONT=latarcyrheb-sun16 rhgb crashkernel=auto  KEYBOARDTYPE=pc KEYTABLE=de rd_LVM_LV=VolGroup00/LogVol01 rd_LVM_LV=VolGroup00/LogVol00 rd_NO_DM
        initrd /initramfs-2.6.32-220.el6.x86_64.img

Before we reboot, we install the libvirt and python-virtinst (which contains the virt-install tool which we will use later on to install Xen VMs) packages:

yum install libvirt python-virtinst

Because the libvirt package from CentOS 6/RedHat 6 has no support for Xen, we must rebuild it with Xen support. To do this, we install a few prerequisites now:

yum groupinstall 'Development Tools'

yum install python-devel xen-devel libxml2-devel xhtml1-dtds readline-devel ncurses-devel libtasn1-devel gnutls-devel augeas libudev-devel libpciaccess-devel yajl-devel sanlock-devel libpcap-devel libnl-devel avahi-devel libselinux-devel cyrus-sasl-devel parted-devel device-mapper-devel numactl-devel libcap-ng-devel netcf-devel libcurl-devel audit-libs-devel systemtap-sdt-devel

Now reboot machine to load new kernel

The system should now automatically boot the new Xen kernel. After the system has booted, we can check that by running

uname -r

[root@server1 ~]# uname -r
2.6.32.54-1.el6xen.x86_64
[root@server1 ~]#

So it’s really using the new Xen kernel!

a. xm list

b. to check if Xen has started. It should list Domain-0 (dom0):

[root@server1 ~]# xm list
Name                                        ID   Mem VCPUs      State   Time(s)
Domain-0                                     0  1024     1     r—–     18.9
[root@server1 ~]#

Instead of using the xm command, I will from now on use the virsh command to manage Xen VMs. This is the preferred way as we are using libvirt.

virsh list

should show this:

[root@server1 ~]# virsh list
Id Name                 State
———————————-
0 Domain-0             running

[root@server1 ~]#

4. Paravirtualization:

CentOS has a nice tool called virt-install with which we can create virtual machines for Xen. To start it, we simply run

virt-install –prompt –network bridge=br0 –virt-type=xen

The tools asks a few questions before it creates a virtual machine. I want to call my first virtual machine vm01, with 1024MB RAM and a disk size of 10GB. I want to store it in the file /var/lib/libvirt/images/vm01.img:

Would you like a fully virtualized guest (yes or no)? This will allow you to run unmodified operating systems.
<– no
What is the name of your virtual machine?
<– vm01
How much RAM should be allocated (in megabytes)?
<– 1024
What would you like to use as the disk (file path)?
<– /var/lib/libvirt/images/vm01.img
How large would you like the disk (/vm/vm01.img) to be (in gigabytes)?
<– 10
What is the install URL?
<– http://ftp.tu-chemnitz.de/pub/linux/centos/6.2/os/x86_64

Regards,

Jeen

This script will show you an example of how to download multiple files concurrently
using the curl_multi commands in PHP 5.While php itself doesn’t support multi threading and concurrency,
libcurl does and php allows us to download multiple files at the same time from php.

1) First create a folder where SSL certs are to be placed

#mkdir /etc/ssl/certs

#cd /etc/ssl/certs

Create key

# openssl genrsa -out abc.com.key 2048

# chmod 600 abc.com.key

Generate CSR

# openssl req -new -key abc.com.key -out abc.com.csr

If all that you need is a self signed certificated, do as follows.

# openssl x509 -req -days 365 -in abc.com.csr -signkey abc.com.key -out abc.com.crt

Otherwise get the cert signed and place it in /etc/ssl/certs/abc.com.crt

Now, open up your nginx config file for this domain.

# vi /etc/nginx/sites-available/abc.com

If you are planning to use both http and https, you need two separate server modules in your config. Hence, copy the config for 80 and put it to the bottom of the page and make modifications. What you need to add to the https server module is given below. Paste it before server_name line.

server {

listen   1.2.1.3:443 ssl;

ssl    on;
ssl_certificate    /etc/ssl/certs/abc.com.crt;
ssl_certificate_key    /etc/ssl/certs/abc.com.key;
server_name abc.com www.abc.com

….

…

}

Now restart nginx.

#/etc/rc.d/init.d/nginx restart

Now try accessing site with https.

This post will explain how to password protect a site in nginx. It is very simple and it uses the normal htpasswd protection

Suppose I need to password protect the site abc.com whose document root is /var/www/abc/public_html

Simple follow the steps given below

Now, your login details are stored to the file /var/www/abc/public_html/.htpasswd and we need to call this file from abc.com’s conf.

Simply add the following two lines before the locations

So your final conf will now look as follows.

All done, save the configuration file and exit. Now restart nginx and see if it starts without errors.

Now clear your browser cache and try accessing the site. Bingo!! isnt’t it protected?

Want to know how the backup of mongo database can be taken. Read below…

Four tools are described here.

1) mongoexport

mongoexport can be used to take the backup of a mongo database. It takes the backup to a CSV, TSV or JSON files. The syntax is as follows.

2) mongoimport

mongoimport can be used to import a backup to a database. You can import from the backup file as follows.

3) mongodump

For those who need a complete backup of the database, you can use mongodump command to do so. Unlike mongoexport, the backup will be done into a folder and not file.

Once completed, the backup will be present in /backuptest/db_test/

4) mongorestore

To restore an entire database, you can use the mongorestore command. Let’s restore the backup that we took in the previous step.

Try it and see, it works

Mongo was working fine in my Ubuntu machine, but whenever I access mongo shell, it will display the following warning.

First I checked, whether my hardware is NUMA(Non-Uniform Access Memory) enabled. I got the following output which said the answer is yes, it is NUMA enabled.

I can simply start mongo as said in the warning message, but what I was looking forward was a permanent fix which will let me start/stop mongo using the startup script.

Unfortunately, numactl command was not present in the server, so I installed the package as follows.

After that, I did the following.

After doing this you need to restart mongodb and check whether mongo shell is accessible without the warning.

Check if mongo is running

Try accessing the mongo shell

Success!!!! In case of error, you can check the log file at /var/log/mongodb/mongodb.log