Monthly Archives: April 2012

Public writable Share in samba

This document describes how to make public writable shares in samba. Samba is an open source Linux software that is used to create shared folder that can be accessed from Windows machines. This procedure was carried out on Debian/Ubuntu Linux, but with minor changes can be used on other Linux distributions too.

1. Install samba
[codesyntax lang="bash"]

sudo su -
apt-get install samba smbclient


2. Make a backup copy of the original configuration files
[codesyntax lang="bash"]

cp -av /etc/samba /etc/samba.orig


3. Create directory to be shared
[codesyntax lang="bash"]

mkdir -p /share
chmod -R a+rwx /share


4. Configure samba to allow public writable shares
[codesyntax lang="bash"]

echo "" > /etc/samba/smb.conf
vim /etc/samba/smb.conf


                workgroup = WORKGROUP
                server string = %h server (Samba)
                dns proxy = no
                log file = /var/log/samba/log.%m
                max log size = 1000
                syslog = 0
                panic action = /usr/share/samba/panic-action %d
                security = share
                encrypt passwords = true
                passdb backend = tdbsam
                obey pam restrictions = yes
                unix password sync = yes
                passwd program = /usr/bin/passwd %u
                passwd chat = *Enter\snew\s*\spassword:* %n\n *Retype\snew\s*\spassword:* %n\n *password\supdated\ssuccessfully* .
                pam password change = yes
                map to guest = bad user
                guest account = nobody
                load printers = yes
                printing = cups
                printcap name = cups
                usershare allow guests = yes

                comment = Printer Drivers
                path = /var/lib/samba/printers
                browseable = yes
                read only = yes
                guest ok = yes

                comment = Printer in Linux
                path = /var/spool/samba
                guest ok = Yes
                printable = Yes
                use client driver = Yes
                browseable = No

                path = /share
                browsable = yes
                writable = yes
                read only = no
                guest only = yes
                create mask = 0644
                directory mask = 0755

Xen 6.0.2 software Raid - installation procedure

This document describes how to install XenServer 6.0.2 on a node without hardware raid.

Install Software

Install XenServer 6.0.2 on /dev/sda and do NOT configure any local storage (it is easier to do that afterwards). /dev/sda should containt three partitions, please verify with the following command:

[codesyntax lang="bash"]

sgdisk -p /dev/sda


The first partition is used for XenServer installation, the second one is used for backups during XenServer upgrades.

1. Now we are going to use /dev/sdb as the mirror disk. Clear the partition table.
[codesyntax lang="bash"]

sgdisk --zap-all /dev/sdb


2. Install a GPT table on /dev/sdb
[codesyntax lang="bash"]

sgdisk --mbrtogpt --clear /dev/sdb


3. Create partitions on /dev/sdb. Please note that the following commands are dependent on your installation. Copy the start and the last sectors from the /dev/sda (output of sgdisk -p /dev/sda)
[codesyntax lang="bash"]

sgdisk --new=1:34:8388641 /dev/sdb
sgdisk --typecode=1:fd00 /dev/sdb
sgdisk --attributes=1:set:2 /dev/sdb
sgdisk --new=2:8388642:16777249 /dev/sdb
sgdisk --typecode=2:fd00 /dev/sdb
sgdisk --new=3:16777250:3907029134 /dev/sdb
sgdisk --typecode=3:fd00 /dev/sdb


4. Create RAID devices
[codesyntax lang="bash"]

mknod /dev/md0 b 9 0
mknod /dev/md1 b 9 1
mknod /dev/md2 b 9 2
mdadm --create /dev/md0 --level=1 --raid-devices=2 missing /dev/sdb1
mdadm --create /dev/md1 --level=1 --raid-devices=2 missing /dev/sdb2
mdadm --create /dev/md2 --level=1 --raid-devices=2 missing /dev/sdb3


5. Create bitmaps for each RAID device. Bitmaps slightly impact throughput but significantly reduce the rebuilt time when the array fails.
[codesyntax lang="bash"]

mdadm --grow /dev/md0 -b internal
mdadm --grow /dev/md1 -b internal
mdadm --grow /dev/md2 -b internal


6. Format the root disk and mount it at /mnt
[codesyntax lang="bash"]

mkfs.ext3 /dev/md0
mount /dev/md0 /mnt


7. Copy the root filesystem to the RAID array (please be patient this step may take a while).
[codesyntax lang="bash"]

cp -vxpR / /mnt


8. Change the root filesystem in /mnt/etc/fstab to /dev/md0.
[codesyntax lang="bash"]

sed -r -i 's,LABEL=root-\w+ ,/dev/md0 ,g' /mnt/etc/fstab


9. Install the bootloader on the second hard disk.
[codesyntax lang="bash"]

mount --bind /dev /mnt/dev
mount -t sysfs none /mnt/sys
mount -t proc none /mnt/proc
chroot /mnt /sbin/extlinux --install /boot
dd if=/mnt/usr/share/syslinux/gptmbr.bin of=/dev/sdb


10. Make a new initrd image which contains a driver for the new root filesystem on the software RAID array.
[codesyntax lang="bash"]

chroot /mnt
mkinitrd -v -f --theme=/usr/share/splash --without-multipath /boot/initrd-`uname -r`.img `uname -r`


11. edit /mnt/boot/extlinux.conf and replace every mention of the old root filesystem (root=LABEL=xxx) with root=/dev/md0.
[codesyntax lang="bash"]

sed -r -i 's,root=LABEL=root-\w+ ,root=/dev/md0 ,g' /mnt/boot/extlinux.conf
sed -r -i 's,root=LABEL=root-\w+ ,root=/dev/md0 ,g' /boot/extlinux.conf


12. Unmount the new root and reboot. Important: Remember to use the boot menu of your BIOS to boot from the second hard disk this time!
[codesyntax lang="bash"]

umount /mnt/proc
umount /mnt/sys
umount /mnt/dev
umount /mnt


13. XenServer is up again, include /dev/sda in the array
[codesyntax lang="bash"]

sgdisk --typecode=1:fd00 /dev/sda
sgdisk --typecode=2:fd00 /dev/sda
sgdisk --typecode=3:fd00 /dev/sda
mdadm -a /dev/md0 /dev/sda1
mdadm -a /dev/md1 /dev/sda2
mdadm -a /dev/md2 /dev/sda3


14. The array needs to complete its initial build/synchronisation. That will take a while.
[codesyntax lang="bash"]

watch --interval=1 cat /proc/mdstat


15. Add /dev/md2 as a local SR to XenServer.
[codesyntax lang="bash"]

xe sr-create content-type=user device-config:device=/dev/md2 name-label="Local Storage" shared=false type=lvm


type=ext is required if you turned on thin provisioning in the installer. Otherwise use type=lvm

Final notes:

* The second partition is used by XenServer for backups, which is why its the same size as the first partition. If you put the install CD in and boot it, an option shows up for "restore XenServer 6.0 from backup partition"

* I have created bitmaps for each raid as well. In the event of the host going down dirty, the raids can require a synch. Simply doing this is enough to add a bitmap for changed pages.

doing cat /proc/mdstat will now say something like

cat /proc/mdstat
Personalities : [raid1]
md0 : active raid1 sda1[1] sdb1[0]
4193216 blocks [2/2] [UU]
bitmap: 128/128 pages [512KB], 16KB chunk

md1 : active raid1 sda2[1] sdb2[0]
4193216 blocks [2/2] [UU]
bitmap: 0/128 pages [0KB], 16KB chunk

md2 : active raid1 sda3[1] sdb3[0]
968372864 blocks [2/2] [UU]
bitmap: 0/231 pages [0KB], 2048KB chunk

* If you are installing on server which can not boot from the second disk, you must physically swap the two drives to make the machine boot off sdb and use /dev/md0 as root

* If you are going to setup a Xen 6 installation over network (via PXE) and the installation process hangs right after "Freeing unused kernel memory: 280k freed", you pass to the kernel (/tftpboot/pxelinux.cfg/ the following parameter xencons as follows:

append xenserver6/xen.gz dom0_mem=752M com1=9600,8n1 console=com1,tty --- xenserver6/vmlinuz console=tty0 console=ttyS0,9600n8 xencons=ttyS0,9600n8 answerfile= install --- xenserver6/install.img

* To speed up the raid build process the following command can be used (default value is 1000):
[codesyntax lang="bash"]

echo 100000 > /proc/sys/dev/raid/speed_limit_min


* TIP: You can use the attached script to automate the steps 1 to 9.

Good luck

The script:


OpenVPN with pam-mysql username/password authentication

This document describes how to install openvpn with pam-mysql username/password authentication. This procedure was carried out on Debian/Ubuntu Linux, but with minor changes can be used on other Linux distributions too.

1. Install openvpn, mysql and pam-mysql
[codesyntax lang="bash"]

sudo su -
mkdir -p /root/work/openvpn
cd /etc/openvpn
apt-get install libpam-mysql openvpn mysql-server


Note: please keep mysql-server password in mind because we are going to use it later (I will refer to this password as 'mysqlpasswd').

2. Create a new openvpn configuration
[codesyntax lang="bash"]

vim /etc/openvpn/server.conf


port 1194
proto udp
dev tun

ca /etc/openvpn/easy-rsa/keys/ca.crt
cert /etc/openvpn/easy-rsa/keys/server.crt
key /etc/openvpn/easy-rsa/keys/server.key
dh /etc/openvpn/easy-rsa/keys/dh1024.pem

ifconfig-pool-persist ipp.txt

keepalive 10 120


max-clients 50


status openvpn-status.log
log-append /var/log/openvpn.log
verb 3
mute 20


plugin /usr/lib/openvpn/ openvpn

3. Follow the commands below to setup OpenVPN server

[codesyntax lang="bash"]

cp -r /usr/share/doc/openvpn/examples/easy-rsa/2.0/ easy-rsa
cd easy-rsa
vim vars # Edit KEY_* vars appropriately


export KEY_CITY="City"
export KEY_ORG="VPN"
export KEY_EMAIL=""

[codesyntax lang="bash"]

source ./vars
./pkitool --initca
./pkitool --server server


4. Allow traffic to be routed from clients to server
[codesyntax lang="bash"]

echo 1 > /proc/sys/net/ipv4/ip_forward
sed -i -e 's/#net.ipv4.ip_forward/net.ipv4.ip_forward/g' /etc/sysctl.conf
sysctl -p
iptables -t nat -A POSTROUTING -s -o eth0 -j MASQUERADE
iptables-save > /root/work/openvpn/iptables_rules


5. Configure PAM. Create a file named openvpn in /etc/pam.d directory
[codesyntax lang="bash"]

vim /etc/pam.d/openvpn


auth optional /lib/security/ user=root passwd=mysqlpasswd host=localhost db=vpn_db table=tbl_user usercolumn=username passwdcolumn=password where=active=1 sqllog=no crypt=1 verbose=0
account required /lib/security/ user=root passwd=mysqlpasswd host=localhost db=vpn_db table=tbl_user usercolumn=userid passwdcolumn=password where=active=1 sqllog=no crypt=1 verbose=0

6. Create the mysql database, the table where we will keep users and insert some test user.

[codesyntax lang="bash"]

mysql -u root -pmysqlpasswd


create database vpn_db;
use vpn_db;
CREATE TABLE `tbl_user` (
  `username` varchar(25) DEFAULT NULL,
  `password` varchar(25) DEFAULT NULL,
  `active` int(11) DEFAULT NULL,
  `sqllog` enum('yes','no') DEFAULT NULL,
  `crypt` int(11) DEFAULT NULL,
  `verbose` int(11) DEFAULT NULL,
  PRIMARY KEY (`id`)

INSERT INTO tbl_user
SET username = "user",
    PASSWORD = Encrypt("test"),
    active = "1"; 

7. Client side operations
7.1. Download and install the latest stable version of openvpn-gui from
7.2. Create a configuration file named server.conf in C:\Program Files\OpenVPN\config (for Windows 32bit version) or C:\Program Files (x86)\OpenVPN\config (for Windows 64bit version). The content of the file should look like:
dev tun
proto udp
remote VPN-SERVER 1194
resolv-retry infinite
ca ca.crt
cipher BF-CBC
verb 4
mute 20


  • VPN-SERVER must be the IP or hostname of  the server we just configured
  • ca.crt was generated on step 3. This file must be copied from the server and given to the client