Thursday, October 30, 2014

Python script to run remote SSH commands with sudo permission

I created a Python script to run remote SSH command with sudo permission. Linux SSH command doesn’t support password as command option, you have to use expect script to connect to multiple servers for automation. plink tool in Windows support password as command option.
The trick to accept sudo password is ‘-S’ option in sudo, which accept sudo password piped from stdin.It seems to be safe, I turned on debug and I couldn’t see the password recorded in secure/messages logs.
There are two versions of the script: the command line one and the class/module one.

The command line version.

if the clear text password is an concern, you can wrap the script by getpasswd module in Python,which read password from stdin.Read password once and apply the password to multiple servers.
[root@~]# ./  -s server1 -u admin -p Passwd123 date
Thu Oct 30 15:36:27 EST 2014

#'service sshd status' command  ran successfully with sudo enabled '-t'
[root@~]# ./  -t -s server1 -u admin -p Passwd123  'service sshd status'
openssh-daemon (pid  15686) is running...

#!/usr/bin/env python
import sys
import paramiko
import argparse
import socket
parser = argparse.ArgumentParser()
parser.add_argument("-s", "--servername", help="hostname or IP", required=True)
parser.add_argument("-P", "--port", help="ssh port default=22", default=22)
parser.add_argument("-t", "--sudo", help="enable sudo,sudo password will use the value of --password",action='store_true')
parser.add_argument("cmd",help="command to run")

host = args.servername
port = args.port
user = args.username 
password = args.password
cmd = args.cmd
if args.sudo:
    fullcmd="echo " + password + " |   sudo -S -p '' " + cmd

#if __name__ == "__main__":
client = paramiko.SSHClient()
#Don't use host key auto add policy for production servers
except (socket.error,paramiko.AuthenticationException) as message:
    print "ERROR: SSH connection to "+host+" failed: " +str(message)
if args.sudo: 
stdout = session.makefile('rb', -1)

The  class version

The class version allow multiple commands to run in an existing SSH transport,which is more efficient.To use the class,copy to a folder and create a new script to import the class 'from pyssh import PySSH',then reference the code in MAIN section without if statement.
#!/usr/bin/env python
import sys
import socket
import paramiko
# Class: PySSH
class PySSH(object):
    def __init__ (self):
        self.ssh = None
        self.transport = None  

    def disconnect (self):
        if self.transport is not None:
        if self.ssh is not None:

    def connect(self,hostname,username,password,port=22):
        self.hostname = hostname
        self.username = username
        self.password = password

        self.ssh = paramiko.SSHClient()
        #Don't use host key auto add policy for production servers
        except (socket.error,paramiko.AuthenticationException) as message:
            print "ERROR: SSH connection to "+self.hostname+" failed: " +str(message)
        return  self.transport is not None

    def runcmd(self,cmd,sudoenabled=False):
        if sudoenabled:
            fullcmd="echo " + self.password + " |   sudo -S -p '' " + cmd
        if self.transport is None:
            return "ERROR: connection was not established"
        #print "fullcmd ==== "+fullcmd
        if sudoenabled:
        stdout = session.makefile('rb', -1)
        return output

if __name__ == '__main__':
    hostname = 'server1'
    username = 'admin'
    password = 'password123'
    ssh = PySSH()
    print output
    output=ssh.runcmd('service sshd status',True)
    print output

Friday, September 5, 2014

Build Puppet module to use Hiera lookup

Puppet can use Hiera to look up data. This helps you disentangle site-specific data from Puppet code, for easier code re-use and easier management of data that needs to differ across your node population

One typical example is IP address and NTP/DNS servers, the IP address is unique for each server and NTP/DNS is global. I built a linux-network test module to demonstrate the usage of Hiera
Hiera supports yaml and Json as backend by default, however you can write your  custom backend using Hiera API.

Define datadir in hiera.yaml
[root@server1 modules]# cat /etc/puppetlabs/puppet/hiera.yaml 
  - yaml

  - defaults
  - "%{clientcert}"
  - "%{environment}"
  - global

# datadir is empty here, so hiera uses its defaults:
# - /var/lib/hiera on *nix
# - %CommonAppData%\PuppetLabs\hiera\var on Windows
# When specifying a datadir, make sure the directory exists.
  :datadir: /etc/puppetlabs/puppet/hieradata

Set all values in YAML file instead of manifest file
You can also add class name in YAML file, then assign class to node with hiera_include
[root@server1 modules]# cat /etc/puppetlabs/puppet/hieradata/global.yaml 
# ntp.conf
ntpservers: [,]

searchdomain: [,]
nameservers: [,]

[root@server1 modules]# cat /etc/puppetlabs/puppet/hieradata/ 
   device: eth1
   routes: [' via', ' via']
   device: eth3
   #routes: [' via', ' via']
Execute the whole class or a function of the class in site.pp, the codes in site.pp become universal.
The site.pp manifest file is just generic code
[root@server1 modules]# cat /etc/puppetlabs/puppet/manifests/site.pp

node "server1" {
include "linux-network"

node "server2" {
linux-network::setinterface { 'eth1': }
linux-network module manifest files
[root@server1 modules]# cat ./linux-network/manifests/init.pp 
class linux-network {
 linux-network::setinterface { 'eth1': ; 'eth3': }
 linux-network::setroute { 'eth1': ; 'eth3':}

 linux-network::setconf_ntp {'ntp.conf':}
 linux-network::setconf_resolv {'resolv.conf':}

[root@server1 modules]# cat ./linux-network/manifests/setconf_ntp.pp 
define linux-network::setconf_ntp  ( ) {


file {"/etc/ntp.conf":
 ensure => present,
 owner => root,
 mode => 644,
 content => template("${module_name}/ntp.conf.erb")

[root@server1 modules]# cat ./linux-network/manifests/setconf_resolv.pp 
define linux-network::setconf_resolv  ( ) {


file {"/etc/resolv.conf":
ensure => present,
owner => root,
mode => 644,
content => template("${module_name}/resolv.conf.erb")

[root@server1 modules]# cat ./linux-network/manifests/setinterface.pp 
define linux-network::setinterface  ( ) {


file {"/etc/sysconfig/network-scripts/ifcfg-$device":
 ensure => present,
 owner => root,
 mode => 644,
 content => template("${module_name}/ifcfg.erb")


[root@server1 modules]# cat ./linux-network/manifests/setroute.pp 
define linux-network::setroute  ( ) {


file {"/etc/sysconfig/network-scripts/route-$device":
ensure => present,
owner => root,
mode => 644,
content => template("${module_name}/route.erb")
linux-network module template files
[root@server1 modules]# cat ./linux-network/templates/ifcfg.erb 
DEVICE=<%=@device %>
<%- if @gateway =~ /(\d{1,3})\.(\d{1,3})\.(\d{1,3})\.(\d{1,3})/   -%>
GATEWAY=<%=@gateway %>
<%- end -%>

[root@server1 modules]# cat ./linux-network/templates/ntp.conf.erb 
 tinker panic 0
 restrict default kod nomodify notrap nopeer noquery
 restrict -6 default kod nomodify notrap nopeer noquery
 restrict -6 ::1
 <%- @ntpservers.each do |x| -%>
 server <%= x %>
<%- end  -%>
 driftfile /var/lib/ntp/drift

 [root@server1 modules]# cat ./linux-network/templates/resolv.conf.erb
# resolver configuration file...
options         timeout:1 attempts:8 rotate
domain       <%=@domainname %>
<%-  if !@searchdomain.empty?   -%>
search <%=@domainname  -%> <%=  @searchdomain.join(' ') %>
<%- end -%>
<%-  @nameservers.each do |  x | -%>
nameserver <%= x %>
<%- end -%>

[root@server1 modules]# cat ./linux-network/templates/route.erb 
<%- if defined?(@routes)   -%>
<%- @routes.each do | x | -%>
<%=x %>
<%- end -%>
<%- end -%>

Thursday, March 13, 2014

Setup SAN Boot for RHEL 6.x using native multipath on EMC storage

1) RHEL 6.x (most apply to RHEL 5.x too, RHEL 5.x use mkinitrd instead of Dracut and the /etc/multipath.conf is slightly different refer to Red Hat KB in reference section)
2) EMC storage was setup with Active/Active (ALUA)
3) Boot LUN was presented with single path for initial install


1. Server boots up after initial install
2. Login to server as root to enable multipath
[root@server1]#mpathconf --enable –-with_multipathd y
3. Edit /etc/multipath.conf and make sure it only contains following valid parameters

blacklist {

defaults {
 user_friendly_names yes
devices {
  device {
    vendor "DGC"
    product ".*"
    product_blacklist "LUNZ"
    hardware_handler "1 alua"   
    path_checker directio    
    prio alua                
4.Find out the logical path the root disk is mapped
[root@server1]#multipath –v3
It should be /dev/mapper/mpatha

5. Create initramfs with multipath module
[root@server1]#dracut --force -–add multipath

6. Make sure multipath.conf is included in initrd image
[root@server1]#lsinitrd /boot/initramfs-*.x86_64.img | grep multipath.conf
-rw-r--r--   1 root     root         2525 Feb 27 13:31 etc/multipath.conf
7. Modify the /boot/grub/ and change
 (hd0) /dev/sda    to
 (hd0) /dev/mapper/mpatha
This is assuming the boot disk is on /dev/mapper/mpatha as verified in step 2 above.

8. Reboot the server.

9. Verify multipath, check hwhandler='1 alua' and member disk sda for mpatha
[root@server1]#multipath –ll 
mpatha (3600601609973310067eb1e1ed69ae311) dm-0 DGC,VRAID
size=150G features='1 queue_if_no_path' hwhandler='1 alua' wp=rw
`-+- policy='round-robin 0' prio=10 status=enabled
  |- 1:0:0:0 sda 8:0   active ready running

10. Ask storage administrator to enable other paths for boot LUN.
11. Reboot server again after multipath is aenabled in storage too
12. Login server to verify all paths, check hwhandler='1 alua' prio>0
if hwhandler='1 emc' or prio=0 means PNR mode

[root@server1]#multipath -ll
mpatha (3600601609973310067eb1e1ed69ae311) dm-0 DGC,VRAID
size=150G features='1 queue_if_no_path' hwhandler='1 alua' wp=rw
|-+- policy='round-robin 0' prio=130 status=active
| |- 1:0:1:0 sdd 8:48  active ready running
| `- 2:0:1:0 sdj 8:144 active ready running
`-+- policy='round-robin 0' prio=10 status=enabled
  |- 1:0:0:0 sda 8:0   active ready running
  `- 2:0:0:0 sdg 8:96  active ready running
mpathb (360060160997331009fd6e124d69ae311) dm-1 DGC,VRAID
size=800G features='1 queue_if_no_path' hwhandler='1 alua' wp=rw
|-+- policy='round-robin 0' prio=130 status=active
| |- 1:0:0:1 sdb 8:16  active ready running
| `- 2:0:0:1 sdh 8:112 active ready running
`-+- policy='round-robin 0' prio=10 status=enabled
  |- 1:0:1:1 sde 8:64  active ready running
  `- 2:0:1:1 sdk 8:160 active ready running
13. Partition other LUNS using fdisk command as normal, but use logical path /dev/mapper/mpathb etc (partition will be created as /dev/mapper/mpathbp1 instead of /dev/mapper/mpathb1
NOTE: any change to /etc/multipath.conf requires re-create initramfs ( dracut --force -–add multipath) and a reboot, because the boot LUN is on SAN, if boot LUN is local disk, change to /etc/multipath.conf only requires multipathd restart

Wednesday, March 12, 2014

Automate Server deployment with Ansible

There are many server automation applications in the market: puppet,chef,cfengine and salt. Ansible is relatively new, but I think it is better than puppet in server deployment automation tasks.
1. Dependency packages
Ansible depends on python, which is installed by default at least for Red Hat alike distributions
Puppet depends on ruby, which is not installed by default.
2. Agent
Ansible is agentless, it rely on SSH
Puppet need agent running in target server as a daemon.
3. Security
Ansible use SSH as transport method, so Username and password are required for each connection.(Ansible is smart enough to cache the SSH and sudo password, so it will be only prompted once for the first server)
Puppet: agent is controlled by master server, if master server is compromised, all hosts can be brought down easily
4. Setup
Ansible is easy to setup, as there is no agent. Ansible server is easy to setup too, there are just python scripts. You can even run it without installing it.
Puppet need packages installed in agent host or server, the agent certificate need to be signed before server can talk agent.
Ansible use SSH TCP port 22, which is standard firewall port already opened in most infrastructure.
Puppet use customized TCP port , typically 8139
5. Command line mode
Ansible supports command line mode for ad-hoc tasks, so you don’t need to write tasks definitions, just pass the command to ansbile such as return date for a number servers.
ansbile myservers –k –K –u admin –m raw –a “date”

The following example show a typical server deployment
[root@centos1 post]# cat setup.yml 
---        #ansible playbook use YAML syntax
- hosts: server1          #It is a server or server group as defined in /etc/ansbile/hosts
  user: admin 
  sudo: yes
    - vars/settings.yml   #global variables
    - vars/{{ ansible_hostname }}.yml             #server specific variable . ansible_hostname is variable, it is server1.yml for server1

  - name: yum
    action: yum name=${item}  state=present      #install yum packages
      - kernel-devel-{{ ansible_kernel }}
      - ed
      - ksh
      - ntp
  - script: ./scripts/        #- The script will insert 'UseDNS no' , - script is shorthand  for - name: XX ,action: YY

  - name: users | Delete users       #delete users delusers is list if users defined in setting.yml
    action: user name=$item state=absent
    with_items: delusers

  - name: ifcfg-eth0 | Configuration file      #ansible template engine is Jinja2
    action: template src=./templates/ifcfg-eth0.j2 dest=/etc/sysconfig/network-scripts/ifcfg-eth0 owner=root group=root

  - name: route-eth0 | Configuration file, /etc/sysconfig/network-scripts/route-eth0
    action: template src=templates/route-eth0.j2 dest=/etc/sysconfig/network-scripts/route-eth0

  - name: resolv.conf | Configuration file, /etc/resolv.conf
    action: template src=templates/resolv.conf.j2 dest=/etc/resolv.conf

  - name: ntpd | Configuration file, /etc/ntp.conf
    action: template src=templates/ntp.conf.j2 dest=/etc/ntp.conf
    - restart ntpd

  - name: snmpd | Configuration file, /etc/snmp/snmpd.conf
    action: copy src=files/snmpd.conf dest=/etc/snmp/snmpd.conf owner=root group=root mode=0644
    - restart snmpd

  - copy: src=files/clock dest=/etc/sysconfig/clock owner=root group=root mode=0644
  - command: ln -fs /usr/share/zoneinfo/Australia/Sydney /etc/localtime

  - name: restart sshd
    action: service name=sshd enabled=yes state=restarted
  - name: restart ntpd
    action: service name=ntpd enabled=yes state=restarted
  - name: restart snmpd
    action: service name=snmpd enabled=yes state=restarted

####----Global variables 
[root@centos1 post]# cat vars/settings.yml 
# ntp.conf
ntpservers: [,]

#users to delete
delusers: [user1, user2]

searchdomain: []
nameservers: [,]

####----Server specific  variable
[root@centos1 post]# cat vars/server1.yml 
   device: eth1
   routes: [' via', ' via']
####----How the tempalate reference the variable
[root@centos1 post]# cat templates/resolv.conf.j2 
# resolver configuration file...
options         timeout:1 attempts:8 rotate
domain          {{domainname}}
search          {{domainname}} {{ searchdomain | join (' ') }}

{% for host in nameservers %}
nameserver {{host}}
{% endfor %}

[root@centos1 post]# cat templates/ifcfg-eth1.j2 
{% if eth1.gateway is defined  %} 

####----a separate playbook to create LVM and file system 
[root@centos1 post]# cat setup-lvm.yml 
- hosts: server1
  user: admin
  sudo: yes
  gather_facts: no
    mntp:  /opt
    vgname: vg01
    pvname: /dev/sdb1
    lv1: opt

  - script: ./scripts/ $pvname       #a script to create LVM partion and create physical volume
  - name: filesystem | Create pv,vg,lv and file systems
    action: lvg  vg=$vgname pvs=$pvname

  #- name: filesystem | create lv
  - lvol: vg=$vgname lv=$lv1 size=51196

 # - name: filesystem | create fs
  - filesystem: fstype=ext4 dev=/dev/${vgname}/${lv1}

  #- name: filesytem | mount dir
  - mount: name=${mntp} src=/dev/${vgname}/${lv1} dump=1 passno=2 fstype=ext4 state=mounted
How to run the playbook?
[root@centos1 post]# ansible-playbook -k -K setup.yml

  -k, --ask-pass        ask for SSH password
  -K, --ask-sudo-pass   ask for sudo password
Download all the files

Thursday, June 20, 2013

VMware PowerCLI: Map datastore name to LUN devicename.

It is not obvious as it is thought to be to map datastore name to LUN devicename in native PowerCLI codes,
The  esxcli interface exposed to PowerCLI  make it very easy.(Tested in ESXi 5.0)
PowerCLI>$esxcli=get-esxcli -vmhost esx01
PowerCLI>$ | ft devicename,volumename -autosize

DeviceName                           VolumeName
----------                           ----------
naa.600601605bc02e00007fb97cacbee211 datastore01
naa.600601605bc02e00fac8cd88acbee211 datastore02

Script to automatically partition a new disk and create LVM PV

It is a very common task to create a single partition on  whole disk  and create LVM PV, How to automate it?

fdisk doesn't support making partition in script mode, sfdisk can, but it is not as good as the powerful parted tool. parted can also optimize partition alignment automatically(parted -a optimal).

#Create a single primary partiton with whole disk size and create LVM PV on it
if [[ -z $disk ]]; then
 echo "Usage: $0 disk device name: e.g $0 /dev/sdb"

if [[ -e ${disk}${partno} ]]; then
 echo "==> ${disk}${partno} already exist"

echo "==> Create MBR label"
parted -s $disk  mklabel msdos
ncyl=$(parted $disk unit cyl print  | sed -n 's/.*: \([0-9]*\)cyl/\1/p')

if [[ $ncyl != [0-9]* ]]; then
 echo "disk $disk has invalid cylinders number: $ncyl"

echo "==> create primary parition  $partno with $ncyl cylinders"
parted -a optimal $disk mkpart primary 0cyl ${ncyl}cyl
echo "==> set partition $partno to type: lvm "
parted $disk set $partno lvm on
partprobe > /dev/null 2>&1
echo "==> create PV ${disk}${partno} "
pvcreate ${disk}${partno}

Friday, April 19, 2013

Understanding SysV-style Initscripts in Red Hat Linux

It is often needed to write your own init start/stop script, the following is the minimum requirement for your script to behave as expected. The discussion is based on Red Hat Linux family, other distributions like Debian use LSB (Linux Standard Base Specification) Init Scripts.

Location of the script

/etc/init.d is the well known location, but actually /etc/rc.d/init.d is the real original location. Since /etc/init.d is a hard link to /etc/rc.d/init.d, it makes no difference.

Header of the script

It needs at least 3 lines.  The shell script interpreter (/bin/sh, /bin/bash .. etc), the chkconfig header and script description
#   chkconfig: 345 56 10
#   description: Startup/shutdown script for the Common UNIX 

Body of the script

Obviously, it need  to accept parameter “start”, which  /etc/rc3.d/S* will call  on OS startup and accept parameter “stop”, which /etc/rc0.d/K* script will call on OS shutdown.
The lockfile is often overlooked, it is used to check the existence of the daemon on OS shutdown, otherwise the stop action won’t be called. If you found an issue that a script started on OS startup but never stop properly on shutdown, you need to create lockfile. note: lockfile is not pidfile which contains PID of the process, lockfile is usually a blank file.
lockfile=/var/lock/subsys/$(basename $0)
case $1 in
  [ $? = 0 ] && touch $lockfile
  [ $? = 0 ] && rf –f  $lockfile


It is recommended to import functions in /etc/rc.d/init.d/functions to use ‘daemon’ to startup your application or killproc to shutdown your application instead of reinventing the wheel.

LSB headers

You may see something like this in an init script.
 # Provides: boot_facility_1 [ boot_facility_2 ...]
 # Required-Start: boot_facility_1 [ boot_facility_2 ...]
 # Required-Stop: boot_facility_1 [ boot_facility_2 ...]
 # Should-Start: boot_facility_1 [ boot_facility_2 ...]
 # Should-Stop: boot_facility_1 [ boot_facility_2 ...]
 # Default-Start: run_level_1 [ run_level_2 ...]
 # Default-Stop: run_level_1 [ run_level_2 ...]
 # Short-Description: short_description
 # Description: multiline_description
They are LSB(Linux Standard Base) headers, they are supported by default in Debian and SUSE Linux.
Red Hat Linux supports this by additional package “redhat-lsb” and it is not installed by default, Be warned,50+ dependences need to installed as well.