LVM

Logical Volume Manager

How to expand existing root partition using LVM

Add a second physical drive.  Scan the system, no reboot needed:
echo "- - -" > /sys/class/scsi_host/host1/scan

Create Logic Group and Volume:

pvcreate datavg /dev/sdb1
vgcreate datavg /dev/sdb1
lvcreate -l 100%FREE -n lvdata datavg

# vgdisplay
  --- Volume group ---
  VG Name               datavg
  System ID             
  Format                lvm2
  Metadata Areas        1
  Metadata Sequence No  2
  VG Access             read/write
  VG Status             resizable
  MAX LV                0
  Cur LV                1
  Open LV               0
  Max PV                0
  Cur PV                1
  Act PV                1
  VG Size               59.99 GiB
  PE Size               4.00 MiB
  Total PE              15358
  Alloc PE / Size       15358 / 59.99 GiB
  Free  PE / Size       0 / 0   
  VG UUID               zWlhGf-YDZa-27xv-aH0t-F6fW-Hs1e-TY3d8t

mkfs.ext3 -m 0 /dev/datavg/lvdata
tune2fs -c0 /dev/datavg/lvdata


Expand existing root LVM partition

pvdisplay
pvcreate /dev/sdb1
vgextend root_partition_name /dev/sdb1
lvextend -l +100%FREE /dev/root_partition_name/root

resize2fs /dev/root_partition_name/root

If you need to reduce it back:

vgreduce -a root_partition_name

HTTP POST into a form from curl

I want to post some data from file.txt into a form on the website. Curl can do it from command line:

curl -X POST -d @filename.txt -u usernamehere:passwordhere https://server.company.com/session/sync.jsp

The content of filename.txt is pairs of name=value separated by &. E.g.

id=1&options=doit&field3=Submit

Code pre-formatted text to Blog

To paste code or pre-formatted text into Blog use pre tags (mind those spaces)

< pre >
< / pre >

Puppet logs on CentOS

By default Puppet sends logs to /var/log/messages Modify /etc/sysconfig/puppet file to send them to /var/log/puppet/ E.g.

# The puppetmaster server
PUPPET_SERVER=puppetmaster

# If you wish to specify the port to connect to do so here
#PUPPET_PORT=8140

# Where to log to. Specify syslog to send log messages to the system log.
PUPPET_LOG=/var/log/puppet/puppet.log

# You may specify other parameters to the puppet client here
#PUPPET_EXTRA_OPTS=--waitforcert=500

Change password without root on a list of servers

Some companies are strict on passwords and force you to to change your password every 30 days, no repeating passwords, the passwords have to be long, contain special characters, etc.  Here is a script that you can add as a cronjob assuming you have your ssh keys setup.

You'd need a file "list.txt" with the list of IPs and "oldpass.txt" file with the current password.  You can just set a cronjob to do reset password on a regular basis (every 25 days for example).

#!/bin/bash
# Generate random new password 24 characters long
newpass=`mkpasswd -l 30 -d 3 -C 5 -s 3`
# Get old password from oldpass file
oldpass=`cat oldpass.txt`
echo Old: $oldpass
echo New: $newpass

# ssh to server and reset password
for server in `cat list.txt`
  do
    echo "Changing $server"
    ssh -t $server 'passwd <<EOF
'$oldpass'
'$newpass'
'$newpass'
EOF'
  done

Sort IP addresses

cat list.txt |sort -t . -k 1,1n -k 2,2n -k 3,3n -k 4,4n

Enable port on Arista switch

Similar to Cisco, enabling port 35 on switch1 for example.

switch1>en
switch1#show interfaces Ethernet 35
switch1#configure
switch1(config)#interface Ethernet 35
switch1(config-if-Et35)#no shutdown
switch1(config-if-Et35)#end

Save your changes:
switch1#copy running-config startup-config

Bash - cross-reference two files

I have two files: list_to_remove and current_list.  I want to remove all servers from list_to_remove from the current list.

for i in $(cat list_to_remove); do grep -v "$i.company.com" current_list > temp && mv temp current_list; done

How to replace a section of text file bash script

Goal:
I want to replace a section of hibernate.cfg.xml with new servers.  I need to remove servers between
                <property name="hibernate.memcached.servers">
server1 server2 server3
                </property>

and replace them with mem1 mem2 mem3

cat replace.sh

#!/bin/bash awk 'BEGIN {A = 1};//{A=0; print "\t\t\n\t\t\t\ mem1.atl.company.com:11212 mem2.atl.company:11212 mem3.atl.company.com:11212 mem4.atl.company.com:11212 mem5.atl.company.com:11212 mem6.atl.company:11212 mem148.atl.company.com:11212 mem149.atl.company.com:11212 mem150.atl.company.com:11212\ \n\t\t"};/.*/ { if ( A == 1) print $0};/<\/property>/{A=1}; ' $1

Run script against any xml file

./replace.sh hibernate.cfg.xml > hibernate.cfg.xml.new

Puppet manifest for multiple servers

Puppet supports regular expressions.

E.g.
Run puppet manifest on all the web servers:
node /^web.*$/ {
  class { 'server_web': }
}

Run on a few (db0-9)
node /^db[0-9]\..*$/ {
  class { 'server_db': }
}

bash script sum

Bash script exercise.
Add variable to the result of the sum.  E.g.
1 1 2 3 5 8 13 21, etc.


#!/bin/bash
x=1
y=1
ans=0

while [ $ans -lt 100 ]
#while true
do
  ans=$(( x + y ))
  echo $x + $y = $ans
  x=$y
  y=$ans
done

Bash "for loop"
How to ping multiple selected servers in selected multiple racks.

for rack in 1 3 4 6 9 {14..27}; do echo $rack; for server in {46..48}; do fping "serv"$server"rack"$rack |grep unreachable |tee -a /tmp/down; done; done

Number of hits from server in bash

Let's say I have a list of servers and I want to calculate how many hits did I have from "client.com" on April 28, 2014

#!/bin/bash
total=0

for server in $(cat server_list)
  do
    echo $server
    echo "Current count = "$total
    servercount=$(ssh $server "zcat /var/log/httpd/access.2014-04-28.log.gz |grep client.com |wc -l")
    echo "Server count ="$servercount
    total=$(($total + $servercount))
done

echo "Total count = "$total

Multiple DNS master servers

It is perfectly fine to have multiple master DNS servers as long as you keep them all in sync.  Here is an example how to make changes to DNS zones in GIT and push the changes to Bind servers.


DNS push script uses dedicated "sysadmin" account.  SSH keys have to be in place.


#!/bin/bash
# OPS branch have to be checked out to ~/git/ops/ to use this script
# I assume you have sudo privileges


usage(){
        echo -e Usage:\\n$0 datacenter
        exit 1
}

if [[ -z "$1" ]]
then
  usage
  exit 1
fi

datacenter=$1

cd ~/git/ops/config/sjc/named/var/named/data/
# Build reverse DNS zones
/usr/bin/mkrdns -root ~/git/ops/config/sjc/named/ ~/git/ops/config/sjc/named/etc/named.conf
# Checking syntax
for zone in `ls`
  do
    test=$(named-checkzone $zone $zone |grep OK)
    if [ "$test" != 'OK' ]
      then
      echo "Zone $zone syntax is wrong!"
      exit 1
    else
      echo "Syntax is fine"
    fi
done

echo "pushing to $datacenter"

# Execute remote dns change
sudo su - sysadmin -c "ssh -t -o StrictHostKeyChecking=no mgr1.$datacenter.company.com \"~/git/ops/scripts/dnspull.sh\""
echo "======================================================"
echo "mgr1.$datacenter.company.com is done"
echo "======================================================"
sudo su - sysadmin -c "ssh -t -o StrictHostKeyChecking=no mgr2.$datacenter.company.com \"~/git/ops/scripts/dnspull.sh\""
echo "======================================================"
echo "mgr2.$datacenter.company.com is done"
echo "======================================================"

DNS pull script will pull your changes from GIT, apply the changes, restart named, test if resolution is working properly (in this case "mgrclust1" server), and push the change to the next server.

#!/bin/bash
# Run it on the actual DNS (mgr1,2) server as user "sysadmin"


# I'm relying on resolv to get DC
DC=$(cat /etc/resolv.conf |grep search |awk '{print $2}' |awk -F. '{print $1}')
echo "=============================================="
echo "Pulling zones for $DC"
echo "=============================================="

# Pull from GITolite
cd ~/git/ops/
git pull origin master

# Copy zones over
rsync -av config/$DC/named/etc/ /var/named/chroot/etc/
rsync -av --delete config/$DC/named/var/named/ /var/named/chroot/var/named/

# Fix permissions
chown sysadmin:named /var/named/chroot/etc/named.conf
chown -R sysadmin:named /var/named/chroot/var/named/

# Restart named, look for OK
named_test=$(sudo /etc/init.d/named restart |grep Starting |awk '{print $4}')
echo $named_test

if [ "$named_test" != 'OK' ]
  then
    echo "Named restart failed!"
    exit 1
  else
    echo "Named restarted"
fi

# Try to resolve mgrclust1
dns_test=$(host mgrclust1 localhost |grep mgrclust1 |awk '{print $4}' |awk -F. '{print $4}')
if [ "$dns_test" != '1' ]
  then
  echo "I can't resolve mgrclust1!"
  exit 1
fi