Showing posts with label linux commands. Show all posts

Saturday, 2 September 2017

Preparing Linux Server for Nagios monitoring tool

In this article we are going to discuss about the best practice to install an Linux server for nagios monitoring tool. As like regular installation will also work but we will face an issue later an while configuring the nagios alerts, integrating with nagvis and pnp4nagios. Preparing Linux Server for Nagios Monitoring tool

Just remember to follow the below steps to prepare an Linux server for nagios monitoring tool.

Preparing Linux server for Nagios monitoring tool

We have consider below steps to make best nagios monitoring tool implementation

Do not install all packages all are not required
Install Linux server with minimal installation
Do remember to install php, perl, shell, basic tools, snmp, httpd, ssh, tar, wget, python and crond
While installing make a separate partition for /usr/ using LVM (As a default installation location if you considered. if you want to change you also do that )
Create all separate partition for Nagios archive Logs
One important thing is to check version compatibility
Use always stable versions to build production servers.

Nagios core Installation in RHEL7 / Centos 7 Step by Step Guide

Nagios Core 4 Installation Step by step guide in RHEL 7 / Centos 7. Nagios Core Installation is simple and easy process but when your doing for the first time you will little bit confused, Installation of Nagios core is plays major role because while installing we have to run configure as nagcmd group or else all the file permissions and configuration files we have to change later.

What is Nagios core..?? How to do Nagios Core Installation

Nagios core is an most popular and enterprise open source monitoring tool. Using this monitoring tool you can monitor any device in this world even UPS / Battery status. This tool will support almost all the scripting languages.

Prepare your Linux server to install Nagios monitoring tool

Nagios Version: 4.1.1

Prerequisites:

Nagios code is written in C language so you required an gcc++ compiler packages to compile and install Nagios.
Required wget package to download the nagios tool directly from web to server
To untar the package required Rar / Zip RPM’s
Web / Apache / Httpd service to host the Nagios
Install php and perl packages to run Nagios plugins

Step1:> Installing prerequisites

~]# yum install -y wget httpd php gcc glibc glibc-common gd gd-devel make net-snmp perl perl-devel openssl

by using above command it will install all the required prerequisites

Step2:> Download the Nagios Core Package from web

~]#wget http://sourceforge.net/projects/nagios/files/nagios-4.x/nagios-4.1.1/nagios-4.1.1.tar.gz

using above command you can download the NagiosCore 4.1.1 package

Step3:> Create Nagios User and Nagcmd group

~]#useradd nagios                ##Creating Nagios User
~]#groupadd nagcmd               ##Creating Nagcmd Group
~]#usermod -a -G nagcmd nagios   ##Adding nagios user to nagcmd group

Step4:> Untar the Package

~]#tar -xzvf nagios-4.1.1.tar.gz

above command will untar the tar file

Step5:> Compiling Nagios code

cd nagios-4.1.1
./configure --with-command-group=nagcmd
make all                                    ##To Make the package
make install                      ##To install the complied package 
make install-init        ##To install init script in /etc/rc.d/init.d
make install-config                    ##To Generate the config files
make install-commandmode        ##To install the command mode enable
make install-webconf                ##To Generate the Web config file

using all above commands in sequence will installation nagios

Step6:> Copy the Event handler directory and change its ownership

~]#cp -rvf contrib/eventhandlers/ /usr/local/nagios/libexec/

Change ownership of copied directory using below command

~]#chown -R nagios:nagcmd /usr/local/nagios/libexec/eventhandlers

Step7:> Create nagiosadmin user and Generate the password to Web Login

create nagiosadmin user and generate password of nagiosadmin using htpasswd command. nagiosadmin we will use to login the web console.

~]#htpasswd -c /usr/local/nagios/etc/htpasswd.users nagiosadmin

Step8:> Start the httpd and nagios services

use below given command to start the httpd and nagios services

~]#systemctl start httpd.service 
~]#systemctl start nagios.service

Check the services status

~]#systemctl status httpd.service 
~]#systemctl status nagios.service

Step9:> Allow 80 port to access the Nagios using remote machine

in RHEL7 / Centos 7 instead of iptables firewalld is introduced use firewalld to allow 80 port

~]#firewall-cmd --zone=public --add-port=80/tcp -permanent 
~]#firewall-cmd --reload

Step10:> Access the Nagios using web browser

open the browser and type http://IPADDRESS/nagios

in above screen you can able to see the Nagios dashboard is showing errors, because we did not yet installed the nagios plugins. After Nagios Core Installation We must install plugins are else we will get above error.

Lets install nagios plugins..!!

Install Nagios plugins on Nagios Server

Nagios plugins will play main role to monitor the service. Its very easy to install the nagios plugins.

nagios plugins are locate yet /usr/local/nagios/libexec/

Download the plugins bundle

~]# wget http://www.nagios-plugins.org/download/nagios-2.0.3.tar.gz

extract the package

~]# tar -xzvf nagios-plugins-2.0.3.tar.gz

Change to directory to install plugins

cd nagios-plugins-2.0.3 
./configure --with-nagios-user=nagios --with-nagios-group=nagcmd 
make 
make install

After installing an nagios plugins just wait for five minutes and open the nagios web console and see.

That’s it…!! your Nagios Core monitoring tool is installed successfully. Nagios Core Installation is Successfully Now you can Monitor Servers / Devices using Nagios Core.

Please provide your valuable comments..!!

referred from ARKIT.CO.IN

Linux Server Monitoring using SNMP (Simple Network Management Protocol) Nagios

If you would like to monitor servers agent less ultimately the best solution is SNMP (Simple Network Management Protocol). Agent less server monitoring using Nagios. In this Article we are going to see how to Linux server Monitoring Using SNMP Nagios.

Why you would like to go with an Agent less monitoring? because when your server is already in production but you don’t want to modify / Install extra packages in them. In this case simple method is enabling SNMP in client which send traps to Nagios server.

Linux Server Monitoring Using SNMP Nagios

Open SNMP communication from Linux client and monitor using Nagios. Let’s see what are steps we have to follow in order to configure.

Complete Step by step guide for SNMP Installation and configuration

[root@Arkit-Serv~]# vi /etc/snmp/snmpd.conf

rocommunity commstring NAGIOS-SERVER-IP

:wq

Just check from Nagios server that SNMP is responding properly, if you get output like below then its working fine.

./check_snmp -H 192.168.1.23 -o .1.3.6.1.2.1.1.3.0 -C commstring
SNMP OK - Timeticks: (60558317) 7 days, 0:13:03.17 |

Define Commands

define command {
 command_name check_service_snmp
 command_line $USER1$/check_snmp -H $HOSTADDRESS$ $ARG1$
}

Now Define your Host and Service Definitions

###############################################################
# #
# ::: Host Defination ::: #
###############################################################

define host {
 host_name LinuxServer.arkit.co.in
 use generic_host
 address 192.168.1.2
 hostgroups linux-servers
 max_check_attempts 5
 check_interval 5
 retry_interval 1
 check_period 24x7
 contacts Linuxadmin
 contact_groups LinuxGroup
 notification_interval 0
 notification_period 24x7
 notifications_enabled 1
 }

###############################################################
# #
# ::: Service Defination ::: #
###############################################################
define service {
 host_name LinuxServer.arkit.co.in
 service_description / Disk Usage
 use Linuxsnmp_storage
 check_command check_service_snmp! -C commstring --v2c -m "^/$" -w 90 -c 95 -f
 max_check_attempts 5
 check_interval 10
 retry_interval 1
 check_period 24x7
 notification_interval 0
 notification_period 24x7
 contacts Linuxadmin
 contact_groups LinuxGroup
 }

define service {
 host_name LinuxServer.arkit.co.in
 service_description CPU Usage
 use linuxsnmp_load
 check_command check_service_snmp! -C commstring --v2c -w 90 -c 95 -f
 max_check_attempts 5
 check_interval 10
 retry_interval 1
 check_period 24x7
 notification_interval 0
 notification_period 24x7
 contacts Linuxadmin
 contact_groups LinuxGroup

}

define service {
 host_name LinuxServer.arkit.co.in
 service_description Memory Usage
 use Linuxsnmp_storage
 check_command check_service_snmp! -C commstring --v2c -m Physical -w 90 -c 95 -f
 max_check_attempts 5
 check_interval 10
 retry_interval 1
 check_period 24x7
 notification_interval 0
 notification_period 24x7
 contacts Linuxadmin
 contact_groups LinuxGroup

}

define service {
 host_name LinuxServer.arkit.co.in
 service_description Ping
 use genericnetdevice_ping_service
 check_command check-host-alive
 max_check_attempts 5
 check_interval 10
 retry_interval 1
 check_period 24x7
 notification_interval 0
 notification_period 24x7
 notifications_enabled 1
 contacts Linuxadmin
 contact_groups LinuxGroup

}

define service {
 host_name LinuxServer.arkit.co.in
 service_description Swap Usage
 use Linuxsnmp_storage
 check_command check_service_snmp! -C commstring --v2c -m 'Swap' -w 90 -c 95 -f
 max_check_attempts 5
 check_interval 10
 retry_interval 1
 check_period 24x7
 notification_interval 0
 notification_period 24x7
 contacts Linuxadmin
 contact_groups LinuxGroup

}

That’s it Go and see in your Nagios web console you can see all specified service status.

Nagios Linux

Conclusion:

If you have Network latency / Network slowness then you will so many false positive alarms from Monitoring tool. If you use NRPE client which reduce little bit of false positive alerts. Nagios Server resource utilization will go high when you use SNMP. Linux server monitoring using snmp

Saturday, 26 August 2017

Practical Examples of Linux Find Command top 35

The Linux Find Command is one of the most important and much used command in Linux sytems. Find command used to search and locate list of files and directories based on conditions you specify for files that match the arguments. Find can be used in variety of conditions like you can find files by permissions, users,groups, file type, date, size and other possible criteria.

Through this article we are sharing our day-to-day Linux find command experience and its usage in the form of examples. In this article we will show you the most used 35 Find Commands examples in Linux. We have divided the section into Five parts from basic to advance usage of find command.

1. Part I: Basic Find Commands for Finding Files with Names

2. Part II: Find Files Based on their Permissions

3. Part III: Search Files Based On Owners and Groups

4. Part IV: Find Files and Directories Based on Date and Time

5. Part V: Find Files and Directories Based on Size

6. Part VI: Find Multiple Filenames in Linux

Part I – Basic Find Commands for Finding Files with Names

1. Find Files Using Name in Current Directory

Find all the files whose name is tecmint.txt in a current working directory.

# find . -name tecmint.txt

./tecmint.txt

2. Find Files Under Home Directory

Find all the files under /home directory with name tecmint.txt.

# find /home -name tecmint.txt

/home/tecmint.txt

3. Find Files Using Name and Ignoring Case

Find all the files whose name is tecmint.txt and contains both capital and small letters in /home directory.

# find /home -iname tecmint.txt

./tecmint.txt

./Tecmint.txt

4. Find Directories Using Name

Find all directories whose name is Tecmint in / directory.

# find / -type d -name Tecmint

/Tecmint

5. Find PHP Files Using Name

Find all php files whose name is tecmint.php in a current working directory.

# find . -type f -name tecmint.php

./tecmint.php

6. Find all PHP Files in Directory

Find all php files in a directory.

# find . -type f -name "*.php"

./tecmint.php

./login.php

./index.php

Part II – Find Files Based on their Permissions

7. Find Files With 777 Permissions

Find all the files whose permissions are 777.

# find . -type f -perm 0777 -print

8. Find Files Without 777 Permissions

Find all the files without permission 777.

# find / -type f ! -perm 777

9. Find SGID Files with 644 Permissions

Find all the SGID bit files whose permissions set to 644.

# find / -perm 2644

10. Find Sticky Bit Files with 551 Permissions

Find all the Sticky Bit set files whose permission are 551.

# find / -perm 1551

11. Find SUID Files

Find all SUID set files.

# find / -perm /u=s

12. Find SGID Files

Find all SGID set files.

# find / -perm /g=s

13. Find Read Only Files

Find all Read Only files.

# find / -perm /u=r

14. Find Executable Files

Find all Executable files.

# find / -perm /a=x

15. Find Files with 777 Permissions and Chmod to 644

Find all 777 permission files and use chmod command to set permissions to 644.

# find / -type f -perm 0777 -print -exec chmod 644 {} \;

16. Find Directories with 777 Permissions and Chmod to 755

Find all 777 permission directories and use chmod command to set permissions to 755.

# find / -type d -perm 777 -print -exec chmod 755 {} \;

17. Find and remove single File

To find a single file called tecmint.txt and remove it.

# find . -type f -name "tecmint.txt" -exec rm -f {} \;

18. Find and remove Multiple File

To find and remove multiple files such as .mp3 or .txt, then use.

# find . -type f -name "*.txt" -exec rm -f {} \;

# find . -type f -name "*.mp3" -exec rm -f {} \;

19. Find all Empty Files

To file all empty files under certain path.

# find /tmp -type f -empty

20. Find all Empty Directories

To file all empty directories under certain path.

# find /tmp -type d -empty

21. File all Hidden Files

To find all hidden files, use below command.

# find /tmp -type f -name ".*"

Part III – Search Files Based On Owners and Groups

22. Find Single File Based on User

To find all or single file called tecmint.txt under / root directory of owner root.

# find / -user root -name tecmint.txt

23. Find all Files Based on User

To find all files that belongs to user Tecmint under /home directory.

# find /home -user tecmint

24. Find all Files Based on Group

To find all files that belongs to group Developer under /home directory.

# find /home -group developer

25. Find Particular Files of User

To find all .txt files of user Tecmint under /home directory.

# find /home -user tecmint -iname "*.txt"

Part IV – Find Files and Directories Based on Date and Time

26. Find Last 50 Days Modified Files

To find all the files which are modified 50 days back.

# find / -mtime 50

27. Find Last 50 Days Accessed Files

To find all the files which are accessed 50 days back.

# find / -atime 50

28. Find Last 50-100 Days Modified Files

To find all the files which are modified more than 50 days back and less than 100 days.

# find / -mtime +50 –mtime -100

29. Find Changed Files in Last 1 Hour

To find all the files which are changed in last 1 hour.

# find / -cmin -60

30. Find Modified Files in Last 1 Hour

To find all the files which are modified in last 1 hour.

# find / -mmin -60

31. Find Accessed Files in Last 1 Hour

To find all the files which are accessed in last 1 hour.

# find / -amin -60

Part V – Find Files and Directories Based on Size

32. Find 50MB Files

To find all 50MB files, use.

# find / -size 50M

33. Find Size between 50MB – 100MB

To find all the files which are greater than 50MB and less than 100MB.

# find / -size +50M -size -100M

34. Find and Delete 100MB Files

To find all 100MB files and delete them using one single command.

# find / -size +100M -exec rm -rf {} \;

35. Find Specific Files and Delete

Find all .mp3 files with more than 10MB and delete them using one single command.

# find / -type f -name *.mp3 -size +10M -exec rm {} \;

That’s it, We are ending this post here, In our next article we will discuss more about other Linux commands in depth with practical examples. Let us know your opinions on this article using our comment sectio.1

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13.5. Removing an Old Disk

Say you have an old IDE drive on /dev/hdb. You want to remove that old disk but a lot of files are on it.

	Backup Your System
	You should always backup your system before attempting a pvmove operation.

13.5.1. Distributing Old Extents to Existing Disks in Volume Group

If you have enough free extents on the other disks in the volume group, you have it easy. Simply run

# pvmove /dev/hdb

pvmove -- moving physical extents in active volume group "dev"

pvmove -- WARNING: moving of active logical volumes may cause data loss!

pvmove -- do you want to continue? [y/n] y

pvmove -- 249 extents of physical volume "/dev/hdb" successfully moved

This will move the allocated physical extents from /dev/hdb onto the rest of the disks in the volume group.

	pvmove is Slow
	Be aware that pvmove is quite slow as it has to copy the contents of a disk block by block to one or more disks. If you want more steady status reports from pvmove, use the `-v` flag.

13.5.1.1. Remove the unused disk

We can now remove the old IDE disk from the volume group.

# vgreduce dev /dev/hdb

vgreduce -- doing automatic backup of volume group "dev"

vgreduce -- volume group "dev" successfully reduced by physical volume:

vgreduce -- /dev/hdb

The drive can now be either physically removed when the machine is next powered down or reallocated to other users.

13.5.2. Distributing Old Extents to a New Replacement Disk

If you do not have enough free physical extents to distribute the old physical extents to, you will have to add a disk to the volume group and move the extents to it.

13.5.2.1. Prepare the disk

First, you need to pvcreate the new disk to make it available to LVM. In this recipe we show that you don't need to partition a disk to be able to use it.

# pvcreate /dev/sdf

pvcreate -- physical volume "/dev/sdf" successfully created

13.5.2.2. Add it to the volume group

As developers use a lot of disk space this is a good volume group to add it into.

# vgextend dev /dev/sdf

vgextend -- INFO: maximum logical volume size is 255.99 Gigabyte

vgextend -- doing automatic backup of volume group "dev"

vgextend -- volume group "dev" successfully extended

13.5.2.3. Move the data

Next we move the data from the old disk onto the new one. Note that it is not necessary to unmount the file system before doing this. Although it is *highly* recommended that you do a full backup before attempting this operation in case of a power outage or some other problem that may interrupt it. The pvmove command can take a considerable amount of time to complete and it also exacts a performance hit on the two volumes so, although it isn't necessary, it is advisable to do this when the volumes are not too busy.

# pvmove /dev/hdb /dev/sdf

pvmove -- moving physical extents in active volume group "dev"

pvmove -- WARNING: moving of active logical volumes may cause data loss!

pvmove -- do you want to continue? [y/n] y

pvmove -- 249 extents of physical volume "/dev/hdb" successfully moved

13.5.2.4. Remove the unused disk

We can now remove the old IDE disk from the volume group.

# vgreduce dev /dev/hdb

vgreduce -- doing automatic backup of volume group "dev"

vgreduce -- volume group "dev" successfully reduced by physical volume:

vgreduce -- /dev/hdb

The drive can now be either physically removed when the machine is next powered down or reallocated to some other users.

13.6. Moving a volume group to another system

It is quite easy to move a whole volume group to another system if, for example, a user department acquires a new server. To do this we use the vgexport and vgimport commands.

vgexport/vgimport is not necessary to move drives from one system to another. It is an administrative policy tool to prevent access to volumes in the time it takes to move them.

13.6.1. Unmount the file system

First, make sure that no users are accessing files on the active volume, then unmount it

# unmount /mnt/design/users

13.6.2. Mark the volume group inactive

Marking the volume group inactive removes it from the kernel and prevents any further activity on it.

# vgchange -an design

vgchange -- volume group "design" successfully deactivated

13.6.3. Export the volume group

It is now necessary to export the volume group. This prevents it from being accessed on the ``old'' host system and prepares it to be removed.

# vgexport design

vgexport -- volume group "design" successfully exported

When the machine is next shut down, the disk can be unplugged and then connected to it's new machine

13.6.4. Import the volume group

When plugged into the new system it becomes /dev/sdb so an initial pvscan shows:

# pvscan

pvscan -- reading all physical volumes (this may take a while...)

pvscan -- inactive PV "/dev/sdb1" is in EXPORTED VG "design" [996 MB / 996 MB free]

pvscan -- inactive PV "/dev/sdb2" is in EXPORTED VG "design" [996 MB / 244 MB free]

pvscan -- total: 2 [1.95 GB] / in use: 2 [1.95 GB] / in no VG: 0 [0]

We can now import the volume group (which also activates it) and mount the file system.

If you are importing on an LVM 2 system, run:

# vgimport design

Volume group "vg" successfully imported

If you are importing on an LVM 1 system, add the PVs that need to be imported:

# vgimport design /dev/sdb1 /dev/sdb2

vgimport -- doing automatic backup of volume group "design"

vgimport -- volume group "design" successfully imported and activated

13.6.5. Activate the volume group

You must activate the volume group before you can access it.

# vgchange -ay design

13.6.6. Mount the file system

# mkdir -p /mnt/design/users

# mount /dev/design/users /mnt/design/users

The file system is now available for use.

13.7. Splitting a volume group

There is a new group of users "design" to add to the system. One way of dealing with this is to create a new volume group to hold their data. There are no new disks but there is plenty of free space on the existing disks that can be reallocated.

13.7.1. Determine free space

# pvscan

pvscan -- reading all physical volumes (this may take a while...)

pvscan -- ACTIVE PV "/dev/sda" of VG "dev" [1.95 GB / 0 free]

pvscan -- ACTIVE PV "/dev/sdb" of VG "sales" [1.95 GB / 1.27 GB free]

pvscan -- ACTIVE PV "/dev/sdc" of VG "ops" [1.95 GB / 564 MB free]

pvscan -- ACTIVE PV "/dev/sdd" of VG "dev" [1.95 GB / 0 free]

pvscan -- ACTIVE PV "/dev/sde" of VG "ops" [1.95 GB / 1.9 GB free]

pvscan -- ACTIVE PV "/dev/sdf" of VG "dev" [1.95 GB / 1.33 GB free]

pvscan -- ACTIVE PV "/dev/sdg1" of VG "ops" [996 MB / 432 MB free]

pvscan -- ACTIVE PV "/dev/sdg2" of VG "dev" [996 MB / 632 MB free]

pvscan -- total: 8 [13.67 GB] / in use: 8 [13.67 GB] / in no VG: 0 [0]

We decide to reallocate /dev/sdg1 and /dev/sdg2 to design so first we have to move the physical extents into the free areas of the other volumes (in this case /dev/sdf for volume group dev and /dev/sde for volume group ops).

13.7.2. Move data off the disks to be used

Some space is still used on the chosen volumes so it is necessary to move that used space off onto some others.

Move all the used physical extents from /dev/sdg1 to /dev/sde and from /dev/sdg2 to /dev/sdf

# pvmove /dev/sdg1 /dev/sde

pvmove -- moving physical extents in active volume group "ops"

pvmove -- WARNING: moving of active logical volumes may cause data loss!

pvmove -- do you want to continue? [y/n] y

pvmove -- doing automatic backup of volume group "ops"

pvmove -- 141 extents of physical volume "/dev/sdg1" successfully moved

# pvmove /dev/sdg2 /dev/sdf

pvmove -- moving physical extents in active volume group "dev"

pvmove -- WARNING: moving of active logical volumes may cause data loss!

pvmove -- do you want to continue? [y/n] y

pvmove -- doing automatic backup of volume group "dev"

pvmove -- 91 extents of physical volume "/dev/sdg2" successfully moved

13.7.3. Create the new volume group

Now, split /dev/sdg2 from dev and add it into a new group called "design". it is possible to do this using vgreduce and vgcreate but the vgsplit command combines the two.

# vgsplit dev design /dev/sdg2

vgsplit -- doing automatic backup of volume group "dev"

vgsplit -- doing automatic backup of volume group "design"

vgsplit -- volume group "dev" successfully split into "dev" and "design"

13.7.4. Remove remaining volume

Next, remove /dev/sdg1 from ops and add it into design.

# vgreduce ops /dev/sdg1

vgreduce -- doing automatic backup of volume group "ops"

vgreduce -- volume group "ops" successfully reduced by physical volume:

vgreduce -- /dev/sdg1

# vgextend design /dev/sdg1

vgextend -- INFO: maximum logical volume size is 255.99 Gigabyte

vgextend -- doing automatic backup of volume group "design"

vgextend -- volume group "design" successfully extended

13.7.5. Create new logical volume

Now create a logical volume. Rather than allocate all of the available space, leave some spare in case it is needed elsewhere.

# lvcreate -L750M -n users design

lvcreate -- rounding up size to physical extent boundary "752 MB"

lvcreate -- doing automatic backup of "design"

lvcreate -- logical volume "/dev/design/users" successfully created

13.7.6. Make a file system on the volume

# mke2fs /dev/design/users

mke2fs 1.18, 11-Nov-1999 for EXT2 FS 0.5b, 95/08/09

Filesystem label=

OS type: Linux

Block size=4096 (log=2)

Fragment size=4096 (log=2)

96384 inodes, 192512 blocks

9625 blocks (5.00<!-- ) reserved for the super user

First data block=0

6 block groups

32768 blocks per group, 32768 fragments per group

16064 inodes per group

Superblock backups stored on blocks:

32768, 98304, 163840

Writing inode tables: done

Writing superblocks and filesystem accounting information: done

13.7.7. Mount the new volume

# mkdir -p /mnt/design/users mount /dev/design/users /mnt/design/users/

It's also a good idea to add an entry for this file system in your /etc/fstab file as follows:

/dev/design/user

/mnt/design/users ext2 defaults 1 2

13.8. Converting a root filesystem to LVM 1

	Backup Your System
	It is strongly recommended that you take a full backup of your system before attempting to convert to root on LVM 1.
	Upgrade Complications
	Having your root filesystem on LVM 1 can significantly complicate upgrade procedures (depending on your distribution) so it should not be attempted lightly. Particularly, you must consider how you will insure that the LVM 1 kernel module (if you do not have LVM 1 compiled into the kernel) as well as the vgscan/vgchange tools are available before, during, and after the upgrade.

Recovery Complications

Having your root filesystem on LVM 1 can significantly complicate recovery of damaged filesystems. If you lose your initrd, it will be very difficult to boot your system. You will need to have a recover disk that contains the kernel, LVM 1 module, and LVM 1 tools, as well as any tools necessary to recover a damaged filesystem. Be sure to make regular backups and have an up-to-date alternative boot method that allows for recovery of LVM 1.

In this example the whole system was installed in a single root partition with the exception of /boot. The system had a 2 gig disk partitioned as:

/dev/hda1 /boot

/dev/hda2 swap

/dev/hda3 /

The / partition covered all of the disk not used by /boot and swap. An important prerequisite of this procedure is that the root partition is less that half full (so that a copy of it can be created in a logical volume). If this is not the case then a second disk drive should be used. The procedure in that case is similar but there is no need to shrink the existing root partition and /dev/hda4 should be replaced with (eg) /dev/hdb1 in the examples.

To do this it is easiest to use GNU parted. This software allows you to grow and shrink partitions that contain filesystems. It is possible to use resize2fs and fdisk to do this but GNU parted makes it much less prone to error. It may be included in your distribution, if not you can download it from ftp://ftp.gnu.org/pub/gnu/parted.

Once you have parted on your system AND YOU HAVE BACKED THE SYSTEM UP:

13.8.1. Boot single user

Boot into single user mode (type linux S at the LILO prompt) This is important. Booting single-user ensures that the root filesystem is mounted read-only and no programs are accessing the disk.

13.8.2. Run Parted

Run parted to shrink the root partition Do this so there is room on the disk for a complete copy of it in a logical volume. In this example a 1.8 gig partition is shrunk to 1 gigabyte This displays the sizes and names of the partitions on the disk

# parted /dev/hda

(parted) p

Now resize the partition:

(parted) resize 3 145 999

The first number here the partition number (hda3), the second is the same starting position that hda3 currently has. Do not change this. The last number should make the partition around half the size it currently is.

Create a new partition

(parted) mkpart primary ext2 1000 1999

This makes a new partition to hold the initial LVM 1 data. It should start just beyond the newly shrunk hda3 and finish at the end of the disk.

Quit parted

(parted) q

13.8.3. Reboot

Reboot the system

13.8.4. Verify kernel config options

Make sure that the kernel you are currently running works with LVM 1 and has CONFIG_BLK_DEV_RAM and CONFIG_BLK_DEV_INITRD set in the config file.

13.8.5. Adjust partition type

Change the partition type on the newly created partition from Linux to LVM (8e). Parted doesn't understand LVM 1 partitions so this has to be done using fdisk.

# fdisk /dev/hda

Command (m for help): t

Partition number (1-4): 4

Hex code (type L to list codes): 8e

Changed system type of partition 4 to 8e (Unknown)

Command (m for help): w

13.8.6. Set up LVM 1 for the new scheme

Initialize LVM 1 (vgscan)

# vgscan

Make the new partition into a PV

# pvcreate /dev/hda4

create a new volume group

# vgcreate vg /dev/hda4

Create a logical volume to hold the new root.

# lvcreate -L250M -n root vg

13.8.7. Create the Filesystem

Make a filesystem in the logical volume and copy the root files onto it.

# mke2fs /dev/vg/root

# mount /dev/vg/root /mnt/

# find / -xdev | cpio -pvmd /mnt

13.8.8. Update /etc/fstab

Edit /mnt/etc/fstab on the new root so that / is mounted on /dev/vg/root. For example:

/dev/hda3 / ext2 defaults 1 1

becomes:

/dev/vg/root / ext2 defaults 1 1

13.8.9. Create an LVM 1 initial RAM disk

# lvmcreate_initrd

Make sure you note the name that lvmcreate_initrd calls the initrd image. It should be in /boot.

13.8.10. Update /etc/lilo.conf

Add an entry in /etc/lilo.conf for LVM 1. This should look similar to the following:

image = /boot/KERNEL_IMAGE_NAME

label = lvm

root = /dev/vg/root

initrd = /boot/INITRD_IMAGE_NAME

ramdisk = 8192

Where KERNEL_IMAGE_NAME is the name of your LVM 1 enabled kernel, and INITRD_IMAGE_NAME is the name of the initrd image created by lvmcreate_initrd. The ramdisk line may need to be increased if you have a large LVM 1 configuration, but 8192 should suffice for most users. The default ramdisk size is 4096. If in doubt check the output from the lvmcreate_initrd command, the line that says:

lvmcreate_initrd -- making loopback file (6189 kB)

and make the ramdisk the size given in brackets.

You should copy this new lilo.conf onto /etc in the new root fs as well.

# cp /etc/lilo.conf /mnt/etc/

13.8.11. Run LILO to write the new boot sector

# lilo

13.8.12. Reboot to lvm

Reboot - at the LILO prompt type "lvm" The system should reboot into Linux using the newly created Logical Volume.

If that worked then you should make lvm the default LILO boot destination by adding the line

default=lvm

in the first section of /etc/lilo.conf

If it did not work then reboot normally and try to diagnose the problem. It could be a typing error in lilo.conf or LVM 1 not being available in the initial RAM disk or its kernel. Examine the message produced at boot time carefully.

13.8.13. Add remainder of disk

Add the rest of the disk into LVM 1. When you are happy with this setup you can then add the old root partition to LVM 1 and spread out over the disk.

First set the partition type to 8e(LVM)