¡Vísitanos en Open Expo Europe, regístrate gratis!

El 6 y 7 de junio vuelve Open Expo a Madrid. Brainupdaters participa por tercer año consecutivo en Open Expo como patrocinador bronce.

Si estás planteandote asistir al evento Open Source & Software Libre más esperado del año en Madrid, nosotros te invitamos.

¡¡ Regístrate Gratis!!

Entra en el enlace e introduce el código de invitación GENERAL PASS: GOE18215

Inscripción

Si quieres descubrir más sobre nosotros y nuestros servicios te animamos a que nos visites en el stand el próximo 6 Y 7 de junio en el Open Expo Madrid, stand 70, lo encontrarás justo antes de la zona de conferencias.

Y no te pierdas la conferencia:

Dia: 06 JUN 2018

Hora: 13:30 – 14:00

Sala: FORUMS 2

Ponente:  Didac Oliveira, cofundador y mantenedor activo en el proyecto DRLM, experto en diseño e implementación de sistemas TI.

DRLM en Acción! GNU/Linux Disaster Recovery, the open source way

La importancia de un plan de recuperación de desastres (DRP)

De las empresas que han sufrido una importante pérdida de datos, un 43% nunca vuelve a abrir, mientras que un 29% cierra al cabo de dos años [1]. Los sistemas informáticos son cada vez más críticos y un paro de los servicios de varias horas o días se convierten directamente en pérdidas económicas muy importantes.
Estudios con un enfoque más holístico concluyen que por cada 1€ de inversión en un plan anterior al desastre puede suponer un ahorro de 4€ en la respuesta y recuperación en el caso de que éste se produzca [2].

La mayoría de las pequeñas empresas no tienen un plan de recuperación de desastres y  se estima que el 25% de estas no vuelve a abrir después de un desastre mayor.

Compartimos con vosotros un interesante artículo dónde podréis profundizar más sobre el tema:

 

https://digital.com/blog/disaster-proof/#ixzz5FP9KC1Ny

 

[1] http://www.continuitycentral.com/feature0660.html
[2] http://nws.weather.gov/nthmp/Minutes/oct-nov07/post-disaster_recovery_planning_forum_uo-csc-2.pdf

BrainUpdaters te invita al Open Expo 2017

Un año más Brain Updaters participa en el Open Expo 2017 como patrocinador bronce del evento Open Source & Software Libre más esperado del año en Madrid.

Si aún no tienes tu entrada y quieres ir, ¡Brain Updaters te invita!

Tu entrada gratis aquí:

Si quieres descubrir más sobre nosotros y nuestros servicios te animamos a que nos visites en el stand el próximo 1 de junio en el Open Expo Madrid, stand 38

Y no te pierdas la conferencia Smart GNU/LINUX Disaster Recovery with DRLM & ReaR:

BrainUpdaters se establece como Technology Partner de RedHat

Technology Partner de RedHat.

Con esta nueva relación ahora contamos con mejores recursos y las herramientas necesarias para proporcionar nuestras soluciones de código abierto sobre tecnología RedHat con las máximas garantías.

Esta asociación confirma nuestra intención de continuar mejorando y seguir ofreciendo el mejor servicio posible a nuestros clientes.

Consulta nuestros servicios.

Setup Nagios Server with nsca-ng for DRLM

One of the methods of error reporting with DRLM is nsca-ng, there is a sample configuration on http://docs.drlm.org/en/latest/ErrorReporting.html . In this document we cover the configuration Nagios Server with nsca-ng and also DRLM Server configuration to monitor errors from DRLM Server when running backups.

Of course we assume you have a Nagios Server configured and a DRLM Server

if not, don’t worry, just take a look on the next links

How to install DRLM

How to install NAGIOS

DRLM Server configuration

Install nsca-ng-client package

$ apt install nsca-ng-client

Set up config files

At least 2 files must be configured, in thes example we’re using 3, default.conf has the default values that can be overwritten in local.conf

/usr/share/drlm/conf/default.conf

# REPORT_TYPE=nagios
# NAGIOS VARIABLES
#
# These are default values and can be overwritten in local.conf according to your NAGIOS installation and configuration.
#

NAGCMD="/usr/sbin/send_nsca"
NAGSVC="DRLM"
NAGHOST="$HOSTNAME"
NAGCONF="/etc/drlm/alerts/nagios.cfg"

Note

Keep an eye on this variable NAGSVC . We’re going to use it on the Nagios server side as a service description it must match.

/etc/drlm/local.conf

NAGSVC="DRLM_Backup"

Note

As you can see this varible was defined previously on default.conf , it is just to show you than it can be overwritten with the /etc/drlm/local.conf file, so if you want, you can dismiss this step.

/etc/drlm/alerts/nagios.cfg

#### DRLM (Disaster Recovery Linux Manager) Nagios error reporting sample configuration file.
#### Default: /etc/drlm/alerts/nagios.cfg

### identity = <string>
#   Send  the  specified  client identity to the server.
#   By default, localhost will be used.

identity = "DRLM"

### server = <string>
#   Connect and talk to the specified server address or hostname.
#   The  default server is "localhost".

server = "Cervell"

### port = <string>
#   Connect  to  the  specified  service  name or port number on the
#   server instead of using the default port (5668).

port = 5668
password = "change-me"

Where:

  • DRLM: Is the name of the DRLM Server
  • Cervell: Is the name of the Nagios Server
  • port: Is the port where the Nagios Server is listening
  • password: Is the default password on the nsca-ng-server

Nagios Server configuration

Once the DRLM Server has been configured we’ll set up the Nagios Server.

Install required packages

$ apt install nsca-ng-server

Set up nsca-ng config files

/etc/nsca-ng/nsca-ng.cfg

command_file = "/usr/local/nagios/var/rw/nagios.cmd"

listen = "Cervell" # only listen on localhost. If you use systemd this
                          # this option is overriden by the
                          # nsca-ng-server.socket file.

user = "nagios" # run as user nagios
pid_file = "/var/run/nsca-ng/nsca-ng.pid" # pid file for nsca-ng

include(/etc/nsca-ng/nsca-ng.local.cfg)

authorize "*" {
   password = "change-me"
   #
   # The original NSCA server permits all authenticated clients to submit
   # arbitrary check results.  To get this behaviour, enable the following
   # lines:
   #
           hosts = ".*"
           services = ".*"
}

Note

This config file has been reduced to only the minimum requirements , if you want to see all options check the original file /etc/nsca-ng/nsca-ng.cfg

/lib/systemd/system/nsca-ng-server.socket

[Unit]
Description=NSCA-ng Socket
Documentation=man:nsca-ng(8) man:nsca-ng.cfg(5)

[Socket]
ListenStream=5668
#BindIPv6Only=both

[Install]
WantedBy=sockets.target

Start nsca-ng-server service

$ systemctl start nsca-ng-server
  • Check the status of the service
$ systemctl status nsca-ng-server
● nsca-ng-server.service - Monitoring Command Acceptor
   Loaded: loaded (/lib/systemd/system/nsca-ng-server.service; static)
   Active: active (running) since Fri 2017-02-17 18:35:46 CET; 5s ago
     Docs: man:nsca-ng(8)
           man:nsca-ng.cfg(5)
 Main PID: 14495 (nsca-ng)
   CGroup: /system.slice/nsca-ng-server.service
           └─14495 /usr/sbin/nsca-ng -c /etc/nsca-ng/nsca-ng.cfg

Feb 17 18:35:46 cervell nsca-ng[14495]: Ignoring `-b'/`listen' when socket activated
Feb 17 18:35:46 cervell nsca-ng[14495]: nsca-ng 1.4 (OpenSSL 1.0.1t, libev 4.15 with epoll) starting up

Nagios Config files

For this kind of configuration we’re using passive checks, the error notification is set for a limited time using the variable freshness_threshold. It’s importatnt to setup the notifications in order to receibe an email in case of error , if not you could miss it.

  • Add a new service on

/usr/local/nagios/etc/objects/templates.cfg

define service{
       name passive_service
       active_checks_enabled 0
       passive_checks_enabled 1 # We want only passive checking
       flap_detection_enabled 0
       register 0 # This is a template, not a real service
       is_volatile 0
       check_period 24x7
       max_check_attempts 1
       normal_check_interval 5
       retry_check_interval 1
       check_freshness 1
       freshness_threshold                     600
       contact_groups admins
       check_command check_dummy!0
       notifications_enabled           1                       ; Service notifications are enabled
       notification_interval 10
       notification_period 24x7
       notification_options w,u,c,r
       stalking_options w,c,u
       }
  • Add the DRLM Server on a hostgroup

/usr/local/nagios/etc/object/hostgroup.cfg

define hostgroup {
      hostgroup_name  Krbulan-Servers
      alias           Servidors Test
      members         DRLM
      }
  • Add a new check

/usr/local/nagios/etc/object/commands.cfg

#NSCA-ng Command
define command{
        command_name check_dummy
        command_line $USER1$/check_dummy $ARG1$
       }
  • Define the host and service

/usr/local/nagios/etc/object/DRLM.cfg

define host{
           use Host-krbulan
           host_name DRLM
           hostgroups  Krbulan-Servers
           alias DRLM
           address 192.168.7.9
           }

define service{
           use passive_service
           service_description DRLM_Backup
           host_name DRLM
           notifications_enabled           1
           }

Warning

service_description has to match with the variable NAGSVC before configured on the DRLM server.

  • Check Nagios configuration files
$ /usr/local/nagios/bin/nagios -v /usr/local/nagios/etc/nagios.cfg

Nagios Core 4.2.0
Copyright (c) 2009-present Nagios Core Development Team and Community Contributors
Copyright (c) 1999-2009 Ethan Galstad
Last Modified: 08-01-2016
License: GPL

Website: https://www.nagios.org
Reading configuration data...
   Read main config file okay...
   Read object config files okay...

Running pre-flight check on configuration data...

Checking objects...
    Checked 16 services.
    Checked 3 hosts.
    Checked 2 host groups.
    Checked 0 service groups.
    Checked 1 contacts.
    Checked 1 contact groups.
    Checked 26 commands.
    Checked 5 time periods.
    Checked 0 host escalations.
    Checked 0 service escalations.
Checking for circular paths...
    Checked 3 hosts
    Checked 0 service dependencies
    Checked 0 host dependencies
    Checked 5 timeperiods
Checking global event handlers...
Checking obsessive compulsive processor commands...
Checking misc settings...

Total Warnings: 0
Total Errors:   0

Things look okay - No serious problems were detected during the pre-flight check

Testing the configuration

From DRLM server exec runbackup (dummy server is not online)

$ root@DRLM:~# drlm -vD runbackup -c dummy
Disaster Recovery Linux Manager 2.1.0 / Git
Using log file: /var/log/drlm/drlm-DRLM-runbackup.20170217.190926.log
ERROR: drlm:runbackup: Client dummy SSH Server is not available (SSH) aborting ...
Aborting due to an error, check /var/log/drlm/drlm-DRLM-runbackup.20170217.190926.log for details
Terminated

On Nagios

 

On the notifications we see that the mail has been send





 

How to install Nagios 4.2.0 (Debian 8)

There are some places where the next process is explained , but since I’ve pending an article explaining how to configure Nagios Server with nsca-ng I’ve been thinking in post first an easy steps to configure Nagios from scratch. This document describes how to install Nagios Core, Plugins, NRPE from source on Debian 8.

Prerequisites

$ sudo apt-get install wget build-essential apache2 php5 php5-gd libgd-dev unzip postfix

$ sudo wget https://github.com/NagiosEnterprises/nrpe/archive/3.0.tar.gz

$ sudo wget https://assets.nagios.com/downloads/nagioscore/releases/nagios-4.2.0.tar.gz

$ sudo wget http://nagios-plugins.org/download/nagios-plugins-2.1.2.tar.gz

Users & Group

$ useradd nagios

$ groupadd nagcmd

$ usermod -a -G nagios,nagcmd www-data

Nagios Core Installation

$ tar zxvf nagios-4.2.0.tar.gz

$ tar zxvf nagios-plugins-2.1.2.tar.gz

$ cd nagios-4.2.0
$ ./configure --with-command-group=nagcmd --with-httpd-conf=/etc/apache2/
$ make all
$ make install
$ make install-init
$ make install-config
$ make install-commandmode
$ make install-webconf
$ cp -R contrib/eventhandlers/ /usr/local/nagios/libexec/
$ chown -R nagios:nagios /usr/local/nagios/libexec/eventhandlers

Check Installation

$ /usr/local/nagios/bin/nagios -v /usr/local/nagios/etc/nagios.cfg

Nagios Core 4.2.0
Copyright (c) 2009-present Nagios Core Development Team and Community Contributors
Copyright (c) 1999-2009 Ethan Galstad
Last Modified: 08-01-2016
License: GPL

Website: https://www.nagios.org
Reading configuration data...
   Read main config file okay...
   Read object config files okay...

Running pre-flight check on configuration data...

Checking objects...
     Checked 8 services.
     Checked 1 hosts.
     Checked 1 host groups.
     Checked 0 service groups.
     Checked 1 contacts.
     Checked 1 contact groups.
     Checked 24 commands.
     Checked 5 time periods.
     Checked 0 host escalations.
     Checked 0 service escalations.
Checking for circular paths...
     Checked 1 hosts
     Checked 0 service dependencies
     Checked 0 host dependencies
     Checked 5 timeperiods
Checking global event handlers...
Checking obsessive compulsive processor commands...
Checking misc settings...

Total Warnings: 0
Total Errors:   0

Configure apache2

Enable rewrite and cgi modules

$ sudo a2enmod rewrite && sudo a2enmod cgi

Copy httpd Template Virtual Host

$ sudo cp sample-config/httpd.conf /etc/apache2/sites-available/nagios4.conf

$ sudo chmod 644 /etc/apache2/sites-available/nagios4.conf

Enable Virtual Host

$ sudo a2ensite nagios

Create user nagiosadmin for web interface

$ sudo htpasswd -c /usr/local/nagios/etc/htpasswd.users nagiosadmin
New password:
Re-type new password:
Adding password for user nagiosadmin

Restart Apache

$ systemctl restart apache2

Install Nagios Plugins

$ cd nagios-plugins-2.1.2/

$ make

$ make install

Enable & Start Nagios

$ systemctl enable nagios
Created symlink from /etc/systemd/system/multi-user.target.wants/nagios.service to /etc/systemd/system/nagios.service.

$ systemctl start nagios

$ systemctl status nagios

● nagios.service - Nagios
   Loaded: loaded (/etc/systemd/system/nagios.service; enabled)
   Active: active (running) since Fri 2016-08-19 16:50:47 CEST; 23s ago
 Main PID: 21272 (nagios)
   CGroup: /system.slice/nagios.service
           ├─21272 /usr/local/nagios/bin/nagios /usr/local/nagios/etc/nagios.cfg
           ├─21273 /usr/local/nagios/bin/nagios --worker /usr/local/nagios/var/rw/nagios.qh
           ├─21274 /usr/local/nagios/bin/nagios --worker /usr/local/nagios/var/rw/nagios.qh
           ├─21275 /usr/local/nagios/bin/nagios --worker /usr/local/nagios/var/rw/nagios.qh
           ├─21276 /usr/local/nagios/bin/nagios --worker /usr/local/nagios/var/rw/nagios.qh
           └─21277 /usr/local/nagios/bin/nagios /usr/local/nagios/etc/nagios.cfg

Aug 19 16:50:47 cervell nagios[21272]: nerd: Fully initialized and ready to rock!
Aug 19 16:50:47 cervell nagios[21272]: wproc: Successfully registered manager as @wproc with query handler
Aug 19 16:50:47 cervell nagios[21272]: wproc: Registry request: name=Core Worker 21276;pid=21276
Aug 19 16:50:47 cervell nagios[21272]: wproc: Registry request: name=Core Worker 21274;pid=21274
Aug 19 16:50:47 cervell nagios[21272]: wproc: Registry request: name=Core Worker 21273;pid=21273
Aug 19 16:50:47 cervell nagios[21272]: wproc: Registry request: name=Core Worker 21275;pid=21275
Aug 19 16:50:47 cervell nagios[21272]: wproc: Registry request: name=Core Worker 21273;pid=21273
Aug 19 16:50:47 cervell nagios[21272]: wproc: Registry request: name=Core Worker 21275;pid=21275
Aug 19 16:50:48 cervell nagios[21272]: Successfully launched command file worker with pid 21277
Aug 19 16:50:48 cervell nagios[21272]: Successfully launched command file worker with pid 21277

Login to the web interface

NRPE

Install NRPE (Server service)

$ sudo apt-get install libssl-dev
$ tar zxvf nrpe-3.0.tar.gz
$ cd nrpe-3.0/
$ ./configure
$ make all
$ make install

Create NRPE service (systemd)

$ make install-init

Create NRPE service (systemd) Manual

service code

$ vi /etc/systemd/system/nrpe.service
[Unit]
Description=NRPE
After=nagios.service

[Install]
WantedBy=multi-user.target

[Service]
Type=simple
PIDFile=/usr/local/nagios/var/nrpe.pid
User=nagios
Group=nagios
ExecStart=/usr/local/nagios/bin/nrpe -c /usr/local/nagios/etc/nrpe.cfg -d
ExecStop=/usr/bin/killall /usr/local/nagios/bin/nrpe

Enable NRPE service

$  systemctl enable nrpe
Created symlink from /etc/systemd/system/multi-user.target.wants/nrpe.service to /etc/systemd/system/nrpe.service.

Start service

$  systemctl start nrpe

Check status

$  systemctl status nrpe
● nrpe.service - NRPE
   Loaded: loaded (/etc/systemd/system/nrpe.service; enabled)
   Active: active (running) since Mon 2016-08-22 15:48:12 CEST; 8s ago
 Main PID: 26435 (nrpe)
   CGroup: /system.slice/nrpe.service
           └─26435 /usr/local/nagios/bin/nrpe -c /usr/local/nagios/etc/nrpe.cfg -d

Aug 22 15:48:12 cervell nrpe[26435]: Starting up daemon
Aug 22 15:48:12 cervell nrpe[26435]: Server listening on 0.0.0.0 port 5666.
Aug 22 15:48:12 cervell nrpe[26435]: Server listening on :: port 5666.
Aug 22 15:48:12 cervell nrpe[26435]: Listening for connections on port 5666
Aug 22 15:48:12 cervell nrpe[26435]: Allowing connections from: 127.0.0.1

Add NRPE on /usr/local/nagios/etc/objectsi/commands.cfg

define command{
        command_name    check_nrpe
        command_line    $USER1$/check_nrpe -H $HOSTADDRESS$ -c $ARG1$
        }

Config files (For new client)

vi /usr/local/nagios/etc/objects/contacts.cfg

define contact{
        contact_name                    nagiosadmin          ; Short name of user
        use                             generic-contact         ; Inherit default values from generic-contact template (defined above)
        alias                           Nagios Admin         ; Full name of user
        email                           nagiosadmin@whatever.com ; ## <<***** CHANGE THIS TO YOUR EMAIL ADDRESS ******
        }
define contactgroup{
        contactgroup_name       admins
        alias                   Nagios Administrators
        members                 nagiosadmin
        }

vi /usr/local/nagios/etc/objects/host-service-definitions.cfg

define host{
        name                            Host-krbulan          ## <<***** CHANGE THIS WITH YOUR PREFERED NAME ******
        use                             generic-host
        check_period                    24x7
        check_interval                  5
        retry_interval                  1
        max_check_attempts              10
        check_command                   check-host-alive
        notification_period             workhours
        notification_interval           30
        notification_options            d,u,r
        contact_groups                  admins
        register                        0
        }
define service{
        name                            Service-krbulan      ## <<***** CHANGE THIS WITH YOUR PREFERED NAME ******
        active_checks_enabled           1
        passive_checks_enabled          1
        parallelize_check               1
        obsess_over_service             1
        check_freshness                 0
        notifications_enabled           1
        event_handler_enabled           1
        flap_detection_enabled          1
        process_perf_data               1
        retain_status_information       1
        retain_nonstatus_information    1
        is_volatile                     0
        check_period                    24x7
        max_check_attempts              3
        normal_check_interval           3
        retry_check_interval            2
        contact_groups                  admins
        notification_options            w,u,c,r
        notification_interval           60
        notification_period             24x7
         register                        0
        }

vi /usr/local/nagios/etc/objects/hostgroup.cfg

define hostgroup {
     hostgroup_name  Krbulan-Servers                          ## <<***** CHANGE THIS WITH YOUR PREFERED NAME ******
     alias           Servidors Krbu CPD
     members         wopr
}

vi /usr/local/nagios/etc/objects/wopr.cfg # This client name is wopr, you can change this with your client name

define host{
   use Host-krbulan                                           ## <<***** CHANGE THIS WITH YOUR NAME DEFINED IN host-service-definitions.cfg ******
   host_name wopr
   hostgroups  Krbulan-Servers                                                                ## <<***** CHANGE THIS WITH YOUR NAME DEFINED IN hostgroup.cfg ******
   alias wopr
   address 192.168.1.10                                                                               ## <<***** CHANGE THIS WITH YOUR IP ******
}

define service{
   use Service-krbulan                                                                                ## <<***** CHANGE THIS WITH YOUR NAME DEFINED IN hostgroup.cfg ******
   host_name wopr
   service_description Current Load
   check_command check_nrpe!check_load
}

define service{
   use Service-krbulan
   host_name wopr
   service_description Total Processes
   check_command check_nrpe!check_total_procs
}

define service {
   use Service-krbulan
   host_name wopr
   service_description Memoria
   check_command check_nrpe!check_memory
}




 

Configuration of Oracle ASMlib disks in GNU/Linux

ASMLib is a support library for the Automatic Storage Management feature of the Oracle Database.

Simplifies database administration and reduces kernel resource usage, but some configurations in the OS disks should be done before ASMlib will work as pretended.

This article will explain the configuration of ASMlib disks in GNU/Linux systems in order to ASM can manage them.
Oracle ASM software should be installed and properly configured previously, see note details.

We will configure the following system disks to be used by ASMlib:

GNU/Linux Device Name ASM label
/dev/mapper/asmdisk_01 ORA_ASM_DISK01
/dev/mapper/asmdisk_02 ORA_ASM_DISK02

Creating Partitions (any node)

First of all we will partition the disks:

Using fdisk:

$ for i in 01 02; do echo -e "o\nn\np\n1\n\n\nw" | fdisk /dev/mapper/asmdisk_$i; done

Using parted:

$ for i in 01 02; do parted -s -a optimal /dev/mapper/asmdisk_$i mklabel gpt mkpart primary 0% 100%; done

Check parititons (any node)

Now, check if partitions were created correctly.

Using fdisk:

$ for i in 01 02; do fdisk -l /dev/mapper/asmdisk_$i; done

...
                  Device Boot      Start         End      Blocks   Id  System
/dev/mapper/asmdisk_01p1               1      104433   838858041   83  Linux

...
                    Device Boot      Start         End      Blocks   Id  System
/dev/mapper/asmdisk_02p1               1       26108   209712478+  83  Linux

Using parted:

$ for i in 01 02; do parted /dev/mapper/asmdisk_$i print; done

...
Disk /dev/mapper/asmdisk_01: 85900MB
Sector size (logical/physical): 512B/512B
Partition Table: gpt

Number  Start   End     Size    File system   Name     Flags
 1      1049kB  85.9GB  85.9GB                primary
...
Disk /dev/mapper/asmdisk_02: 85900MB
Sector size (logical/physical): 512B/512B
Partition Table: gpt
Number  Start   End     Size    File system   Name     Flags
 1      1049kB  85.9GB  85.9GB                primary

Load partitons (all nodes)

The partitions must be loaded on all node’s kernel to properly label them with ASMlib.

$ for i in 01 02; do kpartx -a /dev/mapper/asmdisk_$i; done

Check loaded parts (all nodes)

$ for i in 01 02; do kpartx -l /dev/mapper/asmdisk_$i; done

asmdisk_01p1 : 0 1677716082 /dev/mapper/asmdisk_01 63
asmdisk_02p1 : 0 419424957 /dev/mapper/asmdisk_02 63

Label ASM disks (any node)

If partitions were loaded correctly in all nodes, we will label the partitions in ASMlib:

$ for i in 01 02; do /etc/init.d/oracleasm createdisk ORA_ASM_DISK${i} /dev/mapper/asmdisk_${i}p1; done

Marking disk "ORA_ASM_DISK01" as an ASM disk:             [  OK  ]
Marking disk "ORA_ASM_DISK02" as an ASM disk:             [  OK  ]
$ oracleasm listdisks

ORA_ASM_DISK01
ORA_ASM_DISK02

Scan/List ASM disks (other nodes)

$ oracleasm scandisks

Reloading disk partitions: done
Cleaning any stale ASM disks...
Scanning system for ASM disks...
Instantiating disk "ORA_ASM_DISK01"
Instantiating disk "ORA_ASM_DISK02"
$ oracleasm listdisks

ORA_ASM_DISK01
ORA_ASM_DISK02

Conclusion

Hope this short How-To article will be useful to any GNU/Linux SysAdmin and/or DBA using Oracle ASM with ASMlib.




 

Brief Introduction to Logical Volume Manager (LVM) – Concept and example of application

What if you suddenly run out of space in your home or root partition and want to use the left space from other HD partitions to get by till you make room or you get another HDD, all this on the fly? What if you want to double your home partition space with a spare HDD? Do you ever feel like you need some kind of mirror of your whole setup or a part of it, so you are prevented against hardware failures?

Logical Volume Manager (LVM) is a great answer to all of these questions. It is a tool implemented in the Linux Kernel that let’s you work with logical volumes (LV from now on), volumes that lay between the physical hard drives and the filesystems that will bring these LV to life. A LV needs to belong to a Virtual Grup (VG) in order to operate, as well as a VG can only exist after a Physical Volume (PV), which is the adaptation of a HDD or HDD partition so it can work with LVs. LVs, on its way, are divided in Physical Extents (PE), and they are the ones that determinate the size of a LV, though it is easily translatable to a human readable value. So, more or less, this is what we have:

/wp-content/uploads/LVM-intro/LogicalVolumenManager.jpg

Image source: wikimedia

Initial setup

We created a Centos6 virtual machine environment in order to test the major capabilities of LVM and so we can safely do, undo and redo. Most of the distributions installers are able to work with LVM from the very beginning. We had a ~40GB HDD that we divided this way:

/wp-content/uploads/LVM-intro/centossetup1.png

We created a 500MB ext2 /dev/sda1 standard partition that will contain /boot files. It is recommended not to have the boot partition under LVM as there are bootloaders that cannot read this kind of partitions. We then created a PV out of sda2 with the whole remaining HDD space. We made a VG from this PV named vg_centos6 that will separately contain root, var, home and swap partitions:

/wp-content/uploads/LVM-intro/centossetup2.png

LVM flexibility

If you ever feel lost about any parameter of your LVM configuration, you can always paint it back with these commands:

$ pvs
$ vgs
$ lvs

The first will display information about PVs, the second about VGs and the third one about LVs. So that’s it! Let’s start playing with our LVM setup. To learn about LVM flexibility, let’s imagine a case where our home partition has no space left and we need to somehow extend it, but we don’t have any spare HDD to attach to our PC.

/wp-content/uploads/LVM-intro/homefull.png

However, you realize that at some point you gave your swap space much more GB than those actually needed, always there sitting around. Why not moving them to our home partition? This is how we can do it:

First we need to unmount the swap partition:

$ swapoff

We can now reduce the size of the swap LV:

$ lvreduce -L -2G /dev/vg_centos6/swap

With this command we are shrinking our 4,5GB swap LV by 2GB. As so, we have to reformat it to tell it to occupy the new space created:

$ mkswap /dev/vg_centos6/swap

And we activated back:

$ swapon -va

We can tell the swap space reduction by issuing:

$ free -m

So now, as you can imagine, we have 2GB in our VG that are unallocated:

/wp-content/uploads/LVM-intro/freeVGafterswap.png

Let’s assign them to our home partition:

$ lvextend -L+2G /dev/vg_centos6/home

Now we have given 2GB of our VG free space to the home LV. However, unless we tell the file system to fit again in the partition, it will continue appearing as full. We can arrange that by:

$ resize2fs /dev/vg_centos6/home

Resulting in:

/wp-content/uploads/LVM-intro/homeaftergrowth.png

We brought back to life a file system that was at 100%.

Now imagine we want to expand the root LV with an extra HDD you attached to the OS. To do so we will add a raw 40GB HDD to our virtual machine. Let’s give it LVM format:

$ fdisk -cu /dev/sdb

The new partition id will be 8e (Linux LVM) and it will occupy the whole disk. Once written these parameters to the disk, we have to create a PV out of it:

$ pvcreate /dev/sdb1

We now extend our initial VG vg_centos6 with our latest incorporation:

$ vgextend vg_centos6 /dev/sdb1

/wp-content/uploads/LVM-intro/vgextended.png

We now have 40GB in our VG that are free to assign wherever we want. Let’s add 10GB to the root LV:

$ lvextend -L +10G /dev/vg_centos6/root

Again, we have to issue resize2fs so the file system recognizes the new added space:

$ resize2fs /dev/vg_centos6/root

Before resizing:

/wp-content/uploads/LVM-intro/beforeresize.png

After resizing:

/wp-content/uploads/LVM-intro/afterresize.png

We can say that our root partition is now transparently using space from two physical HDDs at the same time thanks to LVM.

Can I also shrink system partitions online? Yes as long as you are able to unmount them (i.e not in use by the system at a determinate point). We will now free 6GB from our home partition:

  • We unmount the mount point.
$ umount /home
  • We check the file system consistency by:
$ e2fsck -f /dev/vg_centos6/home
  • If the five test steps were passed, we can now shrink the LV to the desired size:
$ resize2fs /dev/mapper/vg_centos6-home 8G

Notice that the latter value refers to the final size, not the reduction itself.

  • We proceed to reduce the LV:
$ lvreduce -L -6G /dev/vg_centos6/home
  • And now we only have to resize the file system so it exactly fits in the new LV size:
$ resize2fs /dev/vg_centos6/home
  • We can safely remount it:
$ mount /home

And that’s it! Our VG will now be 6GB larger ready to assign if in need.

In our first steps with LVM we learned how to expand and shrink LVs on the fly using our own drive remaining space or newly attached HDDs to our OS.

Moving and mirroring LVs

LVMs, due to its flexibility and scalability, is frequently used in High Availability environments (HA). This is why they also implement a set of instructions regarding data replication.

For example, let’s suppose you want to move a PV (/dev/sda2) to a newly installed SSD (/dev/sdb1). The steps would be:

  1. Create a PV out of the newly installed HDD.

  2. Add the PV to the existing VG with vgextend.

  3. Move the old PV to the new PV:

    $ pvmove /dev/sda2 /dev/sdb1

    Keep in mind that this may take a while regarding your configuration

  4. Unattach the old PV from the VG:

    $ vgreduce vg_centos6 /dev/sda2

And by this you could safely physically remove /dev/sda2 from your machine. This is an useful and a straightforward way to migrate PVs. However, this is not the safest way to do it in critical production systems, where data i/o is always being held. It is much more recommendable to use lvconvert.

Having a mirror of your installation is almost an obligation in sensitive setups. If you want to mirror your var LV, you can achieve it under LVM by issuing:

$ lvconvert --corelog -b -m 1 /dev/vg_centos6/var /dev/sdb1

Explanation:

  • The –corelog flag means that the log needed to keep the mirror in sync won’t be stored in the hard drive, and the mirror will be resynchronized in every reboot.
  • -b is to launch the process in the background.
  • -m stands for mirror and is followed by the number of mirrors we want to set.
  • We then set the LV we want to mirror and in which PV (always belonging to the same VG).

The mirror is now set. Every little change produced in the var LV will be reproduced in /dev/sdb1. By issuing:

$ lvs -a -o+devices

we will have full knowledge of what is going on with our LV mirror:

/wp-content/uploads/LVM-intro/lvconvertvar.png

No more need to keep the mirror? We can always detach one of its legs by:

$ lvconvert --corelog -b -m 0 /dev/vg_centos6/var /dev/sda2

/wp-content/uploads/LVM-intro/lvconvertunattach.png

And by this we would have migrated our var LV to another physical partition in the safest way we could.

And what about snapshots?

Imagine that we want a snapshot of the root partition before playing around with some critical software that could in the end break our installation. Firstly we will need to create a LV capable to host all the capacity that is already being used for the volume we are about to take a snapshot, plus all the changes that will occur while the snapshot is on. If the snapshot LV ever reaches its full capacity, the snapshot feature will be broken since it won’t be able anymore to host changes and data will become corrupted.

We are going to create a 15GB snapshot LV of the root LV:

$ lvcreate -L15G -s -n rootsnapshotYYYYMMDD_HHMM /dev/vg_centos6/root

/wp-content/uploads/LVM-intro/snapshot1.png

This newly created LV will increase its Data% capacity in consonance with the LV that is under snapshot. So, for example, if we create a 3GB file in the root LV, we will have:

$ cd root && dd if=/dev/zero of=large.file bs=1024 count=3M

/wp-content/uploads/LVM-intro/snapshot2.png

The snapshot capacity in order to host changes produced has decreased a 20% due to this 3GB file in the root LV. When it reaches its maximum capacity, as said before, the data that it stores will become unusable and we won’t be able to restore the former LV to the point where the snapshot was created. If you happen to mount the LV snapshot, files will remain exactly the same as when it was created and, by this, you will always be able to restore to this original point. We can even tar the whole snapshot files so we can store backups of it in, for example, an external drive, but we can always restore a snapshot by:

$ lvconvert --merge /dev/vg_centos6/rootsnapshotYYYYMMDD_HHMM

However:

/wp-content/uploads/LVM-intro/snapshot3.png

In this particular case, due to the impossibility to unmount the root LV online, we need to place a reboot. After it, the snapshot will be automatically restored and its LV will be removed. No trace of the modifications we did after setting up the snapshot. True is that the machine will be offline for a short period of time, but we will have the chance to recover a broken OS.

Snapshots shouldn’t be considered as the main backup option as they are not as reliable as a mirroring in terms of data consistency or restoring capabilities. However, they can be really useful and save us a headache in some particular scenarios. The key is to combine, know our needs and act accordingly.

Exporting and importing VGs and their configuration

You may find yourself in the need to restore your LVM configuration / layout. For example, if one of your mirrored LVs is hardware damaged and needs to be replaced, with vgcfgrestore you will be able to redraw your LVM configuration to the disk, so it is important that you previously backup your LVM metadata:

/wp-content/uploads/LVM-intro/vgcfg1.png

This file contains every little bit of the LVM layout of the VG configuration we exported. It is good to know that the system automatically creates these backup files under /etc/lvm/backup when doing sensitive operations with LVM, and that they are being archived in /etc/lvm/archive. So, whenever you need to rewrite the VG metadata to a PV, you can do it issuing:

$ pvcreate --uuid  "ObQDtz-DuvG-SY3a-kzM9-u2Dt-TxUZ-pEweti" --restorefile /tmp/vgcfgexport.conf /dev/sdb1

and then

$ vgcfgrestore -f /tmp/vgcfgexport.conf vg_centos6

In here we are creating a PV with the same UUID of our /dev/sdb1 (supposing that its lvm metadata broke), and we are telling to restore the VG configuration we previously exported to a file. We can always know our volumes UUID from the backup configuration files.
Do not forger that vgcfgbackup|restore command only restablishes the broken lvm metadata / structure; the disks must contain by themselves the data.

VGEXPORT and VGIMPORT

Unlike vgcfgbackup|restore, which only refers to LVM metadata backup and restore, vgexport is useful if we want to export our VG to another machine. It does undo the VG without touching any of the data stored in the LVs. To do so, it is necessary to disable the VG and prepare it to exportation. We created data VG that contains two LVs in PV /dev/sdb1 and we will export it to another machine. Firstly we need to unmount the LVs and disable the VG so no data is written

$ umount /dev/data/data1
$ umount /dev/data/data2

And now we disable the VG:

/wp-content/uploads/LVM-intro/vgexport1.png

And then we export the VG:

$ vgexport data

We can now physically extract the PV and attach it to the new machine. The new machine will directly recognize it:

/wp-content/uploads/LVM-intro/vgimport1.png

However:

/wp-content/uploads/LVM-intro/vgimport2.png

We now import the VG:

$ vgimport data

And activate it:

$ vgchange -ay data

/wp-content/uploads/LVM-intro/vgimport3.png

Success! We have our VG data back, with all its files and LVs. We can mount it and work with it as if we were in our previous installation.

Conclusion

LVM is the swissknife tool regarding storage capabilities. Flexibility, scalability, solid backup feature, ease of deployment… After this brief introduction to LVM and its benefits, will you still be considering using the old HDD partitioning way? I, particularly, surely won’t.

 

Brainupdaters participa en la Devroom sobre Backup and Disaster Recovery en FOSDEM 17

El equipo de Brainupdaters ofrecerá el próximo sábado 4 de Febrero un workshop sobre DRLM, una herramienta opensource que nos permite gestionar la copia y recuperación de los sistems operativos GNU/Linux de nuestro centro de datos en caso de desastre, de forma centralizada y a través de la red.

Tendréis la oportunidad de profundizar sobre DRLM (Disaster Recovery Linux Manager). Conoceréis sus características, noticias y un taller completo sobre gestión de DR con ReaR y DRLM.

DRLM FOSDEM 17 MAP

Os animamos a asistir y realizar preguntas a nuestro ponente, Didac Oliveria, cofundador y mantenedor del proyecto DRLM.

También se ofrecerá una charla informal con los usuarios de ReaR, DRLM y Bareos acerca de lo que les gustaría implementar en futuras versiones ReaR, DRLM y Bareos.

Esta conversación concluirá la sesión del programa dedicado a la recuperación de “Backup and Disaster Recovery” en FOSDEM 17.

Os dejamos más detalles de la DEVROOM:

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