SUSE Manager 4 Setup Configuration

Step by step setup of SUSE Manager Server 4.0 configuration

In our previous post of SUSE Manager server installation, we walked you through how to install SUSE Manager step by step including screenshots. In this article, we will walk you through the SUSE Manager 4.0 configuration setup.

Considering you have the system installed with SUSE Manager package you can proceed to start SUSE Manager setup by running below command –

kerneltalks:~ # yast2 susemanager_setup

If you see an error saying No such client module susemanger_setup then you must not have susemanger package installed. Install it using zyapper in susemanager command and you will be able to run above setup command.

Once run, you will be presented with a text-based GUI setup and we will go through it step by step along with screenshots.

Obviously keep in mind you completed the disk space requirements before you start setup. Those are explained in the pre-requisite on the SUSE documentation.

SUSE Manager Setup

The first screen to choose the type of setup which is a pretty obvious choice.

On the second screen, you will be asked to enter the SUSE Manager Administrator email address.

On the next screen, you need to provide details to create an SSL certificate of SUSE Manager.

Now it will ask you for database details to be set. You can choose the database user of your choice.

At this stage, all inputs have been collected and setup is ready to complete configurations. It still gives you another chance to modify your responses in answer file and run setup manually later in below window.

We made the obvious choice and hit the Yes button. Now, it will setup the SUSE manager and show you output as it goes. Finally, the SUSE Manager setup will be completed as below.

Hit Next and you will be shown web URL which can be used to administrator your SUSE Manager along with the instruction to create an account first.

SUSE Manager web console

As given in the last screen of setup, open your browser and head to the URL mentioned. Since I installed in VirtualBox, I used port forwards and opened it on loopback IP –

You need to fill in all the details to create your SUSE Administrator user and hit ‘Create Organization‘ button at the end of the page. And you are done! You will see below home page of the SUSE Manager console.

Now your SUSE Manager setup is completed and you have web page console from where you can manage your SUSE Manager.

As very next step after this setup completion is to add subscription details to it and sync product channels so that it can be used in your organization for patching. We have covered it here in how to add product channels in SUSE Manager

How to configure JBOSS EAP 7 as a service in SUSE Linux

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Step by step procedure to configure JBOSS EAP as service in SUSE Linux

One of the major requirements for Jboss’s basic installations is to configure Jboss as a service in Linux. It’s pretty easy to configure it in RedHat and related families but when it comes to SUSE it pretty difficult since few functions of RedHat family don’t work in Suse. And with default ZIP installation we do not get the SUSE startup file as well which is readily available for RedHat.

We are considering Jboss EAP 7.2 on Suse 12 for this article.

RedHat has a pretty simple tutorial here which is not going to work on SUSE. So I will walk you through steps to get your Jboss eap working as service in SUSE Linux.

Pre-requisite

Make sure you have java installed on the server
Make sure JBoss user exists on the server which is defined in jboss-eap.conf file by parameter JBOSS_USER. Default user is jboss-eap
For default standalone configurations, INSTALL_PATH/standalone/ should be owned by JBOSS_USER
Make changes in init script template to match it with SUSE system as defined in below paragraph

Modification in script

You need to edit default init script INSTALL_PATH/bin/init.d/jboss-eap-rhel.sh to make it compatible with Suse.

Replace /etc/init.d/functions with /etc/rc.status
Replace success with rc_status -v

With JBoss zip install, you will have init script jboss-eap-rhel.sh located under INSTALL_PATH/bin/init.d This is init script which won’t be useful in latest Suse versions since they follow LSB format. So we need to make it work with LSB and here is how to do it.

Copy service configuration file and service init script from the installation directory to respective system directories –

root@kerneltalks # cp INSTALL_PATH/bin/init.d/jboss-eap.conf /etc/default
root@kerneltalks # cp INSTALL_PATH/bin/init.d/jboss-eap-rhel.sh /etc/init.d/jboss-eap
root@kerneltalks # chmod +x /etc/init.d/jboss-eap

Please note that while coping over file we trimmed rhel from its name since it does not make sense to keep that name on the SUSE system! It will also alter the next command as well.

Adding it as a service

root@kerneltalks # chkconfig --add jboss-eap

Till this point, its the same process as RedHat mentioned in its tutorial. Now, if you try to start service it won’t. It will throw below error :

root@kerneltalks # service jboss-eap start
jboss-eap.sh is neither service nor target!?

Import service in sytemd

Now we need to get this service into systemd. To do that, You need to add below block on top of /etc/init.d/jboss-eap.sh . Make sure you edit it exactly since its an LSB compliant format read by the system. This needs to go below the shell opening line of script !/bin/sh and before the rest of the script.

### BEGIN INIT INFO
# Provides:          jboss-eap
# Required-Start:
# Required-Stop:
# Default-Start:     2 3 4 5
# Default-Stop:      0 1 6
# Short-Description: jboss eap service
# Description:       jboss eap server for suse linux
### END INIT INFO

You are almost there! Import the service into systemd using below command –

root@kerneltalks # systemctl enable jboss-eap
jboss-eap.service is not a native service, redirecting to systemd-sysv-install
Executing /usr/lib/systemd/systemd-sysv-install enable jboss-eap

Now your service is available in systemctl to control. You can control service using commands like systemctl start jboss-eap, systemctl stop jboss-eap, systemctl status jboss-eap

root@kerneltalks # systemctl start jboss-eap
● jboss-eap-rhel.service - LSB: jboss eap service
   Loaded: loaded (/etc/init.d/jboss-eap-rhel.sh; bad; vendor preset: disabled)
   Active: active (running) since Thu 2019-06-20 1:23:23 IST; 10s ago
     Docs: man:systemd-sysv-generator(8)
  Process: 10625 ExecStart=/etc/init.d/jboss-eap-rhel.sh start (code=exited, status=0/SUCCESS)
 Main PID: 12346 (java)
......

You have configured Jboss eap to run as service in Suse Linux.

How to start, stop and reload postfix

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This is a quick post that lists commands to start, stop postfix service.

Postfix is a free and open-source mailing service. It was developed by IBM and is a common alternative to Sendmail service.

How to start, stop and reload postfix mail service

You can use postfix command directly or you can use OS service management commands.

[root@kerneltalks ~]# postfix start
postfix/postfix-script: starting the Postfix mail system
[root@kerneltalks ~]# postfix stop
postfix/postfix-script: stopping the Postfix mail system
[root@kerneltalks ~]# postfix reload

Using systemctl or service command to control postfix service.

[root@kerneltalks ~]# service postfix start
Redirecting to /bin/systemctl start postfix.service
[root@kerneltalks ~]# service postfix stop
Redirecting to /bin/systemctl stop postfix.service
[root@kerneltalks ~]# systemctl start postfix
[root@kerneltalks ~]# systemctl stop postfix

IPv6 error in postfix

Sometimes you see below error while dealing with postfix service.

[root@kerneltalks ~]# postfix start
postfix: fatal: parameter inet_interfaces: no local interface found for ::1

This is due to your system is using IPv6 as well along with IPv4. If you don’t need IPv6 then you can safely disable IPv6 and then restart postfix service to resolve the above error.

Another way is to disable postfix IPv6 support and get rid of this error. To do that you need to edit /etc/postfix/main.cf configuration file and change inet_protocols to ipv4.

[root@kerneltalks ~]# vi /etc/postfix/main.cf
#inet_protocols = all 
inet_protocols = ipv4

Save changes and restart postfix service.

SUSE Manager Server 4 installation with screenshots

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SUSE Manager 4 server installation walkthrough along with screenshots.

This is SUSE Manager 4 installation walk-through which was done in Oracle VM VirtualBox Manager. The whole installation process can be split into below phases –

Subscription procurement
Installation with DVD
Booting it first time

Let’s go through one by one without any further delay.

Subscription Procurement

The first thing is you need to have a subscription for using the SUSE Manager module. For this exercise, I procured a free 60 days subscription from SUSE. You can navigate to the product page and get a “60 Day free trial” license. You will get to download one Installer DVD after sign up like below.

If you are trying to set up SUSE Manager in corporate setup then your company must have already procured licenses for the same. You can get required subscription details from the respective team. Or you can click buy now on the product page and walk through the purchase procedure.

Suse Manager 4 download page

Once you have downloaded the DVD, its time to boot server with this DVD. Make sure your server meets specified hardware requirements as stated herein the documentation.

Installation with DVD

Once your system is ready and DVD is downloaded, boot system with DVD. Halt at below screen and press F4 if you want to configure a proxy for an internet connection during setup. If you have direct internet access then skip it.

Proceed with installation after proxy config (if applicable) and select product SUSE manager 4 on the next screen.

Click Next. On the next screen accept the license terms and click next. You will be prompted with a registration window.

Fill in your registration details. Here you can configure the network by clicking the ‘network configuration’ box above. It will open up the standard SUSE network configuration setup. You can set up IP details, hostname, DNS here so that your system can go online on the network and access the internet for registration. Click next and your system will be registered to SUSE.

After successful registration, you will be offered to enable repositories. Choose accordingly. I prefer to enable them during installation to receive the latest updates.

Post that you will be prompted to select SUSE manager extensions and modules to install. Mandatory are selected already.

After selection click, next and setup will register modules to SUSE. Remember previous registration was for system and this one is for module/extensions you selected.

On the next screen, you will be prompted to select any add on products you want. I would skip it and click next. It will ask for a system role in the next window.

The choice is obvious here! Select the SUSE manager server and proceed. On the next screen disk partitioning can be done.

Since this is my test system I will go with the default FS layout which setup offers. You can create a custom layout with expert partitioned here. Especially you need to check /var/lib/pgsql and /var/spacewalk sizes since all patch data going to be dumped here by SUSE Manager.

This followed by “Clone & timezone”, “Local User”, “Root password” standard screens which you normally see during any Linux install. I am skipping their screenshots here.

Finally, you will be greeted with an installation summary. Verify things here and change if you want to like firewall etc. and hit ‘Install’ to start the installation.

Now you can see packages are being downloaded from SUSE and then being installed. If you remember we used only 600+ MB DVD to boot system so its obvious it did not have whole OS packages in it. So setup will download packages and complete installation.

Once installation complete, the system will reboot and you are good to login.

Booting it first time

After the system reboot, type in below command to start the SUSE Manager setup!

kerneltalks:~ # yast2 sysemanager_setup

SUSE Manager setup will begin in text mode GUI which we will walk you through in our next post.

You can verify different susemanager packages are installed on the system using rpm -qa |grep susemanager command. Unless susemanager package is installed on server, the above command won’t work. It will throw below error :

No such client module susemanger_setup

It happens mostly when you choose not to register system during setup and opt to install a system with another packages ISO (when your system don’t have internet access). In that case, you just need to register your system with SUSE first and then install susemanager package using zypper and you are good to go.

Follow the next article which explains how to configure SUSE Manager Server 4.0

How to remove product channels in Suse Manager

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Quick post about how to remove the products channels in Suse Manager

There is a way you can add products and their channels in the Suse Manager server using the command line and webpage GUI. But once added it’s not easy to get them removed from the web console. Web console does not provide a direct option to remove product channels from Suse Manager. Also, the command used for adding channel i.e.. mgr-sync also does not support any option to remove channels.

So many of first time Suse Manager administrators stumble upon roadblock on how to remove product channels which are no more needed.

So let’s get started on the process to remove product channels (using command spacewalk-remove-channel) you might have added by mistake on Suse Manager or which are no longer needed and eating up your disk space.

First, you need to list out all the channels on your Suse Manager using mgr-sync list command –

root@kerneltalks # mgr-sync list channels
Available Channels:


Status:
  - [I] - channel is installed
  - [ ] - channel is not installed, but is available
  - [U] - channel is unavailable

[ ] RHEL6-Pool for x86_64 RHEL6 Base x86_64 [rhel6-pool-x86_64]
[I] SLE-Product-HPC-15-Pool for x86_64 SUSE Linux Enterprise High Performance Computing 15 x86_64 [sle-product-hpc-15-pool-x86_64]
    [ ] SLE-Module-Basesystem15-Debuginfo-Pool for x86_64 Basesystem Module 15 x86_64 [sle-module-basesystem15-debuginfo-pool-x86_64-hpc]
    [ ] SLE-Module-Basesystem15-Debuginfo-Updates for x86_64 Basesystem Module 15 x86_64 [sle-module-basesystem15-debuginfo-updates-x86_64-hpc]
    [I] SLE-Module-Basesystem15-Pool for x86_64 Basesystem Module 15 x86_64 [sle-module-basesystem15-pool-x86_64-hpc]
    [I] SLE-Module-Basesystem15-Updates for x86_64 Basesystem Module 15 x86_64 [sle-module-basesystem15-updates-x86_64-hpc]
...

Here let’s consider we need to remove channel sle-product-hpc-15-pool-x86_64. So first you need to remove all the child channels from this base product channel & then you will be able to remove the base channel. If you try to remove parent channel directly without removing child channels you will hit below error –

root@kerneltalks # spacewalk-remove-channel -c  sle-product-hpc-15-pool-x86_64
Error: cannot remove channel sle-product-hpc-15-pool-x86_64: subchannel(s) exist:
                        sle-module-basesystem15-pool-x86_64-hpc
                        sle-module-basesystem15-updates-x86_64-hpc
                        sle-module-devtools15-pool-x86_64-hpc
....

You can clearly see child channels to be removed before you try for parent channel. This is also a good way to get a child channel list quickly!

Then go ahead, remove the child channel followed by base one. For example, see below child channel removal output –

root@kerneltalks #  spacewalk-remove-channel -c sle-module-devtools15-pool-x86_64-hpc
Deleting package metadata (204):
                  ________________________________________
Removing:         ######################################## - complete

Repeat the process and remove all child channels one by one. You can use shell loops to get it done quicker. Finally, remove your parent channel, and you are done.

root@kerneltalks #  spacewalk-remove-channel -c sle-product-hpc-15-pool-x86_64
Deleting package metadata (3):
                  ________________________________________
Removing:         ######################################## - complete

Once done you can confirm that channel is no more enabled in webpage console or using mgr-sync list command.

How to remove lost physical volume from volume group

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The process to remove the missing disk from LVM configuration.

In this article, we will see how to remove a physical volume from the volume group when the disk is removed from the server. Normally, you need to remove the disk from the volume group first using vgreduce and then remove disk physically. But in some cases where disk went bad or you accidentally remove the disk from the server before you remove from VG, PV status will be shown as unknown in vgdisplay like below.

  --- Physical volumes ---
  PV Name               [unknown]
  PV UUID               fPFkBx-lbnG-R6Zo-3kq5-KOLA-U1ou-LdNIMD
  PV Status             allocatable
  Total PE / Free PE    1535 / 1535

And you will start seeing warnings with disk UUID in LVM commands as below –

WARNING: Device for PV fPFkBx-lbnG-R6Zo-3kq5-KOLA-U1ou-LdNIMD not found or rejected by a filter.
Couldn't find device with uuid fPFkBx-lbnG-R6Zo-3kq5-KOLA-U1ou-LdNIMD.

This is because the disk was removed from the server or disk is disappeared from the server without being gracefully removed from LVM.

How to remove missing PV from VG

Now to clean VG after PV is deleted or removed you need to use vgreduce command with --removemissing switch-

# vgreduce  --removemissing datavg
  WARNING: Device for PV fPFkBx-lbnG-R6Zo-3kq5-KOLA-U1ou-LdNIMD not found or rejected by a filter.
  Couldn't find device with uuid fPFkBx-lbnG-R6Zo-3kq5-KOLA-U1ou-LdNIMD.
  Wrote out consistent volume group datavg.

It will clean up all missing physical volumes from the volume group and thus making VG consistent. You will see no more missing PV warnings now!

How to convert JKS file to KEY file for Apache

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Article explaining how to convert java keystore jks into PEM formatted certificate or key file for Apache configuration

Scenario: I have a key file (*.jks) and CSR file generated in using keytool command i.e. in java. I wanted to convert this jks file to *.key file so that it can be used in Apache webserver configuration.

Read how to create java Keystore file *.jks if you want to know how to create CSR using java keytool.

Solution :

JKS file is Keystore used in java. You need to follow the below steps to get your unencrypted key file. Its a two-step process :

Import key data from keystore to PKC12 format
Convert PKCS12 key to un-encrypted PEM

Import key data from keystore to PKC12 format

We will import key data from jks Keystore to new Keystore in PKC12 format using keytool command where –

-srckeystore : Your jks file
-destkeystore : Name of new keystore to create
-deststoretype : Obv has to be PKCS12

You need to provide a password of the source Keystore and also set a new password to the new Keystore.

[root@kerneltalks ~]# keytool -importkeystore -srckeystore kerneltalks.com.jks -destkeystore keystore.pkcs12 -deststoretype PKCS12
Importing keystore kerneltalks.com.jks to keystore.p12...
Enter destination keystore password:
Re-enter new password:
Enter source keystore password:
Entry for alias server successfully imported.
Import command completed:  1 entries successfully imported, 0 entries failed or cancelled

Convert PKCS12 key to un-encrypted PEM

We now need to convert this PKCS12 key in PEM format so that it can be used in the Apache configuration.

[root@kerneltalks ~]# openssl pkcs12 -in keystore.pkcs12  -nodes -nocerts -out kerneltalks.com.key
Enter Import Password:
MAC verified OK

Now verify your private key file.

[root@kerneltalks ~]# file kerneltalks.com.key
kerneltalks.com.key: ASCII text
[root@kerneltalks ~]# file kerneltalks.com.jks
kerneltalks.com.jks: Java KeyStore
[root@kerneltalks ~]# cat kerneltalks.com.key
Bag Attributes
    friendlyName: server
    localKeyID: 54 69 6D 65 20 31 35 35 36 32 30 38 36 31 33 32 36 34
Key Attributes: <No Attributes>
-----BEGIN PRIVATE KEY-----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-----END PRIVATE KEY-----

To use this key file in Apache configuration you need to strip off a header. Delete all parts till -----BEGIN PRIVATE KEY----- and save the file. Now you are good to use this *.key file in Apache SSL configuration.

How to export certificate from JKS file

As an addon to this post, I will walk you through how to export a certificate from java Keystore to PEM format. This is again two-step exercise as below –

Export certificate in binary

You read from the Keystore file certificate associated with alias and export it to a binary file. I used alias as server while creating this jks file hence options are –

-export : To export data. This is same as exportcert in newer versions
-alias : Enter same alias you used while creating this java key file
-file : Destination binary file in which you will export
-keystore : Your jks key file

[root@kerneltalks ~]# keytool -export -alias server -file kerneltalks.com.der -keystore kerneltalks.com.jks
Enter keystore password:
Certificate stored in file <kerneltalks.com.der>

Warning:
The JKS keystore uses a proprietary format. It is recommended to migrate to PKCS12 which is an industry standard format using "keytool -importkeystore -srckeystore kerneltalks.com.jks -destkeystore kerneltalks.com.jks -deststoretype pkcs12".

Convert exported certificate data to PEM format

Now we will convert certificate binary to PEM format using below command where –

-in : Input binary means exported file in last command
-out : Output file in PEM format

Now verify your certificate file.

[root@kerneltalks ~]# openssl x509 -inform der -in kerneltalks.com.der -out certificate.pem
[root@kerneltalks ~]# file certificate.pem
certificate.pem: PEM certificate
[root@kerneltalks ~]# cat  certificate.pem
-----BEGIN CERTIFICATE-----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How to add UUID entry in /etc/fstab in Linux

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In this short tutorial, we will walk you through how to get UUID of the filesystem so that it can be used in /etc/fstab.

First of all, keep in mind you need to format your logical volume to get UUID registered in the kernel for it. Logical volume without filesystem on it won’t be having UUID attached to it. If you are using partitioning volume manager then disk partitions will have PARTUUID (partition UUID) even if you don’t format them. But it’s not useful in /etc/fstab since fstab deals with formatted partitions.

How to find UUID for logical volume

For this tutorial consider below setup –

[root@kerneltalks ~]# lsblk
NAME           MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
xvda           202:0    0    8G  0 disk
└─xvda1        202:1    0    8G  0 part /
xvdf           202:80   0    1G  0 disk
└─datavg-lvol0 253:0    0 1020M  0 lvm

We have one logical volume named lvol0 in the volume group datavg and now we need to find UUID for it. Use command blkid and grep for your logical volume name to get your desired output –

[root@kerneltalks ~]# blkid |grep lvol0
/dev/mapper/datavg-lvol0: UUID="5caaee32-c3d3-429e-bad7-2898cf923805" TYPE="ext4"

You can see you have UUID for the lvol you mentioned and along with it also sourced its filesystem type which is ext4.

How to add UUID entry in /etc/fstab

Lets add this UUID entry in /etc/fstab using format –

<UUID> <mount directory> <FS type> <mount options> <dump> <pass>

So our entry will look like –

UUID=5caaee32-c3d3-429e-bad7-2898cf923805  /data  ext4  defaults 0 0

We are mounting it on /data directory with default mount options and no fschecks. Add this entry to fstab and run mount -a and mount point established!

[root@kerneltalks ~]# df -Ph /data1
Filesystem                Size  Used Avail Use% Mounted on
/dev/mapper/datavg-lvol0  988M  2.6M  919M   1% /data

How to find UUID for disk partition

Consider below setup for finding UUID for disk partition.

[root@kerneltalks ~]# lsblk
NAME    MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
xvda    202:0    0    8G  0 disk
└─xvda1 202:1    0    8G  0 part /
xvdf    202:80   0    1G  0 disk
└─xvdf1 202:81   0 1023M  0 part

Here we have one non-root disk /dev/xvdf with one full partition /dev/xvdf1 on it. And it’s not yet formatted with any filesystem. Now if you run blkid command you will find PARTUUID for this partition.

[root@kerneltalks ~]# blkid |grep xvdf1
/dev/xvdf1: PARTUUID="6d123669-01"

I format it so that I can mount it on the directory. And after formatting it with the ext4 filesystem here is UUID making an entry!

[root@kerneltalks ~]# blkid | grep xvdf1
/dev/xvdf1: UUID="05ba450d-9c60-43f1-9dd1-8b6f89857961" TYPE="ext4" PARTUUID="6d123669-01"

You can compare this output with earlier one and you can see after formatting with ext4 you get UUID which can be used in /etc/fstab as explained earlier in this post.

Troubleshooting check_mk agent in Linux

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Different steps to troubleshoot check_mk agent in Linux

Before we start you may want to check our tutorial about setting up check_mk monitoring in Linux. You might experience issues when adding a server into check_mk monitoring. Below are a few steps, you can check to validate your configuration and communication between check_mk server and client works well.

Port 6556 communication

check_mk communicate over port 6556 by default. You need to check if port 6556 is open between client and server.

Also, you need to check if port 6556 is listening on your check_mk client so that server can fetch details by querying the client on port 6556.

root@kerneltalks#  netstat -lpn | grep 6556
tcp6       0      0 :::6556                 :::*                    LISTEN      24303/xinetd

You can even check using telnet on client and from server to client.

root@kerneltalks # telnet localhost 6556
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
Connection closed by foreign host.

How to restart check_mk agent

check_mk agent runs on top of xinetd service in Linux. So if you make any changes to the config file then you need to reload configuration or restart the agent.

Reload check_mk configuration using below command –

root@kerneltalks # service xinetd reload
Redirecting to /bin/systemctl reload xinetd.service

Restart check_mk agent using below command –

root@kerneltalks # service xinetd stop
root@kerneltalks # service xinetd start

check_mk configuration file

Make sure you have a proper configuration file in place. check_mk configuration file is located at /etc/xinetd.d/check_mk_agent. The sample configuration file is as below –

# Created by Check_MK Agent Bakery.
# This file is managed via WATO, do not edit manually or you
# lose your changes next time when you update the agent.


service check_mk_agent
{
        type           = UNLISTED
        port           = 6556
        socket_type    = stream
        protocol       = tcp
        wait           = no
        user           = root
        server         = /usr/bin/check_mk_agent
        log_on_success =
        disable        = no
        only_from      = 10.10.1.2 10.10.1.3
}

only_from field denotes check_mk server IPs to which your agent will communicate. It will be populated by RPM you used to install. If it doesn’t reflect proper values you can edit it and reload check_mk configuration by using commands mentioned above.

check_mk agent updater

Check update for check_mk agent and download from the server using check_mk updater.

root@kerneltalks #  cmk-update-agent -v -v
+-------------------------------------------------------------------+
|                                                                   |
|  Check_MK Agent Updater - Update                                  |
|                                                                   |
+-------------------------------------------------------------------+
Read /etc/cmk-update-agent.state.
Getting target agent configuration from deployment server
Fetching URL: http://kerneltalks1/master/check_mk/deploy_agent.py?...
Response from deployment server:
AgentAvailable: False

Read /etc/cmk-update-agent.state.
Saved deployment status to /etc/cmk-update-agent.state.
No agent available for us.

Using this command you can even see to which server client is registered. If the client is not registered with check_mk server then you will see below error –

root@kerneltalks # cmk-update-agent -v -v
+-------------------------------------------------------------------+
|                                                                   |
|  Check_MK Agent Updater - Update                                  |
|                                                                   |
+-------------------------------------------------------------------+
Read /etc/cmk-update-agent.state.
Getting target agent configuration from deployment server
Fetching URL: http://kerneltalks1/master/check_mk/deploy_agent.py?...
ERROR This host is not registered for deployment

cmk-update-agent can not execute binary error

If you come across below error while executing cmk-update-agent command then it’s probably you are running binary of architecture it is not meant to run. e.g. you are running x86 binary on ARM server

/usr/bin/cmk-update-agent: line 8: /usr/lib/check_mk_agent/plugins/21600/cmk-update-agent: cannot execute binary file

Solution: Make sure you install the proper architecture package on your server which matches your server architecture. Generally x86 check_mk package is marked as noarch package but it will land you up in the above issue when you install it on the ARM arch server.

check_mk xinetd error

---------------------------------------------
WARNING
This package needs xinetd to be installed.
Currently you do not have installed xinetd.
Please install and start xinetd or install
and setup another inetd manually.
It's also possible to monitor via SSH without
an inetd.
---------------------------------------------

Solution: Install xinetd package. Start and enable xinetd service. If you are running a newer kernel/OS like Suse 15 SP1, xinetd is not available in it. Its sockets being served by systemd. You need to install a higher version of check_mk agent RPM which identifies systemd sockets and it won’t show you above error. e.g. version 1.4 packages were showing above error to me while when I used version 1.5 package, it got away and installation succeeded.

check_mk python error

---------------------------------------------
ERROR
Failed to install agent: Could not find a
'python' interpreter.
---------------------------------------------

Solution: It means you have a higher version of python like python3 and agent rpm is looking for python. Use the higher version of check_mk agent which understands the latest python binaries (which has nomenclature with like python3 and not python)

How to add new disk in Linux

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Step by step procedure to add disk in Linux machine

In this article, we will walk you through steps to add a new disk in the Linux machine. Adding a raw disk to the Linux machine may vary depending upon the type of server you have but once the disk is presented to the machine, the procedure of getting it to mount points is almost the same.

Objective: Add a new 10GB disk to the server and create a 5GB mount point out of it using LVM and newly created volume group.

Adding raw disk to Linux machine

If you are using the AWS EC2 Linux server, you may follow these steps to add raw disk. If you are on VMware Linux VM you will have a different set of steps to follow to add disk. If you are running a physical rack-mount/blade server then adding disk will be a physical task.

Now once the disk is attached to the Linux machine physically/virtually, it will be identified by the kernel and then our rally starts.

Identifying newly added disk in Linux

After the attachment of the raw disk, you need to ask the kernel to scan a new disk. Mostly it’s done now automatically by the kernel in new versions.

First thing is to identify the newly added disk and its name in the kernel. There are numerous ways to achieve this. I will list a few –

You can observer lsblk output before and after adding/scanning disk to get a new disk name.
Check newly created disk files in /dev filesystem. Match timestamp of file and disk addition time.
Observer fdisk -l output before and after adding/scanning disk to get a new disk name.

For our example, I am using the AWS EC2 server and I added 5GB disk to my server. here is my lsblk output –

[root@kerneltalks ~]# lsblk
NAME    MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
xvda    202:0    0  10G  0 disk
├─xvda1 202:1    0   1M  0 part
└─xvda2 202:2    0  10G  0 part /
xvdf    202:80   0  10G  0 disk

You can see xvdf is our newly added disk. Full path for disk is /dev/xvdf.

Add new disk in LVM

We are using LVM here since its widely used and flexible volume manager on the Linux platform. Make sure you have lvm or lvm2 package installed on your system. If not, install lvm/lvm2 package.

Now, we are going to add this RAW disk in Logical Volume Manager and create 10GB of mount point out of it. List of commands you need to follow are –

If you are willing to add a disk to the existing mount point and use its space to extend mount point then vgcreate should be replaced by vgextend.

Sample outputs from my session –

[root@kerneltalks ~]# pvcreate /dev/xvdf
  Physical volume "/dev/xvdf" successfully created.
[root@kerneltalks ~]# vgcreate vgdata /dev/xvdf
  Volume group "vgdata" successfully created
[root@kerneltalks ~]# lvcreate -L 5G -n lvdata vgdata
  Logical volume "lvdata" created.

Now, you have a logical volume created. You need to format it with the filesystem on your choice and mount it. We are choosing ext4 filesystem here and formatting using mkfs.ext4 .

[root@kerneltalks ~]# mkfs.ext4 /dev/vgdata/lvdata
mke2fs 1.42.9 (28-Dec-2013)
Filesystem label=
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
Stride=0 blocks, Stripe width=0 blocks
327680 inodes, 1310720 blocks
65536 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=1342177280
40 block groups
32768 blocks per group, 32768 fragments per group
8192 inodes per group
Superblock backups stored on blocks:
        32768, 98304, 163840, 229376, 294912, 819200, 884736

Allocating group tables: done
Writing inode tables: done
Creating journal (32768 blocks): done
Writing superblocks and filesystem accounting information: done

Mounting volume from new disk on mount point

Lets mount the logical volume of 5GB which we created and formatted on /data mount point using mount command.

[root@kerneltalks ~]# mount /dev/vgdata/lvdata /data
[root@kerneltalks ~]# df -Ph /data
Filesystem                 Size  Used Avail Use% Mounted on
/dev/mapper/vgdata-lvdata  4.8G   20M  4.6G   1% /data

Verify your mount point with df command as above and you are all done! You can always add an entry in /etc/fstab to make this mount persistent over reboots.

You have attached a 10GB disk to the Linux machine and created a 5GB mount point out of it!