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Category: Ubuntu (Page 1 of 2)

Ubuntu Stops Resolving Address

December 8, 2021 / / 0 Comments

Issue

Pinging any known working internet address is returning the following message:

Temporary failure in name resolution

Example

Pinging www.google.com as follows:

ping: www.google.com: Temporary failure in name resolution

Resolution

Check where you /etc/resolve.conf is pointing using the following command:

 ls -al /etc | grep resolv.conf

If it is not pointing to /run/systemd/resolve/resolv.conf. Do the following:

sudo rm /etc/resolv.conf
sudo ln -s /run/systemd/resolve/resolv.conf  /etc/resolv.conf
sudo systemctl restart systemd-resolved.service

Requesting for Certificate with certbot-auto

October 16, 2020 / / 0 Comments

Requesting for certificate

certbot-auto certonly -m <EMAIL_NAME> --webroot -w <WEBROOT_PATH> -d <DOMAIN_NAMES>

Example

certbot-auto certonly -m admin@example.com --webroot -w /usr/share/nginx/www -d www.example.com

Expanding your certificates

certbot-auto certonly --webroot --agree-tos -w <WEBROOT_PATH> --expand -d <DOMAIN_NAMES>

Example

certbot-auto certonly --webroot --agree-tos -w /usr/share/nginx/blog --expand -d blog.example.com

Display information about certificates you have from Certbot

certbot-auto certificates

Installing Jenkins in Ubuntu

October 16, 2020 / / 0 Comments

Requirement

  • Java 8 +

Installing Jenkins

  1. Install the jenkins key: 
    wget -q -O - https://pkg.jenkins.io/debian/jenkins.io.key | sudo apt-key add -
  2. Register the jenkins source: 
    sudo sh -c 'echo deb http://pkg.jenkins.io/debian-stable binary/ > /etc/apt/sources.list.d/jenkins.list'
  3. Add the universe repository: 
    sudo add-apt-repository universe
  4. Update the repository: 
    sudo apt-get update
  5. Install jenkins: 
    sudo apt-get install jenkins -y

Preparing Jenkins

  1. Access jenkins: 
    http://localhost:8080/
  2. Use the password found from the following file for Administrator Password: 
    sudo less /var/lib/jenkins/secrets/initialAdminPassword
  3. In Getting Started page select: 
    Install suggested plugins
  4. Create the first admin user.
  5. Provide the Jenkins URL in the Instance Configuration.
  6. Click the Start using Jenkins button.

Monitoring Artifactory Service with Nagios

October 15, 2020 / / 0 Comments

Requirement

  • check_jmx plugin

Enable JMX on Artifactory

  1. Update the /var/opt/jfrog/artifactory/etc/default file to add the following: 
    export JAVA_OPTIONS="$JAVA_OPTIONS -Dcom.sun.management.jmxremote -Dcom.sun.management.jmxremote.port=5000 -Dcom.sun.management.jmxremote.local.only=false -Dcom.sun.management.jmxremote.authenticate=false -Dcom.sun.management.jmxremote.ssl=false"

    If you wanted to connect remotely (e.g. jconsole) add the following argument:

    -Djava.rmi.server.hostname=<IP_ADDRESS>
  2. Restart the artifactory service: 
    sudo systemctl restart artifactory.service

Testing with check_jmx plugin

/usr/local/nagios/libexec/check_jmx/nagios/plugin/check_jmx -U service:jmx:rmi:///jndi/rmi://localhost:5000/jmxrmi -O "org.jfrog.artifactory:instance=Artifactory, type=Storage,prop=Binary Storage" -A Size

Expect to see something similar to the following output:

JMX OK Size=377653571

Related Post
Downloading the Nagios check_jmx Plugin in Ubuntu

Downloading the Nagios check_url.pl Plugin in Ubuntu

October 15, 2020 / / 0 Comments

Downloading the check_url.pl plugin

  1. Change to the nagios plugin directory: 
    cd /usr/local/nagios/libexec/
  2. Download the check_url.pl plugin: 
    sudo wget -O check_url.pl "https://exchange.nagios.org/components/com_mtree/attachment.php?link_id=1395&cf_id=24"
  3. Make the plugin executable: 
    sudo chmod 755 check_url.pl
  4. Update the file check_url.pl to replace all tmp_ with /tmp/tmp_ text (i.e. if you are using vi for editing using the following:) 
    %s#tmp_#/tmp/tmp_#g

Testing The Plugin

/usr/local/nagios/libexec/check_url.pl https://www.google.com

Expect to see the following output:

OK: 200  OK

Displaying the Help

/usr/local/nagios/libexec/check_url.pl -h

Downloading the Nagios check_jmx Plugin in Ubuntu

October 15, 2020 / / 0 Comments

Downloading the check_jmx plugin

  1. Change the directory to your home directory: 
    cd ~
  2. Download the check_jmx plugin: 
    wget -O check_jmx.tgz "https://exchange.nagios.org/components/com_mtree/attachment.php?link_id=1274&cf_id=24"
  3. Extract the downloaded plugin: 
    tar xvf check_jmx.tgz
  4. Move the plugin to /usr/local/nagios/libexec/ directory: 
    sudo mv check_jmx /usr/local/nagios/libexec/
  5. Update the file /usr/local/nagios/libexec/check_jmx/nagios/plugin/check_jmx to enclose the $@ with double quotation marks: 
    "$@"

    Thus the whole java line will become:

    java -cp $RDIR/jmxquery.jar org.nagios.JMXQuery "$@"

    The use of the double quote is to handle space character properly

Displaying the Help

/usr/local/nagios/libexec/check_jmx/nagios/plugin/check_jmx -help

Compiling Nagios Plugin 2.3.3 to Ubuntu 20.04

October 13, 2020 / / 0 Comments

Installing the Nagios Plugins

  1. Refresh the repository: 
    sudo apt-get update
  2. Install the dependencies: 
    sudo apt-get install -y autoconf gcc libc6 libmcrypt-dev make libssl-dev wget bc gawk dc build-essential snmp libnet-snmp-perl gettext
  3. Change the directory to your home directory: 
    cd ~
  4. Download the nagios plugins source codes: 
    wget --no-check-certificate -O nagios-plugins.tar.gz https://github.com/nagios-plugins/nagios-plugins/archive/release-2.3.3.tar.gz
  5. Extract the downloaded source codes: 
    tar zxf nagios-plugins.tar.gz
  6. Change to the directory of the newly extracted source codes: 
    cd nagios-plugins-release-2.3.3
  7. Setup and configure: 
    sudo ./tools/setup
sudo ./configure
  8. Compile the source codes: 
    sudo make
  9. Install the plugins to /usr/local/nagios/libexec directory: 
    sudo make install

Configuring NRPE 4 Daemon and Plugin to Ubuntu 20.04

October 12, 2020 / / 0 Comments

Installing NRPE

    1. Refresh the repository: 
      sudo apt-get update
    2. Install the dependencies: 
      sudo apt-get install autoconf automake gcc libc6 libmcrypt-dev make libssl-dev wget openssl -y
    3. Change the directory to your home directory: 
      cd ~
    4. Download the nrpe 4 source codes: 
      wget https://github.com/NagiosEnterprises/nrpe/releases/download/nrpe-4.0.3/nrpe-4.0.3.tar.gz
    5. Extract the downloaded source codes: 
      tar xvf nrpe-4.0.3.tar.gz
    6. Change to the directory of the newly extracted source codes: 
      cd nrpe-4.0.3
    7. Run the configure script that enables the command arguments for clients and uses ssl library: 
      sudo ./configure --enable-command-args --with-ssl-lib=/usr/lib/x86_64-linux-gnu/
    8. Compile the source codes: 
      sudo make all
    9. Install the nagios user and group: 
      sudo make install-groups-users
    10. Install both NRPE daemon and check_nrpe plugin: 
      sudo make install
    11. Install the nrpe config file (i.e. /usr/local/nagios/etc/nrpe.cfg): 
      sudo make install-config
    12. Install the init script: 
      sudo make install-init
    13. Enable the nrpe daemon: 
      sudo systemctl enable nrpe.service
    14. Update allowed_hosts field in the /usr/local/nagios/etc/nrpe.cfg file: to include your nagios server address (e.g. your nagios server address is 10.0.0.174 the allowed hosts is as follows): 
      allowed_hosts=127.0.0.1,::1,10.0.0.174
    15. Update the dont_blame_nrpe field: to 1 on the same configuration file to allow your clients to specify arguments: 
      dont_blame_nrpe=1
    16. Start the nrpe daemon: 
      sudo systemctl start nrpe.service

      The NRPE service is listening with the port 5666 by default.

Testing The NRPE Plugin

/usr/local/nagios/libexec/check_nrpe -H localhost

Expect to see the version of NRPE daemon

Related Post
Compiling NRPE 4 Plugin to Tinkerboard
Compiling Nagios Plugin 2.3.3 to Ubuntu 20.04

Changing the Ubuntu Server Timezone

September 22, 2020 / / 0 Comments

Displaying the current timezone

timedatectl status

Listing the available timezones

timedatectl list-timezones

Changing the active timezone

sudo timedatectl set-timezone <TIMEZONE>

Example

Use the following command to change the timezone to Pacific/Auckland:

sudo timedatectl set-timezone Pacific/Auckland

Configuring Postfix as a Relay

September 15, 2020 / / 0 Comments

Installing Postfix

Run the following commands:

sudo apt-get update
sudo apt-get install postfix

Configuring Postfix

  1. Run the following command: 
    sudo dpkg-reconfigure postfix

    Configuration questions:

    1. Select OK to proceed.
    2. Choose Satellite system.
    3. System Mail Name: <EMAIL_DOMAIN>
    4. SMTP relay host: <RELAY_HOST>

      Where RELAY_HOST must include the port number (e.g. 192.168.1.1:465).

    5. Root and postmaster mail recipient: root
    6. Other destinations to accept mail for: <EMAIL_DOMAIN>, localhost.localdomain, localhost
    7. Force synchronous updates on mail queue? No
    8. Local networks: 127.0.0.0/8 [::ffff:127.0.0.0]/104 [::1]/128
    9. Mailbox size limit (bytes): 0
    10. Local address extension character: +
    11. Internet protocols to use: all

      Feel free to answer the preceding questions based on your setup. Just replace the EMAIL_DOMAIN (i.e. example.com) with a valid value.

  2. Create the file /etc/postfix/sasl_passwd with the following content: 
    <RELAY_HOST> username:password
  3. Create a postfix database based on /etc/postfix/sasl_passwd using the following command: 
    sudo postmap /etc/postfix/sasl_passwd
  4. Edit the file /etc/postfix/main.cf to have the following entries added or updated: 
    smtp_tls_security_level = encrypt
smtp_sasl_auth_enable = yes
smtp_tls_wrappermode = yes
smtp_sasl_security_options =
smtp_sasl_password_maps = hash:/etc/postfix/sasl_passwd
  5. Restart the postfix service with the following command: 
    sudo systemctl restart postfix
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