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  • This agent can be running on a server next to your Jenkins controller/master or in the internal network(s)
  • agent service(s) with service auto-start to assure automatic re-connect to Jenkins controller at any time even after server reboot
    • Install dependencies

      • CentOS 7

        Code Block
        yum install java-11-openjdk-devel git -y
# you can install also other dependencies that will be required for your jobs


      • CentOS 8/9

        Code Block
        yum install java-17-openjdk-devel git -y
# you can install also other dependencies that will be required for your jobs


      • Ubuntu

        Code Block
        apt-get update; apt-get install openjdk-11-jdk git -y
# you can install also other dependencies that will be required for your jobs


    • Installing agent

      • Prepare a folder for config

        Code Block
        mkdir -p /data/configs
mkdir -p /opt/jenkins-agent


      • Create service file /opt/jenkins-agent/jenkins-agent.service

        Code Block
        titlejenkinsope.service
        [Unit]
Description=Jenkins Agent - On Premise Executor
Wants=network.target
After=network.target

[Service]
# EnvironmentFile cannnot be used on Debian/Ubuntu anymore - Reference: https://github.com/varnishcache/pkg-varnish-cache/issues/24
# So we are using drop-in config /etc/systemd/system/jenkins-agent.service.d/local.conf
ExecStart=/usr/bin/java -Xms${JAVA_MEMORY} -Xmx${JAVA_MEMORY} -jar /opt/jenkins-agent/agent.jar -jnlpUrl ${CONTROLLER_URL}/computer/${NODE_NAME}/jenkins-agent.jnlp -secret ${SECRET} -workDir "${WORK_DIR}"
User=jenkins-agent
Restart=always
RestartSec=10
StartLimitInterval=0

[Install]
WantedBy=multi-user.target


      • Create config file /data/configs/jenkins-agent.conf

        Code Block
        JAVA_MEMORY=512m
CONTROLLER_URL=https://jenkins.xxx.tds.customerx.com
NODE_NAME=XXX
SECRET=8b2911d98400bad5d45635b812b5f2e8e7c1d216bbbae9422a3ba57c691bf762
WORK_DIR=/data/jenkins-agent


      • Create script /opt/jenkins-agent/jenkins-agent-install

        Code Block
        #!/bin/bash
set -e
AGENT_APP_HOME=/opt/jenkins-agent
SRV_USER_NAME=jenkins-agent
SRV_USER_ID="900"
SRV_GROUP_NAME=jenkins-agent
SRV_GROUP_ID="900"
WORK_DIR_DEFAULT="/data/jenkins-agent"
AGENT_SERVICE_NAME="jenkins-agent"
AGENT_SERVICE_FILE="/usr/lib/systemd/system/$AGENT_SERVICE_NAME.service"
AGENT_SERVICE_CFG_FOLDER="/etc/systemd/system/$AGENT_SERVICE_NAME.service.d"
MAINCONFIG=/data/configs/jenkins-agent.conf

# Making sure obsolete jenkinsope config is migrated when found
OPE_OLD_MAINCONFIG=/data/configs/jenkinsope.conf
[ -f $OPE_OLD_MAINCONFIG ] && mv -f $OPE_OLD_MAINCONFIG $MAINCONFIG

# Loading configuration
source $MAINCONFIG

# Detecting and migrating obsolete jenkinsope account and data
OPE_OLD_USER=jenkinsope
OPE_OLD_HOME=/home/$OPE_OLD_USER
if [ -d $OPE_OLD_HOME ];then
  sed -i "s#^WORK_DIR.*#WORK_DIR=$WORK_DIR_DEFAULT#g" $MAINCONFIG
  sed -i 's#^MASTER_URL#CONTROLLER_URL#g' $MAINCONFIG
  # Re-loading configuration with new values
  source $MAINCONFIG
  systemctl stop jenkinsope
  sleep 10
  rm -rf /etc/systemd/system/jenkinsope.service.d
  rm -f /usr/lib/systemd/system/jenkinsope.service
  mv $OPE_OLD_HOME $WORK_DIR
  userdel -rf $OPE_OLD_USER
fi

# Detecting and migrating obsolete jenkins-agent account and data from /home to /data
JA_OLD_HOME=/home/$SRV_USER_NAME
if [ -d $JA_OLD_HOME ] && [ $JA_OLD_HOME != $WORK_DIR ];then
  sed -i "s#^WORK_DIR.*#WORK_DIR=$WORK_DIR_DEFAULT#g" $MAINCONFIG
  # Re-loading configuration with new values
  source $MAINCONFIG
  systemctl stop $AGENT_SERVICE_NAME
  sleep 10
  rm -rf $AGENT_SERVICE_CFG_FOLDER
  rm -f $AGENT_SERVICE_FILE
  mv $JA_OLD_HOME $WORK_DIR
fi

echo "Preparing basic home folder structure"
mkdir -p $WORK_DIR/.ssh
chmod 700 $WORK_DIR/.ssh
touch $WORK_DIR/.ssh/config
chmod 600 $WORK_DIR/.ssh/*
ls -lah $WORK_DIR

echo "Preparing group"
getent group $SRV_GROUP_NAME || groupadd --gid $SRV_GROUP_ID $SRV_GROUP_NAME
getent group $SRV_GROUP_ID || groupmod -g $SRV_GROUP_ID $SRV_GROUP_NAME

echo "Preparing user"
getent passwd $SRV_USER_NAME || useradd --shell /bin/bash --uid $SRV_USER_ID --gid $SRV_GROUP_ID --create-home --home-dir /data/jenkins-agent $SRV_USER_NAME
getent passwd $SRV_USER_NAME && usermod --shell /bin/bash --uid $SRV_USER_ID --gid $SRV_GROUP_ID --home /data/jenkins-agent $SRV_USER_NAME
getent passwd $SRV_USER_NAME

echo "Changing ownership of home/work folder ($WORK_DIR) and its content (can take long time with many files)..."
chown $SRV_USER_NAME:$SRV_USER_NAME -R $WORK_DIR
ls -lah $WORK_DIR

echo "Installing agent"
if [ -f $AGENT_SERVICE_FILE ];then
  echo "Previous service found, making sure it is stopped..."
  systemctl stop $AGENT_SERVICE_NAME
  sleep 5
fi
rm -f $AGENT_APP_HOME/agent.jar
curl -s ${CONTROLLER_URL}/jnlpJars/agent.jar -o $AGENT_APP_HOME/agent.jar
chmod 644 $AGENT_APP_HOME/agent.jar
install -D -m 644 $AGENT_APP_HOME/$AGENT_SERVICE_NAME.service $AGENT_SERVICE_FILE

# Check existence of JDK 11/17 and hard code it into service unit, otherwise attempt to use generic java
JDK11="/usr/lib/jvm/java-11/bin/java"
JDK17="/usr/lib/jvm/java-17/bin/java"
if [ -f "$JDK17" ];then
  echo "Setting discovered OpenJDK 17 to be used by Jenkins agent."
  sed -i "s#/usr/bin/java#$JDK17#" $AGENT_SERVICE_FILE
else
  if [ -f "$JDK11" ];then
    echo "Setting discovered OpenJDK 11 to be used by Jenkins agent as alternative."
    sed -i "s#/usr/bin/java#$JDK11#" $AGENT_SERVICE_FILE
  fi
  # Otherwise using generic java
fi

mkdir -p $AGENT_SERVICE_CFG_FOLDER
echo "[Service]" > $AGENT_SERVICE_CFG_FOLDER/local.conf
sed 's#^#Environment=#g' $MAINCONFIG >> $AGENT_SERVICE_CFG_FOLDER/local.conf
systemctl daemon-reload
systemctl restart $AGENT_SERVICE_NAME
systemctl enable $AGENT_SERVICE_NAME
# Using mandatory sleep otherwise checking status too early ends with error
sleep 10
systemctl status $AGENT_SERVICE_NAME

echo "0 4 * * * root $AGENT_APP_HOME/jenkins-agent-install" > /etc/cron.d/jenkins-agent-update


      • Run install script

        Code Block
        chmod +x /opt/jenkins-agent/jenkins-agent-install
/opt/jenkins-agent/jenkins-agent-install


    • Uninstalling agent (for cleanup purposes or if you messed up something)

      • Create script /opt/jenkins-agent/jenkins-agent-uninstall

        Code Block
        systemctl disable jenkins-agent
systemctl stop jenkins-agent
rm -f /usr/lib/systemd/system/jenkins-agent.service
rm -rf /etc/systemd/system/jenkins-agent.service.d
systemctl daemon-reload
userdel -r jenkins-agent
rm -rf /data/jenkins-agent


      • Run install script

        Code Block
        chmod +x /opt/jenkins-agent/jenkins-agent-uninstall
/opt/jenkins-agent/jenkins-agent-uninstall


...