$ whereis android

E.g  android: /var/lib/android-sdk/tools/android

$ vi ~/.bashrc (or vi ~/.rc depending on the shell)

# Insert Android path to shell
export ANDROID_HOME=/var/lib/android-sdk
export PATH=$ANDROID_HOME/platform-tools:$PATH
export PATH=$ANDROID_HOME/tools:$PATH
export PATH=$PATH:$ANDROID_HOME/build-tools 

# Now check below command
$ adb devices

$ cd $ANDROID_HOME/tools/bin
$ ./sdkmanager "system-images;android-25;google_apis;x86"
$ ./sdkmanager --licenses

$ cd $ANDROID_HOME/tools/bin
$ ./avdmanager create avd -n <DeviceName> -k "system-images;android-25;google_apis;x86"

$ cd $ANDROID_HOME/tools/bin
$ ./avdmanager list avds

--------------------
Available Android Virtual Devices:
    Name: testEmulator
    Path: /var/lib/jenkins/.android/avd/credit.avd
  Target: Google APIs (Google Inc.)
          Based on: Android 6.0 (Marshmallow) Tag/ABI: google_apis/x86
--------------------

Name : ANDROID_HOME
Value: /var/lib/android-sdk

Name : PATH
Value: /home/linuxbrew/.linuxbrew/sbin:/home/linuxbrew/.linuxbrew/bin:/var/lib/android-sdk/tools:/var/lib/android-sdk/platform-tools:/var/lib/android-sdk/build-tools

# stop adb
adb kill-server

#Start adb
adb start-server


#Start the emulator
$ANDROID_HOME/tools/emulator -avd <DeviceName> -no-window -wipe-data &
EMULATOR_PID=$!


# Wait for Android to finish booting
WAIT_CMD="adb wait-for-device shell getprop init.svc.bootanim"
until $WAIT_CMD | grep -m 1 stopped; do
  echo "Waiting..."
  sleep 1
done


# Unlock the Lock Screen
adb shell input keyevent 82


# Clear and capture logcat
adb logcat -c
adb logcat > build/logcat.log &
LOGCAT_PID=$!

# Allow “unknown sources” from Terminal without going to Settings App
adb shell settings put global install_non_market_apps 1

# Go to android team project dir
cd /var/lib/jenkins/qa_automation/android_apps/AndroidTeamProject
git checkout -f develop;
git pull origin develop;
./gradlew installStagingDebug;

# Check devices
adb devices;

# Go to testing team project dir
cd ~/qa_automation/test_automation/TesterTeamProject;
mvn clean compile test 


# Stop the background processes
kill $LOGCAT_PID
kill $EMULATOR_PID