diff --git a/src/install/common.py b/src/install/common.py
index 8219865b3..b1208f53c 100644
--- a/src/install/common.py
+++ b/src/install/common.py
@@ -20,7 +20,7 @@ def install_pip(python_command):
             raise InstallationError('Error in pip installation for {}:\n{}'.format(python_command, output))
 
 
-def main(distribution):
+def main(distribution):  # pylint: disable=too-many-statements
     xenial = distribution == 'xenial'
 
     apt_install_packages('apt-transport-https')
@@ -62,7 +62,7 @@ def main(distribution):
 
     # install general python dependencys
     apt_install_packages('libmagic-dev')
-    apt_install_packages('libffi-dev', 'libfuzzy-dev')
+    apt_install_packages('libfuzzy-dev')
     pip3_install_packages('git+https://github.com/fkie-cad/fact_helper_file.git')
     pip3_install_packages('psutil')
     pip3_install_packages('pytest==3.5.1', 'pytest-cov', 'pytest-pep8', 'pylint', 'python-magic', 'xmltodict', 'yara-python==3.7.0', 'appdirs')
diff --git a/src/install/pre_install.sh b/src/install/pre_install.sh
index d2f6c707e..21aa7eafa 100755
--- a/src/install/pre_install.sh
+++ b/src/install/pre_install.sh
@@ -3,17 +3,17 @@
 FACTUSER=$(whoami)
 
 CODENAME=$(lsb_release -cs)
-if [ ${CODENAME} = 'tara' -o ${CODENAME} = 'tessa' ]; then
+if [ "${CODENAME}" = "tara" ] || [ "${CODENAME}" = "tessa" ]; then
     CODENAME=bionic
-elif [ ${CODENAME} = 'sarah' -o ${CODENAME} = 'serena' -o ${CODENAME} = 'sonya' -o ${CODENAME} = 'sylvia' ]; then
+elif [ "${CODENAME}" = "sarah" ] || [ "${CODENAME}" = "serena" ] || [ "${CODENAME}" = "sonya" ] || [ "${CODENAME}" = "sylvia" ]; then
     CODENAME=xenial
-elif [ ${CODENAME} = 'rebecca' -o ${CODENAME} = 'rafaela' -o ${CODENAME} = 'rosa' ]; then
+elif [ "${CODENAME}" = "rebecca" ] || [ "${CODENAME}" = "rafaela" ] || [ "${CODENAME}" = "rosa" ]; then
     CODENAME=trusty
-    sudo apt-get -y install linux-image-extra-$(uname -r) linux-image-extra-virtual
+    sudo apt-get -y install "linux-image-extra-$(uname -r)" linux-image-extra-virtual
 fi
 
 echo "Install Pre-Install Requirements"
-sudo apt-get -y install python3-pip git
+sudo apt-get -y install python3-pip git libffi-dev
 
 echo "Installing Docker"
 
@@ -37,11 +37,11 @@ sudo apt-get -y install docker-ce
 sudo systemctl enable docker
 
 # add fact-user to docker group
-if [ ! $(getent group "docker") ]
+if [ ! "$(getent group docker)" ]
 then
     sudo groupadd docker
 fi
-sudo usermod -aG docker $FACTUSER
+sudo usermod -aG docker "$FACTUSER"
 
 sudo -EH pip3 install --upgrade docker-compose