TurnToJPG -->

In a minimum installed system, do following:

# mount /dev/sr0 /mnt
# vim  /etc/yum.repos.d/local.repo 
# yum makecache
# cat /mnt/repodata/764ce0e938d43b3e9cb1bcca13cf71630aac0c44149f4a61548f642df3c70858-comps-Server.x86_64.xml

Around Line 937-1031, get all of the packges:

# cat list1.txt | awk -F '>' {'print $2'} | awk -F '<' {'print $1'} 

According to the output, install all of the packges:

yum install -y Red_Hat_Enterprise_Linux-Release_Notes-7-en-US
yum install -y audit
yum install -y tboot
yum install -y NetworkManager-config-server

Now do following for getting all of the packages:

# for i in `rpm -qa`; do echo $i.rpm|xargs -I % cp /mnt/Packages/% /root/pkgs; done

Added Base group:

# sed -n 483,632p /mnt/repodata/764ce0e938d43b3e9cb1bcca13cf71630aac0c44149f4a61548f642df3c70858-comps-Server.x86_64.xml  | awk -F '>' {'print $2'} | awk -F '<' {'print $1'} | xargs -I % yum install -y %
# for i in `rpm -qa`; do echo $i.rpm|xargs -I % cp /mnt/Packages/% /root/pkgs; done

Upload the Packages to building server, then:

# mv repodata/ /root/whole_repodata
# mv Packages/ /root/whole_Packages
# mv /root/thinrepodata/ repodata
# mv /root/pkgs/ Packages
# cp repodata/764ce0e938d43b3e9cb1bcca13cf71630aac0c44149f4a61548f642df3c70858-comps-Server.x86_64.xml .
# createrepo -g 764ce0e938d43b3e9cb1bcca13cf71630aac0c44149f4a61548f642df3c70858-comps-Server.x86_64.xml  .
# mkisofs -o /root/new.iso  -b isolinux/isolinux.bin -c isolinux/ --no-emul-boot --boot-load-size 4 --boot-info-table -J -R -V "RHEL-7.4\x20Server.x86_64" . 

Your /root/new.iso will be much more smaller, cause it only contains Core and Base group packages.