You will need to install cifs-utils in order to mount samba shared directory:
sudo yum -y install cifs-utils
To mount in root account, run below commands:
sudo mount -t cifs //192.168.10.21/repository /mnt/nas -ousername=yourUserName,password=yourPassword,file_mode=0664,dir_mode=0775,uid=root,gid=root
If you want to mount the samba shared directory when your server boot, you will need to create your credentials at /your_preferred_directory/config
username=yourUserName password=yourPassword
and add below lines at /etc/fstab
//192.168.10.21/repository /mnt/nas cifs credentials=/your_preferred_directory/config,uid=root,gid=root 0 0
If you want to add some permission for file and folder,
//192.168.10.21/repository /mnt/nas cifs credentials=/opt/config/nas.cfg,uid=root,gid=root,dir_mode=0775,file_mode=0775,sfu 0 0
If you want to take it effect right away, run
sudo mount -a
Otherwise, the samba shared directory will be automatically mounted when you reboot your machine.
By the way, I recommend you to use sshfs instead of samba if you want a better performance based on my experience. You can see more at Mount remote directory by SSHFS in CentOS 7