CentOS 7 /dev/mapper/centos-root at 99% use Disk Full

[Rajasekar29]

My Disk storage is almost full when I checked in the server

[[email protected] ~]# df -h
Filesystem               Size  Used Avail Use% Mounted on
devtmpfs                 908M     0  908M   0% /dev
tmpfs                    920M     0  920M   0% /dev/shm
tmpfs                    920M   18M  902M   2% /run
tmpfs                    920M     0  920M   0% /sys/fs/cgroup
/dev/mapper/centos-root   35G   27G  8.2G  77% /
/dev/sda1               1014M  229M  786M  23% /boot
/dev/mapper/centos-tmp   3.0G   82M  3.0G   3% /tmp
tmpfs                    184M     0  184M   0% /run/user/0

How do I Cleare the /dev/mapper/centos-root/ unwanted memory
Its just a basic blog site with some images not more than 10gb
Am new to handling server expecting answers in simple terms

[[email protected] ~]# du -a |sort -n -r| head -n 20
172096  .
163564  ./postfix-3.2.0
90780   ./postfix-3.2.0/src
38680   ./postfix-3.2.0/libexec
15228   ./postfix-3.2.0/bin
7840    ./postfix-3.2.0/src/util
7760    ./postfix-3.2.0/src/global
6896    ./postfix-3.2.0/lib
5448    ./postfix-3.2.0/src/smtpd
4664    ./postfix-3.2.0/src/smtp
3708    ./postfix-3.2.0/src/cleanup
3492    ./postfix-3.2.0/html
3400    ./maldetect-1.6
3284    ./maldetect-1.6/files
3212    ./postfix-3.2.0/src/tls
3164    ./alldb_before_ugrade.sql
3080    ./maldetect-1.6/files/sigs
2884    ./postfix-3.2.0/src/smtpd/smtpd
2884    ./postfix-3.2.0/libexec/smtpd
2740    ./postfix-3.2.0/src/postconf
[[email protected] ~]#

 

[cPanelLauren]

I think my first question is wondering why you have postfix and if you're using it? cPanel by default uses exim have you implemented any customizations?