Dear Employer,
1) Do you really want to upgrade the OS from Centos 6 to 7? for this you will need separate servers, you cannot upgrade CentOS from 6 to 7. will require fresh server installation.
) Besides this you can go for only upgradation of the required packages ie Apache, PHP MySQL on the same server. Only thing is will need to take backup of your databases before upgradation.
6+ yrs of relevant exp in Linux with followings
1) OS: Redhat,CentOS,Fedora and Ubuntu with Server Management, User management Bash scripting to take daily backups for database and code
2) APPLICATIONS:: a) LAMP Platform MemCache, Opcache
b) SVN server
c) Redmine 2.x installation on CentOS 6
d) Webservers: Apache Nginix
e) Load Balancing Ngnix, HAproxy
3) DATABASE:: MySQL/MariaDB/Percona installation, replication, galera cluster percona cluster,performance tuning and troubleshooting
4) MONITORING TOOLS:: a) Nagios with email and way2sms gateway notifications
b) Zabbix 2.4 with Email and ez-texting notifications.
5) CLOUD: a) AWS:- EC2 with autoscaling, VPC, RDS, Elasticache, S3, CloudFront, Route53 and SES
b) DigitalOcean:
6) OTHER TECHNOLOGIES:: Email marketing, DNS (power DNS setup with replication), LTSP, Redis, XenServer, KVM, DHCP