Combination of any three skills will work:
Familiarity with Linux OS and Kernel, DNS, DHCP, LDAP, and storage setup. Candidate must have experience troubleshooting issues in these realms.
Knowledge of Perl or Python scripting, and excellent analytical & problem solving skills are essential.
Knowledge of Data storage and Networking solutions.
Knowledge of configuration management systems (Ansible, Chef, Puppet, etc.) and version control solutions (Git).
Good understanding of Kerberos and its implementation, Tomcat, Apache/nginx,
Sendmail/Postfix, Procmail, CIFS, Autofs, NFS, GPG, PGP, OpenSSH, OpenSSL and secure certificates is desired.
Experience on Amazon Web Services, Windows Active Directory, Exchange or Office 365 is a plus.