* Systems administation: Linux (RedHat, Debian, Ubuntu), FreeBSD, Windows
* Network administration: VLAN, VPN, Wireless networks, Network equipment managment (Nortel, HP, Cisco), Deep understanding of network architecture,
* High availability: active-passive clusters (RHCS, Linux-HA), load-balancing techniques, clustered file systems (DRBD, GFS/OCFS, GlusterFS)
* Security: firewalling (iptables, ipfw, ipf/pf), antivirus techniques, antispam techniques (both before- and after- queue), SELinux (including writing custom policies), PKI
* Database administration: MySQL, PostgreSQL, Oracle, SQL
* Network services administration: www (apache, nginx), mail (postfix, sendmail, exim, dovecot, cyrus), DNS (bind, dnsmasq), LDAP (openldap)
* Virtualization: Xen, KVM, VMWare (ESX/ESXi, VSphere), libvirt API, OVF
* Programming: Perl, PHP, sh scripting, C/C++, Applescript, VBScript, Python, Java