Web Servers

HAProxy, squid, Apache, nginx, tomcat, mod_python, mod_perl, mod_security, bottle, flask, Django, CherryPy, Load-balancing.

Monitoring

Nagios, Opsview, munin, log analysis, RAID, Backups, Parenting, Off-site Monitoring, End-to-end Testing, All common services.

Storage

iSCSI, GlusterFS, OCFS, NFS, Ceph, Distributed/Replicated Filesystems, btrfs, ReoserFS, SANs, Fibre Channel, RAID, Sheepdog, SSDs, DRBD, High Availability NFS servers, Clustered LVM, Samba.

Distributions

Being production SysAdmins we primarily work with LTS, in particular Ubuntu and Red Hat (and derivatives like CentOS or Scientific Linux).

Infrastructure

Domain Names and DNS, BIND, PowerDNS, NTP, LDAP, Puppet.

E-mail

Postfix, Sendmail, qmail, vPostMaster, Dovecot, SquirrelMail, SASL, Greylisting, SpamAssassin, ClamAV, Amavis.

Networking

Firewalling, iptables, hashlimit, rate-limiting, BGP, On-the-wire Analysis and Debugging, Accounting, TCP/IP, Switching, Jumbo Packets, VPNs, OpenVPN, PPTP, IPSEC, Load-balancing, Bonding, Quagga, ipvsadm, ldirectord, Conference Wireless, Routing, NAT.

Programming

Python, PHP, bash, Unix Shell, TCP/IP Networking, C.

Backups

rsync, rdiff-backup, ZFSBackup, Monitoring and Alerting, iBackup, Snapshots, PHDVBA.

Virtualization

VMWare, ESXi, KVM, Proxmox, Xen, Sheepdog, Live Migration.

High Availability

DRBD, Heartbeat, Corosync, STONITH, Fencing, Bonding, Power Redundancy, Automatic Transfer Switch, UPS, DRBDLinks, ldirectord, ipvsadm.