GNU Linux / Unix Systems Administration

I have been looking after POSIX compliant Operating Systems since first being introduced to RedHat Linux 4.2 in 1997. Mostly Linux (Gentoo, Redhat, Debian, Ubuntu and Centos) but also AIX, Solaris and DG/UX.

Most of these have been servers either for Internet Service Provision or for the deployment of a specific application, my laptop is the only non server I support with Linux installed (dual boot with Windows 7).

Internet Service Provision

Installed, Developed and managed systems for ISPs in South Africa, Greater London and briefly a niche provider in Soho covering rougly these services / applications:-

• Name Servers (Bind pri & sec, PowerDNS (MySQL backend))
• Athentication using Radius (FreeRADIUS) and LDAP (OpenLDAP)
• Web Servers with name based virtual hosting and SSL (all Apache)
• Traffic management (Squid and Class-Based-Queuing)
• Email (Dovecot and Sendmail using MIMEDefang to innovatively hook up an AntiVirus and AntiSpam solution using (SpamAssassin, ClamAV))

Specific Application servers

Installed OS and applications for

1. Agricultural trading application at 20 sites in South Africa, was responsible for main and hot stand by servers (> 40 servers nationwide) serving up to 150 trading users per site. Also responsible for ISDN/Leased line network connecting them and integrating with IP space of 3rd party stake holders. [1998-2005]
2. Online Foreign Exchange trading platform and associated Back Office servers connected to counterparies via FIX for FX trades and SWIFT for payments [2008-2011].

I have used the RRD packacge to monitor application page load times to have an objective view of performance changes, this has been a valuable reference when users make performance complaints and to show trends over time.

Administration / Management

• Shell/Command line access via OpenSSH
• Shell Scripting | adhoc admin tasks, automate backups
• Software RAID (mdadm)
• Backups (dd, rsync, rdiff-backup)
• Resource monitoring using RRD
• Package Management (yum, apt-get) and compiling from source if necessary (including the kernel)
• kernels from 2.6.4 (OS on specialised hardware router) still running.
• uptime range from 100 days to 558 days

[root@wf01LDN ~]# date
Fri Sep  2 02:10:45 BST 2011
[root@wf01LDN ~]# uptime
 02:10:57 up 572 days, 11:27,  1 user,  load average: 0.34, 0.19, 0.18
[root@wf01LDN ~]#