Linux Systems Administration

The Unix operating system was originally developed in 1969 by AT&T Bell Laboratory engineers Ken Thompson and Dennis Ritchie to run the telephone system. The development of Unix also spawned the C programming language, which the Bell engineers used shortly thereafter to rewrite Unix. Through the 1970s and 1980s, Unix was popular as a "mainframe" operating system for major enterprise computer systems. When Intel introduced the x86 processor in the mid 1980s, Unix publishers generally did not flock to adapt Unix to the new processor, opening a Window for Apple and Microsoft. Some computer scientists did have a desire to adapt Unix to the x86 processor, however. Andrew Tannenbaum developed the Minix operating system in 1987 based on Unix. Minux ran on 16 bit x86 processors, so it could be installed on smaller Intel based computers. Linus Torvalds, at the time a college student in his native Finland, was interested in Minix and decided try and adapt it to the newer 32 bit Intel processors, as well as eliminate some of the copyright restrictions that existed with Minix. In 1991 Mr Torvalds released Linux, the first completely free and open source operating system. Linux is built to support many concurrent user sessions, and therefore has been popular throughout its existence as a server operating system, particularly for email, web and database servers. In recent years, more graphical and user friendly Linux releases such as Ubuntu are gradually expanding Linux home computing. Where Linux usage has exploded, however, is in mobile computing. Linux is the underlying operating system used by Apple and Android, along with countless networking and telephony systems.

Howtos, Examples and Observations

Repair a broken ext3 journal file - Repair a broken ext3 journal on Linux

Need to allow a new network to connect to Postgres 9.2 without interrupting replication. - Reload Postgres Configuration On The Fly

Adding fonts to Linux - Installing Linux Fonts

Deleting and creating logical volumes with Logical Volume Manager on Centos 6 - LVM creating or deleting logical volumes on Centos 6

Setting Sendmail to use the hosts file - Getting Sendmail to use /etc/hosts

Bash prompt automation - Writing scripts on the command line

Install ESXI 5.0 on a PC with SATA drive - Installing ESXi 5.0 on a pc with sata drive

Setting the Postfix mailbox size limit - Fixing Postfix "error writing message: File too large" errors

Routing sendmail messages with mailertable - Designating specific mail servers in Sendmail

Allowing DSA encryption in sshd on RHEL and Centos 7 - sshd[pid]: fatal: no hostkey alg [preauth]

sudo NOPASSWD fails - sudo Prompts For A Password Despite NOPASSWD Being Set

Using yum To Download But Not Install - The yum Download Only Option

Changing the firewalld service back to iptables - Revert firewalld to iptables

Fixing the pptpd input output error - Fixing unexpected pptpd input output errors

Troubleshooting bind named startup permission errors on RHEL and Centos 7 - named startup permission errors

Dumping master file permission denied on named slave name server- Dumping master file tmp-xxxxxxxxxx permission denied

resize2fs replaces fsadm on Centos 7 - fsadm replaces resize2fs

rc.local does not work on Centos 7 - rc.local not working

SSH Keepalives - SSH preventing inactivity timeouts