Unix is a multi-user, multi-tasking operating system that was initially developed by Bell Labs in the 1970s. Various similar operating systems that are POSIX compliant (ie compatible with Unix) have since been developed (POSIX is an abbreviation for Portable Operating System Interface for UNIX). These include the following: the BSD family (OpenBSD, FreeBSD, NetBSD, Mac OS/X), Solaris, IRIX, AIX, SunOS, UnixWare, OpenServer and Linux.
Software written for POSIX compliant operating systems is generally able to be compiled for all POSIX platforms with little or no platform-specific changes. This makes the commands and utilities available for this extended family of operating systems very similar, and there are few differences between administering them.
The articles in this section are about useful command line utilities and commonly used application software on POSIX compliant operating systems. For Mac OSX specific articles see my OSX section.
When you connect to an OpenSSH sshd server, it is configured by default to do a hostname lookup on your IP address. If there are any issues with the DNS configuration on the host machine, or with the DNS server it is using, this can lead to a delay when logging in using ssh for around 30 seconds. It is very easy to switch this host name lookup function off in the sshd_config file.
wget is a command line utility for downloading files from FTP and HTTP web servers. By default when you download a file with wget, the file…
I run AWStats on one of my servers and it copies files over from some of the other servers I manage every 15 minutes and processes them. However, I had a server issue yesterday with the machine that AWStats runs on, and it meant the auto process which copies the files over and runs AWStats stopped running for about 12 hours. The end result was some lost information and needing to regenerate stats for the month to date. I needed to override the AWStats LogFile configuration directive on the command line to be able to do this.
The default command line text editor on Linux (and BSD varaiants) determines what is used when you run commands such as "crontab -e" and is often not what you want to use yourself. Typcially vi/vim is the default text editor; many people prefer emacs or other editors, and I prefer to use nano myself.
I process logs on my webservers using AWStats, and use the GeoIP plugin to translate IP addresses into country codes. This article looks at how to install the Geo I PurePerl plugin, which is used by AWStats, and also how to download and install the Geo IP database files which are required by this plugin. The server I installed this onto was a CentOS 5 server, but the instructions here should work equally well on other Linux distributions.
After re-partitioning a hard drive by removing all existing partitions and creating a single primary parition which takes up the entire disk, I formatted it as ext3, mounted it at /mnt/hdh and copied all the ISO images across from the exsting ISO drive. I rebooted, pausing to swap the disk over to a different cable, and got the error message "hdb: unknown partition table".