Simple Owncloud Installation on Raspberry Pi 2

The Raspberry Pi’s low power consumption makes it well suited to the role of always-on server. This post describes how to install Owncloud onto the Pi. Owncloud is an open source software package providing remote file sharing services, similar to Dropbox. But with Owncloud, you retain ownership, security and control of the shared data. Owncloud works well on a Pi 2 and Pi 3 but will run very slowly on a Pi 1.

Update 20th November 2016 – There is a newer version of this article. Please see Simple Nextcloud Installation on Raspberry Pi. Nextcloud was forked from ownCloud in June 2016. It now seems to have become the natural successor to Owncloud. I recommend using Nextcloud rather than Owncloud. This article remains on line because it might be helpful to existing Owncloud users, particularly the parts about upgrading and using external USB media.

UPDATE 16th July 2016 – Nextcloud was forked from Owncloud in June 2016. The procedure below can be used both for Owncloud and the initial release of Nextcloud (version 9.0.52). Thanks to Dan for this information.

My Raspberry Pi 2 was purchased from RS Components in the UK. It was installed with Raspbian “Jessie” (Debian 8) by applying the image “2016-02-09-raspbian-jessie.img” downloaded from the raspberrypi.org downloads page. The following procedure was then performed without any further pre-work (other than enabling ssh in the basic setup). Continue reading

Enable Outgoing Mail on Raspberry Pi

This article explains how to send email from the Raspberry Pi. It is a generic procedure and also works on other Debian distributions. This is not for receiving mail, only for sending it. (Receiving email on the Pi is a much more involved process, requiring your Pi to preform the role of a full mail server).

The ability to send mail across the internet is useful. It enables your scripts and applications to send you email about system events or sending data such as pictures from a webcam. Continue reading

Picture Frames and Captions with ImageMagick

This article discusses some of the caption and border effects available with the ImageMagick image processing package. ImageMagick is freely available for Linux and Windows. It offers a huge number of image processing options, so many in fact, that using the program can be a little tricky.

The following examples were evolved from the ImageMagick online documentation, plus a good deal of trial and error to get the details right. I used Linux, but the same commands should work under Windows. Continue reading

Solaris Tictimed Catastrophic File Error

Solaris administrators may have seen the message “Catastrophic file error – zero length” in their system logs. Although it sounds serious, there is nothing “catastrophic” about it. This post explains how to stop the message from flooding your log files. Continue reading

An Example of Parallel Processing

This post shows how to use parallel processing to get a CPU intensive job done faster in Unix/Linux. By splitting a large task into several parts, it is quite easy to give each part to a separate CPU, and complete the task many times faster than it would on a single processor.

These days, even small PCs and other devices often come equipped with several CPU cores. But some tasks will use only one core, sometimes using 100% of it, while other cores stand by idle. Sometimes this is a waste of resources. Continue reading

bc Rounding Errors

There must be a few people out there who still use bc as a desk calculator. bc is a simple application that comes as standard on most unix and linux systems. It’s nicer to use than a graphical calculator app: less fussy, no mouse needed and you can see what you have typed.

bc Gets it Wrong

A recent mix-up with financial calculations lead me to discover that – unbelievably – bc was getting its sums wrong. This post explains the problem. Continue reading

Resizing /tmp on Red Hat 5.3 (ext3, LVM)

This is how to do a simple file system increase in Logical Volume Manager. For example, increasing /tmp from 512 Mb to 1 Gb.

/tmp is a logical volume:

# df -h /tmp
Filesystem           1K-blocks      Used Available Use% Mounted on
/dev/mapper/vg00-tmpvol
                      496M   19M  452M   4% /tmp

Running “vgdisplay /dev/vg00” showed that volume group vg00 contained 3.5 Gb of free space. Extended the logical volume with lvextend: Continue reading

SSH Authentication and Directory Permissions

Running sshd in the foreground can be an effective way to debug ssh problems. In the following example, a user was unable to access a remote system using ssh keys. Running sshd in debug mode provided a quick resolution. Both source and target systems were Solaris, but the same method applies equally to Linux. Continue reading