Posts Categorized: linux

Apache: unable to open logs

In the annals of “Everyday is a learning day”. I have an Apache server hosting student websites, and the number of websites grew to over 700 within a day and Apache was complaining with error: unable to open logs It took a little while to narrow down the problem as I assumed there was a… Read more »

Locating Excessive Inode Usage

The command to list the directories using the most inodes is: find . -printf “%h\n” | cut -d/ -f-2 | sort | uniq -c | sort -rn However, I first needed to narrow down the directory under root that might be causing the problem: df -i showed that the root directory (/) was the problem…. Read more »

Configure Java Security Settings on Linux

I received the following error message when trying to run a Java JNLP file: Application Blocked by Security Settings Your security settings have blocked a self-signed application from running Assuming I trust the program I found I could get it to run by amending the Java Security Policy: Amending the Java Security Policy The first… Read more »

Intel Xeon Phi Co-Processor Setup

centos logo

Introduction Just adding my notes here in case it helps anyone else who finds themselves in a similar situation to me.I have two machines each with an Intel Xeon Phi Co-Processor board. This (in my basic view of the world) is like an extra machine inside the host machine but contains 240 processors clocking in… Read more »

Fido U2F Security Key

FIDO U2F Key Opening

So I ordered a FIDO U2F Security Key from a French company ‘Plug-Up’ to have a little play.  It is used in 2-factor authentication so when logging in to a service you first enter your username and password and if correct your are prompted for your second factor (a code sent by SMS or a… Read more »

Linux GPS Logging Data

I took part in a swim this weekend – The Battle of Carlingford Lough. My friend Cormac gave his Panasonic Lumix camera to Mary in the kayak and set the camera to log GPS data. He sent me the GPS log file and I opened the log file with BT747 – a Java application that… Read more »

pam_exec.so Execute Commands on User Login

In addition to the normal pam_mkhomedir.so I wanted to create a directory for each user on an alternative disk. To do so I edited: vi /etc/pam.d/password-auth added the line below (just above the line: session optional pam_mkhomedir.so) session     optional      pam_exec.so /usr/local/bin/create_dir.sh Then created the create_dir.sh file: vi /usr/local/bin/create_dir.sh and added the following: #!/bin/bash if [… Read more »

Disk Space Usage on Linux

CBS.log Disk Usage Analyzer

An example of narrowing down disk space usage issues on Linux. Starting with the following command: df -h We see that the root volume has 16% space left. Filesystem            Size  Used Avail Use% Mounted on /dev/mapper/VolGroup00-LogVol00 129G  103G   20G  84% / cd / We need to run the du command but I wanted to exclude… Read more »