Operating Systems

This is caused by additional carriage returns within your script. In Windows the end of a line is denoted by CRLF (Carriage-Return, Line-Feed). In Unix-like systems, the end of a line is donated by a single LF. This means when you try to run your script, every line has an extra carriage return which in turn causes … Read more

Conditional execution is a term used to describe the execution of processes or commands based on specfic conditions. This can also be thought of as conditional logic.  Like with most scripting or programming languages conditional logic is built upon the use of return codes. A return code (exit status)  is returned upon process completion to … Read more

Below is a small method for running Java daemons within Linux. The syntax is as follows: nohup is used so that it doesn’t get killed when user logs off </dev/null is used so that it doesn’t require a command-promt of it’s own & is used so that the Java daemon runs as a background process. … Read more

The following syntax will scan a range of IP addresses. At the point of a ARP response being received it will show a reply message (shown in below example). Note : In this example it will scan IPs between 10.1.1.1-255. if [ -x  /sbin/arping ] ; then for i in {1..255} ; do echo arping … Read more

The following command will place a clock within the top right corner of your shell. while sleep 1;do tput sc;tput cup 0 $(($(tput cols)-25));date;tput rc;done &

INTRODUCTION This article aims to explain the various steps required in configuring Wireless connectivity within Backtrack 4 r2. It is also worth mentioning that as Backtrack is based upon Ubuntu/Debian you may find steps and solutions within this article useful when faced with other Ubuntu/Debian based wireless issues. MY SETUP Backtrack installation consists of a … Read more

When running the command iptables -vL you may find that : the output displays slowly. the output (appears) to have hung. You can further see what IPtables is doing via running iptables -vL. From this you will most likely see iptables trying to run a reverse DNS lookup (and failing). Solution Due to IPtables trying to … Read more

The main cause for this error (see below) is due to su not being set to a setuid of root. su: cannot set groups: Operation not permitted Solution chmod u+s /bin/su

Issue When trying to download a file using wget you recieve a 403 forbidden error. root@Fileserver html# wget [website] –2010-12-20 20:40:40– [website] Resolving www.maani.us… 75.125.128.242Connecting to www.maani.us|75.125.128.242|:80… connected.HTTP request sent, awaiting response… 403 Forbidden2010-12-20 20:40:41 ERROR 403: Forbidden. Solution wget -U firefox [website]

By default VSFTPD does not allow the browsing of symbolic links. When you try to browse sym links you will get a message saying,        550 Failed to change directory In order to overcome this you can use the mount command. Here are the steps : [root@server ftpuser]# pwd/home/ftpuser[root@server ftpuser]# mkdir NEW_DIR[root@server ftpuser]# mount –bind … Read more

Each Syslog message contains a priority value. The priority value is enclosed within the characters < >. The priority value can be between 0 and 191 and consists of a Facility value and a Level value. Facility being the type of message, such as a kernel or mail message. And level being a severity level … Read more

When installing Oracle 11g on Fedora 13 you may get the following error :               Error in invoking target ‘agent nmb nmo nmhs tclexec’ of makefile ‘/u01/app/oracle/product/11.1.0/db_1/sysman/lib/ins_emagent.mk Solution Within the file detailed in the error edit it and find the line that reads ‘$(MK_EMAGENT_NMECTL)’ change this to ‘$(MK_EMAGENT_NMECTL) -lnnz11’ Note : edit this file while … Read more

Below shows you the basic steps in order to configure your Linux Redhat / CentOS server as a Samba server. Install and Configure yum install samba -ychkconfig –level 123 smb on cd /etc/sambamv smb.conf smb.conf.backupvi smb.confcat > /etc/samba/smb.conf [paste the text below][global]workgroup = Workgroupnetbios name = SambaServerserver string = Samba Server %vlog file = /var/log/samba/log.%mencrypt … Read more

In this article we will show you how to set the time, date and timezone within CentOS. Though I’m sure this method will remain the same through the various Linux distributions. Steps Set the time zone Set the time and date Sync the hwclock with the current time and date Commands Below are the commands … Read more

In order to set the hostname on CentOS you will need to change the HOSTNAME section within /etc/sysconfig/network Your hostname will now be updated once you logout and then back in. Its also worth noting that this will survive reboots.

In order configure your Ubuntu/Debian box to access HTTP, HTTPS and FTP via a Proxy you will need to assign some environment variables. Assign Environmental Variables Below shows you the different variables you need to declare : export HTTP_PROXY=[PROXY IP]:[PORT]export HTTPS_PROXY=[PROXY IP]:[PORT]export FTP_PROXY=[PROXY IP]:[PORT] Survive reboot To survive a reboot you need to add these … Read more

Below is a basic template for setting up IPTables on a Linux box : Create LOGDROP CHAIN. Add LOG and DROP to chain. iptables -N LOGDROP iptables -A LOGDROP -j LOG –log-level 6 iptables -A LOGDROP -j DROP Create input and output policies iptables –policy INPUT DROP iptables –policy OUTPUT DROP Add inbound rules iptables … Read more

What is encoding / decoding ? Encoding refers to the process of translating a file into an ASCII based string. Decoding refers to the process of decoding the ASCII based string. In order to perform this decoding/encoding process Base64 is typically used. Base64 is a program that  converts each 6 bits and then converts this … Read more

Please note : This article is based on RHEL5 and grub. Below shows the 2 methods you can use to ensure serial connectivity when booting into single user mode. You may find without changing this setting your connection is lost just after Redhat starts booting.This configuration change can be via the grub.conf or via the … Read more

Issue When you try and run a yum update you receive the following error : root@localhost:/$ yum update Traceback (most recent call last): File “/usr/bin/yum”, line 4, in ? import yum File “/usr/lib/python2.4/site-packages/yum/__init__.py”, line 42, in ? import config File “/usr/lib/python2.4/site-packages/yum/config.py”, line 27, in ? from parser import ConfigPreProcessor File “/usr/lib/python2.4/site-packages/yum/parser.py”, line 3, in ? … Read more