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General Linux

Mobile WiFi NAS on Raspberry Pi with TrueCrypt

Mobile NAS sounds like an idea worth waiting for to run on my mini Raspberry Pi Model A. Unfortunately, it only took me a while, before abandoning it. I’ve waited since writing about Raspberry Pi USB problem, that is to finally cut the backfeeding power line from the el cheapo powered USB hub. There comes [...]

How DHCP/DNS Server Works in Web Proxy Autodiscovery Protocol (WPAD) for Today’s Browsers

Web Proxy Autodiscovery Protocol (WPAD) protocol draft expired in 1999, but today’s major browsers are still supporting it as will be shown later. Two types of DHCP server are tested to describe how WPAD behaves prior to/after starting up the internet browser. To be clear, uploaded packet captures are shared in CloudShark. DNS and domain [...]

Running Two Squid Instances in Upstart Init

After installing squid3 from repository, Ubuntu will place the init in upstart style (instead of /etc/rc*.d/ or /etc/init.d/ style used to maintain backward compatibility to legacy System-V init). The upstart job is placed in /etc/init/squid3.conf with default runlevel (2,3,4 or 5) to start the instance during reboot and relevant start/stop command using service: $ sudo [...]

HTTPS Using Server-Client Certificate Pair (1): Generate & Sign by OpenSSL

Multiple command lines in the process of generating certificates using openssl can be quite confusing and easily mixed up over which-do-what. Most of them are repetitions of almost the same syntax (where the confusion comes). Background: I need to setup an HTTPS site with not just server certificate to secure it, but requiring also client [...]

Python 2.6 in Red Hat 5

I need Gescheit Zabbix API implementation to run on RHEL5.2 Installing RPMs from Geekymedia seems to be the easiest. I only need the following to make it work: python26-2.6-geekymedia1.i386.rpm python26-libs-2.6-geekymedia1.i386.rpm

SNMP: Mistake of Using Tabular OID in Practice

Recently, I retrieve rectifier-related SNMP data from Eltek’s Smartpack Controller. This one has the following rear type where we can connect to the ethernet plug (see the purple area). It is presumably in its default configuration and I can snmpwalk through its corporate specific OIDs (under 12148 tree) to find i.e. output voltage, current, battery [...]

USB WiFi Stick on Beagleboard xM Using wpa_supplicant

One of the most popular USB WiFi sticks in Indonesian market is TP Link which is actually a Ralink wireless adapter (looking at its vendor ID code). Attaching it using wpa_supplicant without explicit driver assignment will return the following error lines ioctl[SIOCSIWENCODEEXT]: Invalid argument ioctl[SIOCSIWENCODEEXT]: Invalid argument Within minutes it will also crash the system [...]

Compile USB Serial Modem Using option.c (Ubuntu on Beagleboard xM)

Despite possibility to use (1) $ modprobe -v usbserial vendor=0x05c6 product=0×0015 or (2) usb-modeswitch, (3) Matthias Urlichs initially wrote option.c driver as a way to insert USB modem as kernel module. This driver exists because the “normal” serial driver doesn’t work too well with GSM modems. Issues: – data loss — one single Receive URB [...]

Write Your Own MIB File (Tabular)


When it comes to writing our own MIB, a practical choice might be to write the whole objects as of scalar type (RFC-1212). That means, let’s say we have 2 battery statuses, each of them must be explicitly written individually within the MIB file. Example of calling their voltages: $ snmpwalk -m +REKTRONIK-MIB -v 1 [...]

Running Raddle (2): snmpd & Replay Custom Private Enterprise MIB

Net-SNMP wiki gives tutorial on extending snmpd using Perl. In basic run of Raddle (previous post) this involves r1.pl called by r1.conf fed to snmpd. Private enterprise MIB i.e.¬†Microchip’s in this example can be replayed without really ever captured the real device’s SNMP data. This is necessary when the actual device is yet existed; normal [...]

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