Manasi Singh’s Post

If your target reads from a USB-stick and happens to fetch the data twice, can this be exploited in real world? Well, sometimes. You can make a fully programmable USB-stick fast and cheap with RPi Zero and a couple of commands like explained here: https://lnkd.in/dFTVxVr9. But the caveat is that modern operating systems cache data read from USB stick. They (correctly) assume that when a stick is plugged in, the only way to legitimately modify data is to go through the OS itself. I tried it on Linux and Android: in both cases the caching was there. I suspect that Windows and MacOS do the same (let me know in the comment if you tried it). Where you can try your luck though is simpler software with much more primitive USB drivers like embedded devices, bootloaders, etc. #offensivesecurity #reverseengineering

Linux Boot Process Illustrated Overview The following diagram outlines the steps involved in the Linux boot process. Step-by-Step Boot Process Step 1: Initial Power-On** - When the system is powered on, the BIOS (Basic Input/Output System) or UEFI (Unified Extensible Firmware Interface) firmware loads from non-volatile memory and performs the Power On Self Test (POST). Step 2: Hardware Detection** - BIOS/UEFI detects and initializes connected hardware components such as the CPU, RAM, and storage devices. Step 3: Boot Device Selection** - A boot device is selected from which to load the operating system. This device could be a hard drive, network server, or CD-ROM. Step 4: Boot Loader Execution** - BIOS/UEFI executes the boot loader (e.g., GRUB). The boot loader provides a menu to select the operating system or kernel options. Step 5: Kernel Initialization** - Once the kernel is loaded, the system switches to user space. The kernel initiates `systemd` as the first user-space process, which manages services and processes, detects remaining hardware, mounts filesystems, and starts the desktop environment. Step 6: Activation of Default Target** - `systemd` activates the default target unit, typically managing the basic system state. Additional units are also executed to fully configure the system. Step 7: Startup Scripts Execution** - The system runs a series of startup scripts to set up the environment. Step 8: User Login** - The system presents a login window to the user, indicating the system is ready for use. This step-by-step process ensures that the Linux operating system boots up correctly, initializes all necessary components, and prepares the system for user interaction. #linux #systems

Device tree in Embedded Linux: The device tree is a critical component in Embedded Linux systems, providing a structured way to describe the hardware configuration of a device. 🤔 What is a Device Tree? 1️⃣ Definition: The device tree is a data structure that conveys information about the hardware components of a system to the Linux kernel. It allows the kernel to initialize and manage hardware without hardcoded configurations. 2️⃣ Purpose: It abstracts the hardware specifics, enabling a single kernel binary to support multiple hardware platforms. This flexibility is especially useful in embedded systems, where different boards or revisions may have varied configurations. 🏛️ Structure 1️⃣ Nodes: The device tree is organized as a hierarchical structure of nodes, each representing a hardware device or subsystem (e.g., I2C controllers, GPIOs, memory regions). 2️⃣ Properties: Each node can have properties that define its attributes, such as memory addresses, interrupt lines, and configuration parameters. ✅ Boot Process 1️⃣ Bootloader Role: During boot, the bootloader (like U-Boot) loads the DTB into memory and passes it to the kernel. 2️⃣ Kernel Initialization: The kernel uses the information in the device tree to initialize the hardware components specified in the tree. 💪 Advantages 1️⃣ Modularity: Supports multiple hardware configurations without modifying the kernel code. 2️⃣ Maintenance: Simplifies updates and maintenance since hardware descriptions are external to the kernel. 3️⃣ Device Support: Facilitates the addition of new devices by updating the device tree rather than changing the kernel. 📒 Use Cases 1️⃣ System on Chips (SoCs): Widely used in SoC-based designs where hardware configurations can vary significantly between models. 2️⃣ Development Boards: Common in development platforms like Raspberry Pi and BeagleBone, where the same kernel can support different hardware configurations through different device trees. #boot #linux #embedded #systemdesign #learning #kernel

We've talked a bit about Diet-Buntu and shared some links and images, but how about some video running on real hardware! This is the OS running on a MacBook Pro A1278 from 12 years ago, while running a screen recorder in the background and not even breaking a sweat (Only around 600-700MB of RAM usage and 60-80% of the CPU idle in most instances)! We'll be sharing more videos on other hardware in the future, but thought we should share this one with you all now! #renu #renu_tech #renu_technologies #linux #ubuntu #apple #macbook #canonical #refurbish #refurbishing #refurbishment

🌟 Choosing the Right IDE: STM32CubeIDE vs. Keil µVision 🌟 When developing with STM32 microcontrollers, selecting the right Integrated Development Environment (IDE) is crucial for productivity and success. Two popular choices are STM32CubeIDE and Keil µVision. Let's dive into the key differences to help you make an informed decision! 🛠️ STM32CubeIDE: It is specifically designed for STM32 microcontrollers, offering a seamless experience tailored to these devices.The IDE is integrated with STM32CubeMX, allowing for easy configuration of peripherals and middleware through a graphical interface. It's free, making it an excellent choice for beginners and those on a budget. Also,STM32CubeIDE runs on Windows, macOS, and Linux, offering flexibility for developers on different platforms. Keil µVision: It supports a wide range of ARM Cortex-M microcontrollers, including STM32, making it a versatile tool for various projects.The IDE features sophisticated debugging and performance analysis tools, helping developers optimize their code effectively.eil µVision can be expensive, with different licensing options based on the size and needs of your project. This might be a consideration for hobbyists or small startups. Which One Should You Choose? If you are focusing on STM32 microcontrollers and prefer a cost-effective, user-friendly solution, STM32CubeIDE is your go-to choice. Its integration with STM32CubeMX and extensive community support make it ideal for beginners and small to medium-sized projects. On the other hand, if you need advanced debugging features, broad ARM Cortex-M support, and are working on professional-grade applications, Keil µVision is worth the investment. Its optimization capabilities and professional tools make it suitable for large-scale, performance-critical projects. Choosing the right tool depends on your project requirements, budget, and familiarity with the platform. Both IDEs have their strengths, and understanding these can help you make the best choice for your development needs. 🔗 #EmbeddedSystems #STM32 #Keil #Microcontrollers #EmbeddedDevelopment #IDE

🚀 **Essential Linux Hardware Commands** 🚀 Hello, tech enthusiasts! 💻 Here’s a handy list of essential Linux hardware commands that every tech professional should know: 1. `lscpu` - Displays information about the CPU architecture 2. `lsblk -a` - Lists information about all the block devices attached to the system 3. `free` - Displays system memory (RAM) details in KB 4. `free -m` - Displays system memory (RAM) details in MB 5. `df` - Reports file system disk space usage 6. `df -h` - Reports file system disk space usage in human-readable format 7. `du <filename>` - Summarizes disk usage of each file, recursively for directories 8. `du -sh <filename>` - Summarizes disk usage in human-readable format 9. `cat /proc/cpuinfo` - Displays information about the CPU architecture 10. `cat /proc/meminfo` - Displays system memory (RAM) details 11. `fdisk -l` - Lists the partition tables for the specified devices 12. `fdisk -s <partition>` - Displays partition size(s) in blocks These commands will help you get detailed information about your system's hardware and manage it effectively. #Linux #SysAdmin #TechTips #ContinuousLearning #IT #SystemAdministration #DevOps #Hardware

Linux Boot Process Explained Almost every software engineer has used Linux before, but only a handful know how its Boot Process works :) Let's dive in. The diagram below shows the steps. Step 1 - When we turn on the power, BIOS (Basic Input/Output System) or UEFI (Unified Extensible Firmware Interface) firmware is loaded from non-volatile memory, and executes POST (Power On Self Test). Step 2 - BIOS/UEFI detects the devices connected to the system, including CPU, RAM, and storage. Step 3 - Choose a booting device to boot the OS from. This can be the hard drive, the network server, or CD ROM. Step 4 - BIOS/UEFI runs the boot loader (GRUB), which provides a menu to choose the OS or the kernel functions. Step 5 - After the kernel is ready, we now switch to the user space. The kernel starts up systemd as the first user-space process, which manages the processes and services, probes all remaining hardware, mounts filesystems, and runs a desktop environment. Step 6 - systemd activates the default. target unit by default when the system boots. Other analysis units are executed as well. Step 7 - The system runs a set of startup scripts and configure the environment. Step 8 - The users are presented with a login window. The system is now ready.

🔍 𝐇𝐨𝐰 𝐭𝐨 𝐭𝐫𝐨𝐮𝐛𝐥𝐞𝐬𝐡𝐨𝐨𝐭 𝐚 𝐋𝐢𝐧𝐮𝐱 𝐩𝐫𝐨𝐜𝐞𝐬𝐬 𝐭𝐡𝐚𝐭’𝐬 𝐜𝐨𝐧𝐬𝐮𝐦𝐢𝐧𝐠 𝐞𝐱𝐜𝐞𝐬𝐬𝐢𝐯𝐞 𝐚𝐦𝐨𝐮𝐧𝐭𝐬 𝐨𝐟 𝐂𝐏𝐔, 𝐦𝐞𝐦𝐨𝐫𝐲, 𝐝𝐢𝐬𝐤 𝐈/𝐎? The diagram and commands below display useful tools and commands that can come in handy when troubleshooting Linux issues. 🔹 ‘𝐥𝐬𝐨𝐟’ - lists open files of the current system. 🔹 ‘𝐭𝐨𝐩/𝐩𝐬 𝐚𝐮𝐱’ - to check the resource usage of the processes and identify which process is consuming excessive resources. 🔹 ‘𝐬𝐭𝐫𝐚𝐜𝐞’ - trace system calls and signals of a running process. 🔹 ‘𝐯𝐦𝐬𝐭𝐚𝐭’ - obtain information about memory, processes, paging, I/O, CPU activity and other system stats. 🔹 ‘𝐢𝐨𝐬𝐭𝐚𝐭’ - reports CPU and input/output statistics for devices and partitions in the system. 🔹 ‘𝐧𝐞𝐭𝐬𝐭𝐚𝐭’ - displays information about network connections, routing tables, interface statistics, and the status of various network protocols. 🔹 ‘𝐩𝐢𝐝𝐬𝐭𝐚𝐭’ - monitors the utilisation of system resources by all or specified processes, including CPU, memory, device IO, task switching, threads, etc. Image creds: Brendan Gregg #linux #networking #troubleshooting

I recently took the plunge and installed Linux on my Mac. The process was smoother than I anticipated, but it did come with a few unexpected challenges. I've created a walkthrough video to help others navigate this process. Key points from my experience: Overall, the installation was more straightforward than I initially thought NVIDIA graphics card users (for Macbook Pro circa 2009): You'll need to use safe graphics mode for a successful install Broadcom WiFi users: The driver isn't included by default. You'll need to connect via Ethernet first to download the necessary packages If you're considering breathing new life into an old Mac or just want to explore Linux on Apple hardware, check out my step-by-step guide. It covers everything from basic setup to troubleshooting common issues. Have you tried running Linux on a Mac? What was your experience? Share your thoughts below! Steps: Download the ISO image of your choice, I did Lubuntu found at https://lnkd.in/gvZR8nFj Create a Bootable USB Drive: You can either download and install Etcher, then in Etcher, click "Flash from file" and select the ISO you downloaded. Select your USB drive under "Select target." Click "Flash!" to start the process. OR do what I did and use the Terminal! 1. Open Terminal and find the USB drive identifier: "diskutil list" 2. Unmount the USB: "diskutil unmountDisk /dev/{your_disk_name}" 3. Use the `dd` command to write the ISO to the USB: "sudo dd if=/path-to-lubuntu.iso of=/dev/{disk_name} bs=1m" Once that is done flashing to the USB, you have your bootable USB!! Then to boot from USB on Mac: 1. Insert the bootable USB into the computer while it is off. 2. Power on and hold the Option key (for Macs) 3. Select the USB drive and press Enter. This will then start the installation After the installation finishes, you'll be prompted to restart the computer. Remove the USB and restart, login, and... chive on? More details and things to know in the video. Video link (YouTube): https://lnkd.in/gymkiQrU #Linux #Lubuntu #MacOS #TechTutorial #OpenSource

why blacklist file in linux /etc/modprobe.d/blacklist.conf file is used in Linux to prevent specific kernel modules from being loaded automatically. Here's an overview of its purpose and how it is used: Purpose: The blacklist.conf file contains a list of kernel modules that should not be loaded automatically by the system. This is useful for preventing the loading of modules that might cause conflicts, are unnecessary, or are known to cause issues on specific hardware. Structure and Usage: The file consists of lines that specify modules to be blacklisted, typically using the blacklist directive. Example entry: blacklist nouveau This entry prevents the nouveau module (an open-source NVIDIA driver) from being loaded. Creating and Editing: You can create or edit the /etc/modprobe.d/blacklist.conf file using a text editor. For example, to blacklist a module named example_module, you would add: blacklist example_module Effect on System: When the system boots or when modprobe is used to load modules, it will refer to the blacklist to avoid loading the specified modules. This helps in customizing the module loading behavior according to specific needs or preferences. Examples of Common Use Cases: Preventing Conflicts: If two modules provide similar functionality, you might blacklist one to prevent conflicts. Disabling Unwanted Modules: For instance, if you use proprietary drivers for your GPU, you might blacklist the open-source drivers. Improving System Stability: If a particular module is known to cause instability on your hardware, you can blacklist it. In short, /etc/modprobe.d/blacklist.conf is a configuration file used to specify kernel modules that should not be loaded by the system, providing a way to prevent conflicts, disable unwanted modules, and improve system stability.