#redhat

[sentientcitysurvival]

Basic Linux Security (Updated 2025)

Install Unattended Upgrades and enable the "unattended-upgrades" service.

Install ClamAV and enable "clamav-freshclam" service.

Install and run Lynis to audit your OS.

Use the "last -20" command to see the last 20 users that have been on the system.

Install UFW and enable the service.

Check your repo sources (eg; /etc/apt/).

Check the /etc/passwd and /etc/shadow lists for any unusual accounts.

User the finger command to check on activity summaries.

Check /var/logs for unusual activity.

Use "ps -aux | grep TERM" or "ps -ef | grep TERM" to check for suspicious ongoing processes.

Check for failed sudo attempts with "grep "NOT in sudoers" /var/log/auth.log.

Check journalctl for system messages.

Check to make sure rsyslog is running with "sudo systemctl status rsyslog" (or "sudo service rsyslog status") and if it's not enable with "sudo systemctl enable rsyslog".

Perform an nmap scan on your machine/network.

Use netstat to check for unusual network activity.

Use various security apps to test you machine and network.

Change your config files for various services (ssh, apache2, etc) to non-standard configurations.

Disabled guest accounts.

Double up on ssh security by requiring both keys and passwords.

Check your package manager for any install suspicious apps (keyloggers, cleaners, etc).

Use Rootkit Scanners (chkrootkit, rkhunter).

Double SSH Security (Key + Password).

Disabled Guest Accounts.

Enabled Software Limiters (Fail2Ban, AppArmor).

Verify System Integrity via fsck.

Utilize ngrep/other networking apps to monitor traffic.

Utilize common honeypot software (endlessh).

Create new system-launch subroutines via crontab or shell scripts.

Ensure System Backups are Enabled (rsnapshot).

Check for suspicious kernel modules with "lsmod"

[juicyyyjuice3]

[nixcraft]

Old but sealed box pack of Red Hat Linux version 4.2 (not the RHEL, this is older than RHEL).

[janeepoetry]

[goldensleekboy]

Red hat

[rainbowburst]

🍄💙❤️Mario orders are lot of food.❤️💙🍄

[archiveosorg]

Plan-B

Plan-B – a Red Hat based live Linux distribution, which loads to RAM memory without installation to a hard drive. https://archiveos.org/planb-linux/

[sgnog]

𝗞𝗡𝗢𝗪𝗟𝗘𝗗𝗚𝗘 𝗘𝗫𝗖𝗛𝗔𝗡𝗚𝗘

Speakers and attendees share their knowledge and experiences both on and off-stage at #SGNOG10. We are encouraged to see the community participating actively as we all learn together.

Join us in #SGNOG11 at One Farrer Hotel!

Photo: Lim Fung

More 𝗦𝗚𝗡𝗢𝗚𝟭𝟬 photos on Facebook.

[shadowglitch90]

RedHat Linux 5.2 running on 86box, emulating an Intel Pentium @ 166 MHz with 64Mb of RAM (because 32 was not enough apparently), using Afterstep DE (Which emulates the neXTStep desktop environment on Linux).

If you want to try it yourself, you have everything you need in the archive: https://archive.org/search?query=RedHat+5.2

The gopher server can be accessed at 143.47.40.29:7070. It works fine on lynx but not on xgopher. There isn't much there, I use it mostly for testing.

[qcsdclabs]

Understanding the Boot Process in Linux

                    Six Stages of Linux Boot Process

Press the power button on your system, and after few moments you see the Linux login prompt.

Have you ever wondered what happens behind the scenes from the time you press the power button until the Linux login prompt appears?

The following are the 6 high level stages of a typical Linux boot process.

                             BIOS        Basic Input/Output System

                             MBR        Master Boot Record executes GRUB

                             GRUB      Grand Unified Boot Loader Executes Kernel

                             Kernel      Kernel executes /sbin/init

                             Init            init executes runlevel programs

                             Runlevel   Runlevel programs are executed from /etc/rc.d/rc*.d/

1. BIOS

BIOS stands for Basic Input/Output System

Performs some system integrity checks

Searches, loads, and executes the boot loader program.

It looks for boot loader in floppy, cd-rom, or hard drive. You can press a key (typically F12 of F2, but it depends on your system) during the BIOS startup to change the boot sequence.

Once the boot loader program is detected and loaded into the memory, BIOS gives the control to it.

So, in simple terms BIOS loads and executes the MBR boot loader.

2. MBR

MBR stands for Master Boot Record.

It is located in the 1st sector of the bootable disk. Typically /dev/hda, or /dev/sda

MBR is less than 512 bytes in size. This has three components 1) primary boot loader info in 1st 446 bytes 2) partition table info in next 64 bytes 3) mbr validation check in last 2 bytes.

It contains information about GRUB (or LILO in old systems).

So, in simple terms MBR loads and executes the GRUB boot loader.

3. GRUB

GRUB stands for Grand Unified Bootloader.

If you have multiple kernel images installed on your system, you can choose which one to be executed.

GRUB displays a splash screen, waits for few seconds, if you don’t enter anything, it loads the default kernel image as specified in the grub configuration file.

GRUB has the knowledge of the filesystem (the older Linux loader LILO didn’t understand filesystem).

Grub configuration file is /boot/grub/grub.conf (/etc/grub.conf is a link to this). The following is sample grub.conf of CentOS.

#boot=/dev/sda

default=0

timeout=5

splashimage=(hd0,0)/boot/grub/splash.xpm.gz

hiddenmenu

title CentOS (2.6.18-194.el5PAE)

          root (hd0,0)

          kernel /boot/vmlinuz-2.6.18-194.el5PAE ro root=LABEL=/

          initrd /boot/initrd-2.6.18-194.el5PAE.img

As you notice from the above info, it contains kernel and initrd image.

So, in simple terms GRUB just loads and executes Kernel and initrd images.

4. Kernel

Mounts the root file system as specified in the “root=” in grub.conf

Kernel executes the /sbin/init program

Since init was the 1st program to be executed by Linux Kernel, it has the process id (PID) of 1. Do a ‘ps -ef | grep init’ and check the pid.

initrd stands for Initial RAM Disk.

initrd is used by kernel as temporary root file system until kernel is booted and the real root file system is mounted. It also contains necessary drivers compiled inside, which helps it to access the hard drive partitions, and other hardware.

5. Init

Looks at the /etc/inittab file to decide the Linux run level.

Following are the available run levels

0 – halt

1 – Single user mode

2 – Multiuser, without NFS

3 – Full multiuser mode

4 – unused

5 – X11

6 – reboot

Init identifies the default initlevel from /etc/inittab and uses that to load all appropriate program.

Execute ‘grep initdefault /etc/inittab’ on your system to identify the default run level

If you want to get into trouble, you can set the default run level to 0 or 6. Since you know what 0 and 6 means, probably you might not do that.

Typically you would set the default run level to either 3 or 5.

6. Runlevel programs

When the Linux system is booting up, you might see various services getting started. For example, it might say “starting sendmail …. OK”. Those are the runlevel programs, executed from the run level directory as defined by your run level.

Depending on your default init level setting, the system will execute the programs from one of the following directories.

Run level 0 – /etc/rc.d/rc0.d/

Run level 1 – /etc/rc.d/rc1.d/

Run level 2 – /etc/rc.d/rc2.d/

Run level 3 – /etc/rc.d/rc3.d/

Run level 4 – /etc/rc.d/rc4.d/

Run level 5 – /etc/rc.d/rc5.d/

Run level 6 – /etc/rc.d/rc6.d/

Please note that there are also symbolic links available for these directory under /etc directly. So, /etc/rc0.d is linked to /etc/rc.d/rc0.d.

Under the /etc/rc.d/rc*.d/ directories, you would see programs that start with S and K.

Programs starts with S are used during startup. S for startup.

Programs starts with K are used during shutdown. K for kill.

There are numbers right next to S and K in the program names. Those are the sequence number in which the programs should be started or killed.

For example, S12syslog is to start the syslog deamon, which has the sequence number of 12. S80sendmail is to start the sendmail daemon, which has the sequence number of 80. So, syslog program will be started before sendmail.

There you have it. That is what happens during the Linux boot process.

for more details visit www.qcsdclabs.com

[qcs01]

Unleashing Efficiency: Containerization with Docker

Introduction: In the fast-paced world of modern IT, agility and efficiency reign supreme. Enter Docker - a revolutionary tool that has transformed the way applications are developed, deployed, and managed. Containerization with Docker has become a cornerstone of contemporary software development, offering unparalleled flexibility, scalability, and portability. In this blog, we'll explore the fundamentals of Docker containerization, its benefits, and practical insights into leveraging Docker for streamlining your development workflow.

Understanding Docker Containerization: At its core, Docker is an open-source platform that enables developers to package applications and their dependencies into lightweight, self-contained units known as containers. Unlike traditional virtualization, where each application runs on its own guest operating system, Docker containers share the host operating system's kernel, resulting in significant resource savings and improved performance.

Key Benefits of Docker Containerization:

Portability: Docker containers encapsulate the application code, runtime, libraries, and dependencies, making them portable across different environments, from development to production.

Isolation: Containers provide a high degree of isolation, ensuring that applications run independently of each other without interference, thus enhancing security and stability.

Scalability: Docker's architecture facilitates effortless scaling by allowing applications to be deployed and replicated across multiple containers, enabling seamless horizontal scaling as demand fluctuates.

Consistency: With Docker, developers can create standardized environments using Dockerfiles and Docker Compose, ensuring consistency between development, testing, and production environments.

Speed: Docker accelerates the development lifecycle by reducing the time spent on setting up development environments, debugging compatibility issues, and deploying applications.

Getting Started with Docker: To embark on your Docker journey, begin by installing Docker Desktop or Docker Engine on your development machine. Docker Desktop provides a user-friendly interface for managing containers, while Docker Engine offers a command-line interface for advanced users.

Once Docker is installed, you can start building and running containers using Docker's command-line interface (CLI). The basic workflow involves:

Writing a Dockerfile: A text file that contains instructions for building a Docker image, specifying the base image, dependencies, environment variables, and commands to run.

Building Docker Images: Use the docker build command to build a Docker image from the Dockerfile.

Running Containers: Utilize the docker run command to create and run containers based on the Docker images.

Managing Containers: Docker provides a range of commands for managing containers, including starting, stopping, restarting, and removing containers.

Best Practices for Docker Containerization: To maximize the benefits of Docker containerization, consider the following best practices:

Keep Containers Lightweight: Minimize the size of Docker images by removing unnecessary dependencies and optimizing Dockerfiles.

Use Multi-Stage Builds: Employ multi-stage builds to reduce the size of Docker images and improve build times.

Utilize Docker Compose: Docker Compose simplifies the management of multi-container applications by defining them in a single YAML file.

Implement Health Checks: Define health checks in Dockerfiles to ensure that containers are functioning correctly and automatically restart them if they fail.

Secure Containers: Follow security best practices, such as running containers with non-root users, limiting container privileges, and regularly updating base images to patch vulnerabilities.

Conclusion: Docker containerization has revolutionized the way applications are developed, deployed, and managed, offering unparalleled agility, efficiency, and scalability. By embracing Docker, developers can streamline their development workflow, accelerate the deployment process, and improve the consistency and reliability of their applications. Whether you're a seasoned developer or just getting started, Docker opens up a world of possibilities, empowering you to build and deploy applications with ease in today's fast-paced digital landscape.

For more details visit www.qcsdclabs.com

[nixcraft]

The "Look at me, I'm the captain now" meme features Debian declaring itself as the new enterprise distribution, taking a jab at Red Hat for restricting RHEL sources to only CentOS Stream. This move has prevented other distros like Oracle Linux, Rocky, and Alma Linux from building bug-to-bug RHEL clones.

[cz3rqv]

It's me:DD

I really miss my red hat that I lost on the bus last year XD

[linuxiarzepl]

Oracle Linux 9.3

Została wydana nowa wersja dystrybucji Oracle Linux 9.3 https://linuxiarze.pl/oracle-linux-9-3/

[rainbowburst]