Linux

SSL Linux

Configure local https on ubuntu
T0 set up a local HTTPS server on Ubuntu, use a tool like 

 mkcert for simplicity or openssl for more control, and then configure your web server (e.g., Apache) to use the generated certificates. The recommended method is to install and use mkcert , which generates a trusted, local Certificate Authority (CA) to create self-signed certificates for localhost or custom hostnames without browser warnings. Alternatively, you can generate a self-signed certificate using openssl , which requires more manual steps to create the key, certificate, and to trust it in your browser.   

 

 

 Method 1: Using mkcert (Recommended) 

 

 This video demonstrates how to set up HTTPS with mkcert and enable HTTPS for localhost:

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 Unconventional Coding 

 YouTube • 31 Dec 2022 

 

 

 

 

 

 

 

 

 

 Install mkcert : Install the tool to manage local certificate authorities and certificates. 

 

 sudo apt install mkcert 

 

 

 Install the local CA : Run mkcert to install a local CA that your system will trust. 

 

 mkcert -install 

 

 

 Create a certificate : Generate a certificate and key for your local site (e.g., localhost ) or domain . Point to note here in case of domain, ip address should be mapped to it  before this command. 

 

 mkcert localhost 127.0.0.1 

 sudo mkcert drupalwithdata.offline.com 

 

 

 

 Configure your server : Configure your specific application or web server to use the generated localhost.pem (certificate) and localhost-key.pem (key) files.   

 

 

 

 Method 2: Using openssl 

 

 

 

 

 

 Install openssl : Ensure openssl is installed. It is usually pre-installed on Ubuntu. 

 Generate a private key and a certificate signing request (CSR) : 

 

 openssl req -new -newkey rsa:2048 -nodes -keyout localhost.key -out localhost.csr 

 

 

 Generate the self-signed certificate : Use the CSR and private key to create the certificate. 

 

 openssl x509 -req -days 365 -in localhost.csr -signkey localhost.key -out localhost.crt 

 

 

 Configure your web server : 

 

 For Apache : 

 

 Enable the SSL module: sudo a2enmod ssl . 

 Configure your site's virtual host to point to your certificate ( localhost.crt ) and private key ( localhost.key ) files. 

 Restart Apache: sudo systemctl restart apache2 . 

 

 

 For other servers : Configure your server's settings to use the .crt and .key files. 

 

 

 Trust the certificate : 

 

 This is an optional but recommended step to avoid browser warnings. 

 Install certificate utilities: sudo apt-get install libnss3-tools . 

 Import and trust the certificate into the browser's database (using pk12util for Firefox or certutil for other applications).   

 

 

 

 

 

 

 

 Final steps for both methods 

 

 

 

 

 

 After generating the certificates and configuring your server, you may still see a browser warning because the certificate is "self-signed" and not issued by a public Certificate Authority. 

 You will need to accept the security risk to proceed to your local serve

install OpenSSL locally on Ubuntu
To install OpenSSL locally on Ubuntu, you can 

 compile and install it from source by first installing build tools, then downloading and extracting the OpenSSL source code, and finally running the config , make , and make install commands with the appropriate prefix and flags . For the simplest local installation, download the source, change to the directory, and use ./config --prefix= /openssl --openssldir= /openssl , followed by make and make install , then update your ~/.bash_profile with the correct PATH and LD_LIBRARY_PATH .   

 

 

 Method 1: Install from source to a local directory 

 

 This method installs a specific version of OpenSSL to a custom directory, like ~/openssl , so it doesn't interfere with the system-installed version. 

 

 

 

 

 

 bash 

 

 

 

 # Install build tools

sudo apt update

sudo apt install build-essential zlib1g-dev

# Create a working directory and download OpenSSL source

cd /usr/local/src/

wget https://www.openssl.org/source/openssl-1.1.1k.tar.gz

tar -xf openssl-1.1.1k.tar.gz

cd openssl-1.1.1k

# Configure and build (using --prefix to specify local install)

./config --prefix=~/openssl --openssldir=~/openssl

make

# Install to the local directory

make install

 

 

 Method 2: Update your environment variables 

 

 After installing from source, you must tell your shell where to find the new binaries and libraries. 

 

 

 Edit the bash profile : 

 

 

 

 bash 

 

 

 

 

 

 nano ~/.bash_profile

 

 

 Add the following lines at the end of the file (adjusting username if necessary): 

 

 

 

 bash 

 

 

 

 

 

 export PATH=$HOME/openssl/bin:$PATH

export LD_LIBRARY_PATH=$HOME/openssl/lib:$LD_LIBRARY_PATH

export LDFLAGS="-L $HOME/openssl/lib -Wl,-rpath,$HOME/openssl/lib"

 

 

 Save and close the file, then reload your profile: 

 

 

 

 bash 

 

 

 

 

 

 source ~/.bash_profile

 

 

 Method 3: Verify the installation 

 

 

 Check the version to ensure you are using the new installation: 

 

 

 

 bash 

 

 

 

 

 

 openssl version

 

 This should output the version you installed (e.g., OpenSSL 1.1.1k 25 Mar 2025 ). 

 

 Verify the path to confirm it's the local one: bash 

 which openssl

 

 This should point to ~/openssl/bin/openssl

MULTIVERSIONS ON UBUNTU BOX
sudo apt install apache2 libapache2-mod-fastcgi sudo apt-get install mysql-server sudo mysql_secure_installation sudo apt install software-properties-common sudo add-apt-repository ppa:ondrej/php sudo apt update Use this command to install different versions of php just changing the string 7.1 to the required version sudo apt install php7.1 php7.1-fpm libapache2-mod-php7.1 NOW ALL SET LAMP is installed and working Now while u will require to change the php version This command will change the php version on system sudo update-alternatives --config php Disable all version apached modules of php installed, just replace the 7.4 in below command sudo a2dismod php7.4 Enable the version u need to use with apache, just replace the 8.0 in below command sudo a2enmod php8.0 Restart the apache sudo service apache2 restart

kernel tuning/troubleshooting
Kernel tuning/troubleshooting involves  adjusting operating system (OS) parameters for performance/stability (tuning) or fixing crashes/issues (troubleshooting) , often using tools like  sysctl ,  ulimit ,  make menuconfig  (Linux), or boot options/diagnostics (Mac/Linux), focusing on memory, filesystems, I/O, and software conflicts to match workloads, requiring careful baselining and testing to avoid instability.   

 

 Kernel Tuning (Linux Focus) 

 

 Goal:  Optimize performance (speed, resource use) for specific workloads (e.g., databases, web servers). 

 Key Areas: 

 

 fs (Filesystem) :  Too many open files ( ulimit -n ), I/O schedulers. 

 vm (Virtual Memory) :  Swappiness ( vm.swappiness ), dirty ratios, memory management. 

 Networking:  TCP/IP settings, buffer sizes. 

 

 

 Tools:   sysctl ,  /etc/sysctl.conf ,  make menuconfig  (for compiling custom kernels),  tuned  (profiles).   

 

 

 Kernel Troubleshooting 

 

 Common Issues:   Kernel Panic  (system crash), slow performance, device failures. 

 Steps: 

 

 Identify Cause:  Check logs ( dmesg ,  /var/log/ ), review crash reports (Mac), use  journalctl  (Linux). 

 Isolate:  Boot in Safe Mode (Mac), use a known good/rescue kernel (Linux), disconnect hardware, remove recent software/drivers. 

 Check Hardware:  Run diagnostics (Apple Diagnostics), check RAM. 

 Software Conflicts:  Look for recently installed or updated apps/drivers causing issues.   

 

 

 

 

 Best Practices 

 

 Baseline:  Measure performance  before  changes. 

 Change Incrementally:  Adjust one or a few parameters at a time. 

 Document:  Keep records of all changes and their effects. 

 Test Thoroughly:  Verify stability and performance after each change.   

 

 

 Jupyter Notebook Kernel Issues (Related but Different) 

 

 If "kernel" means the Jupyter backend: Restart, update packages (Jupyter, Anaconda), check code for errors, monitor memory.  

filesystems tuning
File system tuning  optimizes storage performance by adjusting settings like block size, caching, journaling, and I/O methods (sync/async) to match workloads, improving speed, throughput, and resource use for specific tasks, crucial for servers running databases or virtual machines . Key techniques involve optimizing disk hardware, tuning buffer sizes (like  numfsbufs ), leveraging read-ahead/write-behind, using Direct I/O, and applying system profiles via tools like  tuned-adm  for Linux, all aiming to reduce bottlenecks and enhance efficiency.   

 

 Core Concepts & Parameters 

 

 I/O Operations:  Tuning reads/writes, utilizing asynchronous I/O (AIO) to prevent application blocking, and optimizing read-ahead for sequential access. 

 Block Size:  Affects data efficiency; larger blocks can speed up large file transfers, while smaller ones suit many small files. 

 Caching & Buffers:  Increasing file system buffers ( numfsbufs ) can help with heavy I/O; faster RAM disks for  /tmp  also boost performance. 

 Journaling:  Balancing the performance impact of logging changes for data integrity (e.g., using  commit  options). 

 File System Type:  Different file systems (Ext4, XFS, NTFS) have unique strengths; tuning depends on the chosen one.   

 

 

 Key Tuning Techniques 

 

 Hardware Optimization:  Ensure disk controllers use fast DMA modes. 

 Read-Ahead/Write-Behind:  Boost sequential read/write performance by pre-fetching/delaying writes. 

 Direct I/O (DIO):  Bypasses the kernel's file cache to reduce CPU load and data copies for specific applications. 

 Tuning Profiles  (Linux):  Use  tuned-adm  to apply profiles (e.g.,  throughput-performance ,  virtual-guest ) for workload-specific settings. 

 Application-Level:  Design apps to gather large data chunks and write them sequentially.   

 

 

 How to Approach Tuning 

 

 Monitor:  Identify bottlenecks using tools like  vmstat -v  or  iostat . 

 Select:  Choose parameters relevant to your workload (e.g., database needs high I/O, web server needs low latency). 

 Apply:  Use commands like  mkfs  (for creation), mount options, or  tuned-adm  to change settings. 

 Test:  Verify improvements with performance benchmarks.