Linux Commands
touch test.txt: Create a txt file named test
cd: change directory
ls: List contents of current dir
ls -lart: View files along with their permissions(rwx: read,write,execute stated in order owner, group, public)
chmod: Manage file system access permissions
To create a file by specifying permissions:
- Use chmod calc to find octal value for permissions: https://chmod-calculator.com/
# The first digit represents the owner of the file/directory
# The second digit represents the group that the file/directory belongs to
# The third digit represents all other users
# 0 (no permission)
# 1 (execute only)
# 2 (write only)
# 3 (write and execute)
# 4 (read only)
# 5 (read and execute)
# 6 (read and write)
# 7 (read, write, and execute)
- chmod <octal value> file: Sets permissions with given octal value to the specified filename
Note: For all permissions to owner, group and user octal value is 777
chown: change owner
pwd: present working dir
mkdir: create dir
rmdir -r/-rf: remove dir
cp file1 file2: copy file1 to new or existing file2
vim: :q=exit, :wq=save exit, :q! = undo changes
htop: interactive process view for system monitoring
(sudo) apt update: Update all installed packages
(sudo) apt install <package_name>: Install a package
tar: create/extract .tar archive files(files having one or more files and metadata), Example: tar -xJvf filename.tar.xz
x: ExtractJ: Filter the archive throughxzv: Verbose mode, showing the progressf: Specifies the file name
gzip/gunzip file.txt: gzip to Compress files & gunzip to decompress
ssh username@server_address : Connect to remote server securely
mv example.txt backup/ : Move/rename files
netstat : Display network connection info
route [options] [add/delete/show] : view or configure network routing table
systemctl :control system services and settings
# Start the nginx service
systemctl start nginx
# Check the status of the nginx service
systemctl status nginx
# Stop the nginx service
systemctl stop nginx
useradd : Add new user, Example: useradd testuser
locate file.txt : Locate a file
history : Command history
uname/uname -a : Display system info
uptime : System load and # of current users
df: Display disk space usage
du: Disk usage by file/dir
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Virtualization
In cloud computing, Virtualization simply means creating a virtual version of something rather than a physical form. Examples: Application, Storage, Network, Desktop, Server.
Hypervisors for Server Virtualization: In simple terms, it is a software installed on a server to segregate different VMs.
Two types of HyperVs:
Type 1/Bare Metal:
- Widely used, Self managing, Installed directly on physical hardware, Examples: VMware ESXi, Microsoft Hyper-V, Xen
Type 2/ Hosted:
-
Installed on OS, Create VMs within the OS,
Examples: VMware Workstation, Oracle VirtualBox.
Advantages of HyperVs:
- Cost savings
- Agility+Speed
- Reduced downtimes: Its easy to shift VMs from one hyperV to other
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Linux File System
🗃️ /bin: Binaries — This directory holds the essential user command binaries that all users can access.
🔧 /sbin: System Binaries — Contains the essential binaries used by the system administrator for system maintenance and troubleshooting.
⚙️ /etc: System Configuration — Houses the system configuration files, acting as the control panel on Linux.
⚙️ /etc: System Configuration — Houses the system configuration files, acting as the control panel on Linux. Has info on all grps like docker, ssh etc ;)
💽 /dev: Device Files — Home to all device files, such as hard disks, USB, CD-ROM, etc. 📊 /proc: Process Information — A virtual directory detailing system and process information. 📁 /var: Variable Files — This is the variable data directory storing changing data like logs, mails, print spools, etc.
🗑️ /tmp: Temporary Files — This directory stores temporary files created by the system and users.
👥 /usr: User Binaries — Contains multi-user utilities, applications, and libraries. 🏠 /home: User Home Directories — Contains the home directories for users and other accounts. 📚 /lib: System Libraries — Houses library files that are needed by the system and the users. 🎁 /opt: Optional Software — Stores optional or additional software from vendors. 📝 /mnt: Mount Directory — Used for mounting other temporary file systems. 💿 /media: Removable Media — Acts as a temporary mount directory for removable devices. 🔨 /srv: Service Data — This directory contains server-specific services-related data. 🚀 /boot: Boot Files — Contains boot loader-related files. Keep safe distance from this folder ☠️
👑 /root: Root Home — This is the home directory for the root user.
🔌 /run: Application Information — A tmpfs file system that contains application information.
🧑🔬 /usr/local: User Local — Contains user’s programs that are installed from the source.
📦 /lib64: 64-bit Libraries — This is where the 64-bit library files are stored.
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