LinuxFileSystem for personal use

Linux File System

🔧 System Configuration Files

File Path	Description
/etc/passwd	User account information (usernames, UID, shell).
/etc/shadow	Encrypted user passwords and password aging.
/etc/group	Group definitions.
/etc/sudoers	Sudo access configuration (visudo is recommended).
/etc/hostname	Defines the system's hostname.
/etc/hosts	Static hostnames to IP mappings.
/etc/fstab	Filesystem mount table (auto mounts on boot).
/etc/*release	OS information.
~/.bashrc	Customize PATH, environment variables, aliases, etc (source ~/.bashrc to restart)

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🌐 Networking Files

File Path	Description
/etc/network/interfaces	(Debian/Ubuntu < 18.04) Network interfaces config.
/etc/netplan/*.yaml	(Ubuntu 18.04+) Netplan YAML network config.
/etc/resolv.conf	DNS resolver configuration.
/etc/hosts.allow / /etc/hosts.deny	TCP wrapper access control.
/etc/ssh/sshd_config	SSH daemon configuration (port, auth method, etc).

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🔐 Security & Access Control

File Path	Description
/etc/pam.d/	Directory for PAM (Pluggable Authentication Modules).
/etc/securetty	TTYs from which root can login.
/etc/ssh/sshd_config	Repeated: critical for SSH hardening.
/etc/login.defs	Default values for user account settings (e.g., password expiration).

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🗃️ Log Files (Monitoring & Auditing)

File Path	Description
/var/log/syslog	General system activity log (Debian/Ubuntu).
/var/log/messages	General system activity log (RHEL/CentOS).
/var/log/auth.log	Authentication attempts and sudo access logs.
/var/log/dmesg	Kernel ring buffer messages.
/var/log/cron	Cron job execution log.
/var/log/nginx/access.log / error.log	NGINX logs.
/var/log/httpd/	Apache web server logs.

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📦 Package Management Files

File Path	Description
/etc/apt/sources.list	APT repositories list (Debian/Ubuntu).
/etc/yum.repos.d/*.repo	YUM/DNF repository configs (RHEL/CentOS/Fedora).

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