The kernel is the core foundation of the OS that directly interfaces with system hardware and controls process and memory operations.
Kernal --> its between the computer's hardware and its processes.
SIGTERM (signal 15) is the default termination signal sent by commands like kill, allowing the process to perform clean-up routines.
graceful and clean termination , allowing the application to save its active transactions before closing --> SIGTERM (signal 15).
/etc/shadow contains the secure encrypted password hashes and security aging constraints. --> sensitive system file securely stores encrypted user password hashes and account expiration details , only root user can access.
30 2 * * 1-5 /opt/bank/scripts/eod_report.sh. Exactly when does this script run? --> 30 specifies the minute , 2 specifies the hour (2:30 AM), and 1-5 specifies weekdays (Monday through Friday).
top utility displays a live, refreshing summary of system resource usage and active tasks sorted by resource consumption. --> dynamic, continuous real-time view of active system tasks, CPU utilization metrics, and memory consumption profiles on a Linux server.
sar is used for collecting, reporting, and saving historical system activity data over time.
vmstat reports virtual memory, paging, and block IO statistics, but does not offer an interactive real-time process manager interface.
netstat inspects network connections, routing tables, and interface statistics.
inode --> File names are mapped to inode numbers inside directory files; the inode itself holds the metadata and block pointers, omitting the filename string. It stores file attributes, permissions, and disk pointers, but does NOT store the actual file name.
- /proc/meminfo is a virtual kernel file that provides live metrics regarding total, free, cached, and swap memory usage. --> virtual file system path exposes detailed real-time kernel memory statistics and swap utilization data.
Notes
- what is hardened enterprise Linux environment ?
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