/proc - Virtual Filesystem (in RAM), System & Process Info

The /proc directory is a special virtual filesystem in Linux that provides a window into the kernel's internal data structures. It doesn't contain real files on disk - instead, it's dynamically generated by the kernel to expose system and process information.

Key characteristics

Virtual filesystem: The files in /proc exist only in memory. When you read them, the kernel generates the content on-the-fly. This means they typically show a size of 0 bytes, but still contain data when read.

Process information: Each running process has a subdirectory named by its PID (Process ID). For example, /proc/1234/ contains information about process 1234, including:

• cmdline - the command that started the process
• status - detailed process state information
• maps - memory mappings
• fd/ - symbolic links to open file descriptors
• environ - environment variables

System information: The root /proc directory contains files about the overall system:

• /proc/cpuinfo - CPU details
• /proc/meminfo - memory usage statistics
• /proc/version - kernel version
• /proc/uptime - how long the system has been running
• /proc/loadavg - system load averages
• /proc/mounts - currently mounted filesystems
• /proc/net/ - networking information

Kernel tuning: The /proc/sys/ subdirectory allows you to view and modify kernel parameters at runtime. For example, /proc/sys/vm/swappiness controls how aggressively the kernel swaps memory to disk.

Many system utilities like ps, top, and free get their information by reading from /proc. It's an essential interface between user space and the kernel.

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Backlinks

• Root_dir (/)