Offline Troubleshooting understanding mount -t proc /proc /rescue/proc

What does it mean of following commands which we use to troubleshoot in offline method

mount -t proc /proc /rescue/proc

mount -t sysfs /sys /rescue/sys

mount -o bind /dev /rescue/dev

mount -o bind /dev/pts /rescue/dev/pts

mount -o bind /run /rescue/run

These commands are used in a recovery or rescue environment (often from a live CD/USB or a recovery console) to mount essential filesystems from the original (potentially damaged) system into a temporary location (/rescue in this case). This allows you to access and potentially repair the broken system. Let's break down each command:

1. mount -t proc /proc /rescue/proc:

   • mount: The command for mounting filesystems.
   • -t proc: Specifies the filesystem type as proc. The /proc filesystem is a virtual filesystem that provides information about the running processes and the kernel.
   • /proc: The source of the filesystem (the actual proc filesystem).
   • /rescue/proc: The mount point (where the proc filesystem will be accessible in the rescue environment).

   This command mounts the virtual /proc filesystem from the original system's root directory (which you've likely mounted at /rescue already) to /rescue/proc. This lets you use tools like ps and top within the rescue environment to inspect processes running on the original system.

2. mount -t sysfs /sys /rescue/sys:

   • -t sysfs: Specifies the filesystem type as sysfs. The /sys filesystem provides an interface to the kernel's internal data structures.
   • /sys: The source of the filesystem.
   • /rescue/sys: The mount point.

   Similar to the proc mount, this mounts the /sys filesystem, giving you access to system information and allowing you to manipulate system devices and settings.

3. mount -o bind /dev /rescue/dev:

   • -o bind: This option performs a "bind mount." Instead of creating a new mount point, it makes an existing mount point (in this case, /dev in the original system) accessible at another location (/rescue/dev).
   • /dev: The source (the device files directory).
   • /rescue/dev: The mount point.

   This is crucial because /dev contains device files that are essential for interacting with hardware. Without this mount, commands that need to access hardware (like mounting other partitions or accessing the console) won't work correctly in the rescue environment.

4. mount -o bind /dev/pts /rescue/dev/pts:

   • /dev/pts: This directory contains pseudo-terminal devices, which are used for terminal sessions.
   • /rescue/dev/pts: The mount point.

   This mounts the pseudo-terminal devices, allowing you to have terminal sessions within the rescue environment. This is necessary for interactive shells and using command-line tools.

5. mount -o bind /run /rescue/run:

   • /run: This directory is used for temporary files that are created and deleted during system runtime. It often contains things like PID files and sockets.
   • /rescue/run: The mount point.

   Mounting /run is important for some applications and system services that rely on it. It's often necessary for a more complete rescue environment.

In summary:

These commands are essential steps in a Linux recovery process. They make the original system's crucial filesystems accessible within the rescue environment, enabling you to diagnose and fix problems, recover data, or perform other maintenance tasks. By mounting /proc, /sys, /dev, /dev/pts, and /run, you create a more functional environment in which to work on the potentially damaged system.