Which directory in the Linux root directory contains a file that contains information about the CPU?

The best place to view comprehensive information about your kernel is the proc file system. It contains configuration parameters and other details about different processes, all structurally arranged inside the /proc directory. To view most of these files, you must have root privileges.

Most files in the /proc display information about the hardware and currently running processes, and you can change the permission of the files and modify them whenever necessary.

Understanding the /proc Directory

All the files in this directory are stored as virtual files and listed as zero bytes yet contain extensive information. The files get updated constantly, and their time stamps show the current time and date.

The files in the /proc directory get mounted at boot time and can be viewed using commands, such as less and cat.

The common files and their description are listed below:

1. /proc/fb:
it contains frame buffer devices
2. /proc/devices: it contains drivers configured currently for the kernel
3. /proc/cmdline: it contains the kernel command line details
4. /proc/consoles: all details about current consoles, such as tty
5. /proc/cpuinfo: all CPU information gets stored in the file

Viewing the /proc Files

The different files in the /proc directory represent various details. To view all the files contained, you can use the ls command:

In the previous output, you will note there are numbers and files. The numbers represent the PIDs for processes. As for the files, most have the name representing their purpose. For instance, cpuinfo contains the CPU information.

To view the contents of a specific file, list the contents using cat or less commands.

In the following example, we are viewing the memory file using cat.

From the following output, you will note the file contains different information about the system’s memory, including free space.

Also, to get the CPU information, open the cpuinfo file using cat.

Even though most of the contents of the file are viewable using root privileges, some are unreadable and require other commands, such as top, free, or lspci.

For instance, the top command lists all running processes we saw in the /proc directory.

Similarly, to view the PCI devices, you must run the lspci command as its file is not human-readable.

Editing the Files

Most of the /proc files are read-only. The few that are writable, especially those in the /proc/sys, can be changed to adjust different kernel settings.

The syntax to change the values of the writeable files is:

$ echo [value] > /proc/file

For instance, the hostname gets stored in the /proc/sys/kernel, and you can edit and use a new hostname using the following command. Here, replace the examplehost1 with your preferred hostname:

$ echo examplehost1 > /proc/sys/kernel/hostname

Running the commands with root privileges edits the kernel details as in the previous example. Besides, you can check the values of given variables using the cat command. For instance, you can run the following command to check if ipv4 packet forwarding is enabled.

$ cat /proc/sys/net/ipv4/ip_forward

The output here is binary with zero representing false, meaning port forwarding is not enabled.

Other Directories in the /proc

For different processes, their directories are numbered in blue, and each name represents the process ID and contains details of the specific process. Inside each process directory, you will get different files, such as maps, fd, exe, and cmdline.

Still, you will note other unnumbered directories, which contain other files. One such directory is the /proc/sys, which contains information about the system and kernel features.

Conclusion

This guide covered the /proc file system in Linux that contains different virtual files. We’ve covered how to list the available files and display the contents of a specific file in the directory.

Furthermore, we have seen how you can change the values for the writable files, provided you have root privileges. Hopefully, you now understand working with the /proc file system in Linux.

In Linux everything is a File. When I say this I mean yes! Even a directory aka folder is also considered as a file at first place.

In this article I will demonstrate how Linux Operating System organizes files and directories.

Linux Directory Structure

A standard Linux distribution follows the directory structure known as Filesystem Hierarchy Standard (FHS) maintained by the Linux Foundation.

I love to deal with Linux or any Unix like servers using CLI. Here as well I will try to make you understand you the directory structure from my own system's terminal which is an Ubuntu 18.04 LTS server.

Here I have used tree command to list down the content of a directory in a tree-like format recursively.

You can install tree using following command and then list only the 1st Level of the directory tree starting at / -

This directory (denoted by a slash \) is called as “root.” The starting point for the file system hierarchy. Please note that this has nothing to do with the root superuser account. Everything in Linux resided under root directory even partitions. Only the root user has the right to perform write operations under this directory.

The /bin directory contains executable files. Many of them are required during single-user-mode (maintenance mode) or need to be used when performing file system repairing etc. For e.g. ls, cp, cat, echo, df etc.

All the files which are required during system boot process (static bootloader, kernel executable and configuration files) are placed here.

It contains device files for all the hardware devices part of your system e.g. cdrom, cpu, terminal devices, usb etc. Linux system treats devices also like files and you can read and write devices like they were files. These are not device drivers.

The /etc directory contains the core configuration files of the system, mostly plain text files required by all programs. Mostly System Administrators and DevOps folks will be dealing with these files only. These files includes username, password, network config, application specific config, system startup/shutdown files etc.

This directory contains home directories for all users to store their personal files. When ever a new user is created, it will be assigned a directory with it's name under home directory.

On my system I have two users named vagrant and lco_user. You can see their personal files and directories present under their respective home directories.

root user's home directory is /root.

• /lib and lib64 directories -->

These directories contains shared library files that are required to boot the system. They are similar to DLL's on Windows.

/lib is for 32-bit compatibility libraries and /lib64 is for 64-bit libraries.

• /lost+found directory --> This directory primarily used to store files that are found to be corrupted after a system crash and provide a way to try recover data from them. Each partition has its own /lost+found directory. It is used by file system check tools (fsck).

Any external storage such as media/cdrom when plugged in will be automatically mounted under /media directory.

Directory where sysadmins can mount regular filesystems such as NFS etc. But not used very often nowadays.

This directory contain any third party applications available from individual vendors. It is recommended to install third part applications under /opt or /opt sub directory.

This directory contains information about system processes with a particular process id or pid. Also known as a virtual/pseudo filesystem which has text information about system resources such as cpu/memory. Under this directory the files and directories gets generated as and when system starts or something changes on the system.

Home directory for root user.

This directory acts as a temporary filesystem (tmpfs) which stores system processes volatile runtime data.

This directory contains system executables used for system administration for maintenance. It is similar to /bin, but it contains only the superuser required applications. For e.g. fdisk, fsck, reboot, shutdown, iptables.

This directory contains the mount-points for your snaps and several symlinks which are needed by snapd.

This directory contains data for services provided by your server. For example you are hosting a web server on your Linux box, your web files for your site would go into /srv/http (or /srv/www). In case of FTP server it would go into /srv/ftp.

This is another virtual directory similar to /proc and /dev containing information from devices connected to your computer. It allows modification of the devices connected to the system.

It contains temporary files. Many applications keep their temporary files here which contain data that an application might not need right now, but may need later on. These files will be kept until next boot or application restart.

This directory contains applications, libraries, docs, icons, images and other files which needs to be shared by applications and services. It is basically shareable, read-only data.

There are further sub directories within /usr directory. /usr/bin :- Non-essential command binaries (not needed in single-user mode); for all users.

/usr/include :- Standard include files.

/usr/lib :- Libraries for the binaries in /usr/bin and /usr/sbin.

/usr/lib<qual> :- Alternative-format libraries (e.g., /usr/lib32 for 32-bit libraries on a 64-bit machine (optional)).

/usr/local :- Contains local data specific to this host. Typically has further subdirectories (e.g., bin, lib, share)

/usr/sbin :- Non-essential system binaries (e.g., daemons for various network services).

/usr/share :- Architecture-independent (shared) data.

/usr/src :- Source code (e.g., the kernel source code with its header files).

This directory contains variable files such as log files, lock, mail, cache and temp files that changes constantly when the system is running and are expected to grow further.

There are further sub directories within /var directory.

/var/cache :- Application cache data.

/var/lib :- State information. Persistent data modified by programs as they run (e.g., databases, packaging system metadata, etc.).

/var/lock :- Lock files. Files keeping track of resources currently in use.

/var/log :- Log files. Various logs.

/var/mail :- Mailbox files. In some distributions, these files may be located in the deprecated /var/spool/mail.

/var/opt :- Variable data from add-on packages that are stored in /opt.

/var/run :- Run-time variable data. This directory contains system information data describing the system since it was booted. In FHS 3.0, /var/run is replaced by /run.

/var/spool :- Spool for tasks waiting to be processed (e.g., print queues and outgoing mail queue).

/var/tmp :- Temporary files to be preserved between reboots.

That's all for this tutorial. By now you all will be very clear about how a Linux Operating System organizes files and which place meant for storing what kind of files. It is very crucial to know all this.

Hope you like the article. Stay Tuned for more.

Thank you. Happy learning!