# System Information

## hostnamectl

The `hostnamectl` utility is part of systemd, and it is used to query and change the system hostname. It also displays the Linux distribution and kernel version:

 If `hostnamectl`  is executed by itself, without any additional commands / options, it will output the same information as the command `hostnamectl status`

#### Sample output:

```
  Static hostname:  example
         Icon name: computer-laptop
           Chassis: laptop
        Machine ID: af8ce1d394b844fea8c19ea5c6a9bd09
           Boot ID: 15bc3ae7bde842f29c8d925044f232b9
  Operating System: Ubuntu 18.04.2 LTS
            Kernel: Linux 4.15.0-54-generic
      Architecture: x86-64
```

## uname

The `uname` command displays several system information including, the Linux kernel, processor architecture, name version, and release.

#### Syntax

`uname [OPTIONS]...`

The options are as follows:

* `-s`, (`--kernel-name`) - Prints the kernel name.
* `-n`, (`--nodename`) - Prints the system’s node name (hostname).
* `-r`, (`--kernel-release`) - Prints the kernel release.
* `-v`, (`--kernel-version`) - Prints the kernel version.
* `-m`, (`--machine`) - Prints the name of the machine’s hardware name.
* `-p`, (`--processor`) - Prints the architecture of the processor.
* `-i`, (`--hardware-platform`) - Prints the hardware platform.
* `-o`, (`--operating-system`) - Print the name of the operating system.
* `-a`, (`--all`) - Prints all information, except omit `-p` and `-i` if unknown. 

#### Sample output:

{% code title="uname -srm" %}

```
Linux 4.19.0-9-amd64 x86_64
```

{% endcode %}

## uptime

`uptime` gives a one line display of the following information. The current time, how long the system has been running, how many users are currently logged on, and the system load averages for the past 1, 5, and 15 minutes.

#### Sample output

{% code title="uptime" %}

```
 03:35:55 up  2:46,  1 user,  load average: 0.79, 0.62, 0.74
```

{% endcode %}

## /proc/ folder

The `/proc` directory contains virtual files with information about the system memory , CPU cores , mounted filesystems , processes, and more. 

The numbered directories in `/proc` correspond to process ids running on the system. The `status` file in these folders contains detailed information about the process

Use commands `cat` or `less` to display contents of these files. 

| File in /proc/    | Contents                                                            |
| ----------------- | ------------------------------------------------------------------- |
| /proc/**cmdline** | shows the parameters passed to the kernel at the time it is started |
| /proc/**cpuinfo** | processor information, per core                                     |
| /proc/**meminfo** | memory information                                                  |
| /proc/**version** | kernel information                                                  |

#### Sample output:

{% code title="cat /proc/version" %}

```
Linux version 4.15.0-54-generic (buildd@lgw01-amd64-014) (gcc version 7.4.0 (Ubuntu 7.4.0-1ubuntu1~18.04.1)) #58-Ubuntu SMP Mon Jun 24 10:55:24 UTC 2019
```

{% endcode %}