Viewing System Information

Most of what this chapter covers applies not only to the board but also to the Ubuntu system on the development host. Try running the relevant commands on both platforms to inspect the information and compare the differences.

1 A first look at /proc

Linux does not provide a Task Manager like Windows, but it records system runtime information in files under the /proc directory. Users can access the files in this directory to obtain the corresponding system information.

Run the following command in the board's terminal to view the contents of /proc:

# Run the following command in the board terminal
ls /proc

The information contained in each file under this directory is shown in the table below.

Table: /proc file structure

File name	Purpose
pid*	Usually a number representing a process's PID. Every running process in the system has a corresponding directory (e.g. /proc/1234) that records all the information about that process. The operating system treats each application as a process.
self	A symbolic link pointing to the current process's directory. Accessing /proc/self/ directly yields information about the current process without manually looking up its PID.
thread-self	A symbolic link pointing to the current thread. Accessing this file is equivalent to accessing current-PID/task/current-TID. A process may contain multiple threads, and threads together sustain the process.
version	Records the currently running kernel version; can be viewed with uname –r.
cpuinfo	Records the CPU's vendor, model, core count, frequency, and other configuration.
modules	Records the kernel modules currently loaded on the system.
meminfo	Records memory usage (e.g. free/used memory). The free command reads this file for its data.
filesystems	Records the filesystem types supported by the kernel. When mounting a device without specifying a filesystem, mount tries the types listed here (excluding those marked nodev).

By browsing the contents of the /proc folder, you can obtain the system information you want.

2 View CPU information

The /proc/cpuinfo file stores CPU information. View it with:

cat /proc/cpuinfo

3 View the kernel version

The /proc/version file holds kernel version information, which we can retrieve with the following command.

cat /proc/version

From the figure above we can see the currently used kernel version is 6.1.99.

You can also obtain it with:

uname -a

4 View memory information

The kernel records memory usage in the /proc/meminfo file. We can read the contents of this file to understand memory usage.

The following is the 2GB memory case:

cat /proc/meminfo

In practice, we rarely read this file directly; instead we use the following command to obtain memory-related information.

View the system's memory size with the free command:

free

5 View storage capacity

The /proc/partitions file contains storage partition information. Viewing the partitions tells you the capacity of the onboard FLASH storage.

View it with:

cat /proc/partitions

The figure below is the command output for a board with 32GB eMMC.

The entries starting with mmcblk are all data blocks belonging to the eMMC storage.

6 View running processes

Under the /proc folder there are many directories named with numbers. These directories record the state of currently running processes, and their names are the processes' PID numbers — every process has a PID for identification. The contents of these process directories are largely similar. Use the ls command to view the contents of the folder for PID 1, as shown below. Among them, fd records the file descriptors used by the current process, mountinfo records mount information, and mem records the process's memory usage.

ls /proc/1

Besides the method above, the top command is also commonly used. It works like the Windows Task Manager; its output is as shown above, and it updates each process's usage in real time. Press "q" or "Ctrl + C" to exit.

top

7 View supported filesystems

/proc/filesystems shows the filesystem types supported by the kernel, as shown above. Some filesystems in the figure are prefixed with the "nodev" flag, meaning they do not need a block device to be mounted — for example the network filesystems nfs/nfs4 and the pseudo-filesystem sysfs.

cat /proc/filesystems

8 View the current CPU frequency

Besides the /proc directory, you can also find some system-related information under /sys. For example, the file /sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_cur_freq contains CPU0's current frequency. If the file exists on your system, you can print its contents to view the frequency:

cat /sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_cur_freq

The output above indicates that CPU0's current frequency is 408MHz.

The CPUs on the LubanCat-RK3562/RK3566/RK3568 series boards support frequency scaling: they automatically drop frequency to save power under light load, and automatically raise frequency for higher performance under heavy load.

ls -g /sys/devices/system/cpu/cpu0/cpufreq/