Viewing Information
Most of the content introduced in this chapter applies not only to the board, but also to the Ubuntu system on the development host. Please try executing the relevant commands on both platforms to view information and compare the differences.
1 First Look at the /proc Directory
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 corresponding system information.
Execute the following command in the board's terminal to view the contents of the /proc directory:
#在板卡的终端执行以下命令
ls /proc
The information contained in each file in this directory is shown in the table below.
Table /proc file structure
| File Name | Purpose |
|---|---|
| pid* | Usually a number indicating the process's PID number. Each running process in the system has a corresponding directory (e.g., /proc/1234) that records all information about that process. The operating system treats each application as a process. |
| self | Symbolic link pointing to the current process's directory. Accessing /proc/self/ directly obtains current process information without manually querying the PID. |
| thread-self | Symbolic link pointing to the current thread. Accessing this file is equivalent to accessing the content of 当前进程PID/task/当前线程TID. A process can contain multiple threads, and the threads together support the process's operation. |
| version | Records the currently running kernel version, which can be viewed with the uname –r command. |
| cpuinfo | Records the CPU vendor, model, number of cores, frequency, and other configuration information in the system. |
| modules | Records information about kernel modules currently loaded in the system. |
| meminfo | Records system memory usage (e.g., free/used memory). The free command reads this file to obtain data. |
| filesystems | Records the file system types supported by the kernel. When mounting a device without specifying a file system, mount will try the types listed in this file (excluding file systems marked nodev). |
By accessing the contents of the /proc folder, we can obtain the system information we want.
2 Viewing CPU Information
The /proc/cpuinfo file stores CPU information, which can be viewed with the following command:
cat /proc/cpuinfo
3 Viewing the Kernel Version
The /proc/version file stores the kernel version information, which we can obtain with the following command.
cat /proc/version
From the figure above, we can see that the currently used kernel version is 6.1.99.
You can also obtain it with the following command:
uname -a
4 Viewing Memory Information
The kernel records memory usage in the /proc/meminfo file. We can read the contents of this file to understand our memory usage:
The following shows the case of 2GB of memory.
cat /proc/meminfo
In practical applications, we generally do not read the contents of this file directly, but instead use the following command to obtain memory-related information.
View the system memory size via the free command:
free
5 Viewing Storage Capacity
The /proc/partitions file contains partition information for storage devices. Viewing the partition information lets you understand the capacity of the onboard FLASH storage.
You can view it with the following command:
cat /proc/partitionsThe figure below shows the command output for a 32GB eMMC board.
Those starting with mmcblk are all data blocks belonging to the eMMC storage.
6 Viewing Task Processes
Under the /proc folder, there are many folders named with numbers. These folders are used to record the status of currently running processes, and the file names are their pid numbers. Each process corresponds to a pid number for identification. The contents contained in these process folders are basically similar. Use the ls command to view the contents of the folder with pid 1, as shown in the figure below. Among them, fd records the file descriptors used by the current process, mountinfo records mount information, and mem records the memory usage of the process, etc.
ls /proc/1Besides the method used above, the top command is also commonly used. This command functions similarly to Windows' Task Manager. The execution effect is shown in the figure above. This command updates the usage of each process in real time. Press the "q" key or "Ctrl + C" to exit the command.
top7 Viewing Supported File Systems
/proc/filesystems can be used to view the file system types supported by the kernel, as shown in the figure above. Some file systems in the figure are prefixed with the "nodev" flag, indicating that these file systems do not need to mount a block device, such as the network file systems nfs/nfs4, the pseudo file system sysfs, etc.
cat /proc/filesystems8 Viewing the Current CPU Frequency
In addition to the /proc directory, you can also view some system-related information in the /sys directory. For example, the file /sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_cur_freq contains the current frequency information of CPU0. If the file exists in the system, you can output its contents to view it:
cat /sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_cur_freqThe output shown in the figure above indicates that the current frequency of CPU0 is 408MHz.
The CPU of the LubanCat-RK3562/RK3566/RK3568 series boards has a frequency adjustment function. It automatically downclocks to save energy when the load is low, and automatically raises the frequency to improve performance when high-load scenarios are required.
ls -g /sys/devices/system/cpu/cpu0/cpufreq/