Raspberry Pi OS
Содержание
Raspberry Pi OS is a free operating system based on Debian, optimised for the Raspberry Pi hardware, and is the recommended operating system for normal use on a Raspberry Pi. The OS comes with over 35,000 packages: precompiled software bundled in a nice format for easy installation on your Raspberry Pi.
Raspberry Pi OS is under active development, with an emphasis on improving the stability and performance of as many Debian packages as possible on Raspberry Pi.
Updating and Upgrading Raspberry Pi OS
It’s important to keep your Raspberry Pi up to date. The first and probably the most important reason is security. A device running Raspberry Pi OS contains millions of lines of code that you rely on. Over time, these millions of lines of code will expose well-known vulnerabilities, which are documented in publicly available databases meaning that they are easy to exploit. The only way to mitigate these exploits as a user of Raspberry Pi OS is to keep your software up to date, as the upstream repositories track CVEs closely and try to mitigate them quickly.
The second reason, related to the first, is that the software you are running on your device most certainly contains bugs. Some bugs are CVEs, but bugs could also be affecting the desired functionality without being related to security. By keeping your software up to date, you are lowering the chances of hitting these bugs.
Using APT
The easiest way to manage installing, upgrading, and removing software is using APT (Advanced Packaging Tool) from Debian. To update software in Raspberry Pi OS, you can use the apt tool from a Terminal window.
Keeping your Operating System up to Date
APT keeps a list of software sources on your Pi in a file at /etc/apt/sources.list . Before installing software, you should update your package list with apt update . Go ahead and open a Terminal window and type:
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Next, upgrade all your installed packages to their latest versions with the following command:
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Note that full-upgrade is used in preference to a simple upgrade , as it also picks up any dependency changes that may have been made.
Generally speaking, doing this regularly will keep your installation up to date for the particular major Raspberry Pi OS release you are using (e.g. Stretch). It will not update from one major release to another, for example, Stretch to Buster.
However, there are occasional changes made in the Foundation’s Raspberry Pi OS image that require manual intervention, for example a newly introduced package. These are not installed with an upgrade, as this command only updates the packages you already have installed.
Running Out of Space
When running sudo apt full-upgrade , it will show how much data will be downloaded and how much space it will take up on the SD card. It’s worth checking with df -h that you have enough free disk space, as unfortunately apt will not do this for you. Also be aware that downloaded package files ( .deb files) are kept in /var/cache/apt/archives . You can remove these in order to free up space with sudo apt clean ( sudo apt-get clean in older releases of apt).
Upgrading from Operating System Versions
The latest version of Raspberry Pi OS is based on Debian Buster. The previous version was based on Stretch. To upgrade, first modify the files /etc/apt/sources.list and /etc/apt/sources.list.d/raspi.list . In both files, change every occurrence of the word stretch to buster . (Both files will require sudo to edit.)
Then open a terminal window and execute:
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Answer ‘yes’ to any prompts. There may also be a point at which the install pauses while a page of information is shown on the screen — hold the space key to scroll through all of this and then press q to continue.
Finally, if you are not using PulseAudio for anything other than Bluetooth audio, remove it from the image by entering:
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If moving to a new Raspberry Pi model (for example the Pi 3B+), you may also need to update the kernel and the firmware using the instructions above.
Searching for Software
You can search the archives for a package with a given keyword with apt-cache search :
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You can view more information about a package before installing it with apt-cache show :
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Installing a Package with APT
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Typing this command should inform the user how much disk space the package will take up and asks for confirmation of the package installation. Entering Y (or just pressing Enter , as yes is the default action) will allow the installation to occur. This can be bypassed by adding the -y flag to the command:
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Installing this package makes tree available for the user.
Uninstalling a Package with APT
You can uninstall a package with apt remove :
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The user is prompted to confirm the removal. Again, the -y flag will auto-confirm.
You can also choose to completely remove the package and its associated configuration files with apt purge :
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Using rpi-update
rpi-update is a command line application that will update your Raspberry Pi OS kernel and VideoCore firmware to the latest pre-release versions.
The rpi-update script is supplied by a third party, "Hexxeh", and also supported by Raspberry Pi engineers. The script source can be found on GitHub at https://github.com/Hexxeh/rpi-update
What it does
rpi-update will download the latest pre-release version of the linux kernel, its matching modules, device tree files, along with the latest versions of the VideoCore firmware. It will then install these files to relevant locations on the SD card, overwriting any previous versions.
All the source data used by rpi-update comes from the GitHub repo https://github.com/Hexxeh/rpi-firmware. This repository simply contains a subset of the data from the official firmware repository, as not all the data from that repo is required.
Running rpi-update
If you are sure that you need to use rpi-update , it is advisable to take a backup of your current system first as running rpi-update could result in a non-booting system.
rpi-update needs to be run as root. Once the update is complete you will need to reboot.
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It has a number of options, which are documented at the Hexxeh GitHub repository at https://github.com/Hexxeh/rpi-update
How to get back to safety
If you have done an rpi-update and things are not working as you wish, if your Raspberry Pi is still bootable you can return to the stable release using:
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You will need to reboot your Raspberry Pi for these changes to take effect.
Playing Audio and Video
The simplest way of playing audio and video on Raspberry Pi is to use the installed OMXPlayer application.
This is hardware accelerated, and can play back many popular audio and video file formats. OMXPlayer uses the OpenMAX ( omx ) hardware acceleration interface (API) which is the officially supported media API on Raspberry Pi. OMXPlayer was developed by the Kodi Project’s Edgar Hucek.
The OMXPlayer Application
The simplest command line is omxplayer name of media file . The media file can be audio or video or both. For the examples below, we used an H264 video file that is included with the standard Raspberry Pi OS installation.
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By default the audio is sent to the analog port. If you are using a HDMI-equipped display device with speakers, you need to tell omxplayer to send the audio signal over the HDMI link.
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When displaying video, the whole display will be used as output. You can specify which part of the display you want the video to be on using the window option.
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You can also specify which part of the video you want to be displayed: this is called a crop window. This portion of the video will be scaled up to match the display, unless you also use the window option.
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If you are using the Raspberry Pi Foundation’s touchscreen display, and you want to use it for video output, use the display option to specify which display to use. n is 5 for HDMI, 4 for the touchscreen. With the Raspberry Pi 4 you have two options for HDMI output. n is 2 for HDMI0 and 7 for HDMI1.
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How to Play Audio
To play an MP3 file, navigate to the location of the .mp3 file in the terminal using cd and then type the following command:
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This will play the audio file example.mp3 through either your monitor’s built-in speakers or your headphones, connected via the headphone jack.
If you need an example file you can download one from here using the following command:
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If you cannot hear anything, make sure your headphones or speakers are connected correctly. Note that omxplayer doesn’t use ALSA and so ignores the audio configuration set by raspi-config or amixer .
If omxplayer’s auto-detection of the correct audio output device fails, you can force output over HDMI with:
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Alternatively, you can force output over the headphone jack with:
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You can even force output over both the headphone jack and HDMI with:
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How to Play Video
To play a video, navigate to the location of your video file in the terminal using cd , then type the following command:
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This will play the example.mp4 in full screen. Hit Ctrl + C to exit.
On the Pi 4, hardware support for MPEG2 and VC-1 codecs has been removed, so we recommend the use of the VLC application, which supports these formats in software. In addition, VLC has hardware support for H264 and the new HEVC codec.
An Example Video
A video sample of the animated film Big Buck Bunny is available on your Raspberry Pi. To play it enter the following command into a terminal window:
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On a Pi 4, use the following command for H264 files:
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or for H264, VC1, or MPEG2
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When using VLC, you can improve playback performance by encapsulating the raw H264 stream, for example from the Raspberry Pi Camera Module. This is easily done using ffmpeg . Playback is also improved if VLC is run full screen; either select fullscreen from the user interface, or you can add the —fullscreen options to the vlc command line.
This example command converts video.h264 to a containerised video.mp4 at 30 fps:
ffmpeg -r 30 -i video.h264 -c:v copy video.mp4
Options During Playback
There are a number of options available during playback, actioned by pressing the appropriate key. Not all options will be available on all files. The list of key bindings can be displayed using omxplayer —keys :
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Playing in the Background
omxplayer will close immediately if run in the background without tty (user input), so to run successfully, you need to tell omxplayer not to require any user input using the —no-keys option.
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Adding the at the end of the command runs the job in the background. You can then check the status of this background job using the jobs command. By default, the job will complete when omxplayer finishes playing, but if necessary, you can stop it at any point using the kill command.
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Using a USB webcam
Rather than using the Raspberry Pi camera module, you can use a standard USB webcam to take pictures and video on your Raspberry Pi.
First, install the fswebcam package:
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If you are not using the default pi user account, you need to add your username to the video group, otherwise you will see ‘permission denied’ errors.
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To check that the user has been added to the group correctly, use the groups command.
Basic Usage
Enter the command fswebcam followed by a filename and a picture will be taken using the webcam, and saved to the filename specified:
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This command will show the following information:
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The webcam used in this example has a resolution of 1280 x 720 so to specify the resolution I want the image to be taken at, use the -r flag:
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This command will show the following information:
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Picture now taken at the full resolution of the webcam, with the banner present.
Removing the Banner
Now add the —no-banner flag:
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which shows the following information:
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Now the picture is taken at full resolution with no banner.
Automating Image Capture
You can write a Bash script which takes a picture with the webcam. The script below saves the images in the /home/pi/webcam directory, so create the webcam subdirectory first with:
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To create a script, open up your editor of choice and write the following example code:
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This script will take a picture and name the file with a timestamp. Say we saved it as webcam.sh , we would first make the file executable:
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Which would run the commands in the file and give the usual output:
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Time-Lapse Captures
You can use cron to schedule taking a picture at a given interval, such as every minute to capture a time-lapse.
First open the cron table for editing:
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This will either ask which editor you would like to use, or open in your default editor. Once you have the file open in an editor, add the following line to schedule taking a picture every minute (referring to the Bash script from above):
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Save and exit and you should see the message:
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Ensure your script does not save each picture taken with the same filename. This will overwrite the picture each time.
Useful Utilities
There are several useful command line
tvservice
tvservice is a command line application used to get and set information about the display, targeted mainly at HDMI video and audio.
Typing tvservice by itself will display a list of available command line options.
-p, —preferred
Power on the HDMI output with preferred settings.
-o, —off
Powers off the display output.
A better option is to use the vcgencmd display_power option, as this will retain any framebuffers, so when the power is turned back on the display will be the returned to the previous power on state.
-e, —explicit="Group Mode Drive"
Power on the HDMI with the specified settings
Group can be one of CEA , DMT , CEA_3D_SBS , CEA_3D_TB , CEA_3D_FP , CEA_3D_FS .
Mode is one of the modes returned from the -m, —modes option.
Drive can be one of HDMI , DVI .
-t, —ntsc
Use 59.94Hz (NTSC frequency) rather than 60Hz for HDMI mode.
-c, —sdtvon="Mode Aspect [P]"
Power on the SDTV (composite output) with the specified mode, PAL or NTSC , and the specified aspect, 4:3 , 14:9 , 16:9 . The optional P parameter can be used to specify progressive mode.
-m, —modes=Group
where Group is CEA or DMT .
Shows a list of display modes available in the specified group.
-M, —monitor
Monitors for any HDMI events, for example unplugging or attaching.
-s, —status
Shows the current settings for the display mode, including mode, resolution, and frequency.
-a, —audio
Shows the current settings for the audio mode, including channels, sample rate and sample size.
-d, —dumpid=filename
Save the current EDID to the specified filename. You can then use edidparser filename to display the data in a human readable form.
-j, —json
When used in combination with the —modes options, displays the mode information in JSON format.
-n, —name
Extracts the display name from the EDID data and shows it.
-l, —list
Lists all attached displays and their display ID.
-v, —device=display
Specifies the ID of the device to use; see the output of —list for available IDs.
vcgencmd
The vcgencmd tool is used to output information from the VideoCore GPU on the Raspberry Pi. You can find source code for the vcgencmd utility on Github.
To get a list of all commands which vcgencmd supports, use vcgencmd commands . Some useful commands and their required parameters are listed below.
The vcos command has two useful sub-commands:
version displays the build date and version of the firmware on the VideoCore
log status displays the error log status of the various VideoCore firmware areas
version
Displays the build date and version of the VideoCore firmware.
get_camera
Displays the enabled and detected state of the Raspberry Pi camera: 1 means yes, 0 means no. Whilst all firmware except cutdown versions support the camera, this support needs to be enabled by using raspi-config.
get_throttled
Returns the throttled state of the system. This is a bit pattern — a bit being set indicates the following meanings:
Arm frequency capped
Soft temperature limit active
Under-voltage has occurred
Arm frequency capping has occurred
Throttling has occurred
Soft temperature limit has occurred
measure_temp
Returns the temperature of the SoC as measured by its internal temperature sensor; on Raspberry Pi 4, measure_temp pmic returns the temperature of the PMIC.
measure_clock [clock]
This returns the current frequency of the specified clock. The options are:
Image Sensor Pipeline
PWM block (analogue audio output)
SD card interface
Analogue video encoder
Display Parallel Interface
e.g. vcgencmd measure_clock arm
measure_volts [block]
Displays the current voltages used by the specific block.
VC4 core voltage
SDRAM Core Voltage
SDRAM I/O voltage
SDRAM Phy Voltage
otp_dump
Displays the content of the OTP (one-time programmable) memory inside the SoC. These are 32 bit values, indexed from 8 to 64. See the OTP bits page for more details.
get_config [configuration item|int|str]
Display value of the configuration setting specified: alternatively, specify either int (integer) or str (string) to see all configuration items of the given type. For example:
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returns the total memory on the device in megabytes.
get_mem type
Reports on the amount of memory addressable by the ARM and the GPU. To show the amount of ARM-addressable memory use vcgencmd get_mem arm ; to show the amount of GPU-addressable memory use vcgencmd get_mem gpu . Note that on devices with more than 1GB of memory the arm parameter will always return 1GB minus the gpu memory value, since the GPU firmware is only aware of the first 1GB of memory. To get an accurate report of the total memory on the device, see the total_mem configuration item — see get_config section above.
codec_enabled [type]
Reports whether the specified CODEC type is enabled. Possible options for type are AGIF, FLAC, H263, H264, MJPA, MJPB, MJPG, MPG2, MPG4, MVC0, PCM, THRA, VORB, VP6, VP8, WMV9, WVC1. Those highlighted currently require a paid for licence (see the this config.txt section for more info), except on the Pi 4 and 400, where these hardware codecs are disabled in preference to software decoding, which requires no licence. Note that because the H.265 HW block on the Raspberry Pi 4 and 400 is not part of the VideoCore GPU, its status is not accessed via this command.
get_lcd_info
Displays the resolution and colour depth of any attached display.
mem_oom
Displays statistics on any OOM (out of memory) events occurring in the VideoCore memory space.
mem_reloc_stats
Displays statistics from the relocatable memory allocator on the VideoCore.
read_ring_osc
Returns the current speed voltage and temperature of the ring oscillator.
hdmi_timings
Displays the current HDMI settings timings. See Video Config for details of the values returned.
dispmanx_list
Dump a list of all dispmanx items currently being displayed.
display_power [0 | 1 | -1] [display]
Show current display power state, or set the display power state. vcgencmd display_power 0 will turn off power to the current display. vcgencmd display_power 1 will turn on power to the display. If no parameter is set, this will display the current power state. The final parameter is an optional display ID, as returned by tvservice -l or from the table below, which allows a specific display to be turned on or off.
Note that for the 7" Raspberry Pi Touch Display this simply turns the backlight on and off. The touch functionality continues to operate as normal.
vcgencmd display_power 0 7 will turn off power to display ID 7, which is HDMI 1 on a Raspberry Pi 4.
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