Qserialport linux permition denied

Fix serial port permission denied errors on Linux

The ancient serial port which is no longer found on the latest motherboards and even the not so latest laptops is still used for connecting to the console of networking devices, headless computers and a lot other applications. On computers which do not have built-in serial ports USB-to-Serial adapters can be used. Linux identifies inbuilt serial ports as /dev/ttyS0, /dev/ttyS1,….. /dev/ttySn and USB-to-Serial adapters as /dev/ttyUSB0, …. /dev/ttyUSBn and they can be accessed using terminal emulator applications like PuTTY, minicom and screen.

Normally when the serial console is accessed using the terminal emulator of your choice as a non-root user you’ll get a “permission denied” error. Using PuTTY on Ubuntu I got the following error – “Unable to open connection to: Unable to open serial port“.

PuTTY on Linux throws this error if the user running it does not have permissions to access the serial port device file

This is because the device file of the serial port does not have permissions to allow to currently logged in user to “read” or “write” to the serial device. The following command will confirm that.

So we can see that only the “root” user and the “dialout” group have proper permissions, while chmod can be used to grant access to the required user or everyone it is messy and not a secure way. The easier way is the add the user to the dialout group.

First verify if the user does belong to the dialout group using the “id” command.

Next add the user to the “dialout” supplementary group.

You have to logout and login before changes take effect. After logging back in try the “id” command again.

Now all your terminal emulator applications will work with the serial port without any issues.

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Error opening serial port (Linux)

Overview

When uploading a sketch you may get the following error

or, when opening the serial Monitor

Note: The number in ttyACM* may be different.

If this happens, start by ensuring that you are using the correct port:

• Arduino IDE:Tools > Port > [select port]
• Web Editor: Select port using the dropdown.

If the problem persists there may be an issue with permissions for the serial port. See below for step-by-step instructions on how to set the correct permissions.

How to set serial port permissions

Open Terminal and type

Press enter. Terminal will return something like

What we are interested in is the group name, which is probably called dialout .

Note: The number at the end of ttyACM may be different, or multiple entries might be returned.

Now we want to add your user to that group. Input the following command in the terminal, replacing with the group name from above, and with your username, both without brackets.

Press enter. Input password if prompted.

Lastly, for the new permissions to take effect, you need to log out and in to your user account.

You can verify the changes by typing

into the Terminal and pressing Enter. The group you added should appear in the list.

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Изменение разрешений на последовательный порт

Я использую Arduino IDE в Ubuntu, и у меня проблемы с последовательным портом. В прошлом это работало, но по причинам, которые могут быть излишними, я почувствовал необходимость сменить владельца некоторых файлов с корневого на владение моих пользователей.

Это заставило IDE работать правильно, но я потерял способность использовать правильный последовательный порт. В папке dev нужный мне порт указан как разрешение 166. Кто-то (кто больше не в этом районе, чтобы помочь мне) поменял разрешения на 666, и все это заработало великолепно.

Тем не менее, он вернулся обратно, как только я перезагрузил компьютер, и теперь, если я попытаюсь использовать команду:

Ничего не произошло. Нет сообщений об ошибках, но нет изменения разрешения.

Как я могу изменить это, и как я могу заставить это измениться навсегда.

Я прошу прощения, если этот вопрос слишком упрощен или неясен, я нуб Ubuntu, и я не буду жалеть обратную связь!

Проблема с разрешениями /dev/ttyACM0 может быть навсегда решена путем добавления себя в dialout группу. Вам придется выйти из системы, а затем снова войти в нее, прежде чем изменение группы будет распознано.

Вы можете сделать это с sudo usermod -a -G dialout $USER

Я не смог получить предложение Ринзвинда , потому что он жаловался, что учетная запись пользователя уже существует. Вместо этого я использовал эту команду, чтобы добавить существующего пользователя ( terrik ) в существующую группу ( dialout ), как описано в справочной вики Ubuntu .

Также полезна эта команда для вывода списка ваших текущих групп, хотя, как говорит Ринзвинд, вы должны выйти из системы и войти в систему, прежде чем последовательный порт начнет вас впускать.

Я не мог получить рабочий ответ Террика , но смог бы, если бы сделал эту небольшую корректировку для пути ttyACM0 .

Разместил бы как комментарий, но у меня еще нет привилегий для этого .

Другая возможность — создать файл правил в /etc/udev/rules.d/ каталоге. У меня была похожая проблема, и я создал 50-myusb.rules файл в указанном выше каталоге с таким содержанием:

Обратите внимание, что это даст любому устройству, подключенному к сокету ttyACM права на чтение / запись. Если вам нужно только определенное устройство для получения разрешений на чтение / запись, вы также должны проверить idVendor и idProduct . Вы можете найти их, выполнив lsusb команду дважды: один раз, когда ваше устройство не подключено, и один раз, когда оно подключено, а затем просмотрите дополнительную строку на выходе. Там вы увидите нечто подобное Bus 003 Device 005: ID ffff:0005 . В этом случае idVendor = ffff и idProduct = 0005 . Твой будет другим. Чем вы изменяете файл правил:

Теперь только это устройство получает разрешения. Прочтите это, чтобы узнать больше о написании правил udev.

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Cannot open /dev/ttyUSB0: Permission denied #26

Comments

Navis-Raven commented Jul 18, 2017

I had an issue , while trying to do flash
Cannot open /dev/ttyUSB0: Permission denied

I palliated to this problem with the command » sudo chmod -R 777 /dev/ttyUSB0 » each time I wanted to flash.

Do you know more about these bugs ? This maybe due to an ubuntu bug (Ubuntu 16 LTS) but I don’t know

The text was updated successfully, but these errors were encountered:

ConstantJoe commented Aug 8, 2017

I’m not a dev on this project, just a user so if anyone else wants to jump in please do:

This is not an issue with the esp8266, and its not actually a bug at all, its just part of Linux. Its best practice to not change permissions in /dev unless as a last resort. What you want to do instead is to add yourself to the group which would give you permission to access the tty ports.

To see the groups you are in simply type:

To see all available groups type:

Most of them are self-explanatory, in this case you want to add yourself to either the tty group, or dialout, which you would do by:

sudo usermod -a -G tty yourname

Then your user should have access to tty without use of sudo.

stefanofiorentino commented Mar 28, 2018

After the sudo usermod -a -G tty yourname you have to logout/login to get group addition happens.

kbhuinfo commented Jan 22, 2019

I had to add my user to group «dialout» too (ubuntu). Logout/login required.

bumbalu commented Feb 13, 2019

Thank you people, it helped me to get access to my 3d printer from Klipper on Raspberry Pi!

abstract17 commented Mar 29, 2019

PROPER LOGOUT IS REQUIRED

Taudris commented Apr 21, 2019

Can this issue be added to the install documentation? Or even better, is there a way to automate handling it?

shamo1 commented Nov 11, 2019

this is actually a permission problem u have to allow your Arduino IDE to access the specified port just simply type following commands in your terminal

sudo su
//type your password
cd /
cd dev
chown username ttyUSB0

fr3kz commented Nov 11, 2019

thank you shamo1, it helped me

Vince55 commented Jan 20, 2020

thanks shamo1, that worked for me too!

tdgi commented Jan 24, 2020

I add myself to dialout group and it works:
sudo usermod -a -G dialout your_user_name

BlagoD commented Feb 10, 2020

I had to add my user to group «dialout» too (ubuntu). Logout/login required.

Indeed, without being member of the «dialout» group, the access to the ttyUSB is not granted.
Thanks for pointing it out!

m-atoms commented May 19, 2020

note for future users who are curious about this

Problem
Cannot open /dev/ttyUSB0: Permission denied error is caused by the user not having access to the serial ports as other commenters have mentioned. More specifically, the user is not in the dialout group.

Solution
sudo usermod -a -G dialout $USER

For anyone who likes knowing what they’re running before they run it:
usermod — modify a user account
-a — add the user to supplementary groups
-G — a list of supplementary groups (man page says to use -a only with -G )
dialout — group that controls access to serial ports (and other hardware too)
$USER — Bash variable containing current username (not a builtin, usually automatically set env variable)

bonus notes: This is the ‘linux way’ to solve the problem. Adding the user to the group with permission to use the device is much safer than changing the permissions of the device itself. And as others have mentioned, make sure you log out for the changes to take effect.

thecompoundingdev commented Jun 9, 2020 •

thanks @shamo1 ! I tried adding myself to tty and dialout group and it worked after logging back in. but the next day it gave same error but I was still a member of those groups. Had to add chown ttyUSB0 through root and it worked!

hashc4t commented Jun 25, 2020

For anyone using Arch Linux, Arch has a separate user group for serial ports called uucp.
To add your current user:
sudo usermod -a -G uucp $USER
then logout/login.

duncanhames commented Jul 6, 2020

For anyone using Arch Linux, Arch has a separate user group for serial ports called uucp.
To add your current user:
sudo usermod -a -G uucp $USER
then logout/login.

Thanks for that!

kaustubhKVS commented Jul 13, 2020

this is actually a permission problem u have to allow your Arduino IDE to access the specified port just simply type following commands in your terminal

sudo su
//type your password
cd /
cd dev
chown username ttyUSB0

This worked better for me !! They should include this on documentation !! Thankyou @shamo1 .

ThomasGeor commented Oct 9, 2020

this is actually a permission problem u have to allow your Arduino IDE to access the specified port just simply type following commands in your terminal

sudo su
//type your password
cd /
cd dev
chown username ttyUSB0

This one worked for me with ESP32

loleg commented Oct 30, 2020

In addition to adding my user to the tty and dialout groups on Fedora Linux 32, I also had to follow the instructions here:

On modern distros that use ConsoleKit create the file /etc/udev/rules.d/01-ttyusb.rules containing the following and then reload the udev rules and replug the Arduino device:

kelvin-JR commented Nov 3, 2020

this is actually a permission problem u have to allow your Arduino IDE to access the specified port just simply type following commands in your terminal

sudo su
//type your password
cd /
cd dev
chown username ttyUSB0

it’s helpful ,thank you

diesilveira commented Nov 12, 2020

RicBar10 commented Nov 18, 2020

this is actually a permission problem u have to allow your Arduino IDE to access the specified port just simply type following commands in your terminal

sudo su
//type your password
cd /
cd dev
chown username ttyUSB0

thanks you, it solve the problem, you’re a genius

Bill0412 commented Nov 21, 2020

this is actually a permission problem u have to allow your Arduino IDE to access the specified port just simply type following commands in your terminal

sudo su
//type your password
cd /
cd dev
chown username ttyUSB0

This solves my problem, thanks!

cheng3100 commented Jan 27, 2021

Hi ,just look at this issue and I found a better solution .
Just type this commad to install a udev ruler file:

This ruler file is from platformio.

And you also need to join group dialout and plugdev :

stefanofiorentino commented Jan 27, 2021

And you also need to join group dialout and plugdev:

and remember to logout/login..

MohamedYousof commented Feb 4, 2021

this is actually a permission problem u have to allow your Arduino IDE to access the specified port just simply type following commands in your terminal

sudo su
//type your password
cd /
cd dev
chown username ttyUSB0

This worked for me Ubuntu 20.04

peely commented Feb 10, 2021 •

note for future users who are curious about this

Problem
Cannot open /dev/ttyUSB0: Permission denied error is caused by the user not having access to the serial ports as other commenters have mentioned. More specifically, the user is not in the dialout group.

Solution
sudo usermod -a -G dialout $USER

For anyone who likes knowing what they’re running before they run it:
usermod — modify a user account
-a — add the user to supplementary groups
-G — a list of supplementary groups (man page says to use -a only with -G )
dialout — group that controls access to serial ports (and other hardware too)
$USER — Bash variable containing current username (not a builtin, usually automatically set env variable)

bonus notes: This is the ‘linux way’ to solve the problem. Adding the user to the group with permission to use the device is much safer than changing the permissions of the device itself. And as others have mentioned, make sure you log out for the changes to take effect.

This is the safest, cleanest and most reliable answer. Don’t just go round changing ownership, make yourself a member of that devices ownership group. Thank you @m-atoms for the clear explanation.

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