Arduino IDE - /dev/ttyACM0 Permission denied

uplading without root doesn’t work. monitor work with and without root. cat works before and after chmod 666

Is this the repo version or the one from the arduino website?


Hi, thanks but a+rw = 666 and doesn’t work. I messed sth I think :frowning:


arduino website version. this one almost work :). only starting it is a bit pain. Desktop shortcut doesn’t work, cannot start is from terminal ( comand not found), even if thunar claiming it is a shell script.

Hmm bizzard
I just make this command and it work and complie uWu

Not good enough. :slight_smile:

That’s because your shell is looking for it in $PATH which doesn’t include the directory the script is located in.

You can install the repo version as well, shouldn’t be a problem since the version from the website is not integrated into your system.

a+rw = 666 a means the same as ugo which is user, group, other. +rw means add read and write permissions. = 666 is just wrong. :slight_smile:

That’s nothing compared to the mistakes I’ve made. :slight_smile:

Soo i do a bad thing right ?

No your command was ok, it changes the permissions, it will work but you have to do it every time you connect a device. This is better:

sudo usermod -a -G uucp $USER

Run it once, log out and back in again and you should be able to access the device without changing the permissions ever again. :slight_smile:

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Oh thanks dood
i will try it Uwu

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Which version did you download? :slight_smile:

There’s a compulsory “donation” to get the latest stable version. :grin:


that is a trick. for windows version there is a free download button. just go a page back, go to windows download page, back again and linux download again, the free download button should appear :slight_smile:

reinstalled repo copy of arduino ide. this time working like web copy. uplading with root, monitor in both modes. only fonts are a bit weird this time :slight_smile:

Can’t find a free one, they all lead to the donation page for me, except the hourly and beta builds. Maybe we’re on different sites, or I’ve missed something.

What happens when you try uploading without root? Any error messages? Does echoing to the device still hang? If so reboot, and try again without any chmod or udev.

The fonts may be from the newer java version. Is it just a different font or is it messed up? :slight_smile:

direct download link:

will reboot and check again.

for now:

An error occurred while uploading the sketch
avrdude: ser_open(): can’t open device “/dev/ttyACM0”: Permission denied

rebooted - the same error.
removed udev usb rule and

udevadm control --reload-rules && udevadm trigger

the same

I wish I had the same board to test, but I don’t see how it’s the board if we have communication as root.

ls -l /dev/ttyACM*
echo something > /dev/ttyACM0

[lukas@lukas-20217 ~]$ ls -l /dev/ttyACM*
crw-rw---- 1 root uucp 166, 0 Dec 30 15:15 /dev/ttyACM0
[lukas@lukas-20217 ~]$ echo sth > /dev/ttyACM0
[lukas@lukas-20217 ~]$

I just find sth new. after the first echo next line prompt appear, but when I repeat echo the cursor stuck in the next empty line for about 30 sec and back to prompt. or ctrl+c.

[lukas@lukas-20217 ~]$ echo sth > /dev/ttyACM0
[lukas@lukas-20217 ~]$ echo sth > /dev/ttyACM0
<== here hanged for around 30 sec

That looks as I expected. Ok so try sudo chmod a+rw /dev/ttyACM0 then run those commands again and also try to upload a sketch without root.

Strange, I can’t replicate that, but I think it did it to me once or twice the other night. Didn’t seem to get in the way though.


If that was the cause you’d expect uploads to work without root intermittently. Unless it always writes at least twice.

Did you try running it using sudo --group=uucp like @TriMoon suggested? I assumed you did and it didn’t help.

The user is fine, just the IDE that can’t write. :confused:

Any ideas TriMoon? Just reinstall?

@lukas0 What does ls -l /usr/bin/arduino say and how are you starting the IDE?

No idea what the Java code does, maybe it is using some kind of privilege change…

the result

[lukas@lukas-20217 ~]$ ls -l /usr/bin/arduino
-rwxr-xr-x 1 root root 101 Aug 16 09:23 /usr/bin/arduino

with sudo the arduino IDE working as should. no issues. the problem appear when started as normal user.

reinstalled about 5 or 6 times right now :). I guess reinstalling method works only under ms systems :D.
now have repo version installed as shown above and portable (?) version in Downloads folder from webpage

This is different as plain sudo…

[lukas@lukas-20217 ~]$ sudo arduino --group==uucp
[sudo] password for lukas:
Error: unknown option: --group==uucp
[lukas@lukas-20217 ~]$

something not right…

or sudo -group==uucp arduino? – will check

sudo -g uucp arduino :slight_smile: this form work , but the same:
avrdude: ser_open(): can’t open device “/dev/ttyACM0”: Permission denied