# Error: Permission denied, cannot open /dev/ttyr0

**URL:** <https://discourse.nodered.org/t/error-permission-denied-cannot-open-dev-ttyr0/25148>\
**Category:** Hardware\
**Created:** [19 April 2020 18:50 UTC](https://discourse.nodered.org/t/error-permission-denied-cannot-open-dev-ttyr0/25148 "2020-04-19T18:50:08Z")\
**Posts on this page:** 6\
**Page:** 1

<div class="post-metadata">

**Author:** ![maccoa](https://avatars.discourse-cdn.com/v4/letter/m/a88e57/32.png) [@maccoa](https://discourse.nodered.org/u/maccoa)\
**Post date:** [19 April 2020 18:50 UTC](https://discourse.nodered.org/t/error-permission-denied-cannot-open-dev-ttyr0/25148/1 "2020-04-19T18:50:09Z")

</div>

Hello everyone  
I try to communicate via rs232 over tcp / ip.

I installed the NPort 5110 drivers (1-port RS-232 serial device server)  
but in node I don't have the rights.  
in a terminal I try to understand why.

```auto
ls -l / dev / ttyr *
crw ------- 1 root root 33, 0 April 19 19:56 / dev / ttyr0

```

I told myself that I am not in the right group (dialout)

```auto

sudo chown: dialout / dev / ttyr0
sudo chmod 777 / dev / ttyr0
ls -l / dev / ttyr *
crwxrwxrwx 1 root dialout 33, April 0 19 7:56 PM / dev / ttyr0

```

despite that it did not work.

```auto
dmesg | grep ttyr *
[0.115918] printk: console [tty0] enabled
[1.454256] tty tty4: hash matches
[40.978938] MOXA Async / NPort server family Real TTY driver ttymajor 33 calloutmajor 38 verbose 0 (Ver5.0)
[77.712702] audit: type = 1400 audit (1587318999.001: 30): apparmor = "DENIED" operation = "open" profile = "snap.node-red.node-red" name = "/ dev / ttyr00" pid = 1481 comm = "node" requested_mask = "wr" denied_mask = "wr" fsuid = 0 ouid = 0

```

I must admit that I don't really know what to do, do you have an idea?

---

<div class="post-metadata">

**Author:** ![ghayne](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/ghayne/32/39_2.png) [@ghayne](https://discourse.nodered.org/u/ghayne)\
**Post date:** [19 April 2020 19:28 UTC](https://discourse.nodered.org/t/error-permission-denied-cannot-open-dev-ttyr0/25148/2 "2020-04-19T19:28:44Z")

</div>

> [@maccoa](#):
>
> dialout / dev / ttyr0

That is not a valid path in linux:  
dialout/dev/ttyr0 is correct!

---

<div class="post-metadata">

**Author:** ![TotallyInformation](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/totallyinformation/32/31_2.png) [@TotallyInformation](https://discourse.nodered.org/u/TotallyInformation)\
**Post date:** [19 April 2020 20:18 UTC](https://discourse.nodered.org/t/error-permission-denied-cannot-open-dev-ttyr0/25148/3 "2020-04-19T20:18:14Z")

</div>

> [@maccoa](#):
>
> sudo chown: dialout / dev / ttyr0  
> sudo chmod 777 / dev / ttyr0

You really shouldn't set 777.

```auto
sudo chown root:dialout /dev/ttyr0
sudo chmod 660 /dev/ttyr0

crw-rw---- 1 root dialout 4, 67 Feb 12 22:30 /dev/ttyr0

```

---

<div class="post-metadata">

**Author:** ![TotallyInformation](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/totallyinformation/32/31_2.png) [@TotallyInformation](https://discourse.nodered.org/u/TotallyInformation)\
**Post date:** [19 April 2020 20:21 UTC](https://discourse.nodered.org/t/error-permission-denied-cannot-open-dev-ttyr0/25148/4 "2020-04-19T20:21:33Z")

</div>

> [@maccoa](#):
>
> snap.node-red.node-red

I think this may be your issue - you seem to be using snap? I'm not really familiar with it but think it might have its own security settings?

---

<div class="post-metadata">

**Author:** ![maccoa](https://avatars.discourse-cdn.com/v4/letter/m/a88e57/32.png) [@maccoa](https://discourse.nodered.org/u/maccoa)\
**Post date:** [2 May 2020 14:56 UTC](https://discourse.nodered.org/t/error-permission-denied-cannot-open-dev-ttyr0/25148/5 "2020-05-02T14:56:49Z")

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thank you very much, i reinstalled without snap and i have access to the port.

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<div class="post-metadata">

**Author:** ![system](https://us1.discourse-cdn.com/flex026/uploads/nodered/original/1X/d073cd938eafa2e558d7c2cd59003b3ef4963033.png) [@system](https://discourse.nodered.org/u/system)\
**Post date:** [1 July 2020 14:56 UTC](https://discourse.nodered.org/t/error-permission-denied-cannot-open-dev-ttyr0/25148/6 "2020-07-01T14:56:52Z")

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