# Container can't see new /dev/tty\* device on host

**URL:** <https://forums.balena.io/t/container-cant-see-new-dev-tty-device-on-host/5225>\
**Category:** Product support\
**Tags:** support, raspberrypi3, docker\
**Created:** [February 6, 2019, 9:35am UTC](https://forums.balena.io/t/container-cant-see-new-dev-tty-device-on-host/5225 "2019-02-06T09:35:43Z")\
**Posts on this page:** 15\
**Page:** 1

<div class="post-metadata">

**Author:** ![daghemo](https://sea2.discourse-cdn.com/balena/user_avatar/forums.balena.io/daghemo/32/531_2.png) [@daghemo](https://forums.balena.io/u/daghemo)\
**Post date:** [February 6, 2019, 9:35am UTC](https://forums.balena.io/t/container-cant-see-new-dev-tty-device-on-host/5225/1 "2019-02-06T09:35:43Z")

</div>

My application can’t see a fresh new /dev/tty\* device on host.

The device in question is /dev/ttyXRUSB0, that is an Exar USB device driver, needed by an USB to RJ45 adapter for RS-485 communication.

I had to build a kernel module for that, inspiring on [https://github.com/balena-io-projects/kernel-module-build](https://github.com/balena-io-projects/kernel-module-build).  
In order to see the /dev/ttyXRUSB0 device, I have to load the xr\_usb\_serial\_common.ko module.  
On previous version of resinOS/balenaOS I was able to see the new device within my container, but now, on my Raspberry Pi 3 B running balenaOS 2.29.2+rev1 and Supervisor 9.0.1, I see the device only on the host, not within the container!

To see the device within the container I have to reboot/restart the container.  
Note also that rebooting the device would lead to the same problem.

Is there a way I can refresh the list of /dev/tty\* devices from the host within my container?

Regards,  
Danilo

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<div class="post-metadata">

**Author:** ![shaunmulligan](https://sea2.discourse-cdn.com/balena/user_avatar/forums.balena.io/shaunmulligan/32/34_2.png) [@shaunmulligan](https://forums.balena.io/u/shaunmulligan)\
**Post date:** [February 6, 2019, 9:38am UTC](https://forums.balena.io/t/container-cant-see-new-dev-tty-device-on-host/5225/4 "2019-02-06T09:38:19Z")

</div>

Hi @daghemo, Can you tell me what baseimage your Dockerfile starts `FROM`, it sounds like you don’t have udev running in the container, which is responsible for picking up the addition of dynamic devices in /dev.

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<div class="post-metadata">

**Author:** ![shaunmulligan](https://sea2.discourse-cdn.com/balena/user_avatar/forums.balena.io/shaunmulligan/32/34_2.png) [@shaunmulligan](https://forums.balena.io/u/shaunmulligan)\
**Post date:** [February 6, 2019, 9:39am UTC](https://forums.balena.io/t/container-cant-see-new-dev-tty-device-on-host/5225/5 "2019-02-06T09:39:04Z")

</div>

Can you try set a device environment variable `UDEV` == 1 on you device?

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<div class="post-metadata">

**Author:** ![daghemo](https://sea2.discourse-cdn.com/balena/user_avatar/forums.balena.io/daghemo/32/531_2.png) [@daghemo](https://forums.balena.io/u/daghemo)\
**Post date:** [February 6, 2019, 9:39am UTC](https://forums.balena.io/t/container-cant-see-new-dev-tty-device-on-host/5225/6 "2019-02-06T09:39:50Z")

</div>

Hi @shaunmulligan,  
I’m using:

`FROM balenalib/%%RESIN_MACHINE_NAME%%-python:3.7.2-stretch-20190123`

I’ve also tried with “UDEV=1”.

---

<div class="post-metadata">

**Author:** ![shaunmulligan](https://sea2.discourse-cdn.com/balena/user_avatar/forums.balena.io/shaunmulligan/32/34_2.png) [@shaunmulligan](https://forums.balena.io/u/shaunmulligan)\
**Post date:** [February 6, 2019, 9:44am UTC](https://forums.balena.io/t/container-cant-see-new-dev-tty-device-on-host/5225/7 "2019-02-06T09:44:46Z")

</div>

@daghemo can you post your dockerfile and/or docker-compose.yml here. Would it also be possible for you to post the contents of `/usr/bin/entry.sh` here

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<div class="post-metadata">

**Author:** ![daghemo](https://sea2.discourse-cdn.com/balena/user_avatar/forums.balena.io/daghemo/32/531_2.png) [@daghemo](https://forums.balena.io/u/daghemo)\
**Post date:** [February 6, 2019, 11:15am UTC](https://forums.balena.io/t/container-cant-see-new-dev-tty-device-on-host/5225/8 "2019-02-06T11:15:15Z")

</div>

Ok, I’m goint to strip down my Dockerfile, since it’s over 38k right now. 🙂  
I’ll be back as soon as I reflash my RPi.

---

<div class="post-metadata">

**Author:** ![daghemo](https://sea2.discourse-cdn.com/balena/user_avatar/forums.balena.io/daghemo/32/531_2.png) [@daghemo](https://forums.balena.io/u/daghemo)\
**Post date:** [February 6, 2019, 11:49am UTC](https://forums.balena.io/t/container-cant-see-new-dev-tty-device-on-host/5225/9 "2019-02-06T11:49:29Z")

</div>

I’m back and I was able to reproduce the problem:

```
[daghemo@asgard ~]$ ./sshResin.sh young-fog
connecting to container on young-fog (04d0b30) running application TLtestingEXAR...
Connecting to: 04d0b30
root@04d0b30:/usr/src/app# ls -l /dev/ttyXRUSB0
ls: cannot access '/dev/ttyXRUSB0': No such file or directory
root@04d0b30:/usr/src/app# exit
exit
Connection to ssh.resindevice.io closed.
[daghemo@asgard ~]$ ./sshResin.sh young-fog ashost
connecting to host young-fog (04d0b30) running application TLtestingEXAR...
Connecting to: 04d0b30
=============================================================
    Welcome to balenaOS
=============================================================
root@04d0b30:~# ls -l /dev/ttyXRUSB0
crw-rw---- 1 root dialout 266, 0 Feb 6 11:36 /dev/ttyXRUSB0
root@04d0b30:~# exit
logout
Connection to ssh.resindevice.io closed.

```

Here is my Dockerfile:

```
FROM balenalib/%%RESIN_MACHINE_NAME%%-python:3.7.2-stretch-20190123

ENV INSTALL_EXAR_USB_DRIVER=Yes
ENV RESIN_OS_VERSION="2.29.2+rev1.prod"
ENV INITSYSTEM on
ENV container docker
RUN apt-get update && apt-get install -y --no-install-recommends systemd systemd-sysv \
    && rm -rf /var/lib/apt/lists/*
RUN systemctl mask \
    dev-hugepages.mount \
    sys-fs-fuse-connections.mount \
    sys-kernel-config.mount \
    display-manager.service \
    getty@.service \
    systemd-logind.service \
    systemd-remount-fs.service \
    getty.target \
    graphical.target \
    kmod-static-nodes.service
COPY tlshoot.sh /usr/bin/tlshoot.sh
COPY tlshoot.service /etc/systemd/system/tlshoot.service
RUN chmod a+x /usr/bin/tlshoot.sh
RUN systemctl enable /etc/systemd/system/tlshoot.service
STOPSIGNAL 37
ENTRYPOINT ["/usr/bin/tlshoot.sh"]
ENV UDEV=1
WORKDIR /usr/src/app

RUN echo 'APT::Install-Recommends "false";' >>/etc/apt/apt.conf.d/docker-minimal && \
    echo 'APT::Install-Suggests "false";' >>/etc/apt/apt.conf.d/docker-minimal && \
    echo 'APT::Get::Show-Upgraded "true";' >>/etc/apt/apt.conf.d/docker-minimal && \
    echo 'APT::Get::Assume-Yes "true";' >>/etc/apt/apt.conf.d/docker-non-interactive && \
    echo 'APT::Quiet "true";' >>/etc/apt/apt.conf.d/docker-non-verbose && \
    echo 'Dpkg::Use-Pty 0;' >>/etc/apt/apt.conf.d/docker-non-verbose && \
    echo 'DPkg::Options { "--force-confmiss"; "--force-confnew" };' >>/etc/apt/apt.conf.d/docker-force-config
RUN apt-get update && \
    apt-get install apt-utils \
                    libcurl4-openssl-dev curl \
                    wget git \
                    libmagic1 \
                    libssl-dev \
                    zlib1g-dev \
                    libdbus-1-dev libglib2.0-dev && \
    apt-get clean && \
    rm --recursive --force /var/lib/apt/*
RUN eval ["x$INSTALL_EXAR_USB_DRIVER" = "xYes"] && ( \
        apt-get update && \
        apt-get install build-essential && \
        apt-get clean && \
        rm --recursive --force /var/lib/apt/* && \
        pip install awscli && \
        rm -rf /root/.cache/pip && \
        git clone https://github.com/kasbert/epsolar-tracer.git && \
        curl --silent --location --remote-name https://raw.githubusercontent.com/balena-io-projects/kernel-module-build/master/build.sh && \
        chmod a+x ./build.sh && \
        ./build.sh %%RESIN_MACHINE_NAME%% $RESIN_OS_VERSION epsolar-tracer/xr_usb_serial_common-1a && \
        rm --recursive --force epsolar-tracer/xr_usb_serial_common-1a \
    ) || true

COPY . /usr/src/app
CMD ["bash","/usr/src/app/start.sh"]

```

Here is my /usr/bin/entry.sh:

```
#!/bin/bash

hostname "$HOSTNAME" &> /dev/null
if [[$? == 0]]; then
        PRIVILEGED=true
else
        PRIVILEGED=false
fi

function mount_dev()
{
        mkdir -p /tmp
        mount -t devtmpfs none /tmp
        mkdir -p /tmp/shm
        mount --move /dev/shm /tmp/shm
        mkdir -p /tmp/mqueue
        mount --move /dev/mqueue /tmp/mqueue
        mkdir -p /tmp/pts
        mount --move /dev/pts /tmp/pts
        touch /tmp/console
        mount --move /dev/console /tmp/console
        umount /dev || true
        mount --move /tmp /dev

        # Since the devpts is mounted with -o newinstance by Docker, we need to make
        # /dev/ptmx point to its ptmx.
        # ref: https://www.kernel.org/doc/Documentation/filesystems/devpts.txt
        ln -sf /dev/pts/ptmx /dev/ptmx
        mount -t debugfs nodev /sys/kernel/debug
}

function start_udev()
{
        if ["$UDEV" == "on"]; then
                if $PRIVILEGED; then
                        mount_dev
                        if command -v udevd &>/dev/null; then
                                unshare --net udevd --daemon &> /dev/null
                        else
                                unshare --net /lib/systemd/systemd-udevd --daemon &> /dev/null
                        fi
                        udevadm trigger &> /dev/null
                else
                        echo "Unable to start udev, container must be run in privileged mode to start udev!"
                fi
        fi
}

function init()
{
        # echo error message, when executable file doesn't exist.
        if CMD=$(command -v "$1" 2>/dev/null); then
                shift
                exec "$CMD" "$@"
        else
                echo "Command not found: $1"
                exit 1
        fi
}

UDEV=$(echo "$UDEV" | awk '{print tolower($0)}')

case "$UDEV" in
        '1' | 'true')
                UDEV='on'
        ;;
esac

start_udev
init "$@"

```

The tlshoot.service is:

```
[Unit]
Description=Timelapse.in TLshoot Balena.io Application

[Service]
EnvironmentFile=/etc/docker.env
ExecStart=/etc/TLshootService.sh
StandardOutput=tty
StandardError=tty
TTYPath=/dev/console
Restart=on-failure

[Install]
WantedBy=basic.target

```

The tlshoot.sh is:

```
#!/bin/bash

set -m

# Send SIGTERM to child processes of PID 1.

function signal_handler()

{

kill "$pid"

}

function init_systemd()

{

GREEN='\033[0;32m'

echo -e "${GREEN}Systemd init system enabled."

for var in $(compgen -e); do

printf '%q=%q\n' "$var" "${!var}"

done &gt; /etc/docker.env

echo 'source /etc/docker.env' &gt;&gt; ~/.bashrc

printf '#!/bin/bash\n exec ' &gt; /etc/TLshootService.sh

printf '%q ' "$@" &gt;&gt; /etc/TLshootService.sh

chmod +x /etc/TLshootService.sh

mkdir -p /etc/systemd/system/balena.service.d

cat &lt;&lt;-EOF &gt; /etc/systemd/system/balena.service.d/override.conf

[Service]

WorkingDirectory=$(pwd)

EOF

sleep infinity &amp;

exec env DBUS_SYSTEM_BUS_ADDRESS=unix:path=/run/dbus/system_bus_socket /sbin/init quiet systemd.show_status=0

}

function init_non_systemd()

{

# trap the stop signal then send SIGTERM to user processes

trap signal_handler SIGRTMIN+3 SIGTERM

# echo error message, when executable file doesn't exist.

if CMD=$(command -v "$1" 2&gt;/dev/null); then

shift

"$CMD" "$@" &amp;

pid=$!

wait "$pid"

exit_code=$?

fg &amp;&gt; /dev/null || exit "$exit_code"

else

echo "Command not found: $1"

exit 1

fi

}

INITSYSTEM=$(echo "$INITSYSTEM" | awk '{print tolower($0)}')

case "$INITSYSTEM" in

'1' | 'true')

INITSYSTEM='on'

;;

esac

if ["$INITSYSTEM" = "on"]; then

init_systemd "$@"

else

init_non_systemd "$@"

fi
```

---

<div class="post-metadata">

**Author:** ![cyplo](https://sea2.discourse-cdn.com/balena/user_avatar/forums.balena.io/cyplo/32/1224_2.png) [@cyplo](https://forums.balena.io/u/cyplo)\
**Post date:** [February 6, 2019, 12:25pm UTC](https://forums.balena.io/t/container-cant-see-new-dev-tty-device-on-host/5225/10 "2019-02-06T12:25:08Z")

</div>

Hello !

It seems that you’re using the example code from [here](https://github.com/balena-io-projects/kernel-module-build) to build the module - that’s great !  
I’ve noticed that there is an accompanying script there to nudge the module to be loaded - see `run.sh` in the said repo. Could you try explicitly invoking `insmod` from within the container to see if this helps - this is what the said `run.sh` does.

Thanks !

---

<div class="post-metadata">

**Author:** ![daghemo](https://sea2.discourse-cdn.com/balena/user_avatar/forums.balena.io/daghemo/32/531_2.png) [@daghemo](https://forums.balena.io/u/daghemo)\
**Post date:** [February 6, 2019, 1:28pm UTC](https://forums.balena.io/t/container-cant-see-new-dev-tty-device-on-host/5225/11 "2019-02-06T13:28:09Z")

</div>

No need for run.sh, since it has been replaced by my own start.sh. It contains:

```
#!/bin/bash

while [[`lsmod | grep cdc_acm | tr --squeeze-repeats " " | cut --delimiter " " --fields 3` -ne '0']]
do
    echo "cdc_acm in use, waiting..." 2>&1
    sleep 5
done
rmmod cdc_acm && insmod /usr/src/app/epsolar-tracer/xr_usb_serial_common-1a_raspberrypi3_*.prod/xr_usb_serial_common.ko

```

The module has been loaded, that is, the /dev/ttyXRUSB0 can be seen on the host. But I do expect to see the same device within the container, too.

---

<div class="post-metadata">

**Author:** ![rapha](https://sea2.discourse-cdn.com/balena/user_avatar/forums.balena.io/rapha/32/1239_2.png) [@rapha](https://forums.balena.io/u/rapha)\
**Post date:** [February 6, 2019, 1:46pm UTC](https://forums.balena.io/t/container-cant-see-new-dev-tty-device-on-host/5225/12 "2019-02-06T13:46:41Z")

</div>

Are you running the container in privileged mode?

i.e. in a docker-compose.yml there should be  
`privileged=true`

---

<div class="post-metadata">

**Author:** ![daghemo](https://sea2.discourse-cdn.com/balena/user_avatar/forums.balena.io/daghemo/32/531_2.png) [@daghemo](https://forums.balena.io/u/daghemo)\
**Post date:** [February 6, 2019, 2:14pm UTC](https://forums.balena.io/t/container-cant-see-new-dev-tty-device-on-host/5225/13 "2019-02-06T14:14:20Z")

</div>

Yes. No docker-compose.yml here, but the container is running in privileged more.

---

<div class="post-metadata">

**Author:** ![daghemo](https://sea2.discourse-cdn.com/balena/user_avatar/forums.balena.io/daghemo/32/531_2.png) [@daghemo](https://forums.balena.io/u/daghemo)\
**Post date:** [February 6, 2019, 2:15pm UTC](https://forums.balena.io/t/container-cant-see-new-dev-tty-device-on-host/5225/14 "2019-02-06T14:15:04Z")

</div>

@shaunmulligan, I can also grant access to the device, if you need.

---

<div class="post-metadata">

**Author:** ![daghemo](https://sea2.discourse-cdn.com/balena/user_avatar/forums.balena.io/daghemo/32/531_2.png) [@daghemo](https://forums.balena.io/u/daghemo)\
**Post date:** [February 6, 2019, 5:00pm UTC](https://forums.balena.io/t/container-cant-see-new-dev-tty-device-on-host/5225/15 "2019-02-06T17:00:22Z")

</div>

@shaunmulligan, support access granted for one week. See PM for UUID.

---

<div class="post-metadata">

**Author:** ![daghemo](https://sea2.discourse-cdn.com/balena/user_avatar/forums.balena.io/daghemo/32/531_2.png) [@daghemo](https://forums.balena.io/u/daghemo)\
**Post date:** [February 7, 2019, 3:37pm UTC](https://forums.balena.io/t/container-cant-see-new-dev-tty-device-on-host/5225/16 "2019-02-07T15:37:31Z")

</div>

I solved it on my own.

As shown on [https://www.balena.io/docs/reference/base-images/base-images/#installing-your-own-initsystem](https://www.balena.io/docs/reference/base-images/base-images/#installing-your-own-initsystem), latest balenaOS does not come with an INITSYSTEM anymore, so you have to install your own, if needed. Examples are provided, but these do not take into account mounting /dev as devtmpfs!

---

<div class="post-metadata">

**Author:** ![mikesimos](https://sea2.discourse-cdn.com/balena/user_avatar/forums.balena.io/mikesimos/32/1418_2.png) [@mikesimos](https://forums.balena.io/u/mikesimos)\
**Post date:** [April 1, 2019, 8:05am UTC](https://forums.balena.io/t/container-cant-see-new-dev-tty-device-on-host/5225/17 "2019-04-01T08:05:37Z")

</div>

Hi @daghemo.  
The INITSYSTEM examples have been fixed here: [Fix the entry script in INITSYSTEM examples](https://github.com/balena-io-library/base-images/pull/526/files#)  
Cheers!