Subject: Re: How to wake up the WiFi on a Zero 2W (it was working but has stopped)

On 18/03/2026 12:55, Chris Green wrote:

I have a new[ish] Pi Zero 2W running in a building close to our house
(close means about 30 yards away). When I installed it I configured
one of the possible WiFi SSIDs with rpi-imager, then after installing
I added the other possible SSID (using nmcli I think).

It has run quite happily for a few days but as of yesterday afternoon
shows no sign of being connected.

I have tried restarting it, no effect. I have checked both of the
routers it might connect to and they're both running and haven't
moved. I've even moved one of them into what is effectively line of
sight to the Zero 2W. Still no connection.

What might be wrong and what can I do to get it to connect?

Bring it in and put a terminal and keyboard on it so you can look at the
logs.

I have a 30 metre pi Pico and it connects anywhere between -80dM and
'not at all' for no visible reason - maybe its leaves blowing in the
wind. I dunno.

Right now its a happy little -84dBm. Its having a good day.

30 metres is pretty tough for a pi.


--
Ideas are more powerful than guns. We would not let our enemies have
guns, why should we let them have ideas?

Josef Stalin


--- PyGate Linux v1.5.13
* Origin: Dragon's Lair, PyGate NNTP<>Fido Gate (3:633/10)

Subject: Re: How to wake up the WiFi on a Zero 2W (it was working but has stopped)

Chris Green <cl@isbd.net> wrote:

The Natural Philosopher <tnp@invalid.invalid> wrote:

On 18/03/2026 12:55, Chris Green wrote:

I have a new[ish] Pi Zero 2W running in a building close to our house (close means about 30 yards away). When I installed it I configured
one of the possible WiFi SSIDs with rpi-imager, then after installing
I added the other possible SSID (using nmcli I think).

It has run quite happily for a few days but as of yesterday afternoon shows no sign of being connected.

I think I have discovered the problem, the SD card is faulty/wearing
out. I just tried to boot the system with a display attached and it
sits repeating an error message about "bcm2835 timeout waiting for
hardware interrupt".

Putting the card in a reader in my desktop machine it gets read
**very** slowly and times out before the automount completes.

I think a (some?) new SD card is on the agenda! :-)

--
Chris Green
ú

--- PyGate Linux v1.5.13
* Origin: Dragon's Lair, PyGate NNTP<>Fido Gate (3:633/10)

Subject: Re: How to wake up the WiFi on a Zero 2W (it was working but has stopped)

On 18/03/2026 15:45, Chris Green wrote:

Chris Green <cl@isbd.net> wrote:

The Natural Philosopher <tnp@invalid.invalid> wrote:

On 18/03/2026 12:55, Chris Green wrote:

I have a new[ish] Pi Zero 2W running in a building close to our house
(close means about 30 yards away). When I installed it I configured
one of the possible WiFi SSIDs with rpi-imager, then after installing
I added the other possible SSID (using nmcli I think).

It has run quite happily for a few days but as of yesterday afternoon
shows no sign of being connected.

I think I have discovered the problem, the SD card is faulty/wearing
out. I just tried to boot the system with a display attached and it
sits repeating an error message about "bcm2835 timeout waiting for
hardware interrupt".

Putting the card in a reader in my desktop machine it gets read
**very** slowly and times out before the automount completes.

I think a (some?) new SD card is on the agenda! :-)

Somewhere in my documentation is what I did to my pi zero in order to
avoid any SD card writes at all

Basically I created a ram disk and mounted it on /var/log. And disabled systemd as much as possible.

Then ensure the SD card is mounted with noatime etc.


--
It is the folly of too many to mistake the echo of a London coffee-house
for the voice of the kingdom.

Jonathan Swift



--- PyGate Linux v1.5.13
* Origin: Dragon's Lair, PyGate NNTP<>Fido Gate (3:633/10)

Subject: Re: How to wake up the WiFi on a Zero 2W (it was working but has stopped)

On 18/03/2026 13:56, Chris Green wrote:

The Natural Philosopher <tnp@invalid.invalid> wrote:

On 18/03/2026 12:55, Chris Green wrote:

I have a new[ish] Pi Zero 2W running in a building close to our house
(close means about 30 yards away). When I installed it I configured
one of the possible WiFi SSIDs with rpi-imager, then after installing
I added the other possible SSID (using nmcli I think).

It has run quite happily for a few days but as of yesterday afternoon
shows no sign of being connected.

I have tried restarting it, no effect. I have checked both of the
routers it might connect to and they're both running and haven't
moved. I've even moved one of them into what is effectively line of
sight to the Zero 2W. Still no connection.

What might be wrong and what can I do to get it to connect?

Bring it in and put a terminal and keyboard on it so you can look at the
logs.

That's not very easy, it's a bit of a 'fixed' installation. It might
be easier to move one of the routers nearer to it.

Well keyboards are portable enough. HDMI screen - not so much.

I have a 30 metre pi Pico and it connects anywhere between -80dM and
'not at all' for no visible reason - maybe its leaves blowing in the
wind. I dunno.

Right now its a happy little -84dBm. Its having a good day.

30 metres is pretty tough for a pi.

I just checked the WiFi signal strength using an Android tablet right
next to the Pi Zero and the better of the two SSIDs is around -70dBM
so it **should** be OK I would have thought.

I get up to 20dB variation. Try rebooting it and see if you can get it
back on target
--
Climate is what you expect but weather is what you get.
Mark Twain


--- PyGate Linux v1.5.13
* Origin: Dragon's Lair, PyGate NNTP<>Fido Gate (3:633/10)

Subject: Re: How to wake up the WiFi on a Zero 2W (it was working but has stopped)

On 2026-03-18, The Natural Philosopher <tnp@invalid.invalid> wrote:

Somewhere in my documentation is what I did to my pi zero in order to
avoid any SD card writes at all

Basically I created a ram disk and mounted it on /var/log. And disabled systemd as much as possible.

Then ensure the SD card is mounted with noatime etc.

If you replace /sbin/init (usually symlinked to /lib/systemd/systemd) with a bash script you get to run in a truly read-only environment (root filesystem still mounted ro). Of course nothing in userland works at that point, so
your script has to do some initialisation - setting up a ramdisk for a copuple of directories, as you said, mounting procfs, creating some device nodes, configuring IP, loading kernel modules if you need them (e.g. for wifi).
Useful for small applications (forget running a GUI, obv.).

Brutal, but effective. Here's an example:

----------------------------------------------------------------------------
# cat init-ro
#!/bin/bash

clear
echo "Running ${0}..."


#
# Config...
#

source /etc/ro-config

export OUR_BC="${OUR_IP%.*}.255"
export OUR_GW="${OUR_IP%.*}.1"


#
# Need to set these so we can prime PS1 for bash...
# (see nonsense in /etc/bash.bashrc)...
#

export SUDO_USER=0
export SUDO_PS1="-"


#
# Mount tmpfs filesystems on /run and /tmp,
# as these need to be rw...
#

mount -t tmpfs -o size=256m tmpfs /run
mount -t tmpfs -o size=10m tmpfs /tmp

mkdir /run/lock
mkdir /run/log


#
# Need /dev/pts for ssh...
#

mkdir /dev/pts
mount -t devpts devpts /dev/pts


#
# Need loopback...
#

ifconfig lo up


#
# Need /proc...
#

mount -t proc none /proc


#
# Set host name and domain name...
#

hostname "${OUR_HOSTNAME}"
domainname "${OUR_HOSTNAME#*.}"


#
# If wifi, set up the wireless interface...
#

[ "${WIRED}" != "1" ] && /ro/init-wifi


#
# Wait for interface to appear before
# configuring it...
#

while [ ! -d "/proc/sys/net/ipv4/conf/${OUR_IF}/" ]
do
echo "Waiting for interface \"${OUR_IF}\"..."
sleep 1
done


#
# Bring the interface up...
#

ip link set "${OUR_IF}" up


#
# Check if the MAC address matches the config. If not, don't
# bring up the network, just pop up a shell to allow the config
# to be updated (allows cloning of the image)...
#

real_eth="$(ip addr list ${OUR_IF} | awk '/link\/ether/ {print $2}')"

if [ "${real_eth^^}" != "${OUR_ETH^^}" ]
then
echo "This MAC address (${real_eth^^}) doesn't match config (${OUR_ETH^^})"
echo ""
echo "Please edit config and reboot..."
echo ""

cd /ro
mount -o remount,rw /dev/root /

PS1="RW-SHELL \h:\w# " /bin/bash

reboot -f
fi


#
# Set the IP address and default route...
#

echo "Setting IP address for ${OUR_IF}: ${OUR_IP}/24, gw: ${OUR_GW}"

ip addr add "${OUR_IP}/24" brd "${OUR_BC}" dev "${OUR_IF}"
ip route add 0/0 via "${OUR_GW}"


#
# Wait for network, check by pinging our default gateway...
#

while ! ping -c 1 -q -w 1 "${OUR_GW}" > /dev/null 2>&1
do
echo "Waiting for network, ping gw (${OUR_GW})..."
sleep 1
done


#
# Start ntpd to get the time...
#

echo "Starting ntpd..."

/usr/sbin/ntpd -g

echo "Waiting for time sync..."
ntp-wait -n 30 -s 1
date


#
# Start sshd
#

echo "Starting sshd..."

mkdir /run/sshd
/usr/sbin/sshd


#
# Now start application screen sessions...
#

echo "Starting applications..."

cd /ro

./start-screens


#
# Shell for testing...
#

while true
do
PS1="RO-SHELL \h:\w# " /bin/bash
done


#
# We can't exit from init (causes kernel panic), so force a reboot if we get here...
#

reboot -f

----------------------------------------------------------------------------

--
Ian

"Tamahome!!!" - "Miaka!!!"

--- PyGate Linux v1.5.13
* Origin: Dragon's Lair, PyGate NNTP<>Fido Gate (3:633/10)

Subject: Re: How to wake up the WiFi on a Zero 2W (it was working but has stopped)

The Natural Philosopher <tnp@invalid.invalid> wrote:

On 18/03/2026 12:55, Chris Green wrote:

I have a new[ish] Pi Zero 2W running in a building close to our house (close means about 30 yards away). When I installed it I configured
one of the possible WiFi SSIDs with rpi-imager, then after installing
I added the other possible SSID (using nmcli I think).

It has run quite happily for a few days but as of yesterday afternoon
shows no sign of being connected.

I have tried restarting it, no effect. I have checked both of the
routers it might connect to and they're both running and haven't
moved. I've even moved one of them into what is effectively line of
sight to the Zero 2W. Still no connection.

What might be wrong and what can I do to get it to connect?

Bring it in and put a terminal and keyboard on it so you can look at the logs.

That's not very easy, it's a bit of a 'fixed' installation. It might
be easier to move one of the routers nearer to it.

I have a 30 metre pi Pico and it connects anywhere between -80dM and
'not at all' for no visible reason - maybe its leaves blowing in the
wind. I dunno.

Right now its a happy little -84dBm. Its having a good day.

30 metres is pretty tough for a pi.

I just checked the WiFi signal strength using an Android tablet right
next to the Pi Zero and the better of the two SSIDs is around -70dBM
so it **should** be OK I would have thought.

--
Chris Green
ú

--- PyGate Linux v1.5.13
* Origin: Dragon's Lair, PyGate NNTP<>Fido Gate (3:633/10)

Subject: Re: How to wake up the WiFi on a Zero 2W (it was working but has stopped)

On Wed, 18 Mar 2026 17:48:19 -0000 (UTC), Ian wrote:

# Need /proc...

Don?t you need udev on /dev, and sysfs on /sys, as well?

--- PyGate Linux v1.5.13
* Origin: Dragon's Lair, PyGate NNTP<>Fido Gate (3:633/10)