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fix(network-manager): disable tty output if the console is not usable #1611

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merged 2 commits into from
Oct 21, 2021
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fix(network-manager): disable tty output if the console is not usable #1611

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5ddcd63
fix(network-manager): show output on console only with rd.debug enabled
bengal Sep 27, 2021
aa55f51
fix(network-manager): disable tty output if the console is not usable
bengal Sep 27, 2021
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14 changes: 14 additions & 0 deletions modules.d/35network-manager/nm-config.sh
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Original file line number Diff line number Diff line change
Expand Up @@ -16,6 +16,20 @@ if getargbool 0 rd.debug -d -y rdinitdebug -d -y rdnetdebug; then
echo '[logging]'
echo 'level=TRACE'
) > /run/NetworkManager/conf.d/initrd-logging.conf

if [ -n "$DRACUT_SYSTEMD" ]; then
# Enable tty output if a usable console is found
# See https://github.com/coreos/fedora-coreos-tracker/issues/943
# shellcheck disable=SC2217
if [ -w /dev/console ] && (echo < /dev/console) > /dev/null 2> /dev/null; then
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I assume echo < /dev/console is a test and will fail if the console doesn't work? It seems weird to me to send anything to stdin of echo since it doesn't do anything with it. cat does.

Also:

Suggested change
if [ -w /dev/console ] && (echo < /dev/console) > /dev/null 2> /dev/null; then
if [ -w /dev/console ] && (echo < /dev/console) &> /dev/null; then

I think this is equivalent with less characters.

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@bengal bengal Oct 14, 2021 •
edited
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I assume echo < /dev/console is a test and will fail if the console doesn't work? It seems weird to me to send anything to stdin of echo since it doesn't do anything with it. cat does.

I copied this code from https://github.com/dracutdevs/dracut/blob/055/modules.d/99shutdown/shutdown.sh#L15

The idea is to try to open the console via shell redirection, but don't actually read or write anything from/to it. If /dev/console can't be opened, the command returns a non-zero value which is interpreted as false.

I think this is equivalent with less characters.

The interpreter of this script is /bin/sh, so it must be POSIX compatible.
&> is a bashism and is not POSIX.

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Thanks for the reply/explanation.

mkdir -p /run/systemd/system/nm-initrd.service.d
cat << EOF > /run/systemd/system/nm-initrd.service.d/tty-output.conf
[Service]
StandardOutput=tty
EOF
systemctl --no-block daemon-reload
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any implications of running this daemon-reload here? If we ran this as part of a systemd generator would we need to do the daemon-reload?

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I'm not aware of any side effect of calling daemon-reload here.

A generator would be an alternative and wouldn't require a daemon-reload; I think it requires to ship new service and a script. I like how the current code is self-contained, but I have no objections in turning it into a generator if that's the general consensus.

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@lucab - any thoughts here on the tradeoffs?

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Yes, reloading in the middle of a boot isn't the nicest, a generator would be advisable.
I don't think it directly breaks anything so not strictly a problem, but may trigger some unexpected second-order effects.
For reference, I see there are some dracut modules already shipping a generator in this repository, like modules.d/95nbd/.

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Agree a generator would be slightly cleaner and would make a good follow-up, but if this is already tested IMO it's not worth the respin.

fi
fi
fi

nm_generate_connections
4 changes: 3 additions & 1 deletion modules.d/35network-manager/nm-initrd.service
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Original file line number Diff line number Diff line change
Expand Up @@ -17,7 +17,9 @@ BusName=org.freedesktop.NetworkManager
ExecReload=/usr/bin/busctl call org.freedesktop.NetworkManager /org/freedesktop/NetworkManager org.freedesktop.NetworkManager Reload u 0
ExecStart=/usr/sbin/NetworkManager --debug
KillMode=process
StandardOutput=tty
# The following gets changed to StandardOutput=tty by nm-config.sh
# when debug is enabled and a usable console is found.
StandardOutput=null
Environment=NM_CONFIG_ENABLE_TAG=initrd
Restart=on-failure
ProtectSystem=true
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