Startup Script

Where Startup Scripts Go

/var/lib/webosbrew/init.d. Executable scripts there are run at startup by run-parts, in sorted order.

Two rules that bite:

• A filename may only contain a-zA-Z0-9-_. Anything else and run-parts skips it without a word.
• The directory is not guaranteed to exist. Some root exploits never created it, RootMyTV v1 among them. Make it before you use it.

Symlink, Do Not Copy

If your app ships the script, put a symlink in init.d pointing back into the app directory. Copy it and the script stays behind when the user removes your app, still running at every boot.

Name the link with a two digit prefix for ordering, then something identifying you.

mkdir -p /var/lib/webosbrew/init.d && ln -sf /media/developer/apps/usr/palm/applications/your.app.id/our-startup-script.sh /var/lib/webosbrew/init.d/50-yourappid

Removing it is the mirror image:

rm -rf /var/lib/webosbrew/init.d/50-yourappid

Both are safe to run twice, which matters because your app cannot assume the state it last left. custom-screensaver shows an app wiring this to its own install and remove.

Write a Script

The script custom-screensaver ships is a good shape to copy. It mounts one QML file over the launcher's, and does nothing else.

#!/bin/sh

set -e -o pipefail

MOUNT_TARGET="/usr/palm/applications/com.webos.app.screensaver/qml/main.qml"
QML_PATH="$(dirname "$(realpath "$0")")/screensaver-main.qml"

if [[ ! -f "$MOUNT_TARGET" ]]; then
    echo "[-] Target file does not exist: $MOUNT_TARGET" >&2
    exit 1
fi

if ! findmnt "$MOUNT_TARGET"; then
    mount --bind "$QML_PATH" "$MOUNT_TARGET"
    echo "[+] Enabled succesfully" >&2
else
    echo "[~] Enabled already" >&2
fi

Four things in there are worth copying:

• Find your own files through realpath "$0". The script runs from a symlink in init.d, so $0 is that link. Resolve it to reach the assets next to the real script.
• Check before you act. findmnt tells you the mount is already there, so running twice is harmless. Your script will run again.
• Give up if the target is missing. A file that existed on one webOS release may not on the next. Fail with a message rather than mounting over nothing.
• Write to stderr. Say what you did and why you stopped. Nothing captures it on its own, so pair it with the redirect below, and it becomes the only account you get.

Read the Output

There is no log. The Homebrew Channel starts the whole chain with nohup sh /var/lib/webosbrew/startup.sh & and then runs your script with run-parts /var/lib/webosbrew/init.d. Neither captures anything. Your script inherits whatever stdout and stderr early boot happened to hand it, and nothing is keeping them.

So redirect the output yourself. First line of your script:

exec >>/var/lib/webosbrew/myscript.log 2>&1

Everything printed after that lands in the file, stderr included.

Use /var/lib/webosbrew/ rather than /tmp if you want to compare one boot against the last. /tmp is writable too, and cleared on every boot, which loses the log of the boot that went wrong.

Troubleshooting

rm -f /var/luna/preferences/webosbrew_failsafe && sync -f /var/luna/preferences