How can I run a script on boot?

Question

I'm accustomed to running scripts on boot in Linux, but I'm not sure how to do this in Android. I'd like to start my SSH daemon on start, so I'll always be able to connect. How can I run an arbitrary script on Android boot? It'd be preferable to do this outside of Dalvik.

Answer 1

While looking around my Android filesystem, I found that it did, in fact have a /etc/init.d/ directory. After peeking around in there, I found /etc/init.d/20userinit with the following lines:

if [ -e /data/local/userinit.sh ];
then 
    log -p -i -t userinit "Executing /data/local/userinit.sh";
    busybux chmod +x /data/local/userinit.sh;
    logwrapper /system/bin/sh /data/local/userinit.sh;
    setprop cm.userinit.active 1;
fi;

This being, of course, exactly what I needed, I wrote the following script on my computer then pushed it to my device:

#!/system/bin/sh 

dropbear -s -g 

(pushed to device via scp userinit.sh phone:/data/local/userinit.sh, mind you :] )

Rebooted the device, then ran ps | grep "[d]ropbear", and sure enough, it's running. Coolness!

Answer 2

/data/init.sh runs at boot, if you have root you can edit it as you like. Be careful ;)

Edit: Apparently you might need to shoehorn the edited script into the boot image as well. Info on how to do that here: http://forum.xda-developers.com/showthread.php?t=443994

Answer 3

Look to /etc/ directory. Usually it is placed in /system/ partition which you can mount as RW:

$ ls -l /etc
lrwxrwxrwx 1 root root 11 Jan 1  2009 /etc -> /system/etc
$ su
$ mount -o remount,rw /system
$ chmod o+w /system/etc  # for "adb push"

Some above steps may be replaces with:

$ adb root
$ adb remount

and later remount RO:

$ chmod o-w /system/etc
$ mount -o remount,ro /system

Now your task to find executable or *rc file which you modify to achieve your goal:

$ find /etc -type f -perm +110
$ find /etc -name "*rc"
$ find /etc -name "init*"
$ grep -R /data /etc
$ grep -R /system /etc

Google about each candidate to get know how this file was used.

Good candidate for including custom scripts are lines from:

$ grep service /init*.rc

As each device unique you may need to do own guess about search criteria...

For example I found /etc/mkshrc which used by Korn shell. I update this file to extend PATH env var and now each time I do adb shell I have Busybox symlinks in my PATH!

See also hard way (if you have no luck with finding magic file): https://stackoverflow.com/questions/9768103/make-persistent-changes-to-init-rc

Answer 4

I tried all these methods and none of them worked for me. What worked however was based on lord-ralf-adolf's answer here How to run a script on boot in CM12.1?

basically, find the file /system/etc/install-recovery.sh and add the following line at the beginning /data/init.sh &

then

touch /data/init.sh
chmod 755 /data/init.sh

Done! You can now put whatever you want in /data/init.sh and it will run on startup. If the file /system/etc/install-recovery.sh is not in your system then this answer won't work for you. Don't bother creating it.

Answer 5

If you have magisk installed you can place the .sh to:

/sbin/.magisk/img/.core/service.d/

or to

/sbin/.magisk/img/.core/post-fs-data.d/

Don't forget to make it executable: chmod +x your-script.sh.

More info: https://github.com/topjohnwu/Magisk/blob/master/docs/guides.md#boot-scripts

Answer 6

Things were simple before Android 5 when SELinux wasn't enforcing. You could put your code in any script or replace a binary with script which was executed with root privileges on boot. Another method was to define a custom init service specifically to batch execute scripts from some directory.

Based on these approaches custom ROM developers introduced different pseudo-init.d phenomenon like /etc/init.d/, /etc/install-recovery.sh, /etc/init.qcom.post_boot.sh, /system/bin/debuggerd, /data/init.sh, /data/local/userinit.sh, /data/local/init.d/ etc.

However a process running with UID 0 but in a restricted SELinux context is quite helpless. A service started in init.rc file with u:r:init:s0 context can't even execute a shell script from /system/bin/, so SELinux policy needs to be patched to inject an unrestricted context e.g. Magisk defines u:r:magisk:s0. After that it's possible to run a script directly as init service or from init.d-like directory.

For details see How to run an executable on boot and keep it running?

Answer 7

Simple way (working):

1. Prepare your post boot commands in a script, say /system/xbin/post-boot (set exec perm)

2. Add the above custom script path at the end of /system/etc/init.qcom.post_boot.sh

Eg:

echo /system/xbin/post-boot >> /system/etc/init.qcom.post_boot.sh

Done!

(If you can't find the qcom post_boot (Qualcomm devices), look for any post_boot scripts)