How can I replace a system file

[Mino101]

I am trying to replace a jar under /opt/amazon/ebook/lib from within kindle root terminal (KOReader SSH server) but getting

rm: can't remove '....jar': Read-only file system
How can I do it ?

[slycat]

Just out of curiosity: what do you mean to achieve by modifying that .jar?

When you first connect there is usually a message from dropbear/SSH that says

Rootfs is mounted read-only. Invoke mntroot rw to switch back to a writable rootfs.

That should let you have full reign
The specific file or folder may also be immutable if that does not work

lsattr <dir/file>

and see if you see a lower case "i" in the results. If there is you can then remove the attribute with

chattr -i <dir/file>

[mergen3107]

Also, make sure to
- make backups!
- remember original files' permissions
- make sure to restore the same permissions if they are different after replacement

Generally be careful with system files, Kindles are fragile and take ANY excuse to go into unboot-loop.

Make sure you have your USBNet auto-starting so you can have a chance to change files if it goes into this unboot-loop.

[Mino101]

Originally Posted by slycat

Just out of curiosity: what do you mean to achieve by modifying that .jar?

Trying to find an answer to my own question. Otherwise thanks for the info!

Originally Posted by mergen3107

Also, make sure to
- make backups!
- remember original files' permissions
- make sure to restore the same permissions if they are different after replacement

Generally be careful with system files, Kindles are fragile and take ANY excuse to go into unboot-loop.

Make sure you have your USBNet auto-starting so you can have a chance to change files if it goes into this unboot-loop.

Thanks for the advice! Are these steps really necessary when tampering non critical *.jar files ? I mean, I'm just trying to add some minor features in the built-in reader. And about USBNet, the latest one failed to install from MRI with some message like "script encountered error while running", I guess it isn't compatible with firmware 5.17.x yet. I am using the integrated SSH server in KOReader as a replacement

[mergen3107]

As I said, Kindle firmware is fragile
What you think is not critical, might actually brick it for good.

You need usbnetlite from Marek: https://fw.notmarek.com/khf/

Here be dragons!

[Mino101]

Originally Posted by mergen3107

As I said, Kindle firmware is fragile
What you think is not critical, might actually brick it for good.

You need usbnetlite from Marek: https://fw.notmarek.com/khf/

Here be dragons!

Thanks, I'll set it up as soon as I get my simple test running. So after mounting rootfs to be writable, I was able to replace the target *.jar file and restore the exact permissions (modified a string resource that I know where to find) but even after reboot I see no effect, even though I verified that the files are actually still replaced. Maybe the original files are cached somewhere ? Isn't the ereader code under /opt/amazon/ebook, or is there another location ?

[mergen3107]

Have you found older tweaks were people modified margins?

It was a long time ago, but I vaguely remember that /opt/* stuff is a factory stock stuff.

I'll have a look later how I did it, although on 5.9.7 on PW3

[Mino101]

I trying modifying another resource somewhere else and it worked!

I wonder why the original resource replacement didn't work (I modified a string under /opt/amazon/ebook/lib/wikipedia.jar)