Root Questions

[riffdex]

I've got some questions, I did search and found no answers.

1) What is the difference between kernel and a ROM? How do I know what kernel I am on? I know I am running the SholesMod ROM, but I am considering changing to another ROM. I seem to have FC's quite often and am trying to fix that. If I want to change a ROM will I need to change the kernel to make sure they are compatible?

2) I have SP Recovery installed. Is this part of the kernel? Is this installed in a separate place from the kernel/ROM? I'd like to feel assured that if I am installing a new kernel/ROM and something goes wrong, I don't have to worry about my SP Recovery being affected. But should I?

3) Nandroid backup... does this include everything on the device? Kernel, ROM, AND Recovery Mode?

I'm a newbie to hacking the Droid, but back in my PSP days, I know that the Recovery mode was stored on the same drive as the system files, and if you make a misstep when flashing a new firmware, you could lose recovery access. I'm just wondering where the recovery is located in the phones file system, and if I should really be concerned when flashing ROMs/kernels. Also, is there any way I could redirect it to load recovery from the memory stick, if the default recovery cannot load, just as a failsafe? Or if I lose recovery, could I somehow flash a new recovery via USB?

 

[vincentp]

1) A kernel is baseline code for the phone that lets the software communicate with the hardware. It makes the most difference in the phones actual speed and basic capabilities. A ROM is just a collection of applications, themes and tweaks. You can freely change kernels as long as they are compatible with the correct version of the OS for the ROM you are running. For instance, don't use a kernel intended for 2.0.1 ROMs if you have a 2.1 ERE25 based ROM on your phone.

2) SPRecovery is something completely separate from ROMs and Kernels. It's just the recovery console and will not be replaced if you change a kernel or ROM, though you can update it by flashing a new recovery image if another version is released.

3) Nandroid backup backs up (usually) your system, data and boot partitions, so basically all of the settings of your actual ROM with your data (texts, calls, etc) and whatever kernel you currently have installed.

Unlike on the PSP, the recovery console is not affected by changing a ROM or kernel. It is not stored on any of the partitions that are wiped during a factory reset or nandroid restore. I believe it's a separate image flashed to a part of the phone designed specifically for recovery.

Your best failsafe if something ever goes wrong is just to go back to a completely stock Droid using the SBF method in http://androidforums.com/all-things-root-droid/47349-now-you-can-live-without-fear-bricking.html this thread. Then you can just reroot, reflash SPRecovery and start over. It shouldn't ever really come to this though if you're just swapping ROMs and kernels. You can pretty much do that all you want, just make sure you have at least one (ideally several) stable nandroid backups to restore to should you run into any issues.

 

[riffdex]

1) A kernel is baseline code for the phone that lets the software communicate with the hardware. It makes the most difference in the phones actual speed and basic capabilities. A ROM is just a collection of applications, themes and tweaks. You can freely change kernels as long as they are compatible with the correct version of the OS for the ROM you are running. For instance, don't use a kernel intended for 2.0.1 ROMs if you have a 2.1 ERE25 based ROM on your phone.

2) SPRecovery is something completely separate from ROMs and Kernels. It's just the recovery console and will not be replaced if you change a kernel or ROM, though you can update it by flashing a new recovery image if another version is released.

3) Nandroid backup backs up (usually) your system, data and boot partitions, so basically all of the settings of your actual ROM with your data (texts, calls, etc) and whatever kernel you currently have installed.

Unlike on the PSP, the recovery console is not affected by changing a ROM or kernel. It is not stored on any of the partitions that are wiped during a factory reset or nandroid restore. I believe it's a separate image flashed to a part of the phone designed specifically for recovery.

Your best failsafe if something ever goes wrong is just to go back to a completely stock Droid using the SBF method in http://androidforums.com/all-things-root-droid/47349-now-you-can-live-without-fear-bricking.html this thread. Then you can just reroot, reflash SPRecovery and start over. It shouldn't ever really come to this though if you're just swapping ROMs and kernels. You can pretty much do that all you want, just make sure you have at least one (ideally several) stable nandroid backups to restore to should you run into any issues.

1) To be honest I have no idea what kernel I am running. When I rooted my phone I used the SholeMod Updater, I assume it installed a custom 2.1 kernel, but I don't know for sure >.< Last night I decided to install Smoked Glass 5.0.1 because of all the hype. It does look pretty nice I suppose, I don't know if this installer installed a new kernel or if it kept to the one I had before.

2) Awesome! I was afraid that I could possibly compromise my recovery console when ROMing. Apparently that is not a concern! Are there a lot of alternative Recovery consoles? I'd like it if there was just one version, to ensure compatibility. I'd hate to have to reflash my recovery constantly to keep up to date. >.<

3) So is the kernel under the boot partition, while the ROM data is under system/data? Or am I just completely offbase in this assumption? >.< Bleh when I installed Smoked Glass 5.0.1 I lost my text messages. I suppose if I really want them back, I would be able to reflash my nandroid backup and get them back?

Thanks a lot for explaining this in a way I can understand, by comparing it to the PSP. I'm glad the recovery console is separate from the ROM/Kernels that I will probably be flashing pretty often. Thanks again for all the help!

 

[vincentp]

A custom ROM installer will almost always (In fact I would say always) install its own kernel. After that you can change it if you want, but if you switched to Smoked Glass then you're probably running the kernel it comes with.

There aren't really multiple recoveries. It's basically just SPRecovery 0.99.2b that everyone is using. I believe there might be an update to 0.99.3 but there's not much difference, and everything is generally built and intended to be used with SPRecovery 0.99.2b. It's a pretty well contained ecosystem so you don't have to mess with changing the recovery image.

I'm not sure where exactly the kernel is stored on the filesystem to be honest. It would make sense that it's in the boot partition since the kernel needs to be loaded on boot for anything to work. The ROM apps and system settings are under /system, while /data generally contains all of your application data.

Glad I could help