How to Develop Linux kernel?

How to Develop Linux kernel?
?? How to Develop Linux kernel? Below is the output in Ubuntu:

Root @ myhostname # make
Make: Warning: File 'makefile' has modification time 11 s in the future
Make-C/lib/modules/3.20.- 24-generic/build M =/root modules
Make [1]: Entering directory '/usr/src/linux-headers-3.13.0-24-generic'
Make [2]: Warning: File '/root/Makefile' has modification time 10 s in the future
CC [M]/root/hello-1.o
Make [2]: warning: Clock skew detected. Your build may be incomplete.
Building modules, stage 2.
Make [2]: Warning: File '/root/Makefile' has modification time 8.9 s in the future
MODPOST 1 modules
CC/root/hello-1.mod.o
LD [M]/root/hello-1.ko
Make [2]: warning: Clock skew detected. Your build may be incomplete.
Make [1]: Leaving directory '/usr/src/linux-headers-3.13.0-24-generic'
Make: warning: Clock skew detected. Your build may be incomplete.

~
Root @ myhostname # ls
A B. c hello-1.ko hello-1.o modules. order MyFirstJavaProgram. java
A. c. dns hello-1.mod.c IP.txt Module. symvers SumOfN-thPowersIsAnN-thPower
B hello-1.c hello-1.mod.o Makefile MyFirstJavaProgram. class SumOfN-thPowersIsAnN-thPower.c

~
Root @ myhostname # insmod./hello-1.ko

~
Root @ myhostname # cat/var/log/kern. log
Feb 2 00:48:18 cmt-ub14x64-02 kernel: [8216591.312610] hello_1: module license 'Unspecified 'taints kernel.
Feb 2 00:48:18 cmt-ub14x64-02 kernel: [8216591.312617] Disabling lock debugging due to kernel taint
Feb 2 00:48:18 cmt-ub14x64-02 kernel: [8216591.312641] hello_1: module verification failed: signature and/or required key missing-tainting kernel
Feb 2 00:48:18 cmt-ub14x64-02 kernel: [8216591.313139] Hello world 1.

~
Root @ myhostname # cat/proc/modules
Hello_1 12426 0-Live 0xffffffffffa01e9000 (POF)
Nls_iso8859_1 12713 0-Live 0xffffffffa01e4000
Joydev 17381 0-Live 0xffffffffa0183000
Hid_generic 12548 0-Live 0xffffffffffa01db000
Udfs 89723 0-Live 0xffffffffa01c4000
Crc_itu_t 12707 1 udf, Live 0xffffffffa01bf000
Psmouse 102222 0-Live 0xffffffffa01a5000
Serio_raw 13462 0-Live 0xffffffffa017e000
Hid_hyperv 13059 0-Live 0xffffffffffa012e000
Hyperv_keyboard 12777 0-Live 0xffffffffa00c6000
Hid 106148 2 hid_generic, hid_hyperv, Live 0xffffffffa018a000
Nfsd 280297 2-Live 0xffffffffa0135000
Auth_rpcgss 59338 1 nfsd, Live 0xffffffffa011e000
Nfs_acl 12837 1 nfsd, Live 0xffffffffa00c1000
Nfs 236636 0-Live 0xffffffffa00e3000
Hyperv_fb 17593 1-Live 0xffffffffa00bb000
I2c_piix4 22155 0-Live 0xffffffffa00b0000
Lockd 93977 2 nfsd, nfs, Live 0xffffffffa00cb000
Mac_hid 13205 0-Live 0xffffffffa004f000
Sunrpc 284404 6 nfsd, auth_rpcgss, nfs_acl, nfs, lockd, Live 0xffffffffa0069000
Fscache 63988 1 nfs, Live 0xffffffffa0058000
Lp 17759 0-Live 0xffffffffa0028000
Parport 42348 1 lp, Live 0xffffffffa0043000
Hv_utils 19003 0-Live 0xffffffffa003d000
Hv_storvsc 17785 2-Live 0xffffffffffa0010000
Hv_vmbus 50383 5 hid_hyperv, hyperv_keyboard, hyperv_fb, hv_utils, hv_storvsc, Live 0xffffffffa002f000
Floppy 69370 0-Live 0xffffffffa0016000
Tulip 59672 0-Live 0xffffffffa0000000

~
Root @ myhostname # rmmod hello-1

~
Root @ myhostname # cat/proc/modules
Nls_iso8859_1 12713 0-Live 0xffffffffa01e4000
Joydev 17381 0-Live 0xffffffffa0183000
Hid_generic 12548 0-Live 0xffffffffffa01db000
Udfs 89723 0-Live 0xffffffffa01c4000
Crc_itu_t 12707 1 udf, Live 0xffffffffa01bf000
Psmouse 102222 0-Live 0xffffffffa01a5000
Serio_raw 13462 0-Live 0xffffffffa017e000
Hid_hyperv 13059 0-Live 0xffffffffffa012e000
Hyperv_keyboard 12777 0-Live 0xffffffffa00c6000
Hid 106148 2 hid_generic, hid_hyperv, Live 0xffffffffa018a000
Nfsd 280297 2-Live 0xffffffffa0135000
Auth_rpcgss 59338 1 nfsd, Live 0xffffffffa011e000
Nfs_acl 12837 1 nfsd, Live 0xffffffffa00c1000
Nfs 236636 0-Live 0xffffffffa00e3000
Hyperv_fb 17593 1-Live 0xffffffffa00bb000
I2c_piix4 22155 0-Live 0xffffffffa00b0000
Lockd 93977 2 nfsd, nfs, Live 0xffffffffa00cb000
Mac_hid 13205 0-Live 0xffffffffa004f000
Sunrpc 284404 6 nfsd, auth_rpcgss, nfs_acl, nfs, lockd, Live 0xffffffffa0069000
Fscache 63988 1 nfs, Live 0xffffffffa0058000
Lp 17759 0-Live 0xffffffffa0028000
Parport 42348 1 lp, Live 0xffffffffa0043000
Hv_utils 19003 0-Live 0xffffffffa003d000
Hv_storvsc 17785 2-Live 0xffffffffffa0010000
Hv_vmbus 50383 5 hid_hyperv, hyperv_keyboard, hyperv_fb, hv_utils, hv_storvsc, Live 0xffffffffa002f000
Floppy 69370 0-Live 0xffffffffa0016000
Tulip 59672 0-Live 0xffffffffa0000000

~
Root @ myhostname # cat/var/log/kern. log
Feb 2 00:48:18 cmt-ub14x64-02 kernel: [8216591.312610] hello_1: module license 'Unspecified 'taints kernel.
Feb 2 00:48:18 cmt-ub14x64-02 kernel: [8216591.312617] Disabling lock debugging due to kernel taint
Feb 2 00:48:18 cmt-ub14x64-02 kernel: [8216591.312641] hello_1: module verification failed: signature and/or required key missing-tainting kernel
Feb 2 00:48:18 cmt-ub14x64-02 kernel: [8216591.313139] Hello world 1.
Feb 2 00:53:10 cmt-ub14x64-02 kernel: [8216883.303516] Goodbye world 1.