用grub升级 linux内核 从2.4.20 到 2.4.28 。同事修改一些内核参数

1          优化内核参数

修改下列linux源文件

/usr/src/linux/include/net/tcp.h

/* Change the tcp time_out time from 15 to 5 ( 30 min time_out ) */

#define TCP_RETR2       5

/* decrease the time_wait_length from 60 sec to 20 seconds , but I don’t know where it is used in tcp*.c ,it seems no use */

#define TCP_TIMEWAIT_LEN (20*HZ)

/usr/src/linux/include/linux/limits.h

/* increase the max open files in system and per process */

            #define NR_OPEN         10240

#define OPEN_MAX        8192   /* # open files a process may have */

            /usr/src/linux/include/linux/fs.h

            #define INR_OPEN       32768 

#define NR_FILE  8192   /* this can well be larger on a larger system */

#define NR_SUPER 1024

²          编译内核

cd /usr/src/linux

make mrproper   //整理源代码树, 删除源代码目录中残留的.o文件和其它从属文件。

make menuconfig

Loadable module support à Enable loadable module support  ==  y

Processor type and features à High Memory Support = 4GB

Networking options  ---> IP: TCP syncookie support (disabled per default)  ==y

SCSI support  ---> SCSI CD-ROM support y

SCSI support  ---> SCSI low-level drivers  ---> Adaptec AIC7xxx support  Y 

Network device support  ---> Dummy net driver support   == n

Ethernet (10 or 100Mbit)  à Ethernet (10 or 100Mbit)  == y

Ethernet (1000 Mbit) à Broadcom tigon3 support  ==  Y

File systems à Ext3 journalling file system support ==  Y

File systems à JBD (ext3) debugging support == Y

Sound  --->  Sound card support   n

make dep  //是用于检查依赖关系的, 确保关键文件在正确的位置

make bzImage //编译压缩形式的内核)

make modules

make modules_install

4           修改GRUB  红色是加入的部分，绿色是原来部分，

前提是df看看是否 “/”是sda1

#boot=/dev/sda

default=0         ß修改成，目的是用新的内核启动

timeout=10

splashimage=(hd0,0)/boot/grub/splash.xpm.gz

title Red Hat Linux (2.4.28) 20041228

        root (hd0,0)

        kernel /boot/vmlinuz-2.4.28 ro root=/dev/sda1 hdc=ide-scsi

title Red Hat Linux (2.4.20-8smp)

        root (hd0,0)

        kernel /boot/vmlinuz-2.4.20-8smp ro root=LABEL=/

        initrd /boot/initrd-2.4.20-8smp.img

♣ 建议，由于升级内核会因为机器的具体环境而不同，因此建议在本机用键盘操作，以便升级内核失败之后可以用回原来的内核启动