Managing CentOS/RHEL kernel modules.

Check current OS modules

# lsmod

 

Check modules detail info

# modinfo  st

filename:       /lib/modules/2.6.32-279.22.1.el6.x86_64/kernel/drivers/scsi/st.ko

alias:          scsi:t-0x01*

alias:          char-major-9-*

license:        GPL

description:    SCSI tape (st) driver

author:         Kai Makisara

srcversion:     782F465A959216B1E70B888

depends:

vermagic:       2.6.32-279.22.1.el6.x86_64 SMP mod_unload modversions

parm:           buffer_kbs:Default driver buffer size for fixed block mode (KB; 32) (int)

parm:           max_sg_segs:Maximum number of scatter/gather segments to use (256) (int)

parm:           try_direct_io:Try direct I/O between user buffer and tape drive (1) (int)

parm:           try_rdio:Try direct read i/o when possible (int)

parm:           try_wdio:Try direct write i/o when possible (int)

 

# modinfo -p st            #Only check module st paremeters

try_wdio:Try direct write i/o when possible

try_rdio:Try direct read i/o when possible

try_direct_io:Try direct I/O between user buffer and tape drive (1)

max_sg_segs:Maximum number of scatter/gather segments to use (256)

buffer_kbs:Default driver buffer size for fixed block mode (KB; 32)

 

Load module

# lsmod |grep st

stp                     2173  1 garp

llc                     5546  2 garp,stp

# modprobe st

# lsmod |grep st

st                     38302  0

stp                     2173  1 garp

llc                     5546  2 garp,stp

 

Unload module

# rmmod st

# lsmod |grep st

stp                     2173  1 garp

llc                     5546  2 garp,stp

 

Set default modules parameters

1. Check module's default parameter value

a. Load modules

# modprobe usb_storage

# modprobe st

# modprobe sx8

 

b. Get module's parameter info

# modinfo -p usb_storage

quirks:supplemental list of device IDs and their quirks

delay_use:seconds to delay before using a new device

swi_tru_install:TRU-Install mode (1=Full Logic (def), 2=Force CD-Rom, 3=Force Modem)

option_zero_cd:ZeroCD mode (1=Force Modem (default), 2=Allow CD-Rom

 

# modinfo -p st

try_wdio:Try direct write i/o when possible

try_rdio:Try direct read i/o when possible

try_direct_io:Try direct I/O between user buffer and tape drive (1)

max_sg_segs:Maximum number of scatter/gather segments to use (256)

buffer_kbs:Default driver buffer size for fixed block mode (KB; 32)

 

# modinfo -p sx8

max_queue:Maximum number of queued commands. (min==1, max==30, safe==1)

 

c. Check the default value

# cat /sys/module/usb_storage/parameters/delay_use

1

 

# cat /sys/module/sx8/parameters/max_queue

1

 

2. Modify the default value

a. Set parameter value

# cat /etc/modprobe.d/my.conf

options usb_storage delay_use=3

options sx8 max_queue=15

options st buffer_kbs=256

 

b. Reload modules

# rmmod st

# rmmod sx8

# rmmod usb_storage

# modprobe st

# modprobe sx8

# modprobe usb_storage

 

c. Check you changed value

# cat /sys/module/usb_storage/parameters/delay_use

3

# cat /sys/module/sx8/parameters/max_queue

15

 

3. Set module auto-start with modified parameter

系统是如何自动加载模块呢，我们在/etc/rc.sysinit启动文件中看到下面内容。在系统启动过程中会自动的执行/etc/sysconfig/modules/下所有以.modules结尾的文件。那么我们也可以在该目录下编写自定义的脚本，在配合/etc/modprobe.d/my.conf设置的参数，就可以实现我们设置的参数开机自启动了。

# Load other user-defined modules

for file in /etc/sysconfig/modules/*.modules ; do

  [ -x $file ] && $file

done

 

a. Create self-definition script

# cat /etc/sysconfig/modules/my.modules

modprobe st

modprobe sx8

modprobe usb_storage

 

b. Do not forget add execute permission

# chmod a+x /etc/sysconfig/modules/my.modules

# ls -l /etc/sysconfig/modules/my.modules

-rwxr-xr-x 1 root root 46 Aug 22 09:09 /etc/sysconfig/modules/my.modules

 

4. Disable ipv6 module on RHEL/CentOS 5.

Modify below to files.

/etc/modprobe.conf - Kernel driver configuration file.

/etc/sysconfig/network - RHEL / CentOS networking configuration file.

 

a. Edit /etc/modprobe.conf, and append the following line:

# vi /etc/modprobe.conf

install ipv6 /bin/true

 

b. Edit /etc/sysconfig/network, and update / add as follows:

# vi /etc/sysconfig/network

 

NETWORKING_IPV6=no
IPV6INIT=no

c. Restart network service.

# service network restart

# rmmod ipv6

 

Alternatively, simple reboot the box:

# reboot

 

d. Verify IPv6 is disabled, enter:

# lsmod | grep ipv6

# /sbin/ifconfig

 

5. Disable ipv6 module on RHEL/CentOS 6.

a.Edit /etc/sysconfig/network, and update / add as follows:

NETWORKING_IPV6=no

 

b. Modify file /etc/hosts, and comment out below line：

#::1   localhost localhost6 localhost6.localdomain6

 

c. Restart network service.

# service network restart

# rmmod ipv6

 

d. Disable auto enable across OS reboot. And below contents in file /etc/modprobe.d/ipv6off.conf.

alias net-pf-10 off

options ipv6 disable=1