Linux

turn off fans in linux

作者

after running 'sensors-detect' command, kernel modules controlling fan speed will be loaded.

here is an occasion with 'Nuvoton NCT6102D/NCT6104D/NCT6106D Super IO Sensors' detected.

as nct6775 document said:

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#/sys/class/hwmon/hwmon4
pwm[1-7]
    - this file stores PWM duty cycle or DC value (fan speed) in range:
	   0 (lowest speed) to 255 (full)
 
pwm[1-7]_enable
    - this file controls mode of fan/temperature control:
	* 0 Fan control disabled (fans set to maximum speed)
	* 1 Manual mode, write to pwm[0-5] any value 0-255
	* 2 "Thermal Cruise" mode
	* 3 "Fan Speed Cruise" mode
	* 4 "Smart Fan III" mode (NCT6775F only)
	* 5 "Smart Fan IV" mode
...

ps. if set pwm[1-7]_enable to 0, you will not be able to change it to other value, unless reboot linux.

refer to:
[linux-kernel-src-root]/Documentation/hwmon/nct6775.rst
https://bbs.archlinux.org/viewtopic.php?id=225349

linux命令备忘录

作者

名词

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pie: position-independent executable
pic: position-independent code
aslr: address space layout randomization
got: global offset table
vdso: virtual dynamic shared object

swap文件

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dd if=/dev/zero of=./swap_file bs=1G count=8
mkswap ./swap_file
swapon ./swap_file
swapoff ./swap_file

objcopy

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objcopy -I binary -O elf32-i386 -B i386 test.jpg test.o
objdump -s -b binary test.o
readelf -s test.o

静态链编stdc++

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-Bstatic -lstdc++ -Bdynamic

工具

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systemtap
inotify-tools
windres
reptyr

自启动

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#/lib/systemd/system/mytask.service
#ln -s /lib/systemd/system/mytask.service /etc/systemd/system/multi-user.target.wants/mytask.service
[Unit]
Description=mytask
After=network.target
 
[Service]
Type=simple
ExecStart=mytask.sh
 
[Install]
WantedBy=multi-user.target

refer to:
http://blog.chinaunix.net/uid-28461677-id-5766451.html
https://blog.csdn.net/weixin_33842304/article/details/91443399
https://unix.stackexchange.com/questions/4034/how-can-i-disown-a-running-process-and-associate-it-to-a-new-screen-shell
https://blog.csdn.net/wuzhong8809/article/details/117450302

linux驱动备忘录

作者

驱动签名

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CONFIG_MODULE_SIG=y
# CONFIG_MODULE_SIG_FORCE is not set
CONFIG_MODULE_SIG_ALL=y
 
${KERNEL_SRC}/scripts/sign-file sha512 ${KERNEL_SRC}/certs/signing_key.pem ${KERNEL_SRC}/certs/signing_key.x509 hello.ko

驱动调试

debugee

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MOD_NAME=simple_mod
insmod ./${MOD_NAME}.ko
MOD_TEXT=`cat /sys/module/${MOD_NAME}/sections/.text`
MOD_DATA=`cat /sys/module/${MOD_NAME}/sections/.data`
MOD_BSS=`cat /sys/module/${MOD_NAME}/sections/.bss`
MOD_ADD="add-symbol-file /path/to/${MOD_NAME}.ko ${MOD_TEXT} -s .data ${MOD_DATA} -s .bss ${MOD_BSS}"
echo ${MOD_ADD}

debugger

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(gdb) ${MOD_ADD}

refer to:
https://www.cnblogs.com/rivsidn/p/9481037.html
https://www.cnblogs.com/powerrailgun/p/12161295.html
https://blog.csdn.net/chdhust/article/details/8820628

vmware linux共享文件夹未启动

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# 若vmhgfs-fuse -e执行成功时执行
vmhgfs-fuse -o subtype=vmhgfs-fuse,allow_other /mnt/hgfs/
# mvhgfs-fuse -e 执行失败时执行
mount -f vmhgfs .host:/ /mnt/hgfs

如果还不行，比如更新内核后，就要重新加载linux.iso重装VMWareTools。

refer to: https://www.cnblogs.com/woodyoilove/p/8479458.html

linux关闭或开启网络端口

作者

关闭80端口

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iptables -A INPUT -ptcp --dport 80 -j DROP

而开启80端口要看情况，不能简单的一句

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iptables -A INPUT -ptcp --dport 80 -j ACCEPT

因为其中的-A表示append一条规则到规则链上，之前存在一条DROP链，其后再加一条ACCEPT链，80端口还是会被禁掉。

先用如下命令看一下规则链

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iptables -L

把DROP那一链删掉

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iptables -D INPUT -ptcp --dport 80 -j ACCEPT
iptables -D INPUT -ptcp --dport 80 -j DROP

如果默认是所有端口都禁用，那就在空链里加一条ACCEPT链。

最后保存

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iptables-save

Linux禁止用户访问某个目录

作者

比如root用户生成了一个文件夹dir0，再执行

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chmod o-rwx dir0

那么当非root权限用户usr0访问此目录

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cd dir0/
bash: cd: dir0/: Permission denied