Month: December 2020

MySQL -h option invalid

At first, we should comfirm we create a user, like this


use mysql;
select Host,User from user;

I get this error in Centos+Mysql 5.6

For convenient, I created a user: example_user@%, but I still can not login with mysql -u example_user -h 127.0.0.1 -p, the error message said Access denied for user ‘example_user’@localhost , I specificated the host as 127.0.0.1, why converted to localhost? And the “%” character should match all host.

After a lot of test, 127.0.0.1 is same as localhost, and % not match localhost in this version of MySQL, so, we just have to create a user in localhost.


grant all on example_db.* on "example_user"@"localhost" identified by "your password";
flush privileges;

How to connect MySQL Server in wampserver

Open port will cause a security issue, so do that ONLY for dev or debug

I trust we all know that we should set an account for remote access in MySQL, such as 


grant all on example_db.* on "example_user"@"%" identified by "your password";
flush privileges;

So, the reason is not misconfig of MySQL, it’s windows firewall, we have to open port by follow actions.

Search(win+Q)->Firewall-> Windows Defender Firewall-> inbound rule

create rule -> port -> release 3306 (sorry I don’t know what is it in English version)

[SOLVED]using dkms to install driver with errors

0X01 Cause

The standby time of my lapta\op (ThinkPad X1C 2014) when running linux is sooo short, but when running windows, the time is OK. So I searched on web: what can I do, and find TLP, it’s easy to use, basically, we can use default configuration. As we now, Lenovo have a threshold config for battery, I do care about it, because each of my laptop, the battery damage fist, TLP support this config (ThinkPad only), location at /etc/default/tlp, we need the module called acpi-call.

The installation is smoothly.


sudo apt-get update && sudo apt-get install acpi-call-dkms
# OK, let's check if we success 

sudo tlp-stat
# unfortunately, it still inactive

sudo dpkg -l | grep dkms # first, we have to check if we installed this package

sudo dkms install # I guess we should use like this.

# we will get a tip, tell us should not use like this, use help subcommand 

sudo dkms help # oh, this autoinstall is OK

Usage: /usr/sbin/dkms [action] [options]
[action] = { add | remove | build | install | uninstall | match | autoinstall
| mkdriverdisk | mktarball | ldtarball | mkrpm | mkkmp | mkdeb | mkbmdeb | status }
[options] = [-m module] [-v module-version] [-k kernel-version] [-a arch]
[-d distro] [-c dkms.conf-location] [-q] [--force] [--all]
[--templatekernel=kernel] [--directive='cli-directive=cli-value']
[--config=kernel-.config-location] [--archive=tarball-location]
[--kernelsourcedir=source-location] [--no-prepare-kernel] [--no-initrd]
[--binaries-only] [--source-only] [-r release (SuSE)] [--verbose]
[--size] [--spec=specfile] [--media=floppy|iso|tar] [--legacy-postinst=0|1]
[--no-depmod]
[-j number]
Error! No action was specified.
sudo dkms autoinstall

0X02 What happened

I find the error message below. It said we don’t have the function copy_from_user.

DKMS make.log for acpi_call-1.2.0 for kernel 4.12.1-chrysalis (x8664)
Thu Jul 13 19:31:39 CEST 2017
make -C /lib/modules/4.12.1-chrysalis/build M=/var/lib/dkms/acpi_call/1.2.0/build modules
make[1]: Entering directory ‘/tmp/linux-4.12.1’
CC [M] /var/lib/dkms/acpi_call/1.2.0/build/acpi_call.o
/var/lib/dkms/acpi_call/1.2.0/build/acpi_call.c: In function ‘acpi_proc_write’:
/var/lib/dkms/acpi_call/1.2.0/build/acpi_call.c:307:9: error: implicit declaration of function ‘copy_from_user’ [-Werror=implicit-function-declaration]
if (copy_from_user( input, buff, len )) {
^~~~~~~~~~~~~~
cc1: some warnings being treated as errors
make[2]: *** [scripts/Makefile.build:309: /var/lib/dkms/acpi_call/1.2.0/build/acpi_call.o] Error 1
make[1]: *** [Makefile:1512: _module/var/lib/dkms/acpi_call/1.2.0/build] Error 2
make[1]: Leaving directory ‘/tmp/linux-4.12.1’
make: *** [Makefile:7: default] Error 2

I find several possibly solution:

  • Add -Werror=implicit-function-declaration compile option
  • use define to declare ( not suitable, I haven’t try it)
  • we have not import right header (at first, I think it should not have this error, it’s system official package)

And when I read the web page above, I find the function copy_from_user may locate at two location: <asm/uaccess.h> or <linux/uaccess.h>, use locate command to finde the source code, it import <asm/uaccess.h>, I changed asm to linux, then run command below, I success.


sudo dkms autoinstall