小水实验室 – 海外主机，网站不定时抽风

iptables add a rule

# 查看当前规则
iptables -nL --line-number

# 在INPUT组 第六条后添加规则 开放tcp的 55660端口
iptables -I INPUT 6 -p tcp -m tcp --dport 55660 -j ACCEPT
service iptables save
service iptables restart

# 查看当前规则

iptables -nL --line-number

# 在INPUT组第六条后添加规则开放tcp的 55660端口

iptables -I INPUT 6 -p tcp -m tcp --dport 55660 -j ACCEPT

service iptables save

service iptables restart

PHP好用的图片缩略图函数

//resize and crop image by center
function resize_crop_image($max_width, $max_height, $source_file, $dst_dir, $quality = 80){
    $imgsize = getimagesize($source_file);
    $width = $imgsize[0];
    $height = $imgsize[1];
    $mime = $imgsize['mime'];
 
    switch($mime){
        case 'image/gif':
            $image_create = "imagecreatefromgif";
            $image = "imagegif";
            break;
 
        case 'image/png':
            $image_create = "imagecreatefrompng";
            $image = "imagepng";
            $quality = 7;
            break;
 
        case 'image/jpeg':
            $image_create = "imagecreatefromjpeg";
            $image = "imagejpeg";
            $quality = 80;
            break;
 
        default:
            return false;
            break;
    }
     
    $dst_img = imagecreatetruecolor($max_width, $max_height);
    $src_img = $image_create($source_file);
     
    $width_new = $height * $max_width / $max_height;
    $height_new = $width * $max_height / $max_width;
    //if the new width is greater than the actual width of the image, then the height is too large and the rest cut off, or vice versa
    if($width_new > $width){
        //cut point by height
        $h_point = (($height - $height_new) / 2);
        //copy image
        imagecopyresampled($dst_img, $src_img, 0, 0, 0, $h_point, $max_width, $max_height, $width, $height_new);
    }else{
        //cut point by width
        $w_point = (($width - $width_new) / 2);
        imagecopyresampled($dst_img, $src_img, 0, 0, $w_point, 0, $max_width, $max_height, $width_new, $height);
    }
     
    $image($dst_img, $dst_dir, $quality);
 
    if($dst_img)imagedestroy($dst_img);
    if($src_img)imagedestroy($src_img);
}

//resize and crop image by center

function resize_crop_image($max_width, $max_height, $source_file, $dst_dir, $quality = 80){

$imgsize = getimagesize($source_file);

$width = $imgsize[0];

$height = $imgsize[1];

$mime = $imgsize['mime'];

switch($mime){

case 'image/gif':

$image_create = "imagecreatefromgif";

$image = "imagegif";

break;

case 'image/png':

$image_create = "imagecreatefrompng";

$image = "imagepng";

$quality = 7;

break;

case 'image/jpeg':

$image_create = "imagecreatefromjpeg";

$image = "imagejpeg";

$quality = 80;

break;

default:

return false;

break;

}

$dst_img = imagecreatetruecolor($max_width, $max_height);

$src_img = $image_create($source_file);

$width_new = $height * $max_width / $max_height;

$height_new = $width * $max_height / $max_width;

//if the new width is greater than the actual width of the image, then the height is too large and the rest cut off, or vice versa

if($width_new > $width){

//cut point by height

$h_point = (($height - $height_new) / 2);

//copy image

imagecopyresampled($dst_img, $src_img, 0, 0, 0, $h_point, $max_width, $max_height, $width, $height_new);

}else{

//cut point by width

$w_point = (($width - $width_new) / 2);

imagecopyresampled($dst_img, $src_img, 0, 0, $w_point, 0, $max_width, $max_height, $width_new, $height);

}

$image($dst_img, $dst_dir, $quality);

if($dst_img)imagedestroy($dst_img);

if($src_img)imagedestroy($src_img);

}

sample shell : restart golang web program run in background

set -e

exename=golangwebexe
echo "old version sha1: "
sha1sum ./$exename

if [ ! -f "$exename.rc" ]; then
    echo "do not have RC exe file"
    exit
fi

pgrep $exename
pkill -f $exename

rm ./$exename
chmod +x ./$exename.rc
mv ./$exename.rc ./$exename
echo "old version sha1: "
sha1sum ./$exename

nohup ./$exename > run.log 2>&1 & 

sleep 3
pgrep $exename

set -e

exename=golangwebexe

echo "old version sha1: "

sha1sum ./$exename

if [ ! -f "$exename.rc" ]; then

echo "do not have RC exe file"

exit

pgrep $exename

pkill -f $exename

rm ./$exename

chmod +x ./$exename.rc

mv ./$exename.rc ./$exename

echo "old version sha1: "

sha1sum ./$exename

nohup ./$exename > run.log 2>&1 &

sleep 3

pgrep $exename

systemd （systemctl）简单开机自启动任务

编写类似文件 xxxxx.service 放置到/usr/lib/systemd/system 目录下

注意 /root/services/XXXXXX/start.sh 这个文件需要 +x 赋予可执行权限

[Unit]   
Description=judged hz
After=mariadb.service redis.service

[Service]  
Type=forking     
KillMode=control-group   
Restart=no        
ExecStart=/root/services/XXXXXX/start.sh    

[Install]   
WantedBy=multi-user.target

[Unit]

Description=judged hz

After=mariadb.service redis.service

[Service]

Type=forking

KillMode=control-group

Restart=no

ExecStart=/root/services/XXXXXX/start.sh

[Install]

WantedBy=multi-user.target

openwrt pppoe拨号后动作

#!/bin/sh
sleep 5
if [ ${DEVICE} == 'pppoe-wan' && ${ACTION} == 'ifup' ]; then
    wget http://remebermyrequest.ip/index.php?mark=1 -O /dev/null
fi

#!/bin/sh

sleep 5

if [ ${DEVICE} == 'pppoe-wan' && ${ACTION} == 'ifup' ]; then

wget http://remebermyrequest.ip/index.php?mark=1 -O /dev/null

/etc/hotplug.d/iface

cobbler ubuntu 自动应答脚本

网卡自动选择不生效的问题

d-i netcfg/choose_interface select auto 没效果

是个bug ，官方建议如此操作修改ubuntu的发行版的内核引导参数，如下：

cobbler distro edit --name=ubuntu-16.04-x86_64 --kopts="netcfg/choose_interface=auto"

1	cobbler distro edit --name=ubuntu-16.04-x86_64 --kopts="netcfg/choose_interface=auto"

ubuntu 18.04 更新dns设置

先说重点：

* 有多种修改方法
* 直接修改/etc/resolv.conf文件是临时的
* 一般来说 /etc/resolv.conf 是由 resolvconf 命令生成的

修改/run/resolvconf/interface/ethxxx ( 每个网卡一个) 添加最多3个dns 地址
例如：
nameserver 202.106.0.20
nameserver 223.5.5.5

然后 resolveconf -u 更新生效

建议：第一个dns设置服务器所在地的运营商dns ，比如北京联通dns ，第二个dns 设置成公用的dns

远不如 centos 直接从网卡配置文件设置 dns 来的直接

调整linux 系统 tcp 网络参数更好的发送给大量请求

https://stackoverflow.com/questions/410616/increasing-the-maximum-number-of-tcp-ip-connections-in-linux
vim /etc/sysctl.conf

主要是这四个参数
sysctl net.ipv4.tcp_tw_recycle=1
sysctl net.ipv4.tcp_tw_reuse=1
sysctl net.ipv4.ip_local_port_range=”15000 61000″
sysctl net.ipv4.tcp_fin_timeout=30

mysql 提示不能通过root@127.0.0.1连接的问题

在 my.cnf中注释 skip-name-relove
GRANT ALL PRIVILEGES ON *.* TO 'root'@'127.0.0.1' IDENTIFIED BY 'PASSWORD' WITH GRANT OPTION; flush privileges;

tcpdump usage

一、获取适配器列表
$ tcpdump -D

二、监听适配器
使用 -i 或 –interface 参数监听适配器，适配器可以用序号或名字来表示，这些内容可以通过 -D 参数获取。macOS 下监听适配器的话，必须使用 root 权限。
　如果需要详细查看报内容，可以使用 -X 参数。

$ tcpdump -i en0 -X

三、监听适配器过滤
1、过滤主机
抓取所有经过 eth1，目的或源地址是 192.168.1.1 的网络数据
$ tcpdump -i en0 host 192.168.1.1

限定源地址
$ tcpdump -i eth1 src host 192.168.1.1

限定目标地址
$ tcpdump -i eth1 dst host 192.168.1.1

2、过滤端口
抓取所有经过 eth1，目的或源端口是 25 的网络数据
$ tcpdump -i eth1 port 25

限定源端口
$ tcpdump -i eth1 src port 25

限定目标端口
$ tcpdump -i eth1 dst port 25

3、过滤网段
$ tcpdump -i eth1 net 192.168

$ tcpdump -i eth1 src net 192.168

$ tcpdump -i eth1 dst net 192.168

4、协议过滤

$ tcpdump -i eth1 arp
$ tcpdump -i eth1 ip
$ tcpdump -i eth1 tcp
$ tcpdump -i eth1 udp
$ tcpdump -i eth1 icmp

5、使用表达式
与：&& 或 and
或：|| 或 or
非：! 或 not

$ tcpdump -i eth1 ‘((tcp) and (port 80) and ((dst host 192.168.1.254) or (dst host
192.168.1.200)))’