PHPor 的Blog

容器的1号进程果然不一般

现象：

你无法kill掉容器的1号进程，包括kill -11 kill -6 ，包括 kill -9，因为内核对于进程空间的1号进程是特殊对待的，不会安装默认信号处理程序。
如果你的进程是容器中的1号进程，那么在进程崩溃的时候，是不会有coredump文件产生的。

Hi folks,
I have looked into this issue and I want to share the results of my investigation, which turned out to be quite intriguing.

The contained application has PID 1, which means that the Linux kernel treats it as a standalone init process for this namespace. The Linux kernel handles signals differently for the init process than it does for other processes. Signal handlers are not automatically registered for this process, meaning that signals will not take effect by default.
Since the contained application does not have user-defined signal handlers and the kernel does not register the default ones, the SIGABRT signal sent by the abort function is not handled at all.
In this situation, abort tries to kill the application by executing a forbidden asm instruction “HLT”. As a result, the CPU sets the GPF interruption and the kernel kills the contained application with SIGSEGV, which leads to the exit code 139. Docker just sets its exit code accordingly.

The easiest way to make the contained application to have the default signal handlers is to run docker with the flag –init.

For an expanded explanation on how signals are handled in a docker container, I have provided a detailed answer with visual examples in my article.

Perhaps we should expand the description in https://github.com/docker/cli/blob/v20.10.2/docs/reference/run.md#foreground and/or link to that post. Currently it mentions;

Note

A process running as PID 1 inside a container is treated specially by Linux:
it ignores any signal with the default action. As a result, the process will
not terminate on SIGINT or SIGTERM unless it is coded to do so.

Contributions welcome if someone is interested.

参考：

Docker container exit code is zero when program is terminated with SIGSEGV · Issue #41454 · moby/moby (github.com)

Docker container exit code has unexpected value when program aborts · Issue #30593 · moby/moby (github.com)

How signals are handled in a docker container | Dmitry Danilov (ddanilov.me)

Exit codes in docker when a program aborts | Dmitry Danilov (ddanilov.me)

递归

A loop within loops, Seeking the base case to find, Endless paths unwind.

— create by openai

顶级域名都有哪些

View the Public Suffix List

Public Suffix List

publicsuffix/list: The Public Suffix List (github.com)

要实现一个http client，可能就会涉及cookiejar，这就需要了解cookie的存储，就和域名有关系，你不能把 a.com.cn 和 a.cn 的cookie都存到 .cn下面，因为.cn 是个顶级域名；也不能把 a.com.cn 好 b.com.cn 的cookie都存在.com.cn 下面，因为.com.cn也是个顶级域名；但是1.a.cn 和 2.a.cn 这两个域名的cookie就可以都设置在 a.cn下面，因为这个a.cn 不是顶级域名。没有一个算法快速判断哪个域名是否顶级域名，只能把所有顶级域名都存起来，就是上面的public suffix list，比如，golang中就有一个net.publicsuffix ，这个是硬编码的。

eTLD: effective top level domain

Qq

天气通 – 关注天气，开启美好生活来自 Weibo Internet Technology (China) Co.Ltd.

https://apps.apple.com/cn/app/%E5%A4%A9%E6%B0%94%E9%80%9A-%E5%85%B3%E6%B3%A8%E5%A4%A9%E6%B0%94-%E5%BC%80%E5%90%AF%E7%BE%8E%E5%A5%BD%E7%94%9F%E6%B4%BB/id458032309

-fvisibility=hidden 测试

man gcc

gcc 编译时，如果使用了 -fvisibility=hidden 选项，编译的so文件中的函数默认是不导出的，就是动态链接是链接不到的；不仅有隐藏的效果（使用nm还是能看到的，所以，该选项不是出于安全考虑，主要是实现private的效果），也有利于编译器的进一步优化。由于历史代码可能不期望这个行为，所以该选项也不是默认行为（好像在object-c中是默认行为）。

下面测试一下：

main

#include<stdlib.h>
#include<stdio.h>
#include "f.h"


int main(int ac, char** av) {
    printf("%d\n", a());
    return 0;
}

#include<stdlib.h>

#include<stdio.h>

#include "f.h"

int main(int ac, char** av) {

printf("%d\n", a());

return 0;

}

f.h

int a();

int a();

这个头文件太简单了🤦‍♀️

libf.c

// __attribute__((visibility ("default")))   // 打开该注释就可以显式导出
int a() {
	return 1;
}

// __attribute__((visibility ("default"))) // 打开该注释就可以显式导出

int a() {

return 1;

}

编译main.c

gcc -lf -L . main.c f.h
#使用clang也行，参数都一样

1 2	gcc -lf -L . main.c f.h #使用clang也行，参数都一样

编译libf.c

// 隐藏的编译方式，编译后，运行报错
gcc -shared -fvisibility=hidden -o libf.so libf.c

1 2	// 隐藏的编译方式，编译后，运行报错 gcc -shared -fvisibility=hidden -o libf.so libf.c

    private static MemoryHistory getHistory()
    {
        return getHistory(new File(getUserHome(), ".presto_history"));
    }

private static MemoryHistory getHistory()

{

return getHistory(new File(getUserHome(), ".presto_history"));

}

较新的版本（如： 0.284 ）就可以通过环境变量 PRESTO_HISTORY_FILE 来设置了：

    private static MemoryHistory getHistory()
    {
        String historyFilePath = System.getenv("PRESTO_HISTORY_FILE");
        File historyFile;
        if (isNullOrEmpty(historyFilePath)) {
            historyFile = new File(getUserHome(), ".presto_history");
        }
        else {
            historyFile = new File(historyFilePath);
        }
        return getHistory(historyFile);
    }

private static MemoryHistory getHistory()

{

String historyFilePath = System.getenv("PRESTO_HISTORY_FILE");

File historyFile;

if (isNullOrEmpty(historyFilePath)) {

historyFile = new File(getUserHome(), ".presto_history");

}

else {

historyFile = new File(historyFilePath);

}

return getHistory(historyFile);

}

查看presto版本号：

$ presto --version
Presto CLI 0.207-dirty

1 2	$ presto --version Presto CLI 0.207-dirty

容器的1号进程果然不一般

递归

文心一言

顶级域名都有哪些

Qq

-fvisibility=hidden 测试

Cat

edge浏览器升级

presto cli 设置history file

build.gradle学习