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今天碰到SpringBoot调用mysqldump数据库备份报Permission denied，第一眼看到感觉很简单，添加权限就行，mysqldump和备份目录都加载权限，还是问题依旧。

1. 认为是mysql版本问题，因为另一台机器可以。
2. 手动执行备份是正常的，只有报个Warning，说密码不能放到命令中。
3. 备份目录权限问题。

但最终发现都不是

这里直接strace看结果，主要是找到这个方法：

sudo strace -f -e trace=execve /home/app/jdk-17.0.9/bin/java TestPermission  

结果：发现是/home/app/jdk-17.0.9/lib/jspawnhelper没有权限

execve("/home/app/jdk-17.0.9/bin/java", ["/home/app/jdk-17.0.9/bin/j"..., "TestPermission"], 0x7ffcda3fd620 /* 13 vars */) = 0
strace: Process 26967 attached
[pid 26967] --- SIGSEGV {si_signo=SIGSEGV, si_code=SEGV_MAPERR, si_addr=NULL} ---
strace: Process 26968 attached
...
[pid 26985] execve("/home/app/jdk-17.0.9/lib/jspawnhelper", ["10:13"], 0x7fff76f01b30 /* 13 vars */) = -1 EACCES (Permission denied)
[pid 26985] +++ exited with 127 +++
[pid 26966] --- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=26985, si_uid=0, si_status=127, si_utime=0, si_stime=0} ---
Exception in thread "main" java.io.IOException: Cannot run program "/usr/bin/mysqldump": error=13, Permission deniedat java.base/java.lang.ProcessBuilder.start(ProcessBuilder.java:1143)at java.base/java.lang.ProcessBuilder.start(ProcessBuilder.java:1073)at TestPermission.main(TestPermission.java:8)
Caused by: java.io.IOException: error=13, Permission deniedat java.base/java.lang.ProcessImpl.forkAndExec(Native Method)at java.base/java.lang.ProcessImpl.<init>(ProcessImpl.java:314)at java.base/java.lang.ProcessImpl.start(ProcessImpl.java:244)at java.base/java.lang.ProcessBuilder.start(ProcessBuilder.java:1110)... 2 more
[pid 26983] +++ exited with 0 +++
...

TestPermission 代码：

public class TestPermission {public static void main(String[] args) throws Exception {ProcessBuilder pb = new ProcessBuilder("/usr/bin/mysqldump", "--version");pb.redirectErrorStream(true);Process p = pb.start();BufferedReader reader = new BufferedReader(new InputStreamReader(p.getInputStream()));String line;while ((line = reader.readLine()) != null) {System.out.println(line);}p.waitFor();}
}