普通用户无法使用crontab故障排除

kingbase执行添加定时备份脚本时提示没有权限问题排查及解决步骤

操作系统环境：统信uos V20。

1、crontab -e手动添加定时任务脚本也保存不了，尝试了将用户添加至cron.allow白名单，重启定时计划任务后，crontab -e还是保存不了。
crontab -e添加定时计划后保存时提示以下报错：

```powershell
 crontab -e no crontab for kingbase - using an empty one crontab: installing new crontab fchown: 不允许的操作

2、kingbase执行自动备份脚本时，添加定时任务时提示没**权限；*

[kingbase@localhost logical]$ ./fast_deploy_backup8.sh 
This tool help use to deploy logical backup (backup8.sh) schedual into crontab, must execute in local server

1.check back dest:
back dest is exist, do not create it
 
2.check backup8.sh script:
sucess to execute backup8.sh

3.add backup job:
/var/spool/cron/kingbase: 权限不够
/var/spool/cron/kingbase: 权限不够
/var/spool/cron/#tmp.localhost.localdomain.XXXXjntRKG: 权限不够
complated

4.show current crontab list:
/var/spool/cron/kingbase: 权限不够

end

[kingbase@localhost logical]$
[kingbase@localhost logical]$ exit
先把/var/spool/cron的权限设置为777。
进入目录/var/spool/cron/

[root@localhost insatll]# chmod -R 777 /var/spool/

[root@localhost insatll]# su - kingbase
[kingbase@localhost ~]$ cd KingbaseES/V8/Server/kb_scripts/kb_backup/logical/

[kingbase@localhost logical]$ ./fast_deploy_backup8.sh 
This tool help use to deploy logical backup (backup8.sh) schedual into crontab, must execute in local server
1.check back dest:
back dest is exist, do not create it
 
2.check backup8.sh script:
sucess to execute backup8.sh

3.add backup job:
no crontab for kingbase
no crontab for kingbase
fchown: 不允许的操作
complated
4.show current crontab list:
no crontab for kingbase

end

[kingbase@localhost logical]$ exit

(即使把/var/spool/cron的权限设置为777，也一样会提示 fchown：没有权限操作)

检查 /usr/bin/crontab 的属性```

[root@localhost insatll]# ls `which crontab` -al
-rwxr--r-- 1 root root 63160  3月 14 05:47 /usr/bin/crontab

检查发现是 /usr/bin/crontab 的属性有问题，没有给予它s属性，因此低权限有误就无法使用crontab来往/var/spool/cron下写入文件

[root@localhost insatll]# chmod  u+s /usr/bin/crontab 
[root@localhost insatll]# ls -rtl /usr/bin/crontab 
-rwsrwxrwx 1 root root 63160  3月 14 05:47 /usr/bin/crontab

[root@localhost insatll]# 
[root@localhost insatll]# 
[root@localhost insatll]# su - kingbase
上一次登录：四 7月 20 14:47:49 CST 2023pts/0 上
Welcome to 4.19.0-91.82.152.uelc20.x86_64

[kingbase@localhost ~]$ cd KingbaseES/V8/Server/kb_scripts/kb_backup/logical/
[kingbase@localhost logical]$ ./fast_deploy_backup8.sh 
This tool help use to deploy logical backup (backup8.sh) schedual into crontab, must execute in local server

1.check back dest:
back dest is exist, do not create it
 
2.check backup8.sh script:
sucess to execute backup8.sh

3.add backup job:
no crontab for kingbase
no crontab for kingbase
complated

4.show current crontab list:
0 2 * * * sh /home/kingbase/KingbaseES/V8/Server/kb_scripts/kb_backup/logical/backup8.sh >>/home/kingbase/KingbaseES/V8/Server/kb_scripts/kb_backup/logical/logical_backup.log 2>&1 &
end
[kingbase@localhost logical]$

脚本执行成功。

总结：

s权限是 sid ，和passwd 一样，虽然普通用户没有passwd 的读、写、执行权限，但是加入了sid，就可以继承该文件拥有者的权限，比如写 /etc/shadow。crontab也是一样