1.因为不是root用户拒绝了我

bash-5.0$ ping 172.18.0.4
PING 172.18.0.4 (172.18.0.4): 56 data bytes
ping: permission denied (are you root?)  

#无法直接切换到root
bash-5.0$ su root
su: must be suid to work properly    

2.排查ping 命令的位置

bash-5.0$ which ping
/bin/ping

#进入bin目录查看ping 权限 发现实际路径在/bin/busybox
bash-5.0$ cd /bin/
bash-5.0$ ls -l ping
lrwxrwxrwx    1 root     root            12 May 29 14:20 ping -> /bin/busybox


bash-5.0$ ls -l /bin/busybox
-rwxr-xr-x    1 root     root        841288 May 22 06:59 /bin/busybox

3.使用root登录并赋予权限

#也可以一键使用这个命令
$ docker  exec  -u root 75 chmod u+s /bin/busybox

root@u-55:/etc/docker# docker exec -u root -it 75 sh
/usr/share/zabbix # chmod u+s /bin/busybox

/usr/share/zabbix # ping 172.18.0.3
PING 172.18.0.3 (172.18.0.3): 56 data bytes
64 bytes from 172.18.0.3: seq=0 ttl=64 time=0.105 ms
64 bytes from 172.18.0.3: seq=1 ttl=64 time=0.055 ms
64 bytes from 172.18.0.3: seq=2 ttl=64 time=0.070 ms

4.使用普通用户登录

#ping 也可以使用
root@u-55:/etc/docker# docker exec -it 75 sh
/usr/share/zabbix $ ping 172.18.0.3
PING 172.18.0.3 (172.18.0.3): 56 data bytes
64 bytes from 172.18.0.3: seq=0 ttl=64 time=0.089 ms
64 bytes from 172.18.0.3: seq=1 ttl=64 time=0.055 ms

ps:使用–help查看如何使用root账户进入

root@u-55:/etc/docker# docker exec --help

Usage:  docker exec [OPTIONS] CONTAINER COMMAND [ARG...]

Run a command in a running container

Options:
  -d, --detach               Detached mode: run command in the background
      --detach-keys string   Override the key sequence for detaching a container
  -e, --env list             Set environment variables
  -i, --interactive          Keep STDIN open even if not attached
      --privileged           Give extended privileges to the command
  -t, --tty                  Allocate a pseudo-TTY
  -u, --user string          Username or UID (format: <name|uid>[:<group|gid>])
  -w, --workdir string       Working directory inside the container