几经搜索，发现了群晖的Diagnosis Tool工具，里面有78个工具，其中就包括iperf3，方法很简单。
群晖NAS内网速度测试
- SSH登录群晖NAS，并切换到管理员权限
$ sudo -i
- 安装Diagnosis Tool，
$ sudo synogear install
- 运行
$ /var/packages/DiagnosisTool/target/tool/iperf3 -c 192.168.188.1
群晖NAS外网速度测试
- 运行：/var/packages/DiagnosisTool/target/tool/speedtest-cli.py
- 会在结果可以找到Download: 138.89 Mbit/s；Upload: 63.01 Mbit/s（这是我千兆移动的测试结果）
如果不想使用synogear了， 一个命令就可移除：
$ sudo synogear remove
78个群晖的Diagnosis Tool工具命令行参考
/var/packages/DiagnosisTool/target/tool/addr2name /var/packages/DiagnosisTool/target/tool/arping /var/packages/DiagnosisTool/target/tool/ash /var/packages/DiagnosisTool/target/tool/bash /var/packages/DiagnosisTool/target/tool/cifsiostat /var/packages/DiagnosisTool/target/tool/clockdiff /var/packages/DiagnosisTool/target/tool/dig /var/packages/DiagnosisTool/target/tool/domain_test.sh /var/packages/DiagnosisTool/target/tool/file /var/packages/DiagnosisTool/target/tool/fix_idmap.sh /var/packages/DiagnosisTool/target/tool/free /var/packages/DiagnosisTool/target/tool/gcore /var/packages/DiagnosisTool/target/tool/gdb /var/packages/DiagnosisTool/target/tool/gdbserver /var/packages/DiagnosisTool/target/tool/iftop /var/packages/DiagnosisTool/target/tool/iostat /var/packages/DiagnosisTool/target/tool/iotop /var/packages/DiagnosisTool/target/tool/iperf /var/packages/DiagnosisTool/target/tool/iperf3 /var/packages/DiagnosisTool/target/tool/kill /var/packages/DiagnosisTool/target/tool/killall /var/packages/DiagnosisTool/target/tool/ldd /var/packages/DiagnosisTool/target/tool/lsof /var/packages/DiagnosisTool/target/tool/ltrace /var/packages/DiagnosisTool/target/tool/mpstat /var/packages/DiagnosisTool/target/tool/name2addr /var/packages/DiagnosisTool/target/tool/ncat /var/packages/DiagnosisTool/target/tool/ndisc6 /var/packages/DiagnosisTool/target/tool/nethogs /var/packages/DiagnosisTool/target/tool/nfsiostat-sysstat /var/packages/DiagnosisTool/target/tool/nmap /var/packages/DiagnosisTool/target/tool/nping /var/packages/DiagnosisTool/target/tool/nslookup /var/packages/DiagnosisTool/target/tool/perf-check.py /var/packages/DiagnosisTool/target/tool/pgrep /var/packages/DiagnosisTool/target/tool/pidof /var/packages/DiagnosisTool/target/tool/pidstat /var/packages/DiagnosisTool/target/tool/ping6 /var/packages/DiagnosisTool/target/tool/ping /var/packages/DiagnosisTool/target/tool/pkill /var/packages/DiagnosisTool/target/tool/pmap /var/packages/DiagnosisTool/target/tool/ps /var/packages/DiagnosisTool/target/tool/pstree /var/packages/DiagnosisTool/target/tool/pwdx /var/packages/DiagnosisTool/target/tool/rarpd /var/packages/DiagnosisTool/target/tool/rdisc6 /var/packages/DiagnosisTool/target/tool/rdisc /var/packages/DiagnosisTool/target/tool/rltraceroute6 /var/packages/DiagnosisTool/target/tool/sa1 /var/packages/DiagnosisTool/target/tool/sa2 /var/packages/DiagnosisTool/target/tool/sadc /var/packages/DiagnosisTool/target/tool/sadf /var/packages/DiagnosisTool/target/tool/sar /var/packages/DiagnosisTool/target/tool/sh /var/packages/DiagnosisTool/target/tool/sid2ugid.sh /var/packages/DiagnosisTool/target/tool/slabtop /var/packages/DiagnosisTool/target/tool/sockstat /var/packages/DiagnosisTool/target/tool/speedtest-cli.py /var/packages/DiagnosisTool/target/tool/strace /var/packages/DiagnosisTool/target/tool/sysctl /var/packages/DiagnosisTool/target/tool/sysstat /var/packages/DiagnosisTool/target/tool/tcpdump /var/packages/DiagnosisTool/target/tool/tcpdump_wrapper /var/packages/DiagnosisTool/target/tool/tcpspray6 /var/packages/DiagnosisTool/target/tool/tcptraceroute6 /var/packages/DiagnosisTool/target/tool/telnet /var/packages/DiagnosisTool/target/tool/tload /var/packages/DiagnosisTool/target/tool/top /var/packages/DiagnosisTool/target/tool/tracepath /var/packages/DiagnosisTool/target/tool/traceroute6 /var/packages/DiagnosisTool/target/tool/tracert6 /var/packages/DiagnosisTool/target/tool/uptime /var/packages/DiagnosisTool/target/tool/vmstat /var/packages/DiagnosisTool/target/tool/w /var/packages/DiagnosisTool/target/tool/watch /var/packages/DiagnosisTool/target/tool/zblacklist /var/packages/DiagnosisTool/target/tool/zmap /var/packages/DiagnosisTool/target/tool/ztee