[root@dev-xx-xx ~]# tc qdisc del dev eth0 root netem delay 100ms
RTNETLINK answers: Invalid argument
[root@dev-xx-xx ~]# tc qdisc show
qdisc mq 0: dev eth0 root
qdisc pfifo_fast 0: dev eth0 parent :1 bands 3 priomap 1 2 2 2 1 2 0 0 1 1 1 1 1 1 1 1
qdisc pfifo_fast 0: dev eth0 parent :2 bands 3 priomap 1 2 2 2 1 2 0 0 1 1 1 1 1 1 1 1
qdisc pfifo_fast 0: dev eth0 parent :3 bands 3 priomap 1 2 2 2 1 2 0 0 1 1 1 1 1 1 1 1
qdisc pfifo_fast 0: dev eth0 parent :4 bands 3 priomap 1 2 2 2 1 2 0 0 1 1 1 1 1 1 1 1
[root@dev-xx-xx ~]# tc qdisc add dev eth0 root netem delay 100ms
[root@dev-xx-xx ~]# ping 192.168.102.124
PING 192.168.102.124 (192.168.102.124) 56(84) bytes of data.
64 bytes from 192.168.102.124: icmp_seq=1 ttl=64 time=0.074 ms
64 bytes from 192.168.102.124: icmp_seq=2 ttl=64 time=0.066 ms
64 bytes from 192.168.102.124: icmp_seq=3 ttl=64 time=0.080 ms
64 bytes from 192.168.102.124: icmp_seq=4 ttl=64 time=0.043 ms
64 bytes from 192.168.102.124: icmp_seq=5 ttl=64 time=0.084 ms
64 bytes from 192.168.102.124: icmp_seq=6 ttl=64 time=0.094 ms
^C
--- 192.168.102.124 ping statistics ---
12 packets transmitted, 12 received, 0% packet loss, time 11131ms
rtt min/avg/max/mdev = 0.043/0.081/0.107/0.018 ms
[root@dev-xx-xx ~]# tc qdisc del dev eth0 root netem delay 100ms
[root@dev-xx-xx ~]# tc qdisc del dev eth0 root netem delay 100ms
RTNETLINK answers: Invalid argument