iam new in programming and using linux. My Question is, is it possible to add Netem Filter Rules later ? I want to create an PHP-Interface for Netem and I don't know how much filters were required. This should be some kind of dynamically. In Example : A user with a static IP starts an Netem Command (Latency) with PHP Interface this means these five command werde executed by php in the first step $classid = 11; $handle = 10; "sudo tc qdisc add dev eth0 handle 1: root htb"; "sudo tc class add dev eth0 parent 1: classid 1:1 htb rate 100Mbps"; "sudo tc class add dev eth0 parent 1:1 classid 1:$classid htb rate 100Mbps"; "sudo tc qdisc add dev eth0 parent 1:$classid handle $handle: netem delay 100ms"; "sudo tc filter add dev eth0 protocol ip parent 1:0 prio 3 u32 match ip dst $dest flowid 1:$classid"; Now, if there would be a second user who wants to use Netem independent of the first user, i only want to execute the last 3 commands, like "sudo tc class add dev eth0 parent 1:1 classid 1:$classid htb rate 100Mbps"; "sudo tc qdisc add dev eth0 parent 1:$classid handle $handle: netem delay 100ms"; "sudo tc filter add dev eth0 protocol ip parent 1:0 prio 3 u32 match ip dst $dest flowid 1:$classid"; There is an Algorithmus for increasing variables $classid and $handle. This should work. Now my Question: Is it possible only to add these 3 commands to add a new class with new qdisc and a new filter rule ? Or how can i realize it ? The Apache Error_log tells me "sh: line 1: flowid: command not found" but i can't find any mistake. I hope you could help Best regards fontsix