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#!/bin/bash 

#USAGE: sudo ./netspeed -l limit_in_kbit -s
usage="sudo $(basename "$0") -l speed_limit -s
  -l speed_limit - speed limit with units (eg. 1mbit, 100kbit, more on \`man tc\`)
  -s - remove all limits
"

# default values
LIMIT=0

nevermosby

### 1. local port forward on k8s server
#
#   :8080 ---> 127.0.0.1:12345(k8s api server local port)
#
sudo socat TCP-LISTEN:8080,reuseaddr,fork tcp:127.0.0.1:12345

### 2. local port foward on k8s client host
#
#   :8888 ---> 1.2.3.4:8080(the external ip of k8s server)
#

nevermosby

Disassembly of section tc:
tc_drop_tcp:
       0:	bf 16 00 00 00 00 00 00 	r6 = r1
       1:	b7 01 00 00 00 00 00 00 	r1 = 0
       2:	73 1a f4 ff 00 00 00 00 	*(u8 *)(r10 - 12) = r1
       3:	b7 01 00 00 69 6f 6e 0a 	r1 = 175009641
       4:	63 1a f0 ff 00 00 00 00 	*(u32 *)(r10 - 16) = r1
       5:	18 01 00 00 20 74 63 20 00 00 00 00 73 65 63 74 	r1 = 8386658476233028640 ll
       7:	7b 1a e8 ff 00 00 00 00 	*(u64 *)(r10 - 24) = r1
       8:	18 01 00 00 45 6e 74 65 00 00 00 00 72 69 6e 67 	r1 = 7453010373394067013 ll

nevermosby

Disassembly of section tc:
tc_drop_tcp:
       0:	bf 16 00 00 00 00 00 00 	r6 = r1
       1:	b7 01 00 00 69 6f 6e 0a 	r1 = 175009641
       2:	63 1a f8 ff 00 00 00 00 	*(u32 *)(r10 - 8) = r1
       3:	18 01 00 00 20 74 63 20 00 00 00 00 73 65 63 74 	r1 = 8386658476233028640 ll
       5:	7b 1a f0 ff 00 00 00 00 	*(u64 *)(r10 - 16) = r1
       6:	18 01 00 00 45 6e 74 65 00 00 00 00 72 69 6e 67 	r1 = 7453010373394067013 ll
       8:	7b 1a e8 ff 00 00 00 00 	*(u64 *)(r10 - 24) = r1
       9:	b7 01 00 00 00 00 00 00 	r1 = 0

nevermosby

## for some distributions of Linix, like ubuntu 18.04
## `curl` does not include `c-ares` module so that you cannot do `curl --dns-servers 8.8.8.0 www.example.com`
## you will get error message as below:
## curl: (4) A requested feature, protocol or option was not found built-in in this libcurl due to a build-time decision.

# build curl from source code
# You can do that with building `curl` from souce code. below is tested against ubuntu 18.04

# download the code from git repo
git clone https://github.com/curl/curl.git && cd curl

nevermosby

#!/bin/sh

# 1. delete pv, pv会变成terminating状态
kubectl delete pv [pv-name]

# 2. delete pvc, pvc会变成terminating状态
kubectl delete pvc [pvc-name-related-to-pv]

# 3. patch pvc to remove protection, 具体可以看这里：https://stackoverflow.com/questions/51358856/kubernetes-cant-delete-persistentvolumeclaim-pvc，然后pv和pvc就被干净删除了
kubectl patch pvc [pvc-name] -p '{"metadata":{"finalizers": []}}' --type=merge

nevermosby

use etcdctl for etcd v3 API

if you have access to the etcd server, you can use the following steps to try etcd v3 API to fetch Kubernetes cluster data

1. set environment to use v3 API

# set ETCDCTL_API
export ETCDCTL_API=3

2. use etcdctl tool to fetch all the namespaces

# fetch all the namespaces

nevermosby

// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

// Deep equality test via reflection

package reflect

import "unsafe"

nevermosby

# go help modules
A module is a collection of related Go packages.
Modules are the unit of source code interchange and versioning.
The go command has direct support for working with modules,
including recording and resolving dependencies on other modules.
Modules replace the old GOPATH-based approach to specifying
which source files are used in a given build.

Preliminary module support

nevermosby

ss -ltn # list out all the listening sockets
ss -ltp # list out all the listening socketes and the related process name with pid
ss -t4 state time-wait # list all Ipv4 tcp sockets that are in "time-wait" state

# state list
1. established
2. syn-sent
3. syn-recv
4. fin-wait-1
5. fin-wait-2