find . -name "FILE-TO-FIND" -exec rm -rf {} \;

 find . -name "FILE-TO-FIND" -exec rm -rf {} \;

compiling on macbook - xcrun error

error:

xcrun: error: invalid active developer path

solution:

1. install xcode

2. xcode-select --install

* The long retry limit - default 4: applies to frames longer than the RTS threshold.

        A frame requiring RTS/CTS clearing is retransmitted four times before it is discarded and reported to higher-level protocols.

* The short retry limit - default 7: applies to frames shorter than the RTS threshold.

Adding a dummy monitor

 

sudo apt-get install xserver-xorg-video-dummy

sudo vi /etc/X11/xorg.conf

Section "Device"

    Identifier  "Configured Video Device"

    Driver      "dummy"

EndSection

Section "Monitor"

    Identifier  "Configured Monitor"

    HorizSync 31.5-48.5

    VertRefresh 50-70

EndSection

Section "Screen"

    Identifier  "Default Screen"

    Monitor     "Configured Monitor"

    Device      "Configured Video Device"

    DefaultDepth 24

    SubSection "Display"

    Depth 24

    Modes "1024x800"

    EndSubSection

EndSection

Disabling DHCP and DNS role - OpenWrt

uci set dhcp.lan.ignore="1"

uci set dhcp.@dnsmasq[0].port="0"

uci commit dhcp

/etc/init.d/dnsmasq restart

/etc/init.d/odhcpd restart

kernel config config.gz

zcat /proc/config.gz

zcat /proc/config.gz | grep SKB

ifdef if defined if !defined

#if defined(LINUX) || defined(ANDROID)

#if !defined(MANUF) || !defined(SERIAL) || !defined(MODEL)

#if defined(LINUX) && !defined(MODEL)

#endif

shell if statement

reference: https://ryanstutorials.net/bash-scripting-tutorial/bash-if-statements.php

if [ <some test> ]
then
<commands>
fi

================== compare number ================
#!/bin/bash
# Basic if statement
if [ $1 -gt 100 ]
then
    echo Hey that\'s a large number.
    pwd
fi
================== compare string ================
#!/bin/sh
if [ -z $1 ]
then
   echo "no input string given"
   return
fi
==============================================

Operator	Description
! EXPRESSION	The EXPRESSION is false.
-n STRING	The length of STRING is greater than zero.
-z STRING	The lengh of STRING is zero (ie it is empty).
STRING1 = STRING2	STRING1 is equal to STRING2
STRING1 != STRING2	STRING1 is not equal to STRING2
INTEGER1 -eq INTEGER2	INTEGER1 is numerically equal to INTEGER2
INTEGER1 -gt INTEGER2	INTEGER1 is numerically greater than INTEGER2
INTEGER1 -lt INTEGER2	INTEGER1 is numerically less than INTEGER2
-d FILE	FILE exists and is a directory.
-e FILE	FILE exists.
-r FILE	FILE exists and the read permission is granted.
-s FILE	FILE exists and it's size is greater than zero (ie. it is not empty).
-w FILE	FILE exists and the write permission is granted.
-x FILE	FILE exists and the execute permission is granted.

= is slightly different to -eq. [ 001 = 1 ] will return false as = does a string comparison (ie. character for character the same) whereas -eq does a numerical comparison meaning [ 001 -eq 1 ] will return true.

When we refer to FILE above we are actually meaning a path. Remember that a path may be absolute or relative and may refer to a file or a directory.

bash> test 001 = 1

bash> echo $?

bash> 1

bash> test 001 -eq 1

bash> echo $?

bash> 0

bash> touch myfile

bash> test -s myfile

bash> echo $?

bash> 1

bash> ls /etc > myfile

bash> test -s myfile

bash> echo $?

bash> 0

How to configure routing between LAN and WAN

https://monoinfinito.wordpress.com/series/setting-up-a-linux-gatewayrouter-a-guide-for-non-network-admins/

dhcp perf tools

1. How to install
    kea-admin contains perfdhcp binary

$ sudo apt install kea-admin

$ sudo perfdhcp -p 60 -r 100 -d 5 -R 50 192.168.1.1

2. User manual
https://users.isc.org/~tomasz/perfdhcp/dhcp-perf-guide.html#perfdhcp-commandline-examples
- adding delayed-ack 32 that allows packets to queue before send
- max-ack-delay that increase time to fsync
- ping-check false
- dont-use-fsync to true

3. Build your own
    build/install from source

$ sudo apt -y install automake libtool pkg-config build-essential ccache

$ sudo apt -y install libboost-dev libboost-system-dev liblog4cplus-dev libssl-dev

$ git clone https://gitlab.isc.org/isc-projects/kea.git

$ cd kea

$ autoreconf --install

$ ./configure [your additional options here]

$ make -j4

$ sudo make install

$ echo "/usr/local/lib/hooks" > /etc/ld.so.conf.d/kea.conf

$ ldconfig

git submodule

*** sync submodule

$ git checkout master

M meta-openembedded

M poky

$ git submodule update

git submodule add https://git.kernel.org/pub/scm/linux/kernel src/linux

git config examples)
.git/config
[submodule "linux"]
url = https://git.kernel.org/pub/scm/linux/kernel

.gitmodules
[submodule "linux-msm"]
path = src/linux
url = https://git.kernel.org/pub/scm/linux/kernel
rev = b27efee486f8a24682f36908fb2693a7b310303b

git clone --recurse-submodules --branch <branch name> <git url>

git clone --single-branch --recurse-submodules --branch <branch name> <git url>

git submodule sync
    Synchronizing submodule url for 'xxx'
    fatal: no submodule mapping found in .gitmodules for path 'yyy'
git rm -r yyy --cached

trouble shootings)
git rm --cached src/linux
rm -rf src/linux
rm -rf .git/modules/src/linux

git submodule [--quiet] add [-b branch] [-f|--force]
      [--reference <repository>] [--] <repository> [<path>]
git submodule [--quiet] status [--cached] [--recursive] [--] [<path>…​]
git submodule [--quiet] init [--] [<path>…​]
git submodule [--quiet] update [--init] [-N|--no-fetch] [--rebase]
      [--reference <repository>] [--merge] [--recursive] [--] [<path>…​]
git submodule [--quiet] summary [--cached|--files] [--summary-limit <n>] [commit] [--] [<path>…​]
git submodule [--quiet] foreach [--recursive] <command>
git submodule [--quiet] sync [--] [<path>…​]


*** Update git submodule to their remote origin

# Get the submodule initially
git submodule add ssh://bla submodule_dir
git submodule init

# Time passes, submodule upstream is updated
# and you now want to update

# Change to the submodule directory
cd submodule_dir

# Checkout desired branch
git checkout master

# Update
git pull

# Get back to your project root
cd ..

# Now the submodules are in the state you want, so
git commit -am "Pulled down update to submodule_dir"


git submodule foreach git pull origin master

mount squashfs image on ubuntu

sudo mount -o loop -t squashfs ./root.squashfs ./mnt

apt clean

sudo rm /var/lib/apt/lists/*
sudo rm /var/cache/apt/*.bin

sudo apt update

VirtualBox clone / resize

/Users/peteroh/VirtualBox VMs/Ubuntu-16.04/Ubuntu-16.04.vdi

VBoxManage clonehd Ubuntu-16.04.vdi Ubuntu-16.04-2.vdi --format VDI --variant Standard

VBoxManage modifyhd Ubuntu-16.04.vdi --resize 50000

FCC Telecommunication Ref

https://www.ecfr.gov/cgi-bin/text-idx?SID=42a02d0348e514926b26630eb40d4777&mc=true&tpl=/ecfrbrowse/Title47/47tab_02.tpl


https://apps.fcc.gov/oetcf/eas/reports/GenericSearchResult.cfm?RequestTimeout=500

https://apps.fcc.gov/oetcf/kdb/index.cfm

https://apps.fcc.gov/oetcf/kdb/forms/FTSSearchResultPage.cfm?id=240776&switch=P

Errors: Linux System Errors

https://www-numi.fnal.gov/offline_software/srt_public_context/WebDocs/Errors/unix_system_errors.html

linux kernel scheduling class

ps -deo pid,cls,cmd | grep -e RR -e FF

       cls       CLS    scheduling class of the process. (alias policy, class).
                        Field's possible values are:
                        -   not reported
                        TS  SCHED_OTHER
                        FF  SCHED_FIFO
                        RR  SCHED_RR
                        B   SCHED_BATCH
                        ISO SCHED_ISO
                        IDL SCHED_IDLE
                        ?   unknown value

root@:/proc/sys/kernel# cat sched_rt_period_us
1000000
root@:/proc/sys/kernel# cat sched_rt_runtime_us
950000

kernel abort

arch/arm/mm/fsr-2level.c , fsr-3level.c

static struct fsr_info fsr_info[] = {
/*
* The following are the standard ARMv3 and ARMv4 aborts.  ARMv5
* defines these to be "precise" aborts.
*/
{ do_bad, SIGSEGV, 0, "vector exception"    },
{ do_bad, SIGBUS, BUS_ADRALN, "alignment exception"    },
{ do_bad, SIGKILL, 0, "terminal exception"    },
{ do_bad, SIGBUS, BUS_ADRALN, "alignment exception"    },
{ do_bad, SIGBUS, 0, "external abort on linefetch"    },
{ do_translation_fault, SIGSEGV, SEGV_MAPERR, "section translation fault"    },
{ do_bad, SIGBUS, 0, "external abort on linefetch"    },
{ do_page_fault, SIGSEGV, SEGV_MAPERR, "page translation fault"    },
{ do_bad, SIGBUS, 0, "external abort on non-linefetch"  },
{ do_bad, SIGSEGV, SEGV_ACCERR, "section domain fault"    },
{ do_bad, SIGBUS, 0, "external abort on non-linefetch"  },
{ do_bad, SIGSEGV, SEGV_ACCERR, "page domain fault"    },
{ do_bad, SIGBUS, 0, "external abort on translation"    },
{ do_sect_fault, SIGSEGV, SEGV_ACCERR, "section permission fault"    },
{ do_bad, SIGBUS, 0, "external abort on translation"    },
{ do_page_fault, SIGSEGV, SEGV_ACCERR, "page permission fault"    },
/*
* The following are "imprecise" aborts, which are signalled by bit
* 10 of the FSR, and may not be recoverable.  These are only
* supported if the CPU abort handler supports bit 10.
*/
{ do_bad, SIGBUS,  0, "unknown 16"    },
{ do_bad, SIGBUS,  0, "unknown 17"    },
{ do_bad, SIGBUS,  0, "unknown 18"    },
{ do_bad, SIGBUS,  0, "unknown 19"    },
{ do_bad, SIGBUS,  0, "lock abort"    }, /* xscale */
{ do_bad, SIGBUS,  0, "unknown 21"    },
{ do_bad, SIGBUS,  BUS_OBJERR, "imprecise external abort"    }, /* xscale */
{ do_bad, SIGBUS,  0, "unknown 23"    },
{ do_bad, SIGBUS,  0, "dcache parity error"    }, /* xscale */
{ do_bad, SIGBUS,  0, "unknown 25"    },
{ do_bad, SIGBUS,  0, "unknown 26"    },
{ do_bad, SIGBUS,  0, "unknown 27"    },
{ do_bad, SIGBUS,  0, "unknown 28"    },
{ do_bad, SIGBUS,  0, "unknown 29"    },
{ do_bad, SIGBUS,  0, "unknown 30"    },
{ do_bad, SIGBUS,  0, "unknown 31"    },
};

static struct fsr_info ifsr_info[] = {
{ do_bad, SIGBUS,  0, "unknown 0"    },
{ do_bad, SIGBUS,  0, "unknown 1"    },
{ do_bad, SIGBUS,  0, "debug event"    },
{ do_bad, SIGSEGV, SEGV_ACCERR, "section access flag fault"    },
{ do_bad, SIGBUS,  0, "unknown 4"    },
{ do_translation_fault, SIGSEGV, SEGV_MAPERR, "section translation fault"    },
{ do_bad, SIGSEGV, SEGV_ACCERR, "page access flag fault"    },
{ do_page_fault, SIGSEGV, SEGV_MAPERR, "page translation fault"    },
{ do_bad, SIGBUS, 0, "external abort on non-linefetch"  },
{ do_bad, SIGSEGV, SEGV_ACCERR, "section domain fault"    },
{ do_bad, SIGBUS,  0, "unknown 10"    },
{ do_bad, SIGSEGV, SEGV_ACCERR, "page domain fault"    },
{ do_bad, SIGBUS, 0, "external abort on translation"    },
{ do_sect_fault, SIGSEGV, SEGV_ACCERR, "section permission fault"    },
{ do_bad, SIGBUS, 0, "external abort on translation"    },
{ do_page_fault, SIGSEGV, SEGV_ACCERR, "page permission fault"    },
{ do_bad, SIGBUS,  0, "unknown 16"    },
{ do_bad, SIGBUS,  0, "unknown 17"    },
{ do_bad, SIGBUS,  0, "unknown 18"    },
{ do_bad, SIGBUS,  0, "unknown 19"    },
{ do_bad, SIGBUS,  0, "unknown 20"    },
{ do_bad, SIGBUS,  0, "unknown 21"    },
{ do_bad, SIGBUS,  0, "unknown 22"    },
{ do_bad, SIGBUS,  0, "unknown 23"    },
{ do_bad, SIGBUS,  0, "unknown 24"    },
{ do_bad, SIGBUS,  0, "unknown 25"    },
{ do_bad, SIGBUS,  0, "unknown 26"    },
{ do_bad, SIGBUS,  0, "unknown 27"    },
{ do_bad, SIGBUS,  0, "unknown 28"    },
{ do_bad, SIGBUS,  0, "unknown 29"    },
{ do_bad, SIGBUS,  0, "unknown 30"    },
{ do_bad, SIGBUS,  0, "unknown 31"    },
};

How to get different colors in terminal

• set the LSCOLORS environment variable
• create an alias for ls so that it shows colors by default

In your ~/.bash_profile add the following:

#export LSCOLORS="EHfxcxdxBxegecabagacad"

export LSCOLORS="exfxcxdxbxegedabagacad"
alias ls='ls -lGH'

alias ls='ls -lGH'        <-----This shows in list format, follow symlinks colorized

The the colors are set by each bit above; the first being foreground and the second being background. The first two characters refer to directories having a bold blue foreground and a light grey background.

However, there's a great online utility to see what each of the colors mean and look like in real time. It will even generate the "code" for you. (I am not affiliated with this at all). It will work in both MacOS/FreeBSD and Linux. Make sure you select the BSD option for macOS.

LSCOLORS Calculator

---

The order of the attributes are as follows:

1.   directory

2.   symbolic link

3.   socket

4.   pipe

5.   executable

6.   block special

7.   character special

8.   executable with setuid bit set

9.   executable with setgid bit set

10.   directory writable to others, with sticky bit

11.   directory writable to others, without sticky

The color designators are as follows:

a    black

b    red

c    green

d    brown

e    blue

f    magenta

g    cyan

h    light grey

A    bold black, usually shows up as dark grey

B    bold red

C    bold green

D    bold brown, usually shows up as yellow

E    bold blue

F    bold magenta

G    bold cyan

H    bold light grey; looks like bright white

x    default foreground or background

DFS regions

dfs_region = reg_get_dfs_region(wdev->wiphy);