system | book

references:
drop caches
$ sudo bash -c "echo 3 > /proc/sys/vm/drop_caches"

hardware spec

[!TIP|label:hardware spec] list info
glances
hwinfo
lshw
lscpu
lsmem
lspci
lsscsi
lsusb
inxi ( inxi --recommends, inxi -F|--full )
lsblk
lsof
ncdu - a disk utility for Unix systems
fdisk
blkid - command-line utility to locate/print block device attributes
mount
free
dmidecode
hdparm
lstopo-no-graphics
hwloc-ls
/proc
/proc/cpuinfo
/proc/meminfo
/proc/version
/proc/scsi/scsi
/proc/partitions
performance & analysis
vmstat - shows system memory, processes, interrupts, paging, block I/O, and CPU info
iostat - for storage I/O statistics.
iotop - interactive I/O viewer. Get an overview of storage r/w activity
netstat – for network statistics
iftop - network traffic viewer
nload - a super simple, command-line network interface monitoring tool
mtr - network diagnostic tool
dig - DNS lookup utility tool
nethogs - network traffic analyzer
apropos - search man page names and descriptions
fsck - tool for checking the consistency of a file system
vnstat
dstat
mpstat
ss - socket statistics
sar
nethogs - network traffic analyzer

lshw Classes
address
bridge
bus
communication
disk
display
generic
input
memory
multimedia
network
power
printer
processor
storage
system
tape
volume

os

$ lsb_release -a
LSB Version    : :core-4.1-amd64:core-4.1-noarch
Distributor ID : CentOS
Description    : CentOS Linux release 7.9.2009 (Core)
Release        : 7.9.2009
Codename       : Core

$ uname  -a
Linux my-computer 3.10.0-1160.42.2.el7.x86_64 #1 SMP Tue Sep 7 14:49:57 UTC 2021 x86_64 x86_64 x86_64 GNU/Linux

$ cat /etc/centos-release
CentOS Linux release 7.9.2009 (Core)

hardware

$ sudo dmidecode -s

[!TIP]

$ sudo yum install -y hwloc
$ lstopo-no-graphics
$ hwloc-ls
$ hwloc-info
$ lstopo-no-graphics -p

system information

$ sudo dmidecode | grep -A5 '^System Information'
  System Information
    Manufacturer: HPE
    Product Name: ProLiant DL380 Gen10
    Version: Not Specified
    Serial Number: S*************0
    UUID: 0******0-0**0-0**0-0**0-3**********e

# or display system [m]anufacture
$ inxi -M
    Machine:   Type: Server Mobo: HPE model: ProLiant DL380 Gen10 serial: <root required> UEFI: HPE v: U30
               date: 06/15/2018
# or
$ sudo inxi --dmidecode -Mxxx
    Machine:   Type: Rack Mount Chassis Mobo: HPE model: ProLiant DL380 Gen10 serial: PFARA%%LMAZ6XB BIOS: HPE
           v: U30 rev: 1.40 date: 06/15/2018 rom size: 16384 kB

manufacturer

$ sudo dmidecode -s system-manufacturer
    HPE

# or
$ sudo dmidecode -s baseboard-manufacturer
HPE

# or
$ cat /sys/devices/virtual/dmi/id/sys_vendor
HPE

product name and version

product name only

$ sudo dmidecode -s system-product-name
    ProLiant DL380 Gen10

# or
$ sudo dmidecode -s baseboard-product-name
ProLiant DL380 Gen10

# or
$ cat /sys/devices/virtual/dmi/id/product_name
ProLiant DL380 Gen10

# or
$ sudo dmidecode | grep -i prod
        Product Name: Vostro 5560
        Product Name: 04YDT0

uuid

$ sudo dmidecode | grep -i uuid | awk '{print $2}' | tr '[:upper:]' '[:lower:]'

cpu

references:

$ cat /proc/cpuinfo | egrep "core id|physical id" | tr -d "\n" | sed s/physical/\\nphysical/g | grep -v ^$ | sort | uniq | wc -l
36

# or
$ grep -c processor /proc/cpuinfo
32

# or
$ nproc --all
32

# or
$ getconf _NPROCESSORS_ONLN
32

# or
$ cat /sys/devices/system/cpu/present
0-31

# or CPUs = Threads per core X cores per socket X socket
$ lscpu | grep -E '^Thread|^Core|^Socket|^CPU\('
CPU(s):                32
Thread(s) per core:    2
Core(s) per socket:    8
Socket(s):             2
$ lscpu | grep --color=none -E '^(Thread|Core|Socket|CPU\(|NUMA|Model\ name)'
CPU(s):              128
Thread(s) per core:  2
Core(s) per socket:  64
Socket(s):           1
NUMA node(s):        1
Model name:          AMD EPYC 7742 64-Core Processor
NUMA node0 CPU(s):   0-127

# or
$ sudo dmidecode -t 4 | grep -E 'Socket Designation|Count'
  Socket Designation: CPU1
  Core Count: 8
  Thread Count: 16
  Socket Designation: CPU2
  Core Count: 8
  Thread Count: 16

# list clock speed
$ sudo lscpu | grep --color=none -E '^(Thread|Core|Socket|CPU\(|NUMA\ node\(|Model\ name|CPU.+MHz|BogoMIPS)'
CPU(s):              32
Thread(s) per core:  2
Core(s) per socket:  8
Socket(s):           2
NUMA node(s):        2
Model name:          Intel(R) Xeon(R) CPU E5-2667 v4 @ 3.20GHz
CPU MHz:             1719.616
CPU max MHz:         3600.0000
CPU min MHz:         1200.0000
BogoMIPS:            6399.86

others

$ lscpu --all --extended
$ lscpu --all --parse=CPU,SOCKET,CORE | grep -v '^#'

check CPU support 64 bit or not

$ sudo dmidecode --type=processor | grep -i -A 1 Characteristics
    Characteristics:
            64-bit capable

cat /proc/cpuinfo

$ lscpu
Architecture:          i686
CPU op-mode(s):        32-bit, 64-bit
Byte Order:            Little Endian
CPU(s):                4
On-line CPU(s) list:   0-3
....

cpu info

$ sudo dmidecode -t processor

# or
$ sudo lshw -C cpu

# or
$ sudo dmidecode -t 4 | egrep -i "Designation|Intel|core|thread"

# or
$ inxi -C
CPU:
  Info: 2x 8-core model: Intel Xeon E5-2667 v4 bits: 64 type: MT MCP SMP cache: L2: 2x 2 MiB (4 MiB)
  Speed (MHz): avg: 1324 min/max: 1200/3600 cores: 1: 1202 2: 1202 3: 1251 4: 1200 5: 1201
    6: 1376 7: 1260 8: 1205 9: 1203 10: 1202 11: 1201 12: 1201 13: 1201 14: 1202 15: 1201 16: 1202
    17: 1200 18: 1200 19: 1600 20: 1199 21: 1201 22: 1287 23: 1892 24: 1201 25: 1200 26: 1201
    27: 3200 28: 1200 29: 1200 30: 1701 31: 1201 32: 1200

memory

references:
RAM: Random Access Memory is a temporary memory. This information will go away when the computer is turned off.
ROM: Read Only Memory is permanent memory, that holds the data even if the system is switched off.

list total memory

[!TIP|label:references:]
$ vmstat 1 | awk '{now=strftime("%Y-%m-%d %T "); print now $0}'

$ hwinfo --memory | grep 'Memory Size'
  Memory Size: 128 GB

$ sudo lshw -short | grep 'System Memory'
/0/2c                           memory         128GiB System Memor

$ vmstat -s -S M | egrep -ie 'total memory'
       128817 M total memory

$ vmstat -s | grep "total memory"
    131909608 K total memory

$ vmstat -s | awk '{print $1 / 1024 / 1024}' | head -1
125.799

$ inxi -F | grep "Memory"
  Processes: 414 Uptime: 87d 17h 40m Memory: 125.8 GiB used: 27.21 GiB (21.6%) Init: systemd

$ sudo dmidecode -t memory | grep  Size: | grep -v "No Module Installed" | awk '{sum+=$2}END{print sum}'
131072

$ egrep 'MemTotal|MemFree|MemAvailable' /proc/meminfo
MemTotal:       131909608 kB
MemFree:        95760488 kB
MemAvailable:   104355708 kB

$ vmstat -s

list only installed RAM modules

$ sudo dmidecode -t memory | grep  Size: | grep -v "No Module Installed"
$ sudo dmidecode -t memory | grep -E '(^Memory Device|^\s+(Size:|Type:|Type Detail:|Serial Number:|Part Number:|Memory Technology:|Manufacturer))' --color=never | grep -v -E 'Not Specified|No Module Installed|Unknow|None|OUT OF SPEC'

memory information

$ sudo dmidecode -t memory
$ sudo dmidecode -t memory | grep -E '(^Memory Device|^\s+(Size:|Type:|Type Detail:|Serial Number:|Part Number:|Memory Technology:|Configured Memory Speed:|Manufacturer))' --color=never
Memory Device
  Size: 16384 MB
  Type: DDR4
  Type Detail: Synchronous Registered (Buffered)
  Manufacturer: 00AD063200AD
  Serial Number: 44965EB1
  Part Number: HMA82GR7DJR8N-XN
  Configured Memory Speed: 2933 MT/s
  Memory Technology: DRAM
# or
$ sudo dmidecode -t memory | grep -E '(^Memory Device|^\s+(Size:|Type:|Type Detail:|Serial Number:|Part Number:|Memory Technology:|Configured Memory Speed:|Manufacturer))' --color=never | grep -v -E 'Not Specified|No Module|Unknow|None|<OUT OF SPEC>'

# or
$ sudo lshw -C memory
$ sudo lshw -short -class memory

# Physical Memory Array
$ sudo dmidecode --type 16

# get Memory Device
$ sudo dmidecode --type 17

# Memory Array Mapped Address
$ sudo dmidecode --type 19

print memory only

$ ps -o comm,%mem,args -u marslo | more
COMMAND         %MEM COMMAND
gnome-keyring-d  0.0 /usr/bin/gnome-keyring-daemon --daemonize --login
init             0.0 init --user
ssh-agent        0.0 ssh-agent
dbus-daemon      0.0 dbus-daemon --fork --session --address=unix:abstract=/tmp/dbus-i5FUVjzADG
upstart-event-b  0.0 upstart-event-bridge
window-stack-br  0.0 /usr/lib/i386-linux-gnu/hud/window-stack-bridge
upstart-dbus-br  0.0 upstart-dbus-bridge --daemon --session --user --bus-name session
upstart-dbus-br  0.0 upstart-dbus-bridge --daemon --system --user --bus-name system
upstart-file-br  0.0 upstart-file-bridge --daemon --user
ibus-daemon      0.1 /usr/bin/ibus-daemon --daemonize --xim
....

check memory in time

$ free -h -s 5

# or
$ vmstat -w

# or
$ dmesg | grep "Memory"
[    0.995127] Memory: 131882904K/134101416K available (12300K kernel code, 2504K rwdata, 3684K rodata, 2340K init, 3240K bss, 2218512K reserved, 0K cma-reserved)
[    1.139890] x86/mm: Memory block size: 2048MB

bios

$ sudo dmidecode -t bios

disk

hwinfo

$ hwinfo --disk --only /dev/sda
192: SCSI 20.0: 10600 Disk
  [Created at block.245]
  Unique ID: R7kM.qzo5k6MLsu5
  Parent ID: svHJ.VbV94345RfA
  SysFS ID: /class/block/sda
  SysFS BusID: 0:2:0:0
  SysFS Device Link: /devices/pci0000:00/0000:00:02.0/0000:03:00.0/host0/target0:2:0/0:2:0:0
  Hardware Class: disk
  Model: "AVAGO SMC3108"
  Vendor: "AVAGO"
  Device: "SMC3108"
  Revision: "4.68"
  Driver: "megaraid_sas", "sd"
  Driver Modules: "megaraid_sas"
  Device File: /dev/sda (/dev/sg1)
  Device Files: /dev/sda, /dev/disk/by-id/scsi-360030480243a18012424538006708dc9, /dev/disk/by-id/wwn-0x60030480243a18012424538006708dc9, /dev/disk/by-path/pci-0000:03:00.0-scsi-0:2:0:0
  Device Number: block 8:0-8:15 (char 21:1)
  BIOS id: 0x80
  Drive status: no medium
  Config Status: cfg=new, avail=yes, need=no, active=unknown
  Attached to: #37 (RAID bus controller)

disk type

[!INFO] Check disk interface types
Advanced technology attachment (ATA)
Integrated Drive Electronics (IDE)
Serial ATA (SATA)
Small Computer system interface (SCSI)
Serial attached SCSI (SAS)
Fibre Channel

lsblk

$ lsblk -do name,tran
NAME TRAN
sdb  sas
sdc  sas

lshw

$ sudo lshw -c storage -c disk
  ...
  *-sas
       description: Serial Attached SCSI controller
       product: Smart Storage PQI 12G SAS/PCIe 3
       vendor: Adaptec
       physical id: 0
       bus info: pci@0000:5c:00.0
       logical name: scsi1
       version: 01
       width: 64 bits
       clock: 33MHz
       capabilities: sas pm msix pciexpress bus_master cap_list
       configuration: driver=smartpqi latency=0
       resources: irq:32 memory:e9100000-e9107fff ioport:8000(size=256)
     *-disk:0
          description: SCSI Disk                            # SCSC
          product: LOGICAL VOLUME
          vendor: HPE
          physical id: 1.0.0
          bus info: scsi@1:1.0.0
          logical name: /dev/sdb
          version: 1.99
          serial: P************C
          size: 1788GiB (1920GB)
          capabilities: 15000rpm gpt-1.00 partitioned partitioned:gpt
          configuration: ansiversion=5 guid=eda10475-9cdb-44cd-8dbd-28bf482b0e25 logicalsectorsize=512 sectorsize=4096

hdparm

$ sudo hdparm -I /dev/sdb

/dev/sdb:
SG_IO: bad/missing sense data, sb[]:  7***

ATA device, with non-removable media
Standards:
  Likely used: 1
Configuration:
  Logical   max current
  cylinders 0 0
  heads   0 0
  sectors/track 0 0
  --
  Logical/Physical Sector size:           512 bytes
  device size with M = 1024*1024:           0 MBytes
  device size with M = 1000*1000:           0 MBytes
  cache/buffer size  = unknown
Capabilities:
  IORDY not likely
  Cannot perform double-word IO
  R/W multiple sector transfer: not supported
  DMA: not supported
  PIO: pio0

SSD or HHD

[!INFO]
0: SSD
1: HHD references:

check rotational

# HHD
$ cat /sys/block/sd*/queue/rotational
1
1

# SSD
$ lsscsi
[0:0:0:0]    disk    Generic- SD/MMC CRW       1.00  /dev/sda
[1:0:0:0]    enclosu HPE      Smart Adapter    1.99  -
[1:1:0:0]    disk    HPE      LOGICAL VOLUME   1.99  /dev/sdb
[1:1:0:1]    disk    HPE      LOGICAL VOLUME   1.99  /dev/sdc
[1:2:0:0]    storage HPE      P408i-a SR Gen10 1.99  -
[devops@dc5-ssdfw11 ~]$ cat /sys/block/sd*/queue/rotational
1
0
0

lsblk

## SSD
$ lsblk -d -o name,rota
NAME ROTA
sdb     0
sdc     0

# or
## SSD
$ lsblk -d -e 7 -o NAME,ROTA,DISC-MAX,MODEL
NAME ROTA DISC-MAX MODEL
sdb     0       0B LOGICAL VOLUME
sdc     0       0B LOGICAL VOLUME
## HHD
$ lsblk -d -e 7 -o NAME,ROTA,DISC-MAX,MODEL
NAME ROTA DISC-MAX MODEL
sdb     1       0B SMC3108
sda     1       0B SMC3108

smartctl ( $ yum install smartmontools; $ apt install smartmontools )

$ sudo smartctl -a /dev/sdb1
smartctl 7.0 2018-12-30 r4883 [x86_64-linux-4.19.12-1.el7.elrepo.x86_64] (local build)
Copyright (C) 2002-18, Bruce Allen, Christian Franke, www.smartmontools.org

=== START OF INFORMATION SECTION ===
Vendor:               AVAGO
Product:              SMC3108
Revision:             4.68
Compliance:           SPC-3
User Capacity:        7,679,267,307,520 bytes [7.67 TB]
Logical block size:   512 bytes
Physical block size:  4096 bytes
Logical Unit id:      0x60030480243a7b0124d58c0646f9617d
Serial number:        007d61f946068cd524017b3a24800403
Device type:          disk
Local Time is:        Thu Mar 30 10:51:52 2023 PDT
SMART support is:     Unavailable - device lacks SMART capability.

=== START OF READ SMART DATA SECTION ===
Current Drive Temperature:     0 C
Drive Trip Temperature:        0 C

## SSD
$ sudo smartctl -a /dev/sdc
smartctl 6.6 2017-11-05 r4594 [x86_64-linux-4.18.0-193.28.1.el8_2.x86_64] (local build)
Copyright (C) 2002-17, Bruce Allen, Christian Franke, www.smartmontools.org

=== START OF INFORMATION SECTION ===
Vendor:               HPE
Product:              LOGICAL VOLUME
Revision:             1.99
User Capacity:        1,920,349,855,744 bytes [1.92 TB]
Logical block size:   512 bytes
Rotation Rate:        Solid State Device                          # SSD
Logical Unit id:      0x600508b1001c5be1882c0a4afb83c8ec
Serial number:        P************C
Device type:          disk
Local Time is:        Thu Mar 30 10:53:12 2023 PDT
SMART support is:     Available - device has SMART capability.
SMART support is:     Enabled
Temperature Warning:  Disabled or Not Supported

=== START OF READ SMART DATA SECTION ===
SMART Health Status: OK
Current Drive Temperature:     0 C
Drive Trip Temperature:        0 C

/proc/scsi/scsi

## SSD
$ cat /proc/scsi/scsi
Attached devices:
Host: scsi0 Channel: 00 Id: 00 Lun: 00
  Vendor: Generic- Model: SD/MMC CRW       Rev: 1.00
  Type:   Direct-Access                    ANSI  SCSI revision: 06
Host: scsi1 Channel: 00 Id: 00 Lun: 00
  Vendor: HPE      Model: Smart Adapter    Rev: 1.99
  Type:   Enclosure                        ANSI  SCSI revision: 05
Host: scsi1 Channel: 01 Id: 00 Lun: 00
  Vendor: HPE      Model: LOGICAL VOLUME   Rev: 1.99
  Type:   Direct-Access                    ANSI  SCSI revision: 05
Host: scsi1 Channel: 01 Id: 00 Lun: 01
  Vendor: HPE      Model: LOGICAL VOLUME   Rev: 1.99
  Type:   Direct-Access                    ANSI  SCSI revision: 05
Host: scsi1 Channel: 02 Id: 00 Lun: 00
  Vendor: HPE      Model: P408i-a SR Gen10 Rev: 1.99
  Type:   RAID                             ANSI  SCSI revision: 05

check status

$ lsblk
$ pvs
$ lvs
$ vgs
$ pvscan
$ lvscan
$ pvdisplay
$ vgdisplay
$ lvdisplay
$ fdisk -l
$ sfdisk -l -uM
$ lshw -class disk
$ hwinfo --block --short
$ cat /proc/partitions
$ sudo hdparm -I /dev/sda

RAID Info

[!NOTE|label:references:]

$ sudo apt install -y smartmontools

# RAID1
$ sudo smartctl --scan
/dev/sda -d scsi # /dev/sda, SCSI device
/dev/bus/0 -d megaraid,0 # /dev/bus/0 [megaraid_disk_00], SCSI device
/dev/bus/0 -d megaraid,1 # /dev/bus/0 [megaraid_disk_01], SCSI device

RAID details info

$ sudo smartctl --all -d megaraid,1 /dev/sda
smartctl 7.1 2019-12-30 r5022 [x86_64-linux-5.15.0-107-generic] (local build)
Copyright (C) 2002-19, Bruce Allen, Christian Franke, www.smartmontools.org

=== START OF INFORMATION SECTION ===
Device Model:     HF***********9N
Serial Number:    EJ*************4P
LU WWN Device Id: 5 ace42e 02565881c
Add. Product Id:  DELL(tm)
Firmware Version: DZ02
User Capacity:    960,197,124,096 bytes [960 GB]
Sector Sizes:     512 bytes logical, 4096 bytes physical
Rotation Rate:    Solid State Device
Form Factor:      2.5 inches
Device is:        Not in smartctl database [for details use: -P showall]
ATA Version is:   ACS-4 (minor revision not indicated)
SATA Version is:  SATA 3.3, 6.0 Gb/s (current: 6.0 Gb/s)
Local Time is:    Wed Jun  5 16:34:16 2024 PDT
SMART support is: Available - device has SMART capability.
SMART support is: Enabled

# or even more details
$ sudo smartctl --xall -d megaraid,1 /dev/sda

network

get network cards

$ sudo lshw -short -class network
H/W path            Device        Class          Description
============================================================
/0/100/1/0          enp1s0f0      network        I350 Gigabit Network Connection
/0/100/1/0.1        enp1s0f1      network        I350 Gigabit Network Connection
/0/100/1.1/0        enp2s0f0      network        Ethernet Controller X710 for 10GbE SFP+
/0/100/1.1/0.1      enp2s0f1      network        Ethernet Controller X710 for 10GbE SFP+
/0/2/0              enp131s0f0    network        Ethernet Controller 10-Gigabit X540-AT2
/0/2/0.1            enp131s0f1    network        Ethernet Controller 10-Gigabit X540-AT2
/3                  veth8c9c4570  network        Ethernet interface
/4                  flannel.1     network        Ethernet interface
/5                  veth8d141a78  network        Ethernet interface
/6                  veth3cc4bf19  network        Ethernet interface
/7                  cni0          network        Ethernet interface
/8                  docker0       network        Ethernet interface
/9                  veth179b5dab  network        Ethernet interface

network speed

$ ifstat -n -i en7
       en7
 KB/s in  KB/s out
    7.35      1.15
    4.91      1.02
    6.05      0.80
    8.36      1.78

get the public ip address

$ curl ifconfig.me

environment variables

show PATH

$ echo src::${PATH} | awk 'BEGIN{pwd=ENVIRON["PWD"];RS=":";FS="\n"}!$1{$1=pwd}$1!~/^\//{$1=pwd"/"$1}{print $1}'
/home/marslo/src
/home/marslo
/home/marslo/.vim/tools/bin
/usr/local/mysql/bin
/usr/local/bcompare/bin
/usr/lib/lightdm/lightdm
/usr/local/sbin
/usr/local/bin
/usr/sbin
/usr/bin
/sbin
/bin
/usr/games
/usr/local/games
OR
$ echo "${PATH//:/$'\n'}"

graphics card driver

[!NOTE|label:references:]

get system info

references:

top

batch mode

[!TIP] references:

$ top -bn1

# or
$ top -n 1 d 2

get only summary of top command

$ top -bn1 | sed -n '/^top.*/,/^\s*$/p'

## or
$ top -bn1 | sed -e '/^$/Q'

ps

[!TIP|label:references:]

$ G=$(stty -g); stty rows $((${LINES:-50}/2)); top -n1; stty $G; unset G

get cpu

$ ps -eocomm,pcpu | egrep -v '(0.0)|(%CPU)'
systemd          0.2
rcu_sched        0.2
sshd             0.5
java             8.2
java             0.6
dockerd         16.1
docker-containe  0.6
...

get memory

$ ps -eocomm,pmem | egrep -v '(0.0)|(%MEM)'
java             0.1
java             0.1
java             0.8
gvfs-udisks2-vo  0.1
kube-apiserver   0.1

sort process by PID
```
$ ps -axww
```
check the group PID
```
$ ps -xj
```
```
$ ps aux | sort -nk +4 | tail
```
```
$ ps -eo pid,lstart,cmd
```
```
$ ps -o lstart <pid>
```

$ watch -n 1 'ps -eo pid,ppid,cmd,%mem,%cpu --sort=-%mem | head'

$ echo "tee can split a pipe in two"|tee >(rev) >(tr ' ' '_')

find the zombie process

$ ps aux | awk '{ print $8 " " $2 " " $11}' | grep -w Z

set system info

clear duplicated PATH

$ export PATH=`echo -n $PATH | awk -v RS=":" '{ if (!x[$0]++) {printf s $0; s=":"} }'`

sysctl

# permanent
$ sudo bash -c "echo fs.inotify.max_user_watches=524288 >> /etc/sysctl.conf"
$ sudo sysctl -p

# temporary
$ sudo sysctl fs.inotify.max_user_watches=524288

verify

$ cat /proc/sys/fs/inotify/max_user_watches

change net.bridge

$ sudo modprobe br_netfilter
$ sudo sysctl net.bridge.bridge-nf-call-iptables=1
$ sudo sysctl net.bridge.bridge-nf-call-ip6tables=1

# or
$ sudo bash -c "cat >  /etc/sysctl.d/k8s.conf" << EOF
net.bridge.bridge-nf-call-ip6tables = 1
net.bridge.bridge-nf-call-iptables = 1
EOF

check status
```
$ sudo sysctl --system
```

LS_COLORS

[!NOTE|label:references:]

pattern

name

comments

bd

device

block device

ca

cap

cd

device

char device

cl

clear end of line

di

directory

directory

do

Solaris door

ec

end color, unused

ex

executable

executable

fi

file

file

fl

file, default

lc

left, unused

ln

link

symlink

mh

multi hardlink

mi

missing file

no

normal

or

orphan

orphaned symlink

ow

other-writable

pi

fifo

pipe

rc

right, unused

rs

reset

sg

setgid

so

socket

socket

st

sticky

su

setuid

tw

ow with sticky

show database

$ dircolors --print-database
$ which -a dircolors
/usr/local/opt/coreutils/libexec/gnubin/dircolors

$ echo $COLORTERM
truecolor
$ echo $TERM
xterm-256color

setup LS_COLORS

# with background color
$ export LS_COLORS='*.patch=48;5;197;38;5;232;1:'

# with italic
$ export LS_COLORS='*.bak=38;5;241;3'

# with underline
$ export LS_COLORS='*.xlsxm=38;5;112;4:'

# with italic and underline
$ export LS_COLORS='*.patch=38;5;197;3;4:'

# with italic and underline and blink
$ export LS_COLORS='*.patch=38;5;197;3;4;5:"'
#                            ^       ^ ^ ^
#                            +       + + + blink
#                            +       + + underline
#                            +       + italic
#                            + frontend color

( # Run in a subshell so it won't crash current color settings
  dircolors -b >/dev/null
  IFS=:
  for ls_color in ${LS_COLORS[@]}; do # For all colors
      color=${ls_color##*=}
      ext=${ls_color%%=*}
      echo -en "\E[${color}m${ext}\E[0m " # echo color and extension
  done
  echo
)

declare -A descriptions=(
    [bd]="block device"
    [ca]="file with capability"
    [cd]="character device"
    [di]="directory"
    [do]="door"
    [ex]="executable file"
    [fi]="regular file"
    [ln]="symbolic link"
    [mh]="multi-hardlink"
    [mi]="missing file"
    [no]="normal non-filename text"
    [or]="orphan symlink"
    [ow]="other-writable directory"
    [pi]="named pipe, AKA FIFO"
    [rs]="reset to no color"
    [sg]="set-group-ID"
    [so]="socket"
    [st]="sticky directory"
    [su]="set-user-ID"
    [tw]="sticky and other-writable directory"
)

IFS=:
for ls_color in $LS_COLORS; do
    color="${ls_color#*=}"
    type="${ls_color%=*}"

    # Add description for named types.
    desc="${descriptions[$type]}"

    # Separate each color with a newline.
    if [[ $color_prev ]] && [[ $color != "$color_prev" ]]; then
        echo
    fi

    printf "\e[%sm%s%s\e[m " "$color" "$type" "${desc:+ ($desc)}"

    # For next loop
    color_prev="$color"
done
echo

settings

$ cat ~/.bashrc
LS_COLORS='bd=38;5;68:ca=38;5;17:cd=38;5;113;1:di=38;5;108:do=38;5;127:ex=38;5;31;1:pi=38;5;126:fi=0:ln=target:mh=38;5;222;1:no=0:or=48;5;196;38;5;232;1:ow=38;5;220;1:sg=48;5;3;38;5;0:su=38;5;220;1;3;100;1:so=38;5;197:st=38;5;86;48;5;234:tw=48;5;235;38;5;139;3:'
LS_COLORS+='*.7z=38;5;64:*.WARC=38;5;64:*.a=38;5;64:*.arj=38;5;64:*.br=38;5;64:*.bz2=38;5;64:*.cpio=38;5;64:*.gz=38;5;64:*.lrz=38;5;64:*.lz=38;5;64:*.lzma=38;5;64:*.lzo=38;5;64:*.rar=38;5;64:*.s7z=38;5;64:*.sz=38;5;64:*.tar=38;5;64:*.tbz=38;5;64:*.tgz=38;5;64:*.warc=38;5;64:*.xz=38;5;64:*.z=38;5;64:*.zip=38;5;64:*.zipx=38;5;64:*.zoo=38;5;64:*.zpaq=38;5;64:*.zst=38;5;64:*.zstd=38;5;64:*.zz=38;5;64:*@.service=38;5;45:'
LS_COLORS+='*.pub=1;3:*.1p=38;5;7:*.32x=38;5;213:*.3g2=38;5;115:*.3ga=38;5;137;1:*.3gp=38;5;115:*.3p=38;5;7:*.82p=38;5;121:*.83p=38;5;121:*.8eu=38;5;121:*.8xe=38;5;121:*.8xp=38;5;121:*.A64=38;5;213:*.BUP=38;5;241:*.CFUserTextEncoding=38;5;239:*.F=38;5;81:*.F03=38;5;81:*.F08=38;5;81:*.F90=38;5;81:*.F95=38;5;81:*.IFO=38;5;114:*.M=38;5;110:*.PDF=38;5;141:*.PFA=38;5;66:*.PL=38;5;160:*.RData=38;5;178:*.Rproj=38;5;11:*.S=38;5;110:*.S3M=38;5;137;1:*.SKIP=38;5;244:*.TIFF=38;5;97:*.VOB=38;5;115;1:*.a00=38;5;213:*.a52=38;5;213:*.a64=38;5;213:*.a78=38;5;213:*.aac=38;5;137;1:*.accdb=38;5;60:*.accde=38;5;60:*.accdr=38;5;60:*.accdt=38;5;60:*.adf=38;5;213:*.adoc=38;5;184:*.afm=38;5;66:*.agda=38;5;81:*.agdai=38;5;110:*.ai=38;5;99:*.aiff=38;5;136;1:*.alac=38;5;136;1:*.allow=38;5;112:*.am=38;5;242;3:*.amr=38;5;137;1:*.application=38;5;116:*.aria2=38;5;241:*.asciidoc=38;5;184:*.asf=38;5;115:*.asm=38;5;81:*.ass=38;5;117:*.astro=38;5;135;1:*.atr=38;5;213:*.au=38;5;137;1:*.automount=38;5;45:*.bib=38;5;178:*.bsp=38;5;215:*.cab=38;5;215:*.caf=38;5;137;1:*.cap=38;5;29:*.car=38;5;57:*.cbr=38;5;141:*.cbz=38;5;141:*.cda=38;5;136;1:*.cdi=38;5;213:*.cdr=38;5;97:*.chm=38;5;141:*.cjs=38;5;074;1:*.cl=38;5;81:*.clj=38;5;41:*.cljc=38;5;41:*.cljs=38;5;41:*.cljw=38;5;41:*.cnc=38;5;7:*.coffee=38;5;079;1:*.comp=38;5;136:*.cp=38;5;75:*.cr=38;5;81:*.crx=38;5;215:*.cs=38;5;81:*.csv=38;5;78:*.ctp=38;5;81:*.cue=38;5;116:*.dart=38;5;51:*.dat=38;5;137;1:*.db=38;5;60:*.def=38;5;7:*.deny=38;5;196:*.description=38;5;116:*.device=38;5;45:*.dhall=38;5;178:*.dicom=38;5;97:*.diff=38;5;197;3;4:*.directory=38;5;116:*.divx=38;5;114:*.djvu=38;5;141:*.dmp=38;5;29:*.doc=38;5;111:*.docm=38;5;111;4:*.docx=38;5;111:*.drw=38;5;99:*.dtd=38;5;178:*.dts=38;5;137;1:*.dwg=38;5;216:*.dylib=38;5;241:*.ear=38;5;215:*.ejs=38;5;135;1:*.el=38;5;81:*.elc=38;5;241:*.eln=38;5;241:*.eml=38;5;90;1:*.entitlements=1:*.epf=1:*.eps=38;5;99:*.epsf=38;5;99:*.epub=38;5;141:*.err=38;5;160;1:*.error=38;5;160;1:*.etx=38;5;184:*.ex=38;5;7:*.example=38;5;7:*.f=38;5;81:*.f03=38;5;81:*.f08=38;5;81:*.f4v=38;5;115:*.f90=38;5;81:*.f95=38;5;81:*.fcm=38;5;137;1:*.feature=38;5;7:*.flac=38;5;136;1:*.flif=38;5;97:*.flv=38;5;115:*.fm2=38;5;213:*.fmp12=38;5;60:*.fnt=38;5;66:*.fon=38;5;66:*.for=38;5;81:*.fp7=38;5;60:*.frag=38;5;136:*.ftn=38;5;81:*.fvd=38;5;202:*.fxml=38;5;178:*.gb=38;5;213:*.gba=38;5;213:*.gbc=38;5;213:*.gbr=38;5;7:*.gel=38;5;213:*.gemspec=38;5;41:*.ger=38;5;7:*.gg=38;5;213:*.ggl=38;5;213:*.gp3=38;5;115:*.gp4=38;5;115:*.gs=38;5;81:*.hi=38;5;110:*.hidden-color-scheme=38;5;241;3:*.hidden-tmTheme=38;5;241;3:*.hin=38;5;242;3:*.hjson=38;5;178:*.hpp=38;5;110:*.hs=38;5;81:*.htm=38;5;125;1:*.http=38;5;90;1:*.hxx=38;5;110:*.ii=38;5;110:*.iml=38;5;166:*.in=38;5;242;3:*.info=38;5;184:*.ini=1:*.ipa=38;5;215:*.ipk=38;5;213:*.ipynb=38;5;41:*.j64=38;5;213:*.jad=38;5;215:*.jhtm=38;5;125;1:*.jsm=38;5;079;1:*.jsonc=38;5;178:*.jsonl=38;5;178:*.jsonnet=38;5;178:*.jsp=38;5;079;1:*.jsx=38;5;074;1:*.jxl=38;5;97:*.kak=38;5;172:*.key=38;5;166:*.lagda=38;5;81:*.lagda.rst=38;5;81:*.lagda.tex=38;5;81:*.last-run=1:*.lhs=38;5;81:*.libsonnet=38;5;142:*.lisp=38;5;81:*.lnk=38;5;97;5:*.localized=38;5;239:*.localstorage=38;5;60:*.m=38;5;110:*.m2v=38;5;114:*.m3u=38;5;116:*.m3u8=38;5;116:*.m4=38;5;242;3:*.m4a=38;5;137;1:*.m4v=38;5;114:*.map=38;5;7:*.md5=38;5;116:*.mdb=38;5;60:*.mde=38;5;60:*.mdx=38;5;184:*.merged-ca-bundle=1:*.mf=38;5;7:*.mfasl=38;5;7:*.mht=38;5;125;1:*.mi=38;5;7:*.mid=38;5;136;1:*.midi=38;5;136;1:*.mjs=38;5;074;1:*.mkd=38;5;184:*.mkv=38;5;114:*.ml=38;5;81:*.mm=38;5;7:*.mobi=38;5;141:*.mod=38;5;137;1:*.moon=38;5;81:*.mount=38;5;45:*.mpg=38;5;114:*.msg=38;5;178:*.mtx=38;5;7:*.mustache=38;5;135;1:*.mysql=38;5;222:*.nc=38;5;60:*.ndjson=38;5;178:*.nds=38;5;213:*.nes=38;5;213:*.nfo=38;5;184:*.nib=38;5;57:*.nim=38;5;81:*.nimble=38;5;81:*.nix=38;5;155:*.nrg=38;5;202:*.nth=38;5;97:*.numbers=38;5;112:*.o=38;5;241:*.odb=38;5;111:*.odp=38;5;166:*.ods=38;5;112:*.odt=38;5;111:*.oga=38;5;137;1:*.ogg=38;5;137;1:*.ogm=38;5;114:*.ogv=38;5;115:*.opus=38;5;137;1:*.otf=38;5;66:*.pacnew=38;5;33:*.pages=38;5;111:*.pak=38;5;215:*.part=38;5;239:*.patch=38;5;197;3;4:*.path=38;5;45:*.pbxproj=1:*.pc=38;5;7:*.pcap=38;5;29:*.pcb=38;5;7:*.pcf=1:*.pcm=38;5;136;1:*.pdf=38;5;141:*.pfa=38;5;66:*.pfb=38;5;66:*.pfm=38;5;66:*.pgn=38;5;178:*.pgsql=38;5;222:*.pi=38;5;7:*.pid=38;5;248:*.pk3=38;5;215:*.pl=38;5;208:*.plist=1:*.plt=38;5;7:*.ply=38;5;216:*.pm=38;5;203:*.png=38;5;97:*.pod=38;5;184:*.pot=38;5;7:*.pps=38;5;166:*.ppt=38;5;166:*.ppts=38;5;166:*.pptsm=38;5;166;4:*.pptx=38;5;166:*.pptxm=38;5;166;4:*.prisma=38;5;222:*.properties=38;5;116:*.prql=38;5;222:*.ps=38;5;99:*.psd=38;5;97:*.psf=1:*.pug=38;5;135;1:*.pxd=38;5;97:*.pxm=38;5;97:*.qcow=38;5;202:*.rdata=38;5;178:*.rdf=38;5;7:*.rkt=38;5;81:*.rlib=38;5;241:*.rmvb=38;5;114:*.rnc=38;5;178:*.rng=38;5;178:*.rom=38;5;213:*.rss=38;5;178:*.rst=38;5;184:*.rstheme=1:*.rtf=38;5;111:*.s3m=38;5;137;1:*.sample=38;5;114:*.sc=38;5;41:*.scan=38;5;242;3:*.sch=38;5;7:*.scm=38;5;7:*.scpt=38;5;219:*.scss=38;5;105;1:*.sed=38;5;172:*.service=38;5;45:*.sfv=38;5;116:*.sgml=38;5;178:*.sid=38;5;137;1:*.sis=38;5;7:*.sms=38;5;213:*.socket=38;5;45:*.sparseimage=38;5;202:*.spl=38;5;7:*.spv=38;5;217:*.srt=38;5;117:*.ssa=38;5;117:*.st=38;5;213:*.state=38;5;248:*.stderr=38;5;160;1:*.stl=38;5;216:*.storyboard=38;5;196:*.strings=1:*.sty=38;5;7:*.sub=38;5;117:*.sublime-*=1:*.sug=38;5;7:*.sup=38;5;117:*.svelte=38;5;135;1:*.svg=38;5;99:*.swo=38;5;244:*.sx=38;5;81:*.target=38;5;45:*.tdy=38;5;7:*.tfnt=38;5;7:*.tfstate=38;5;168:*.tfvars=38;5;168:*.tg=38;5;7:*.theme=38;5;116:*.tif=38;5;97:*.tiff=38;5;97:*.timer=38;5;45:*.tmTheme=1:*.toast=38;5;202:*.tsv=38;5;78:*.tsx=38;5;074;1:*.ttf=38;5;66:*.twig=38;5;81:*.typelib=38;5;60:*.urlview=38;5;116:*.user-ca-bundle=1:*.v=38;5;81:*.vala=38;5;81:*.vapi=38;5;81:*.vcard=38;5;7:*.vcd=38;5;202:*.vcf=38;5;7:*.vdf=38;5;215:*.vdi=38;5;202:*.vert=38;5;136:*.vfd=38;5;202:*.vhd=38;5;202:*.vhdx=38;5;202:*.vmdk=38;5;202:*.vob=38;5;115;1:*.vpk=38;5;215:*.vtt=38;5;117:*.vue=38;5;135;1:*.wav=38;5;136;1:*.webloc=38;5;116:*.webm=38;5;115:*.webp=38;5;97:*.wgsl=38;5;97:*.woff=38;5;66:*.woff2=38;5;66:*.wrl=38;5;216:*.wv=38;5;136;1:*.wvc=38;5;136;1:*.xcf=38;5;7:*.xcsettings=1:*.xcuserstate=1:*.xcworkspacedata=1:*.xib=38;5;208:*.xla=38;5;76:*.xln=38;5;7:*.xls=38;5;112:*.xlsx=38;5;112:*.xlsxm=38;5;112;4:*.xltm=38;5;73;4:*.xltx=38;5;73:*.xpi=38;5;215:*.xpm=38;5;97:*.xsd=38;5;178:*.xsh=38;5;41:*.z[0-9]{0,2}=38;5;239:*.zig=38;5;81:*.zwc=38;5;241:*.zx[0-9]{0,2}=38;5;239:'
# encrypted files
LS_COLORS+='*.enc=38;5;69;3:*.gpg=38;5;69;3:*.p12=38;5;69;3:*.p7s=38;5;69;3:*.pem=38;5;69;3:*.pgp=38;5;69;3:*.sig=38;5;69;3:*.signature=38;5;69;3:*.asc=38;5;69;3:*.bfe=38;5;69;3:*.current=38;5;69;3:'
# packages
LS_COLORS+='*.apk=38;5;215:*.deb=38;5;215:*.dll=38;5;241:*.dmg=38;5;215:*.rpm=38;5;215:*.war=38;5;215:*.bin=38;5;202:*.iso=38;5;202:*.jar=38;5;215:*.out=38;5;242;3:'
# dump/log
LS_COLORS+='*.bak=38;5;241;3:*.dump=38;5;241;3:*.mdump=38;5;241;3:*.stackdump=38;5;241;3:*.zcompdump=38;5;241;3:*.snapshot=38;5;45:*.swap=38;5;241;3:*.swp=38;5;241;3:*.tmp=38;5;241;3:*.viminfo=1;3:*vim_mru_files=1;3:*.DS_Store=38;5;239;3:*.old=38;5;239;3:*.org=38;5;241;3:*.norg=38;5;241;3:*.orig=38;5;241;3:*.sav=38;5;241;3:*.log=38;5;241;3:*.un~=38;5;241;3:'
# audio/video
LS_COLORS+='*.wma=38;5;137;1:*.wmv=38;5;114:*.JPG=38;5;97:*.MOV=38;5;114:*.ape=38;5;136;1:*.avi=38;5;114:*.bmp=38;5;97:*.gif=38;5;97:*.icns=38;5;97:*.ico=38;5;97:*.ics=38;5;7:*.img=38;5;202:*.jpeg=38;5;97:*.jpg=38;5;97:*.mov=38;5;114:*.mp3=38;5;137;1:*.mp4=38;5;114:*.mp4a=38;5;137;1:*.mpeg=38;5;114:*.torrent=38;5;116:*.ts=38;5;074;1:'
# docs
LS_COLORS+='*AUTHORS=38;5;172;1:*CHANGELOG=38;5;172;1:*CHANGES=38;5;172;1:*CODEOWNERS=38;5;172;1:*CONTRIBUTING=38;5;172;1:*CONTRIBUTORS=38;5;172;1:*COPYING=38;5;172;1:*COPYRIGHT=38;5;172;1:*CodeResources=38;5;239:*Containerfile=38;5;143:*INSTALL=38;5;220;1:*LICENSE=38;5;220;1:*LS_COLORS=38;5;197;1;3;4:*MANIFEST=38;5;243:*[Mm]akefile=38;5;143:*NOTICE=38;5;220;1:*PATENTS=38;5;220;1:*PkgInfo=38;5;239:*README.rst=38;5;172;1:*VERSION=38;5;172;1:*authorized_keys=1;3:*core=38;5;241:*config=1;3:*lock=38;5;248:*lockfile=38;5;248:*pm_to_blib=38;5;264:'
# git
LS_COLORS+='*.git=38;5;133;3:*.gitattributes=38;5;133;3:*.gitignore_global=38;5;60;3:*.gitignore=38;5;60;3:*.github=38;5;133:*.gitmodules=38;5;198;3:'
# system rc
LS_COLORS+='*history=38;5;242;3:*rc=38;5;66;3:*.profile=1;3:*.bash_login=1;3:*.bash_logout=1;3:*.bash_profile=1;3:*.zlogin=1;3:*.zlogout=1;3:*.zprofile=1;3:*.zshenv=1;3:*id_dsa=38;5;192;3:*id_ecdsa=38;5;192;3:*id_ed25519=38;5;192;3:*id_rsa=38;5;192;3:*known_hosts=1;3:*known_hosts.old*=1;3:*cfg=1;3:*conf=1;3:*ignore=38;5;60;3:*ignore_global=38;5;60;3:*.containerignore=38;5;60;3:*.dockerignore=38;5;60;3:'
# program/script
LS_COLORS+='*.bat=38;5;134:*.BAT=38;5;134:*.sh=38;5;143:*.bash=38;5;143:*.fish=38;5;134:*.zsh=38;5;134:*.py=38;5;99:*.pyc=38;5;105:*.go=38;5;81:*.h=38;5;110:*.h++=38;5;110:*.c=38;5;75:*.cc=38;5;75:*.c++=38;5;75:*.cpp=38;5;75:*.cxx=38;5;75:*.tcc=38;5;110:*.r=38;5;143:*.R=38;5;143:*.r[0-9]{0,2}=38;5;239:*.rake=38;5;155:*.rb=38;5;184:*.ahk=38;5;184:*.awk=38;5;184:*.less=38;5;105;1:*.css=38;5;105;1:*.html=38;5;125;1:*.java=38;5;079;1:*.json=38;5;178:*.json5=38;5;178:*.markdown=38;5;134:*.md=38;5;134:*.msql=38;5;222:*.php=38;5;81:*.sass=38;5;105;1:*.sassc=38;5;244:*.swift=38;5;219:*.tcl=38;5;64;1:*.txt=38;5;253:*.vim=38;5;134:*.xml=38;5;178:*.yaml=38;5;178:*.yml=38;5;178:*.vb=38;5;81:*.vba=38;5;81:*.vbs=38;5;81:*.js=38;5;074;1:*.lua=38;5;178:*.rs=38;5;178:*.ru=38;5;7:*.s=38;5;110:*.scala=38;5;114:*.sql=38;5;222:*.sqlite=38;5;60:*.t=38;5;114:*.tex=38;5;184:*.textile=38;5;184:*.tf=38;5;168:*.tfm=38;5;7:*.toml=38;5;178:*[Dd]ockerfile=38;5;143:'
export LS_COLORS

way to verify

# i.e.:
LS_COLORS='bd=38;5;68:ca=38;5;17:cd=38;5;113;1:di=38;5;108:do=38;5;127:ex=38;5;31;1:pi=38;5;126:fi=0:ln=target:mh=38;5;222;1:no=0:or=48;5;196;38;5;232;1:ow=38;5;220;1:sg=48;5;3;38;5;0:su=38;5;220;1;3;100;1:so=38;5;197:st=38;5;86;48;5;234:tw=48;5;235;38;5;139;3:'

# check via
$ echo -e """
  \033[38;5;68m               bd=  \033[0m
  \033[38;5;17m               ca=  \033[0m
  \033[38;5;113;1m            cd=  \033[0m
  \033[38;5;108m              di=  \033[0m
  \033[38;5;127m              do=  \033[0m
  \033[38;5;31;1m             ex=  \033[0m
  \033[38;5;126m              pi=  \033[0m
  \033[38;5;222;1m            mh=  \033[0m
  \033[48;5;196;38;5;232;1m   or=  \033[0m
  \033[38;5;220;1m            ow=  \033[0m
  \033[48;5;3;38;5;0m         sg=  \033[0m
  \033[38;5;220;1;3;100;1m    su=  \033[0m
  \033[38;5;197m              so=  \033[0m
  \033[38;5;86;48;5;234m      st=  \033[0m
  \033[48;5;235;38;5;139;3m   tw=  \033[0m
  """

$ cat /etc/resolv.conf
# Dynamic resolv.conf(5) file for glibc resolver(3) generated by resolvconf(8)
# DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTEN
nameserver 8.8.8.8
nameserver 8.8.4.4
nameserver 127.0.1.1

$ cat /etc/resolvconf/resolv.conf.d/head
# Dynamic resolv.conf(5) file for glibc resolver(3) generated by resolvconf(8)
# DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTEN
nameserver 8.8.8.8
nameserver 8.8.4.4
$ sudo resolvconf -u

# or
$ cat /etc/dhcp/dhclient.conf | grep "prepend domain-name-servers"
prepend domain-name-servers 8.8.8.8, 8.8.4.4;

# or
$ cat /etc/network/interfaces | grep dns
    dns-nameservers 8.8.8.8 8.8.4.4

disable firewall

$ sudo systemctl stop firewalld
$ sudo systemctl disable firewalld
$ sudo systemctl mask firewalld

check result

$ sudo systemctl is-enabled firewalld
$ sudo systemctl is-active firewalld
$ sudo firewall-cmd --state

off swap

$ sudo swapoff -a
$ sudo bash -c "/usr/bin/sed -e 's:^\\(.*swap.*\\)$:# \\1:' -i /etc/fstab"

disable selinux

$ setenforce 0
$ sudo bash -c "/usr/bin/sed 's/^SELINUX=enforcing$/SELINUX=permissive/' -i /etc/selinux/config"

references:

installation
```
$ yum -y install setools-console
```

setup for exiting account

$ semanage login -a -s staff_u <account>

# or
$ semanage login -a -s staff_u -r s0-s0:c0.c100 <account>

Modifying an existing mapping

$ semanage login -m -s sysadm_u <account>

delete a mapping
```
$ semanage login -d <account>
```
list mappings
```
$ semanage user -l
```

tips

about `whatis`

$ whatis whois
whois (1)            - client for the whois directory service
$ whatis which
which (1)            - locate a command
$ whatis whereis
whereis (1)          - locate the binary, source, and manual page files for a command

$ ntpdate pool.ntp.org && hwclock --systohc && hwclock --adjust

$ rsync -a --link-dest=/media/backup/$HOSTNAME/$PREVDATE '--exclude=/[ps][ry][os]' --exclude=/media/backup/$HOSTNAME / /media/backup/$HOSTNAME/$DATE/

service

enable/disable service

$ sudo systemctl enable --now kubelet
Created symlink /etc/systemd/system/multi-user.target.wants/kubelet.service → /etc/systemd/system/kubelet.service
$ sudo systemctl disable --now docker

check service enable or not

$ sudo systemctl is-enabled firewalld
$ sudo systemctl is-active firewalld

or
```
$ sudo firewall-cmd --state
not running
```

start/stop service

$ sudo system start <service>
$ sudo system stop <service>

check log

$ journalctl -u docker -f

system encoding

references:
/etc/default/locale – on Ubuntu/Debian
/etc/locale.conf – on CentOS/RHEL
important files:
/etc/default/locale
/etc/locale.gen
/etc/environment
/usr/share/locales
/var/lib/locales/supported.d/local
/usr/local/share/i18n/SUPPORTED
/usr/share/i18n/SUPPORTED

setup via environment

$ sudo bash -c 'cat >> /etc/bash.bashrc' << EOF
export LANG=en_US.UTF-8
export LANGUAGE=$LANG
export LC_COLLATE=$LANG
export LC_CTYPE=$LANG
export LC_MESSAGES=$LANG
export LC_MONETARY=$LANG
export LC_NUMERIC=$LANG
export LC_TIME=$LANG
export LC_ALL=$LANG
EOF

$ source /etc/bash.bashrc

check locale for account

$ sudo su -l -c locale <account>

# i.e.:
$ sudo su -l -c locale marslo
LANG=en_US.UTF-8
LC_CTYPE="en_US.UTF-8"
LC_NUMERIC="en_US.UTF-8"
LC_TIME="en_US.UTF-8"
LC_COLLATE="en_US.UTF-8"
LC_MONETARY="en_US.UTF-8"
LC_MESSAGES="en_US.UTF-8"
LC_PAPER="en_US.UTF-8"
LC_NAME="en_US.UTF-8"
LC_ADDRESS="en_US.UTF-8"
LC_TELEPHONE="en_US.UTF-8"
LC_MEASUREMENT="en_US.UTF-8"
LC_IDENTIFICATION="en_US.UTF-8"
LC_ALL=en_US.UTF-8

setup via `locale` command

$ apt-get install -y locales

$ sudo locale-gen en_US.UTF-8
$ sudo update-locale LANG=en_US.UTF-8
$ source /etc/default/locale

# or
$ sudo dpkg-reconfigure locales

# or
$ sudo localectl set-locale LANG=en_US.UTF-8,LC_ALL=en_US.UTF-8

setup environment files

$ sudo bash -c 'cat >> /etc/environment' << EOF
LANG="en_US.UTF-8"
LANGUAGE="en_US:en:en_US:en"
EOF

locales

CentOS8

installation

references:
locale.conf files support the following environment variables.
LANG
LANGUAGE
LC_ADDRESS
LC_COLLATE
LC_CTYPE
LC_IDENTIFICATION
LC_MEASUREMENT
LC_MESSAGES
LC_MONETARY
LC_NAME
LC_NUMERIC
LC_PAPER
LC_TELEPHONE
LC_TIME

$ sudo dnf install -y langpacks-en glibc-all-langpacks glibc-langpack-en glibc-langpack-zh
$ sudo localectl set-locale LANG=en_US.UTF-8

# or
$ sudo localectl set-locale LANG=en_US.UTF-8 LANGUAGE=en_US:en:C:es_E

# option
$ sudo localedef -c -f UTF-8 -i en_US en_US.UTF-8

check

$ locale
LANG=en_US.UTF-8
LC_CTYPE="en_US.UTF-8"
LC_NUMERIC="en_US.UTF-8"
LC_TIME="en_US.UTF-8"
LC_COLLATE="en_US.UTF-8"
LC_MONETARY="en_US.UTF-8"
LC_MESSAGES="en_US.UTF-8"
LC_PAPER="en_US.UTF-8"
LC_NAME="en_US.UTF-8"
LC_ADDRESS="en_US.UTF-8"
LC_TELEPHONE="en_US.UTF-8"
LC_MEASUREMENT="en_US.UTF-8"
LC_IDENTIFICATION="en_US.UTF-8"
LC_ALL=en_US.UTF-8

$ localectl status
   System Locale: LANG=en_US.UTF-8
                  LANGUAGE=en_US:en:C:es_ES
       VC Keymap: us
      X11 Layout: us

$ localectl [--no-pager] list-locales

more options

$ yum list available | grep glibc-langpack

get infomation

$ locale -k LC_TIME
$ locale -k LC_TELEPHONE
$ locale -k LC_PAPER

# list all
$ locale -a

# or
$ localedef --list-archive

print out terminfo descriptions

references:

$ infocmp
$ tput rmm
$ sudo yum install *terminfo

langpacks

references:

list

$ sudo yum list langpacks-*
$ sudo yum list installed langpacks*
$ sudo yum list available langpacks*
$ sudo yum repoquery --whatsupplements langpacks-<locale_code>

install

$ sudo yum install langpacks-<locale_code>
# i.e.:
$ sudo yum install -y langpacks-en langpacks-en_GB langpacks-zh_CN

# or saving disk space by using glibc-langpack-<locale_code>
$ sudo yum install -y glibc-common glibc-all-langpacks
# or
$ sudo yum install -y *langpacks
# or
$ sudo yum install -y glibc-minimal-langpack
# or
$ sudo yum install -y glibc-langpack-en

chinese

$ sudo yum groupinstall "Chinese Support"

applications

disable lock screen in CentOS 8

manually
- Applications -> Settings -> Poswer Manager -> Display
- Applications -> Settings -> Screensaver -> Lock Screen

$ xset s off
$ xset s noblank
# disable the power management using dpms to power monitor down
$ xset -dpms

via script

#!/bin/sh
export DISPLAY=:0.0
xset s off
xset s noblank
xset -dpms

[!NOTE|label:references:]

$ gconftool-2 --type int  --set /desktop/gnome/session/idle_delay 1
$ gconftool-2 --type bool --set /desktop/gnome/lockdown/disable_lock_screen false

sogou Pinyin input method

$ sudo add-apt-repository ppa:fcitx-team/nightly
$ sudo apt-get update
$ sudo apt-get install fcitx-sogoupinyin
$ # sudo apt-get remove ibus

specified terminal size

$ gnome-terminal --geometry=123x42+0+0

burn bootable usb stick

[!NOTE|label:references:]

Disk Utility -> Erase
- format: MS-DOS (FAT)
- scheme: GUID Partition Map

remove system

[!NOTE|label:references:]

remove initrd.img and vmlinuz-*

$ ls -altrh /boot/vmlinuz-6.2.0-39-generic /boot/initrd.img-6.2.0-39-generic
-rw------- 1 root root 14M Nov 16 01:50 /boot/vmlinuz-6.2.0-39-generic
-rw-r--r-- 1 root root 71M Jan  5 19:58 /boot/initrd.img-6.2.0-39-generic

$ sudo rm -rf /boot/vmlinuz-6.2.0-39-generic /boot/initrd.img-6.2.0-39-generic

update grub

$ sudo update-grub
Sourcing file `/etc/default/grub'
Sourcing file `/etc/default/grub.d/init-select.cfg'
Generating grub configuration file ...
Found linux image: /boot/vmlinuz-6.5.0-14-generic
Found initrd image: /boot/initrd.img-6.5.0-14-generic
Found linux image: /boot/vmlinuz-6.2.0-39-generic
Found initrd image: /boot/initrd.img-6.2.0-39-generic
Memtest86+ needs a 16-bit boot, that is not available on EFI, exiting
Warning: os-prober will not be executed to detect other bootable partitions.
Systems on them will not be added to the GRUB boot configuration.
Check GRUB_DISABLE_OS_PROBER documentation entry.
Adding boot menu entry for UEFI Firmware Settings ...
done

Q&A

yum issue after python upgrade to 3.x

[!NOTE|label:references:]

issue

SyntaxError: invalid syntax
  File "/usr/libexec/urlgrabber-ext-down", line 28
    except OSError, e:
                  ^

solution

$ sed -r '1s/^(.*python)$/\12/g' -i /usr/libexec/urlgrabber-ext-down

or change shebang from #! /usr/bin/python to #! /usr/bin/python2

$ vim /usr/libexec/urlgrabber-ext-down
... change '#! /usr/bin/python' to  '#! /usr/bin/python2'

none of the providers can be installed in `dnf upgrade`

issue

$ sudo dnf update
...
Last metadata expiration check: 0:01:44 ago on Tue 08 Aug 2023 08:43:40 PM PDT.
Error:
 Problem 1: package authselect-compat-1.1-2.el8.x86_64 requires authselect(x86-64) = 1.1-2.el8, but none of the providers can be installed
  - cannot install both authselect-1.2.2-3.el8.x86_64 and authselect-1.1-2.el8.x86_64
  - cannot install both authselect-1.1-2.el8.x86_64 and authselect-1.2.2-3.el8.x86_64
  - cannot install the best update candidate for package authselect-compat-1.1-2.el8.x86_64
  - cannot install the best update candidate for package authselect-1.1-2.el8.x86_64
 Problem 2: package dbus-x11-1:1.12.8-9.el8.x86_64 requires dbus-daemon = 1:1.12.8-9.el8, but none of the providers can be installed
  - cannot install both dbus-daemon-1:1.12.8-14.el8.x86_64 and dbus-daemon-1:1.12.8-9.el8.x86_64
  - cannot install both dbus-daemon-1:1.12.8-9.el8.x86_64 and dbus-daemon-1:1.12.8-14.el8.x86_64
  - cannot install the best update candidate for package dbus-x11-1:1.12.8-9.el8.x86_64
  - cannot install the best update candidate for package dbus-daemon-1:1.12.8-9.el8.x86_64
 Problem 3: package libstdc++-devel-8.3.1-4.5.el8.x86_64 requires libstdc++(x86-64) = 8.3.1-4.5.el8, but none of the providers can be installed
 ...

upgrade bypass issue

[!NOTE] issue stills exists, but upgrade will be executed successfully

$ sudo yum upgrade --allowerasing --nobest

Last metadata expiration check: 0:02:43 ago on Tue 08 Aug 2023 08:43:40 PM PDT.
Dependencies resolved.

 Problem 1: cannot install the best update candidate for package cups-client-1:2.2.6-28.el8.x86_64
 ...
 Problem 2: cannot install the best update candidate for package gcc-8.3.1-4.5.el8.x86_64
 ...
 Problem 3: package rpm-libs-4.14.3-19.el8.x86_64 requires liblua-5.3.so()(64bit), but none of the providers can be installed
 ...
 Problem 4: cannot install the best update candidate for package python3-gobject-3.28.3-1.el8.x86_64
 ...
=======================================================================================================================
 Package                                    Arch       Version                              Repository            Size
=======================================================================================================================
Upgrading:
 NetworkManager                             x86_64     1:1.32.10-4.el8                      centos-baseos        2.6 M
 NetworkManager-libnm                       x86_64     1:1.32.10-4.el8                      centos-baseos        1.8 M
 NetworkManager-team                        x86_64     1:1.32.10-4.el8                      centos-baseos        148 k
 NetworkManager-tui                         x86_64     1:1.32.10-4.el8                      centos-baseos        336 k
 ...

fix with erase conflict packges permanently

$ sudo dnf repolist
repo id                                       repo name
baseos                                        CentOS Linux 8 - BaseOS
epel                                          Extra Packages for Enterprise Linux 8 - x86_64
extras                                        CentOS Linux 8 - Extras
jfrog-cli                                     jfrog-cli
mono-centos8-stable                           mono-centos8-stable

$ sudo dnf update --refresh --allowerasing
$ sudo dnf distro-sync -y

ls: Argument list too long

references:

[!NOTE] config files
/etc/sysctl.conf
/etc/system
/etc/security/limits.conf
#Each line describes a limit for a user in the form:
#
#<domain>        <type>  <item>  <value>
#
#Where:
#<domain> can be:
#        - a user name
#        - a group name, with @group syntax
#        - the wildcard *, for default entry
#        - the wildcard %, can be also used with %group syntax,
#                 for maxlogin limit
/etc/limits.conf
/etc/security/limits.d/*.conf
/etc/security/limits.d/99-nproc-devops.conf
all modifications requires logout and login again
$ sudo pkill -u <username>

check the limit

$ getconf ARG_MAX
2097152

# or
$ echo $(( $(ulimit -s)*1024 / 4 ))
2097152

# check all
$ ulimit -a
core file size          (blocks, -c) unlimited
data seg size           (kbytes, -d) unlimited
scheduling priority             (-e) 0
file size               (blocks, -f) unlimited
pending signals                 (-i) 320869
max locked memory       (kbytes, -l) 16384
max memory size         (kbytes, -m) unlimited
open files                      (-n) 1024
pipe size            (512 bytes, -p) 8
POSIX message queues     (bytes, -q) 819200
real-time priority              (-r) 0
stack size              (kbytes, -s) 8192
cpu time               (seconds, -t) unlimited
max user processes              (-u) 320869
virtual memory          (kbytes, -v) unlimited
file locks                      (-x) unlimited

# or
$ grep Huge /proc/meminfo
AnonHugePages:     43008 kB
ShmemHugePages:        0 kB
HugePages_Total:       0
HugePages_Free:        0
HugePages_Rsvd:        0
HugePages_Surp:        0
Hugepagesize:       2048 kB
Hugetlb:               0 kB

check page size

$ cat /proc/sys/vm/nr_hugepages
0
# modify
$ echo 17290 > /proc/sys/vm/nr_hugepages

# or
$ grep Hugepagesize /proc/meminfo
Hugepagesize:       2048 kB

## centos7
$ grep GRUB_CMDLINE_LINUX /etc/default/grub
GRUB_CMDLINE_LINUX="crashkernel=auto rd.lvm.lv=centos/root rd.lvm.lv=centos/swap rhgb quiet"
# append `default_hugepagesz=1G` to GRUB_CMDLINE_LINUX
GRUB_CMDLINE_LINUX="crashkernel=auto rd.lvm.lv=centos/root rd.lvm.lv=centos/swap rhgb quiet default_hugepagesz=1G"

## centos8
$ grep kernelopts /boot/grub2/grubenv
kernelopts=root=/dev/mapper/rhel-root ro crashkernel=auto resume=/dev/mapper/rhel-swap rd.lvm.lv=rhel/root rd.lvm.lv=rhel/swap rhgb quiet
# append default_hugepagesz=1G to kernelopts
kernelopts=root=/dev/mapper/rhel-root ro crashkernel=auto resume=/dev/mapper/rhel-swap rd.lvm.lv=rhel/root rd.lvm.lv=rhel/swap rhgb quiet default_hugepagesz=1G

rebuid bios & efi

# for bios booting
$ sudo grub2-mkconfig -o /boot/grub/grub.cfg
# for efi booting
$ sudo grub2-mkconfig -o /boot/efi/EFI/redhat/grub.cfg

setup ulimit

$ ulimit -s
8192

$ ulimit -s 65536
$ ulimit -s
65536

via limits.d

$ cat /etc/security/limits.d/99-nproc-devops.conf
devops soft    nproc    32768
devops soft    nofile 65535

modify open file

# via sysctl
$ sudo sysctl -w fs.file-max=500000
fs.file-max = 500000
$ cat /proc/sys/fs/file-max
500000

# or via sysctl.conf
$ echo 'fs.file-max = 500000' >> /etc/sysctl.conf

# or via ulimit
$ ulimit -Sn 5000
#         |
#         v
#  soft open file
$ ulimit -Hn 50000
#         |
#         v
#  hard open file

# or
$ cat /etc/security/limits.conf
* hard nofile 50000
* soft nofile 5000

setup for particular group

# setup for group `marslo` and `docker`
$ cat /etc/security/limits.conf
...
@marslo   - nofile    65535
@docker   - nofile    65535

others

motd

$ sudo chmod -x /etc/update-motd.d/00-header \
                /etc/update-motd.d/10-help-text \
                /etc/update-motd.d/50-motd-news

$ cat << 'EOF' > /etc/landscape/client.conf
[sysinfo]
exclude_sysinfo_plugins = Temperature, LandscapeLink
EOF

motd upgrade disable

$ sudo mv /etc/update-motd.d/90-updates-available /etc/update-motd.d/org.90-updates-available.org

cockpit

$ sudo systemctl enable --now cockpit.socket
Created symlink /etc/systemd/system/sockets.target.wants/cockpit.socket → /usr/lib/systemd/system/cockpit.socket.

# visit via http://<ip.address>:9090

disable

$ sudo systemctl stop cockpit.socket
$ sudo systemctl disable cockpit.socket

motd

```
$ sudo yum remove -y cockpit-ws
```

disable in hard way

$ sudo ln -sfn /dev/null /etc/motd.d/cockpit

# details
# https://serverok.in/centos-8-disable-activate-the-web-console#comment-35367
$ cat /etc/issue.d/cockpit.issue                // issue shows before login
$ cat /etc/motd.d/cockpit                       // moted shows after login

$ la /etc/motd.d/cockpit
lrwxrwxrwx. 1 root root 17 Mar 15  2021 /etc/motd.d/cockpit -> /run/cockpit/motd
$ la /etc/issue.d/cockpit.issue
lrwxrwxrwx. 1 root root 17 Mar 15  2021 /etc/issue.d/cockpit.issue -> /run/cockpit/motd
$ la /run/cockpit/motd
lrwxrwxrwx. 1 root root 11 Jan  6 03:11 /run/cockpit/motd -> active.motd
$ la /run/cockpit/active.motd
-rw-r-----. 1 root wheel 80 Jan  6 03:11 /run/cockpit/active.motd

package info

 $ sudo yum search cockpit
 cockpit.x86_64 : Web Console for Linux servers

 $ sudo yum list installed | grep cockpit
 cockpit.x86_64                                     251.1-1.el8                                   @baseos
 cockpit-bridge.x86_64                              251.1-1.el8                                   @baseos
 cockpit-packagekit.noarch                          251.1-1.el8                                   @appstream
 cockpit-podman.noarch                              33-1.module_el8.5.0+890+6b136101              @appstream
 cockpit-storaged.noarch                            251.1-1.el8                                   @appstream
 cockpit-system.noarch                              251.1-1.el8                                   @baseos
 cockpit-ws.x86_64                                  251.1-1.el8                                   @baseos

 $ rpm -ql cockpit-ws.x86_64
 /etc/cockpit
 /etc/cockpit/ws-certs.d
 /etc/issue.d/cockpit.issue
 /etc/motd.d/cockpit                 // for moted
 /etc/pam.d/cockpit
 ...

hardware spec

os

hardware

cpu

memory

bios

disk

RAID Info

network

environment variables

graphics card driver

get system info

top

ps

find the zombie process

set system info

clear duplicated PATH

sysctl

change net.bridge

LS_COLORS

disable firewall

off swap

disable selinux

tips

about whatis

service

enable/disable service

start/stop service

check log

system encoding

setup via environment

setup via locale command

locales

langpacks

applications

disable lock screen in CentOS 8

sogou Pinyin input method

specified terminal size

burn bootable usb stick

remove system

Q&A

yum issue after python upgrade to 3.x

none of the providers can be installed in dnf upgrade

ls: Argument list too long

others

motd

motd

about `whatis`

setup via `locale` command

none of the providers can be installed in `dnf upgrade`