Releases

Syslog Message Severities

https://tools.ietf.org/html/rfc5424#section-6.2.1

0       Emergency: system is unusable
1       Alert: action must be taken immediately
2       Critical: critical conditions
3       Error: error conditions
4       Warning: warning conditions
5       Notice: normal but significant condition
6       Informational: informational messages
7       Debug: debug-level messages

User & Permission

add user to group

sudo adduser foobar www-data
sudo usermod -a -G ftp tony

rename

pkill -9 -u ubuntu
usermod --login fzinfz --move-home --home /home/fzinfz ubuntu
sed -i 's/ubuntu/fzinfz/' /etc/sudoers

password

echo user:pwd | chpasswd

sudoers

sudo visudo
    root    ALL=(ALL) ALL # {terminals}=({users}) {commands}
    %supergroup  ALL=(ALL) NOPASSWD:ALL

chown

chown -h myuser:mygroup mysymbolic

Package Management

Ubuntu

Main - Canonical-supported free and open-source software.
Universe - Community-maintained free and open-source software.
Restricted - Proprietary drivers for devices.
Multiverse - Software restricted by copyright or legal issues. 

# https://mirror.tuna.tsinghua.edu.cn/help/ubuntu/
deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial main restricted universe multiverse

Debian

→ experimental
→ unstable(Sid) → testing → stable
Unstable - repository where new & untested packages are introduced.
Testing - repository with packages from unstable, if no bug are found within 10 days.

main consists of DFSG-compliant packages, which do not rely on software outside this area to operate. These are the only packages considered part of the Debian distribution.
contrib packages contain DFSG-compliant software, but have dependencies not in main (possibly packaged for Debian in non-free).
non-free contains software that does not comply with the DFSG. 

deb http://mirror.sjtu.edu.cn/debian/ bullseye main contrib non-free

dpkg

dpkg --get-selections   # list installed

To install .deb manually, visit linux/kernel page.

apt

apt-get install linux-base -t jessie-backports
apt-cache search linux-image | grep linux-image-4
apt install linux-image-4.10.0-9-generic linux-image-extra-4.10.0-9-generic

apt show linux-image-extra-4.10*

apt-get install --only-upgrade docker-engine

apt policy docker-ce | head -n 20

apt-get autoclean
apt list --installed

rm -r /var/lib/apt/lists/*

echo 'Acquire::http::Proxy "http://192.168.88.25:7890"; ' > /etc/apt/apt.conf.d/proxy

ssh server

deb http://.../debian/ buster main contrib non-free

apt install openssh-server # not "openssl"

journalctl -u ssh # fix： ssh-rsa not in PubkeyAcceptedAlgorithms
PubkeyAcceptedAlgorithms  +ssh-rsa

Serial

https://help.ubuntu.com/community/SerialConsoleHowto

GRUB_CMDLINE_LINUX="console=tty0 console=ttyS0,115200n8"

client

screen /dev/ttyUSB0 115200
picocom -b 115200 /dev/ttyUSB0

Benchmark

http://www.brendangregg.com/Perf/linux_benchmarking_tools.png

    sysbench --test=cpu --cpu-max-prime=20000 --num-threads=32 run

    wget http://www.numberworld.org/y-cruncher/y-cruncher%20v0.7.9.9510-static.tar.xz
    tar -xf y-cruncher*.tar.xz

mosh

apt install mosh -y
ss -lntup | grep mosh # 60000:61000/udp | **after** client connected

sshd

mobaxterm login failed: No supported authentication methods

PubkeyAcceptedAlgorithms +ssh-rsa # sshd_config # journalctl -u ssh

ssh redirect

ssh -L 9000:public.com:80   # visit local:9000 -> public.com:80
ssh -L 0.0.0.0:54321:127.0.0.1:54321 remote -p 22
ssh -R 9000:localhost:3000  # visit remote:9000 -> local:3000, "GatewayPorts yes" in sshd_config
    -nNT -L ...   # port forwarding only, no shell

font

apt-get install  xfonts-base

SELinux

getenforce
semanage port -a -t mongod_port_t -p tcp 27017

I18N & I10N

apt install -y locales-all
locale -a
dpkg-reconfigure locales

yum grouplist chinese-support

sudo apt-get install -y ttf-wqy-microhei  #文泉驿-微米黑
sudo apt-get install -y ttf-wqy-zenhei  #文泉驿-正黑
sudo apt-get install -y xfonts-wqy #文泉驿-点阵宋体

cache diagnostics

https://hoytech.com/vmtouch/

git clone https://github.com/hoytech/vmtouch.git
cd vmtouch && make && sudo make install

Discovering which files your OS is caching
Telling the OS to cache or evict certain files or regions of files
Locking files into memory so the OS won't evict them
Preserving virtual memory profile when failing over servers
Keeping a "hot-standby" file-server
Plotting filesystem cache usage over time
Maintaining "soft quotas" of cache usage
Speeding up batch/cron jobs

WOL

ethtool enp1s0  | grep Wake-on

p (PHY activity)
u (unicast activity)
m (multicast activity)
b (broadcast activity)
g (magic packet activity) *
a (ARP activity)
d (disabled)

CPU

getconf LONG_BIT

check_cpu_core_mapping

https://www.ibm.com/support/knowledgecenter/en/SSQPD3_2.6.0/com.ibm.wllm.doc/mappingcpustocore.html
same physical/core ID =》 simultaneous multi threads (SMTs) / HT

cat /proc/cpuinfo  | grep -P 'processor|physical id|core id|^$'

pip install walnut    # pretty print
for c in sorted([ ( int(c['processor']), int(c['physical id']), int(c['core id']) ) for c in cpu.dict().values()]): print c

USB Persistence

https://docs.kali.org/downloading/kali-linux-live-usb-persistence
http://antix.mepis.org/index.php?title=Using_liveusb_with_persistence

kali

x86/M1/Live/VM/WSL/etc: https://www.kali.org/get-kali
Docker: https://hub.docker.com/u/kalilinux/

ssh

Since 2022.1: https://www.kali.org/docs/general-use/ssh-configuration/ - kali-tweaks -> Hardening -> Strong Security (the default) and Wide Compatibility

ls -l /etc/ssh/ssh_host_*
systemctl disable regenerate-ssh-host-keys.service

tools

https://www.kali.org/tools/
screenshots/cheat sheet: https://www.comparitech.com/net-admin/kali-linux-cheat-sheet/#Kali_Linux_tools

Video

https://askubuntu.com/questions/28033/how-to-check-the-information-of-current-installed-video-drivers

dpkg -l amdgpu-pro
glxinfo | grep direct
GALLIUM_HUD=help glxgears

OpenCL

installable client driver loader (ICD Loader) may expose multiple separate vendor installable client drivers (Vendor ICDs) for OpenCL.

sudo apt install ocl-icd-opencl-dev

zFCP

device driver that supplements the Linux SCSI stack.

Diagram

https://commons.wikimedia.org/wiki/File:Free_and_open-source-software_display_servers_and_UI_toolkits.svg

diskless

https://help.ubuntu.com/community/DisklessUbuntuHowto

https://drbl.org/

docker run --network=host -d leejoneshane/drbl-server

http://web.mst.edu/~vojtat/pegasus/administration.htm
based on Scientific Linux 7 / CentOS 7 / Red Hat Enterprise Linux 7