Linux

FFMPEG

Speed up audio of a file

NOTE: ACCELERATION can be a value from “0.5” (1/2 speed) to “2.0” (double speed)

ffmpeg -i INPUT_FILE -filter:a "atempo=ACCELERATION" -vn OUTPUT_FILE

GZip

Compress a File Without Removing It

gzip < file > file.gz

Systemd

Setting OS Limits with systemd

Edit /etc/systemd/user.conf and /etc/systemd/systemd.conf, add the following line to each file:
```
DefaultLimitNOFILE=NEW_LIMIT
```
Edit /etc/security/limits.conf and set the usual limit details:
```
USER soft nofile NEW_LIMIT
USER hard nofile NEW_LIMIT
```
Restart your system for the changes to take effect.

Command Line Tricks

Recursively Set +x for Only Directories

Set the executable bit for directories (and not files) using +X (upper case) instead of +x (lower case).

chmod g+rX *

Prevent sudo Password Prompts

If you don’t have NOPASSWD set in sudoers, you can still bypass the password prompt by setting SUDO_ASKPASS to a binary that echos your password.

echo "echo mypassword" > ~/.local/bin/sudopass.sh
chmod 755 ~/.local/bin/sudopass.sh
export SUDO_ASKPASS=${HOME}/.local/bin/sudopass.sh

SELinux

Set Context for Container to Access Path

semanage fcontext -a -t container_file_t '<path_root>(/.*)?'
restorecon -R <path_root>

MegaRAID

Get Enclosure ID

e=$(/opt/MegaRAID/MegaCli/MegaCli64 pdlist -a0 | grep Enc | grep -v 252 | awk ‘{print $4}' | sort | uniq  -c | awk ‘{print $2}')

Create RAID-1

/opt/MegaRAID/MegaCli/MegaCli64 \
    -CfgLdAdd \
    -r1 \
    [${e}:SLOT0,${e}:SLOT1] \
    wb ra nocachedbadbbu strpsz1024 -a

Create RAID-10

/opt/MegaRAID/MegaCli/MegaCli64 \
    -CfgSpanAdd \
    -r10 \
    -Array0[${e}:SLOT0,${e}:SLOT1] \
    -Array1[${e}:SLOT2,${e}:SLOT3] \
    wb ra nocachedbadbbu strpsz1024 -a

Add Dynamic Hot Spare to Disk Group(s)

/opt/MegaRAID/storcli/storcli64 /c0/e${e}/s${slot} add hotsparedrive dgs=DG0[,DG1]

Delete JBODs

/opt/MegaRAID/storcli/storcli64 /c0/e${e}/s${slot} set good force

Delete Virtual Drive

/opt/MegaRAID/storcli/storcli64 /c0/v${virtual_drive_num} delete

Delete Hot Spare

/opt/MegaRAID/storcli/storcli64 /c0/e${e}/s${slot} delete hotsparedrive

Show Critical Events

/opt/MegaRAID/storcli/storcli64 /c0 show events filter=critical

Change Cache Config

/opt/MegaRAID/MegaCli/MegaCli64 -LDSetProp WB -L${virtual_drive_num} -a0
/opt/MegaRAID/MegaCli/MegaCli64 -LDSetProp RA -L${virtual_drive_num} -a0

GPG

Generate New Key

gpg --full-generate-key

List Keys

gpg --list-secret-keys --keyid-format LONG

Export Key

gpg --armor --export KEY_ID

macOS

Apps

Locking macOS Dock Content

defaults write com.apple.Dock position-immutable -bool yes; killall Dock

Locking macOS Dock Size

defaults write com.apple.Dock size-immutable -bool yes; killall Dock

Show CMD-TAB App Switcher On All Monitors

defaults write com.apple.Dock appswitcher-all-displays -bool true; killall Dock

Prevent sudo Password Prompts

See Linux - Prevent sudo Password Prompts

Disabling auto-hide scroll bars

System Preferences -> General -> Show scroll bars = Always

Disable Touchpad Swipe Back

# Chrome
defaults write com.google.Chrome AppleEnableSwipeNavigateWithScrolls -bool FALSE
# FireFox
defaults write org.mozilla.firefox AppleEnableSwipeNavigateWithScrolls -bool FALSE
# Brave
defaults write com.brave.Browser AppleEnableSwipeNavigateWithScrolls -bool FALSE
# Safari
defaults write com.apple.Safari AppleEnableSwipeNavigateWithScrolls -bool FALSE

Disable Dock Bouncing Icons

defaults write com.apple.dock no-bouncing -bool TRUE; killall Dock

Add Trusted Certificate Authority

security add-trusted-cert -d -r trustRoot -k ~/Library/Keychains/login.keychain-db <CA_CERTIFICATE>

Set Where Homebrew Installs Applications

export HOMEBREW_CASK_OPTS="--appdir=~/Applications"

Add Default SSH Key Passphrase to macOS Keychain

ssh-add -K