Disable password prompting for updates in Ubuntu

If you want to run the Synaptic packet manager in Ubuntu/Lubuntu without it requiring a password, you must add a PolicyKit local definition. For this purpose create a file, named for instance /etc/polkit-1/localauthority/50-local.d/allow-user-update-wo-password.pkla, and add the following content to it:
[Allow User Updates Without Password]
Identity=*
Action=com.ubuntu.pkexec.synaptic
ResultAny=no
ResultInactive=no
ResultActive=yes

Customize GRUB2 menu colors in Ubuntu

The procedure for customizing GRUB2 menu colors in Ubunt is as follows:
1) Edit (or create) the file "/lib/plymouth/themes/default.grub" to add the appropriate menu color information.
Example:
# Color of the highlighted menu entry and its background within the menu box
set menu_color_highlight=yellow/dark-gray
# Color of non-selected menu entries within the menu box
set menu_color_normal=black/light-gray
# Color of the text and background outside the menu box
set color_normal=light-gray/black
2) Regenerate the the grub configuration file by running 'sudo update-grub'.

Customize other OS menu entries in GRUB2

The procedure for customizing menu entries for other OSes in GRUB2 is as follows:
1) Copy the menu entry you wish to customize from "/boot/grub/grub.cfg"
to "/etc/grub.d/40_custom".
2) Change the name of the menu entry as you wish.
3) Disable the OS prober to prevent regenerating the old menu entry by using the option "GRUB_DISABLE_OS_PROBER=true" in "/etc/default/grub".
4) Regenerate the the grub configuration file by running 'sudo update-grub'.

Enable Keychain use for ssh in macOS

In order to enable the use of passwords/passphrases stored by the Keychain Access service on macOS, the following specific ssh option is available starting with macOS 10.12:
  UseKeychain=yes

The setting can be provided either on the command line, or in the ssh configuration files (/etc/ssh/ssh_config, ~/.ssh/config).