clear cache

Sudo rm -Rf /Library/Caches/*

Sudo rm -Rf /System/Library/Caches/*

Sudo rm -Rf ~/Library/Caches/*

Flush DNS

Step 1: Open the Terminal
Navigate to Applications -> Utilities -> Terminal

Step 2: Flush DNS – Type the following command and hit enter.
Mac OS X Yosemite and later

sudo killall -HUP mDNSResponder

Mac OS X Yosemite v10.10 through v10.10.3

sudo discoveryutil mdnsflushcache

Mac OS X Mavericks, Mountain Lion and Lion

sudo killall -HUP mDNSResponder

Mac OS X Snow Leopard

sudo dscacheutil -flushcache

Setting Hostname, ComputerName, LocalHostName

Example:

scutil --set HostName yosemite.local
scutil --set ComputerName yosemite
scutil --set LocalHostName yosemite

scutil --get LocalHostName yosemite

notes: flush directory service cache

rm .ssh/known_hosts

NAME
dsmemberutil — various operations for the membership APIs, including state dump, check memberships, UUIDs, etc.

Example:

dsmemberutil flushcache

NAME
dscacheutil — gather information, statistics and initiate queries to the Directory Service cache.

Example:

dscacheutil -flushcache

notes: flush directory service cache