Linux

• General

  • filesystem hierarchy
  • environment variables
  • common user configuration files
  • shell tricks and keyboard shortcuts
  • some important files
  • common daemons
  • list of useful commands

• Useful commands with more details/examples

  • chown & chmod (change the owner and permissions of a file)
  • find (search for local files)
  • ps (list current processes)

• Encryption

  • full disk encryption with luks
  • encrypt files with gnupg

• OpenSSL

  • Create a csr and a private key in one line
  • Create a self-signed certificate in one line
  • Create your own Certification Authority (CA) with OCSP (protocol to check certificate validity online)
  • convert and export a certificate to the pfx format
  • Authenticate with a certificate with the curl command line
  • test ssl connectivity with openssl s_client
  • other useful openssl commands

• OpenSSH (technically OpenBSD ported to linux)

  • generate a 4096 bits key with the EdDSA algorithm (scheme SHA-512 curve 25519 (ed25519))
  • ssh port forwarding and sock5 proxy (ssh tunnels)
  • force sftp and chroot individual users
  • sshfs : mount a remote server/directory

• DNS

  • the dig command
  • bind zone file
  • dnssec stuff

• Other common servers

  • nfs server (network file system)
  • vsftpd server (file transfer protocol daemon)

• Advanced file permissions

  • ACL (access control list)
  • Files attributes

• Goodies

  • mimic a windows tracert
  • sysreq keys (magic sysrq keys)
  • tainted kernel codes
  • tune2fs reserve diskspace for privileged process