Ian Chilton

If you use VirtualBox and try to copy/clone a hard disk (VDI) file to use with another virtual machine, it will not let you add it because it complains that there is already an image with that UUID.

Fortunately the fix is simple – there is a hidden command available to generate a new UUID:

VBoxManage internalcommands setvdiuuid myfile.vdi

To recursively chmod all files in the current directory (and sub-directories), you can do this:

find . -type d -exec chmod 755 {} \;

To do the same with just files, you can use:

find . -type f -exec chmod 644 {} \;

It’s really useful to not only be able to see the user and directory in your prompt but to have different colours for different users/servers – like a different colour for root or production boxes. Here is the code I use – just put it in a .profile in the users’s home directory (or in /etc/profile for globally):

# Set xterm title:
SHOSTNAME=`hostname -s`
PROMPT_COMMAND='if [ "${TERM}" = "xterm" -o "${TERM}" = "xterm-color" ];
then
   if [ -n "${XTITLE}" ];
   then
      echo -ne "\033]0;${XTITLE}\007";
   else
      echo -ne "\033]0;[${USER}@${SHOSTNAME}:${PWD}]\007" | sed -e "s@${HOME}@\~@";
   fi;
fi'    

# Set Bash Prompt:
if [ "$BASH" ]; then
  PS1='\[\033[1;36m\][\u@\h:\w]\$\[\033[0m\] '
#  alias ls='ls --color'
else
  if [ "`id -u`" -eq 0 ]; then
    PS1='# '
  else
    PS1='$ '
  fi
fi  

export PS1 PROMPT_COMMAND SHOSTNAME

You can change the colours using the following codes:

# Black       0;30     Dark Gray     1;30
# Blue        0;34     Light Blue    1;34
# Green       0;32     Light Green   1;32
# Cyan        0;36     Light Cyan    1;36
# Red         0;31     Light Red     1;31
# Purple      0;35     Light Purple  1;35
# Brown       0;33     Yellow        1;33
# Light Gray  0;37     White         1;37