<HTML ><HEAD ><TITLE >Using a file instead of a partition</TITLE ><META NAME="GENERATOR" CONTENT="Modular DocBook HTML Stylesheet Version 1.7"><LINK REL="HOME" TITLE="Cryptoloop HOWTO" HREF="index.html"><LINK REL="PREVIOUS" TITLE="Mounting the encrypted file system" HREF="mounting-filesystem.html"></HEAD ><BODY CLASS="sect1" BGCOLOR="#FFFFFF" TEXT="#000000" LINK="#0000FF" VLINK="#840084" ALINK="#0000FF" ><DIV CLASS="NAVHEADER" ><TABLE SUMMARY="Header navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TH COLSPAN="3" ALIGN="center" >Cryptoloop HOWTO</TH ></TR ><TR ><TD WIDTH="10%" ALIGN="left" VALIGN="bottom" ><A HREF="mounting-filesystem.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="80%" ALIGN="center" VALIGN="bottom" ></TD ><TD WIDTH="10%" ALIGN="right" VALIGN="bottom" > </TD ></TR ></TABLE ><HR ALIGN="LEFT" WIDTH="100%"></DIV ><DIV CLASS="sect1" ><H1 CLASS="sect1" ><A NAME="filebased" ></A >7. Using a file instead of a partition</H1 ><P > It is just as easy to create an encrypted file system within a file on another file system. This is especially useful if you want to back up this file by burning it to a DVD, etc. You can then easily move the file around to other machines as well. </P ><P >To initially create a 100MB file containing random data use the following command: </P ><TABLE BORDER="0" BGCOLOR="#E0E0E0" WIDTH="100%" ><TR ><TD ><FONT COLOR="#000000" ><PRE CLASS="screen" >dd if=/dev/urandom of=/mystuff.aes bs=1k count=100000</PRE ></FONT ></TD ></TR ></TABLE ><P > If you want to change the size of the file, change the <TT CLASS="varname" >count</TT > value accordingly. The above command creates 100000 blocks of 1k in size, but you can change this to whatever you like. Just make sure it is not too small to hold the file system you chose. You can choose any file name and path you want instead of <TT CLASS="filename" >/mystuff.aes</TT > as long as there's enough space on the partition. </P ><P >You can then create the encrypted file system within this file, similar to the way it is done above: </P ><TABLE BORDER="0" BGCOLOR="#E0E0E0" WIDTH="100%" ><TR ><TD ><FONT COLOR="#000000" ><PRE CLASS="screen" >losetup -e aes-256 /dev/loop0 /mystuff.aes</PRE ></FONT ></TD ></TR ></TABLE ><P >Now you can create the file system:</P ><TABLE BORDER="0" BGCOLOR="#E0E0E0" WIDTH="100%" ><TR ><TD ><FONT COLOR="#000000" ><PRE CLASS="screen" > mkfs.ext3 /dev/loop0 </PRE ></FONT ></TD ></TR ></TABLE ><P > and mount it: </P ><TABLE BORDER="0" BGCOLOR="#E0E0E0" WIDTH="100%" ><TR ><TD ><FONT COLOR="#000000" ><PRE CLASS="screen" > mount -t ext3 /dev/loop0 /mnt/crypto </PRE ></FONT ></TD ></TR ></TABLE ><P > Finally, unmount and detach the loop device: </P ><TABLE BORDER="0" BGCOLOR="#E0E0E0" WIDTH="100%" ><TR ><TD ><FONT COLOR="#000000" ><PRE CLASS="screen" > umount /mnt/crypto losetup -d /dev/loop0 </PRE ></FONT ></TD ></TR ></TABLE ><P > You can then mount the file system later on as follows: </P ><TABLE BORDER="0" BGCOLOR="#E0E0E0" WIDTH="100%" ><TR ><TD ><FONT COLOR="#000000" ><PRE CLASS="screen" >mount /mystuff.aes /mnt/crypto -oencryption=aes-256</PRE ></FONT ></TD ></TR ></TABLE ><P >If you want to move the file or burn it to a CD or DVD, make sure you <B CLASS="command" >unmount</B > it first. </P ></DIV ><DIV CLASS="NAVFOOTER" ><HR ALIGN="LEFT" WIDTH="100%"><TABLE SUMMARY="Footer navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" ><A HREF="mounting-filesystem.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="index.html" ACCESSKEY="H" >Home</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" > </TD ></TR ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" >Mounting the encrypted file system</TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" > </TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" > </TD ></TR ></TABLE ></DIV ></BODY ></HTML >
