"On-the-Fly" Read-Write Compressed Filesystem

I recently had a problem where "SARG" (SQUID Proxy reporting tool) completely chew up all root filesystem space as reports was generated daily and stored under /var/www/html/sarg. Quick solution... I thought this can also come in handy for future reference... "On-the-Fly read-write compressed filesystem"

I did this on CentOS 5.5:

rpm -Uhv http://apt.sw.be/redhat/el5/en/x86_64/rpmforge/RPMS//rpmforge-release-0.3.6-1.el5.rf.x86_64.rpm

yum -y install squashfs-tools fuse-unionfs

mv /var/www/html/sarg /root/sarg-old
mkdir /var/www/html/sarg

mksquashfs /root/sarg-old /.sarg-compressed.sqfs -check_data

mkdir -p /var/squashed/{ro,rw}

Add the following to /etc/fstab:
/.sarg-compressed.sqfs  /var/squashed/ro  squashfs  loop,ro  0 0
unionfs#/var/squashed/rw=rw:/var/squashed/ro=ro /var/www/html/sarg fuse default_permissions,allow_other,use_ino,nonempty,suid,cow 0 0

mount -all

touch /var/www/html/sarg/test
rm -rf /var/www/html/sarg-old

Check that your new fuse filesystem is mounted:

df -h

By doing this, all files writen to /var/www/html/sarg is actually being written "inside" /.sarg-compressed.sqfs (The compressed filesystem) Files like text or html in this instance are compressed at a massive ratio.