Filesystem
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squashfs
squashfs is a heavy-compression based read-only filesystem that is capable of compressing 2 to 3 GB of data onto a 700MB. Linux liveCD are built using squashfs. These CDs make use of a read-only compressed filesystem which keeps the root filesystem on a compressed file. It can be loopback mounted and loads a complete Linux env. Thus when some file are required by processes, they are decompressed and loaded onto the RAM and used.
- https://en.wikipedia.org/wiki/SquashFS
- http://squashfs.sourceforge.net/
- http://elinux.org/Squash_FS_Howto
- Ubuntu's snaps use the squashfs filesystem,
- The snap file format is a single compressed SquashFS filesystem from Introduction to snapcraft.
- A technical comparison between snaps and debs
# create a squashfs file sudo mksquashfs /etc test.squashfs # mount the squashfs file mkdir /mnt/squash mount -o loop compressedfs.squashfs /mnt/squash # you can acess the contents at /mnt/squashfs # exclude files sudo mksquashfs /etc test.squashfs -e /etc/passwd /etc/shadow # or specify a list of exclude files given in a file cat excludelist # /etc/passwd sudo mksquashfs /etc test.squashfs -ef excludelist
BTRFS
COW (copy on write) file system
The cow filesystem was found on xubuntu live CD. See http://en.wikipedia.org/wiki/Copy-on-write
How To Protect Your Server Against the Dirty COW Linux Vulnerability (10/21/2016)