#!/usr/bin/perl (this is only for editors)

# To use this file as e.g. /etc/squashmount.pl, copy it to that path and
# remove this comment and the following "fatal()" command from the file
# and write into the subsequent configuration of the variables
# (in particular of @mounts) what is appropriate for your system!
#
# It is impossible to guess which mount-points you want and for which purpose;
# this default file contains just some examples showing what *might* be useful
# for you (and sometimes even only to demonstrate the syntax and some
# possibilities).
# Do not use it unchanged!
#
# Use "squashmount man" for further details and a full list of options
# (only a few are used in this file).
#fatal('The file /etc/squashmount.pl is not yet set up!',
#'It must be configured first for the mount-points you want.',
#'See "squashmount man". Examples for the file /etc/squashmount.pl',
#'can be found in /usr/lib/squashmount.pl or /lib/squashmount.pl');

# The configuration might depend on the hostname: Test the variable $hostname
# to use the same file for different configs on different machines.
# (We do not employ this possibility in this example file).
# The following line initializes $hostname appropriately:
# use Sys::Hostname;
# my $hostname = ($ENV{'HOSTNAME'} // hostname());

# First we specify the tools which we have (possibly) installed;
# if possible, only the first in this list is used, but the others are
# successively a fallback if that fails.
# The last fallback is automatically bind --mount
#
# In this example, we deviate from the defaults by changing some of the flags:
# We skip unionfs and funionfs tacitly unless *surely* available.
# (Note that if you compiled e.g. unionfs as a module but /sys/module and
# /proc/config.gz are not available this means that unionfs is not used
# even if it could be).
#
# We also skip overlay and overlayfs if the module cannot be loaded
# successfully. Note again that this means that overlayfs is skipped
# if compiled into the kernel. Use "overlay? overlayfs?" instead
# if you want a more reliable check for that case.

@order = qw(overlay overlayfs aufs! unionfs-fuse! unionfs??# funionfs??#);

# The tool to mount squash files (currently: kernel or user-space squashfuse)
# is determined according to squashorder. The following is the default
# if not changed by any options:
# @squashorder = qw(squashfs!? squashfuse!);
# Use this if you always want to use squashfuse (slower but can be done
# fully with user permissions, only):
# @squashorder = qw(squashfuse!);
# If in doubt, do not set it explicitly.

# Set $obsolete_overlayfs = 1 if you normally use a kernel older than 3.15.
# Set $obsolete_overlayfs = undef if you only use >=kernel-3.15
# Set $obsolete_overlayfs = 'force' if you never use overlayfs or
# never use >=kernel-3.15 (and <kernel-3.18)
# Leave the default ($obsolete_overlayfs = '') if it might happen that
# you sometimes use kernels between 3.15 and (less than) 3.18 and
# also want a fallback for older kernels.
#$obsolete_overlayfs = 1;

# The following variables all default to 1 (true).
# Uncomment the corresponding line if you want to have different defaults.
# Normally, this is not needed.
# $lazy = '';
# $squash_verbose = '';
# $modprobe_loop = '';
# $modprobe_squash = '';

# These are the defaults:
# $lsof = 1;
# $lsof_ro = 0;

# Uncomment the following if you prefer (globally) resquashing on start
# instead of resquashing on umount/stop. You can override this individually
# per mount-point by setting RESQUASH_ON_START for that mount-point:
# $resquash_on_start = 1;  # the default is ''

# Uncomment the following line if you do not want to remove /run/squashmount
# on "squashmount stop". The default is 1 which means to remove it if empty
# (but not its parent directories). You can also specify a negative number
# to remove all its empty parent directories or a positive number + 1 for
# the number of parent directories to remove.
# $rm_rundir

# Specify the default for RM_DIR, RM_CHANGES, RM_WORKDIR, RM_READONLY.
# The number has the analogous meaning to $rm_rundir for the corresponding
# directories.
# $rm_dir = 0;  # This is the default
# $rm_changes = $rm_workdir = $rm_readonly = 1;  # This is the default.
# Unless you use temporary directories (not recommended),
# you will probably want to keep the created directories:
$rm_changes = $rm_workdir = $rm_readonly = 0;

# The default of $locking depends on the command used.
# Normally, there is no reason to uncomment the following line:
# $locking = 1;  # lock always, even if it appears unnecessary

# Do not override the default of $squashmount_quiet for a flexible config.
# For quicker execution, specify which version of mksquashfs is installed:
# $squashmount_quiet = 'qn-';  # if mksquashfs knows about -quiet
# $squashmount_quiet = 'rn+';  # if mksquashfs redirects progress to stderr
# $squashmount_quiet = 'n-';  # if <=mksquashfs-4.3 is unpatched
# $squashmount_quiet = 'r-n-r+n+';# for silent output only on terminals

# Unless you have a particular reason, it is wise to leave the choice
# of -processors and -mem to mksquashfs. So the default is '':
# $processors = '';
# $mem = '';

# The following is only needed if you want/need to hack umount options.
# The following lines add option -i unless something was passed by
# --umount or --umount-ro, respectively (in which case nothing is added).
# push(@umount, '-i') unless (@umount);
# push(@umount_ro, '-i') unless (@umount_ro);

# This is the default:
# @fumount = ();
# @fumount_ro = ();

# The following is the default: If these files exist, we do not squash
# $killpower = [ '/etc/killpower', '/etc/nut/killpower', '/etc/nosquash' ]

# Even if we would not set anything in the following hash, it is recommended
# to use this local variable throughout, so that "defaults" for all
# mount-points can be changed without modifying every mount-point manually.

my $defaults = {
	COMPRESSION => 'lz4',   # We could omit this line as lz4 is default.
	COMPOPT_LZ4 => '-Xhc',  # We could omit this line as -Xhc is default
	# In case of COMPRESSION => 'xz', we use the following option.
	# Note that this option roughly doubles the squashing time for only
	# slightly better compression of binaries.
	COMPOPT_XZ => ['-Xbcj', 'x86'],
};
# Add $pure_text, if the archive is essentially pure text:
my $pure_text = {
	COMPOPT_XZ => undef,  # "-Xbcj x86" is slower for pure text archives
};
# Add $git to avoid recompression of git-compressed data.
# The archive will usually be slightly larger, but speed gain can be huge.
# See https://github.com/plougher/squashfs-tools/issues/24
my $git = { MKSQUASHFS => [
	'-action', 'uncompressed@subpathname(*/.git/objects/pack)' ],
};

# We use here the @mounts = ( ... ); syntax (do not forget the semicolon!)
# but we could use as well: push(@mounts, .... );
# The latter has the advantage that it can be used repeatedly to
# successively add mount-points.

@mounts = (
	# This first example does not honor anything set in $defaults:
#	{
#		TAG => 'fixed',
#		DIR => '/fixed/dir',
#		FILE => '/fixed/content.sfs',
#		READONLY => 1,  # Do not use overlayfs/aufs/...
#	},
	# To make $defaults effective, we use the added_hash() function:
#	added_hash($defaults, {
#		TAG => 'guest',
#		DIR => '/home/guest',
#		FILE => '/home/guest-skeleton.sfs',
#		CHMOD => 0400,  # squash-file readonly by user
#		CHOWN => [ (getpwnam('guest'))[2],  # user and group of new ...
#			(getgrnam('guest'))[2] ],   # ... squash-file's owner
#		KILL => 1,  # normally remove data on every umount/remount
		# Clean temporary directories, independent of defaults:
#		RM_CHANGES => 1, RM_WORKDIR => 1, RM_READONLY => 1,
		# If you want to cancel this KILL temporarily
		# (e.g. to make modifications on guest-skeleton.sqsf)
		# use something like "squashmount --nokill set"
		# In such a case, we must no postpone resquashing
		# even if $resquash_on_start should be true, because
		# CHANGES is a temporary directory:
#		RESQUASH_ON_START => '',
#	}),
	# The above block "added_hash(...)," is actually equivalent to
	# {
	#	COMPRESSION => 'xz',
	#	TAG => 'guest',
	#	DIR => '/home/guest',
	#	FILE => '/home/guest-skeleton.sfs',
	#	KILL => 1,
	#	RESQUASH_ON_START => '',
	# },
	# because added_hash() "adds" our values to that from $defaults.

	# If you want to use portage's sync-type = squashdelta
	# a similar setup is useful. Start by putting the following into your
	# /etc/portage/repos.conf:

	# [gentoo]
	# location = /srv/repo-gentoo  # Do *not* use /var/db/... (see below)
	# sync-type = squashdelta
	# sync-uri = mirror://gentoo/../snapshots/squashfs
	# auto-sync = yes

	# (Do *not* use the default location /var/db/repos/gentoo, if you
	# mount also /var/db with the recommended mount-point below,
	# since "stacking" mount-points is not a good idea: You would have to
	# take care about the order whenever you mount/umount.)

	# With squashmount, we can now mount the downloaded squash-file
	# read-writable. In this case, we keep all changes only temporary.
	# We will also have to hook into portage's sync mechanism to remount
	# after syncing:
	# The file etc/portage/repo.postsync.d/50-squashmount-gentoo is such a
	# hook (which requires that this mount-point as well as the repository
	# be called "gentoo", and that the sync-uri contains the string
	# "/squash").
#	added_hash($defaults, $pure_text, $git, {
#		TAG => 'gentoo',
#		DIR => '/srv/repo-gentoo',
#		FILE => '/var/cache/portage/squashfs/gentoo-current.sfs',
#		KILL => 1,
#		RM_CHANGES => 1, RM_WORKDIR => 1, RM_READONLY => 1,
#		RESQUASH_ON_START => '',
#	}),
	# Here is yet another useful example:
#	added_hash($defaults, $pure_text, {
#		TAG => 'db',
#		DIR => '/var/db',
#		FILE => '/var/db.mount/db.sfs',
#		BACKUP => '.bak',  # keep a backup in /var/db.mount/db.sfs.bak
			# For an absolute path, we could have written:
			# BACKUP => '/backup-disk/db.sfs'
#		CHANGES => '/var/db.mount/changes',
#		WORKDIR => '/var/db.mount/workdir',
#		READONLY => '/var/db.mount/readonly',

		# If /var is on a separate partition, you want probably that
		# the squash-file is first generated in /var/tmp so that it
		# can be moved without actually copying the data.
		# In this case, uncomment the following line:
		#TEMPDIR => '/var/tmp',

		# Do not resquash on every umount/remount but only when
		# 30 megabytes of fresh data are reached:
#		THRESHOLD => '30m',
		# Since this directory contains only very small files,
		# we cheat with this size by using that each file takes
		# at least a full block:
		# Hence, the number of files is more important for THRESHOLD
		# than their size. In Gentoo, one installed package thus
		# "counts" about 2m in size
		# (although it produces actually only 20 very short files):
#		BLOCKSIZE => 65536,
#	}),
# Instead of specifying TAG, DIR, FILE, CHANGES explicitly,
# we use now that they are specified analogously to the above example
# with the standard_mount function.
#	standard_mount('kernel', '/usr/src', $defaults),
# If you fetch kernel sources with git, you should use instead:
#	standard_mount('kernel', '/usr/src', $defaults, $git),
# The above single line produces the equivalent of
#	added_hash({
#		TAG => 'kernel',
#		DIR => '/usr/src',
#		FILE => '/usr/src.mount/src.sfs',
#		CHANGES => '/usr/src.mount/changes',
#		WORKDIR => '/usr/src.mount/workdir',
#		READONLY => '/usr/src.mount/readonly',
#	}, $defaults),
# which in turn is effectively equivalent to
#	{
#		TAG => 'kernel',
#		DIR => '/usr/src',
#		FILE => '/usr/src.mount/src.sfs',
#		CHANGES => '/usr/src.mount/changes',
#		WORKDIR => '/usr/src.mount/workdir',
#		READONLY => '/usr/src.mount/readonly',
#		COMPRESSION => 'xz',
#	},
# (the WORKDIR is omitted if $no_workdir = 1 is set)
#
# You might want to add (before the end of the above brace:
# {
#	BACKUP => '.bak',  # Always keep a backup.
#	THRESHOLD => 1m,   # Do not recompress for less than 1 MB changes
#	KILL => -1,        # If there are less than 1 MB, kill them at "umount"
# }
# Note that the KILL => -1 means for kernel directory that e.g. a temporary
# kernel reconfiguration is "forgotten" unless it is used to recompile most
# of the kernel data: Thus, "tiny experiments" are cleaned up automatically.
# (Be aware that this feature can be very irritating if you forget about it...)

# We configure tex as in the "squashmount man" example:
#	standard_mount('tex', '/usr/share/texmf-dist', $defaults, $pure_text, {
#		DIFF => [
#			qr{^ls-R$},
#			qr{^tex(/generic(/config(/language(\.(dat(\.lua)?|def)))?)?)?$}n
#		],
#	}),
# The following example is useful if you use portage with a "traditional"
# sync-type (like rsync, webrsync or also git). An example for
# sync-type = squashdelta is given later.
	standard_mount('portage', '/usr/portage', $defaults, $pure_text, {
		# We know that no hardlinks or similar "tricky" things are used
		# in the portage tree, hence we "can" omit the umount helpers
		# of e.g. aufs. (This is only an example! Use this only if you
		# have problems and understand what you are doing; usually,
		# there is no reason to omit the umount helpers!)
		# In the following example, we use -i if nothing is passed
		# through --umount (or through the setting of @umount above).
		# *If* --umount is specified, we do not define UMOUNT, i.e.
		# the default value (the passed options) is chosen.
		UMOUNT => ((@umount) ? undef : '-i'),
		# It is reasonable to not recompress the directory always:
		THRESHOLD => '40m',
		# Any change in the local/ subdirectory (except in the .git
		# subdirectory) should lead to a resquash, even if the
		# threshold is not reached.
		FILL => qr{^local/(?!\.git(/|$))}n,
		# However, ignore identical rewrites of profiles/use.local.desc
		# in the local/ or layman/*/ subdirectories (which happens e.g.
		# if you use egencache --update-use-local-desc for repositories
		# in these subdirectories. Similarly for the files/dirs
		# .git/FETCH_HEAD, .git/index, and metadata/md5-cache
		DIFF => qr{^(local|(layman(/[^/]*)?))((/profiles(/use\.local\.desc)?)|(/\.git(/FETCH_HEAD|/index)?)|(/metadata(/md5\-cache)?))?$}n,
	}),
#	standard_mount('games', '/usr/share/games', $defaults, {
		# games is huge: use the fastest compression algorithm for it.
		# (Note that this possibly overrides $defaults):
#		COMPRESSION => 'lz4',
#		COMPOPT_LZ4 => '',
#	}),
#	standard_mount('office', '/usr/lib/libreoffice', $defaults, {
		# Make sure to use the algorithm with best compression ratio,
		# possibly overriding $defaults:
#		COMPRESSION => 'xz',
#	})
);


# In the following example, we use mount --bind to provide a copy of
# /usr/portage (from the mount-point portage) to /srv/copy
# (This is an extension of the example from "squashmount man"):

#$after_mount = sub {
#	my ($mountpoint, $store, $config) = @_;
#	return 1 unless ($mountpoint eq 'portage');
#	system('mount', '--bind', $config->{DIR} // $store->{DIR}, '/srv/copy');
#	1  # return a true value!
#};

#$before_umount = sub {
#	my ($mountpoint, $store, $config) = @_;
#	return 1 unless ($mountpoint eq 'portage');
#	system('umount /srv/copy');
#	1  # return a true value!
#};

# In case the user mounted /srv/copy without using squashmount,
# we undo this, before mounting the portage directory with squashmount:

#$before_mount = sub {
#	my ($mountpoint, $store, $config) = @_;
#	return 1 unless ($mountpoint eq 'portage');
#	system('umount /srv/copy >/dev/null 2>&1');
#	1  # return a true value!
#};



# Now we give an example of a mount-point "custom" which is only available
# if a corresponding path to a squash file was passed with the option
# --arg=file (or -a file).

# This is the "luxury" variant of the code described with "squashmount man".

# We use the variable "$custom" to indicate whether the mount-point is visible.
# By default, it is only visible if an option was passed with --arg:

#my $custom = @ARGV;
#my $file = undef;
#if ($custom) {
#	$file = pop(@ARGV);
#	fatal("argument '$file' of --arg is not a file") unless (-f $file);

	# If B<--arg> was provided once, store it for later usage
#	$locking = $storing = 1  # don't set $storing without $locking!
#}

# The following is important:
# The mount-point should always be visible if there is data stored for it
# in $rundir. This is important so that when the init-system calls
# "squashmount stop", this will properly shut down the mount-point
# (even if the special option --arg=something does not occur in this command.)
# This also has the nice side effect that the mount-point will appear
# with "squashmount list", once it is mounted.

#$custom ||= have_stored_data('custom');

# Uncomment, if you want to hide "custom" only for "squashmount start":
# $custom ||= ($command ne 'start');

# Uncomment, if you want to make "custom" visible to all query commands like
# "squashmount list" or "squashmount print-...":
# $custom ||= $storing;

# We use a callback function to store/restore $file:

#$before = sub {
	# These are the 3 parameters provided to callback functions:
#	my ($mountpoint, $store, $config) = @_;

	# Handle only that mount-point which is of interest for us:
#	return 1 unless ($mountpoint eq 'custom');

#	my $stored = $store->{FILE};

#	if (defined($stored)) {
#		if (defined($file) && ($stored ne $file)) {
#			error("stored path $stored",
#			"differs from --arg $file",
#			'Use "squashmount stop|forget custom"');
			# We return a false value to skip the action:
#			return ''
#		}
#	} else {
		# Store $file for future usage:
#		$store->{FILE} = $stored = $file
#	}
	# Note that $stored is undefined here if no data was stored and
	# if no --arg argument was provided

	# Use the stored value as the configuration value for FILE
	# (provided $stored is defined; if it undefined do not touch anything)
#	$config->{FILE} = $stored if (defined($stored));

#	1  # return a true value!
#};

# Finally, we make the mount-point available if $custom is true

#push(@mounts,  # append the following to @mounts:

# In this example, we use /var/custom as DIR, and
# /var/custom.mount/{readonly,changes,workdir} as READONLY,CHANGES,WORKDIR.
# Since almost everything is the setting of "standard_mount", we only
# need to override FILE:
#	standard_mount('custom', '/var/custom', {
		# if $file is undefined, we use some "dummy" path instead
		# (it should be an absolute path to avoid error messages)
#		FILE => ($file // '/default.sfs'),
#	})
# now we finish the above push command, indicating that this push command
# should be executed only if $custom is true:
#) if ($custom);


1;  # The last executed command in this file should be a true expression