working proof of concept version

impermanence.pl

@@ -0,0 +1,151 @@
+#!/usr/bin/env perl
+
+use strict;
+use warnings;
+use YAML;
+use File::Basename qw(fileparse);
+use List::MoreUtils qw(uniq);
+use Getopt::Std;;
+use Data::Dumper;
+use File::HomeDir;
+use File::Path qw(make_path);
+use 5.010;
+
+# return a perl structure by reader a YAML file
+sub read_yml_file_to_struct {
+    my $file = shift;
+    open my $fh, '<', $file or die;
+    $/ = undef;
+    my $data = <$fh>;
+    close $fh;
+    return Load($data);
+}
+
+
+# some files or directories may be included in a listed directory
+# remove those from the list and print a warning
+sub remove_transclusion {
+    my $data = shift;
+    my @files = uniq @{$data->{"files"}};
+    my @directories = uniq @{$data->{"directories"}};
+
+    for(my $i=0; $i <= $#directories; $i++) {
+        my $dir = $directories[$i];
+        next if ($dir eq "");
+
+        # check if a file is contained by a directory
+        foreach my $file (@files) {
+            my($filename, $dirs, $suffix) = fileparse($file);
+            if($dirs =~ m/^$dir/) {
+                say STDERR "WARNING: $dir contains $file";
+                $file = "";
+            }
+        }
+
+        # check if a directory is contained by another directory
+        # if so, mark them for deletion later
+        # we can't remove directly from the array because we
+        # are iterating in it in the main loop
+        for(my $j=0; $j <= $#directories; $j++) {
+            if($j != $i) {
+                my $dir2 = $directories[$j];
+                next if ($dir2 eq "");
+                if($dir =~ m/$dir2/) {
+                    say STDERR "WARNING: $dir2 contains $dir";
+                    $directories[$i] = "";
+                }
+            }
+        }
+    }
+
+    # remove empty entries
+    @directories = sort grep { /^./ } @directories;
+    @files = sort grep { /^./ } @files;
+    $data->{"files"} = \@files;
+    $data->{"directories"} = \@directories;
+
+    return $data;
+}
+
+my %opts;
+my ($impermanence_home, $persist_home, $configuration_file, $data, $ret);
+getopts("t:d:u:", \%opts);
+
+# check if using test mode to validate a configuration file
+if(defined $opts{t}) {
+    say STDERR "WARNING: test mode enabled";
+    $configuration_file = $opts{t};
+} else {
+
+    # -d and -u flags are mandatory
+    if(! defined $opts{d} || ! defined $opts{u}) {
+        say STDERR "usage: $0 [-t] -d directory -u user";
+        exit 1;
+    }
+
+    # test if root
+    if($< != 0) {
+        say STDERR "$0 must be run as root.";
+        exit 1;
+    }
+
+    $impermanence_home = File::HomeDir->users_home($opts{u});
+    $persist_home = $opts{d};
+    $configuration_file = $persist_home."/".$opts{u}."/impermanence.yml";
+}
+
+if ( ! -f $configuration_file ) {
+    say STDERR "The file ".$configuration_file." can't be found";
+    exit 1;
+}
+
+$data = read_yml_file_to_struct($configuration_file);
+$data = remove_transclusion $data;
+
+if(defined $opts{t}) {
+    exit 0;
+}
+
+# is this already mounted?
+$ret = `df $impermanence_home | awk -v dest=$impermanence_home '/^mfs/ && \$NF == dest { print }'`;
+if ($ret =~ m/^mfs/) {
+    say STDERR "ERROR: $impermanence_home is already mounted with MFS";
+    exit 2;
+}
+my $fs = `swapctl | tail -n 1 | cut -d ' ' -f 1 | tr -d '\n'`;
+
+$ret = system("mount_mfs", "-s", $data->{size}, $fs, $impermanence_home);
+if($ret != 0) {
+    say STDERR "ERROR: mounting the mfs filesystem errored with error $ret";
+    exit 2;
+}
+
+foreach (@{$data->{files}}) {
+    my $old_file = $persist_home."/".$opts{u}."/".$_;
+    my $new_file = $impermanence_home."/".$_;
+
+    my ($filename, $dirs, $suffix) = fileparse($new_file);
+
+    # recursively create missing directories to hold files
+    # give ownership to the user and apply chmod 700
+    if ( ! -e $dirs ) {
+        make_path($dirs, { chmod => 0700, owner => $opts{u} });
+    }
+    symlink($old_file, $new_file);
+}
+
+foreach (@{$data->{directories}}) {
+    my $old_dir = $persist_home."/".$opts{u}."/".$_;
+    my $new_dir = $impermanence_home."/".$_;
+
+    my ($dir, $dirs, $suffix) = fileparse($new_dir);
+    say "$old_dir / $new_dir / $dir / $dirs ";
+
+    # recursively create missing directories to hold dir symlinks
+    # give ownership to the user and apply chmod 700
+    if ( ! -e $dirs ) {
+        make_path($dirs, { chmod => 0700, owner => $opts{u} });
+    }
+    symlink($old_dir, $new_dir);
+}
+