diff --git a/index.html b/index.html index c779213..2a0b312 100644 --- a/index.html +++ b/index.html @@ -1,5 +1,10 @@ + + Keeping filesystem images sparse @@ -51,14 +56,13 @@ all the free space: The disadvantage of dd in this context is that it destroys any sparseness that exists: free blocks that were originally represented as holes in the image file are replaced with actual blocks containing -zeroes. +zeroes. Also, filling up a live filesystem is probably a bad idea.

As an alternative approach, and as practice in mucking about with ext2 filesystems, I've written a utility which scans the free blocks in an ext2 filesystem and fills any non-zero blocks with zeroes. -The source, zerofree-1.0.3.tgz, is -available for download. It's also available in a git repository: -git clone http://intgat.tigress.co.uk/rmy/git/zerofree.git +The source, zerofree-1.1.1.tgz, is +available for download.

-Better than either of these would be to have the guest kernel keep the free -blocks empty. My original inspiration was the - -ext2fs privacy (i.e. secure deletion) patch described in a Linux -kernel mailing list thread. I've also made use of a later patch for ext3 -entitled -Secure Deletion Functionality in ext3 -from the linux-fsdevel mailing list. (See also the authors' paper on -Secure Deletion File Systems.) -I've modified the patches to make them more suitable for the present purpose. -

-When a filesystem is mounted with the zerofree option (added -by these patches) all the blocks freed when a file is deleted are filled -with zeroes. -Remember, this extra work will hurt disk performance. -Note that the ext3 patch doesn't support data journalling -mode, so deleted metadata isn't zeroed. It also hasn't been tested -as thoroughly as the patch for ext2. And neither has been maintained for a -very long time. -

-However, the above techniques are only half the story: the empty free +However, this is only half the story: the empty free blocks still consume space in the underlying filesystem, so something -must to be done to reclaim that space. For filesystems and kernels that -support it the fallocate call with FALLOC_FL_PUNCH_HOLE can -be used to deallocate space in a file. +must to be done to reclaim that space.

-An existing alternative is to use the sparse file handling capabilities +A common suggestion is to use the sparse file handling capabilities of the GNU cp command to take a copy of the filesystem image with cp --sparse=always (though this does require the original and sparse files to exist at the same time, which may be inconvenient).

-As an alternative alternative I've written a utility which can make -any specified files on an ext2 filesystem -sparse, sparsify.c. This doesn't require any -additional disk space to work its magic, but it does require that the -filesystem containing the filesystem image is unmounted, which is just a -different sort of inconvenience. -

-

-

-As an example, suppose we have an unmounted filesystem -image, fs.image, in the directory /data, which is the -root of the /dev/hda2 filesystem. We can reclaim deleted -blocks and make it sparse like so: -

-

-   zerofree /data/fs.image
-   umount /data
-   sparsify /dev/hda2 /fs.image
-   mount /data
-
+If your kernel and util-linux are sufficiently modern and you have a supported +filesystem you can use fallocate -d to 'dig holes' in a file. +This makes the file sparse in-place, without using extra disk space.

-Ron Yorston
-9th August 2012 +Ron Yorston
+18th April 2004 (updated 19th February 2018)
+Some obsolete information has been moved to a +separate page.
diff --git a/sources b/sources index 38a03b9..05a7873 100644 --- a/sources +++ b/sources @@ -1 +1 @@ -7fffca9639a2acc9c889c49b3f94a0c6 zerofree-1.0.3.tgz +SHA512 (zerofree-1.1.1.tgz) = 2d7ee57a877bff2491c48054338a26d624ae75c238ac2b0568a75de88b6621c16cc1e7d65500879825d14d8ba44a5173587a061459072769c165bee47c3f9f1c diff --git a/zerofree.8 b/zerofree.8 index b0be0d2..ee306b5 100644 --- a/zerofree.8 +++ b/zerofree.8 @@ -1,25 +1,36 @@ .TH "ZEROFREE" "8" .SH "NAME" -zerofree \(em zero free blocks from ext2/3 file-systems +zerofree \(em zero free blocks from ext2, ext3 and ext4 file-systems .SH "SYNOPSIS" .PP -\fBzerofree\fR [\fB-n\fP] [\fB-v\fP] \fIfilesystem\fR +\fBzerofree\fR [\fB-n\fP] [\fB-v\fP] [\fB-f fillval\fP] \fIfilesystem\fR .SH "DESCRIPTION" .PP \fBzerofree\fR finds the unallocated, -non-zeroed blocks in an ext2 or ext3 +blocks with non-zero value content in an ext2, ext3 or ext4 \fIfilesystem\fR (e.g. /dev/hda1) and -fills them with zeroes. This is useful if the device on which -this file-system resides is a disk image. In this case, +fills them with zeroes (or another octet of your choice). + + +.PP +Filling unused areas with zeroes is useful if the device on +which this file-system resides is a disk image. In this case, depending on the type of disk image, a secondary utility may be able to reduce the size of the disk image after zerofree has -been run. +been run. + +.PP +Filling unused areas may also be useful with solid-state +drives (SSDs). On some SSDs, filling blocks with ones (0xFF) +is reported to trigger Flash block erasure by the firmware, +possibly giving a write performance increase. + .PP The usual way to achieve the same result (zeroing the unallocated blocks) is to run \fBdd\fR (1) to create a file full of zeroes that takes up the entire free space on the drive, and then delete this file. This has many -disadvantages, which zerofree alleviates: +disadvantages, which zerofree alleviates: .IP " \(bu" 6 it is slow; .IP " \(bu" 6 @@ -27,7 +38,8 @@ it makes the disk image (temporarily) grow to its maximal extent; .IP " \(bu" 6 it (temporarily) uses all free space on the disk, so other -concurrent write actions may fail. +concurrent write actions may fail. + .PP \fIfilesystem\fR has to be unmounted or mounted read-only for \fBzerofree\fR to work. It @@ -36,17 +48,36 @@ will exit with an error message if the remount the root file-system readonly, you can first switch to single user runlevel (\fBtelinit 1\fR) then use \fBmount \-o remount,ro -\fIfilesystem\fR\fR. +\fIfilesystem\fR\fR. + .PP -\fBzerofree\fR has been written to be -run from GNU/Linux systems installed as guest OSes inside a -virtual machine. It may however be useful in other -situations. +\fBzerofree\fR has been written to be run +from GNU/Linux systems installed as guest OSes inside a virtual +machine. In this case, it is typically run from within the guest +system, and a utility is then run from the host system to shrink +disk image (\fBVBoxManage modifyhd \-\-compact\fR, +provided with virtualbox, is able to do that for some disk image +formats). + +.PP +It may however be useful in other situations: for instance +it can be used to make it more difficult to retrieve deleted +data. Beware that securely deleting sensitive data is not in +general an easy task and usually requires writing several times +on the deleted blocks. + .SH "OPTIONS" .IP "\fB-n\fP " 10 Perform a dry run (do not modify the file-system); .IP "\fB-v\fP " 10 -Be verbose. +Be verbose: show the number of blocks modified by +\fBzerofree\fR (or that would be modified, +in case the \fB-n\fP is used), the number of free +blocks and the total number of blocks on the +filesystem; +.IP "\fB-f value\fP " 10 +Specify the octet value to fill empty blocks with (defaults to +0). Argument must be within the range 0 to 255. .SH "SEE ALSO" .PP dd (1). @@ -62,4 +93,4 @@ later version published by the Free Software Foundation. On Debian systems, the complete text of the GNU General Public License can be found in /usr/share/common-licenses/GPL-2. -.\" created by instant / docbook-to-man, Wed 25 Nov 2009, 17:45 +.\" created by instant / docbook-to-man, Thu 31 Dec 2020, 01:06 diff --git a/zerofree.sgml b/zerofree.sgml index e5c43a3..1c40f71 100644 --- a/zerofree.sgml +++ b/zerofree.sgml @@ -9,7 +9,7 @@ Thibaut"> Paumard"> - February 6, 2008"> + April 3rd, 2012"> 8"> <paumard@users.sourceforge.net>"> @@ -44,7 +44,7 @@ &dhpackage; - zero free blocks from ext2/3 file-systems + zero free blocks from ext2, ext3 and ext4 file-systems @@ -54,6 +54,8 @@ + + filesystem @@ -61,14 +63,21 @@ DESCRIPTION &dhpackage; finds the unallocated, - non-zeroed blocks in an ext2 or ext3 + blocks with non-zero value content in an ext2, ext3 or ext4 filesystem (e.g. /dev/hda1) and - fills them with zeroes. This is useful if the device on which - this file-system resides is a disk image. In this case, + fills them with zeroes (or another octet of your choice). + + Filling unused areas with zeroes is useful if the device on + which this file-system resides is a disk image. In this case, depending on the type of disk image, a secondary utility may be able to reduce the size of the disk image after zerofree has been run. + Filling unused areas may also be useful with solid-state + drives (SSDs). On some SSDs, filling blocks with ones (0xFF) + is reported to trigger Flash block erasure by the firmware, + possibly giving a write performance increase. + The usual way to achieve the same result (zeroing the unallocated blocks) is to run dd (1) to create a file full of zeroes that takes up the entire free @@ -94,10 +103,19 @@ mount -o remount,ro filesystem. - &dhpackage; has been written to be - run from GNU/Linux systems installed as guest OSes inside a - virtual machine. It may however be useful in other - situations. + &dhpackage; has been written to be run + from GNU/Linux systems installed as guest OSes inside a virtual + machine. In this case, it is typically run from within the guest + system, and a utility is then run from the host system to shrink + disk image (VBoxManage modifyhd --compact, + provided with virtualbox, is able to do that for some disk image + formats). + + It may however be useful in other situations: for instance + it can be used to make it more difficult to retrieve deleted + data. Beware that securely deleting sensitive data is not in + general an easy task and usually requires writing several times + on the deleted blocks. @@ -115,7 +133,19 @@ - Be verbose. + Be verbose: show the number of blocks modified by + &dhpackage; (or that would be modified, + in case the is used), the number of free + blocks and the total number of blocks on the + filesystem; + + + + + + + Specify the octet value to fill empty blocks with (defaults to + 0). Argument must be within the range 0 to 255. diff --git a/zerofree.spec b/zerofree.spec index b906d9a..45118bc 100644 --- a/zerofree.spec +++ b/zerofree.spec @@ -1,29 +1,26 @@ -Summary: Utility to force unused ext2 inodes and blocks to zero +Summary: Utility to force unused ext2/3/4 inodes and blocks to zero Name: zerofree -Version: 1.0.3 -Release: 4%{?dist} -License: GPL+ - -URL: http://intgat.tigress.co.uk/rmy/uml/ - -Source0: http://intgat.tigress.co.uk/rmy/uml/%{name}-%{version}.tgz -Source1: http://intgat.tigress.co.uk/rmy/uml/sparsify.c -Source2: http://intgat.tigress.co.uk/rmy/uml/index.html - +Version: 1.1.1 +Release: 18%{?dist} +License: GPL-2.0-only +URL: https://frippery.org/uml/ +Source0: https://frippery.org/uml/%{name}-%{version}.tgz +Source1: https://frippery.org/uml/sparsify.c +Source2: https://frippery.org/uml/index.html # zerofree.sgml is the source for the man page from Debian. -# Unfortunately we cannot build this in Fedora because of an apparent -# bug in our DocBook tools. Therefore I also include the generated -# man page (generated on a Debian system from this source). +# Unfortunately we cannot build this in Fedora because we do not have +# docbook-to-man, just docbook2man and db2x_docbook2man. The included +# man page was generated on a Debian system from this source. Source3: zerofree.sgml Source4: zerofree.8 - +BuildRequires: gcc +BuildRequires: make BuildRequires: e2fsprogs-devel - %description zerofree is a utility to set unused filesystem inodes and blocks of an -ext2 filesystem to zero. This can improve the compressibility and -privacy of an ext2 filesystem. +ext2/3/4 filesystem to zero. This can improve the compressibility and +privacy of an ext2/3/4 filesystem. This tool was inspired by the ext2fs privacy (i.e. secure deletion) patch described in a Linux kernel mailing list thread. @@ -32,32 +29,102 @@ WARNING: The filesystem to be processed should be unmounted or mounted read-only. The tool tries to check this before running, but you should be careful. - %prep %setup -q -cp -p %{SOURCE1} . -cp -p %{SOURCE2} . - +cp -p %{SOURCE1} %{SOURCE2} . %build -make CC="gcc $RPM_OPT_FLAGS" -gcc $RPM_OPT_FLAGS sparsify.c -o sparsify -lext2fs - +make CC="%{__cc} $RPM_OPT_FLAGS $RPM_LD_FLAGS" +%{__cc} $RPM_OPT_FLAGS $RPM_LD_FLAGS -o sparsify sparsify.c -lext2fs %install install -D -p -m 755 zerofree $RPM_BUILD_ROOT%{_sbindir}/zerofree install -D -p -m 755 sparsify $RPM_BUILD_ROOT%{_sbindir}/sparsify install -D -p -m 644 %{SOURCE4} $RPM_BUILD_ROOT%{_mandir}/man8/zerofree.8 - %files -%doc COPYING index.html +%license COPYING +%doc index.html %{_sbindir}/zerofree %{_sbindir}/sparsify %{_mandir}/man8/zerofree.8* - %changelog +* Fri Jul 17 2026 Fedora Release Engineering - 1.1.1-18 +- Rebuilt for https://fedoraproject.org/wiki/Fedora_45_Mass_Rebuild + +* Sat Jan 17 2026 Fedora Release Engineering - 1.1.1-17 +- Rebuilt for https://fedoraproject.org/wiki/Fedora_44_Mass_Rebuild + +* Fri Jul 25 2025 Fedora Release Engineering - 1.1.1-16 +- Rebuilt for https://fedoraproject.org/wiki/Fedora_43_Mass_Rebuild + +* Sun Jan 19 2025 Fedora Release Engineering - 1.1.1-15 +- Rebuilt for https://fedoraproject.org/wiki/Fedora_42_Mass_Rebuild + +* Sat Jul 20 2024 Fedora Release Engineering - 1.1.1-14 +- Rebuilt for https://fedoraproject.org/wiki/Fedora_41_Mass_Rebuild + +* Sat Jan 27 2024 Fedora Release Engineering - 1.1.1-13 +- Rebuilt for https://fedoraproject.org/wiki/Fedora_40_Mass_Rebuild + +* Sat Jul 22 2023 Fedora Release Engineering - 1.1.1-12 +- Rebuilt for https://fedoraproject.org/wiki/Fedora_39_Mass_Rebuild + +* Sat Jan 21 2023 Fedora Release Engineering - 1.1.1-11 +- Rebuilt for https://fedoraproject.org/wiki/Fedora_38_Mass_Rebuild + +* Sat Jul 23 2022 Fedora Release Engineering - 1.1.1-10 +- Rebuilt for https://fedoraproject.org/wiki/Fedora_37_Mass_Rebuild + +* Sat Jan 22 2022 Fedora Release Engineering - 1.1.1-9 +- Rebuilt for https://fedoraproject.org/wiki/Fedora_36_Mass_Rebuild + +* Fri Jul 23 2021 Fedora Release Engineering - 1.1.1-8 +- Rebuilt for https://fedoraproject.org/wiki/Fedora_35_Mass_Rebuild + +* Thu Jan 28 2021 Fedora Release Engineering - 1.1.1-7 +- Rebuilt for https://fedoraproject.org/wiki/Fedora_34_Mass_Rebuild + +* Wed Jul 29 2020 Fedora Release Engineering - 1.1.1-6 +- Rebuilt for https://fedoraproject.org/wiki/Fedora_33_Mass_Rebuild + +* Fri Jan 31 2020 Fedora Release Engineering - 1.1.1-5 +- Rebuilt for https://fedoraproject.org/wiki/Fedora_32_Mass_Rebuild + +* Sat Jul 27 2019 Fedora Release Engineering - 1.1.1-4 +- Rebuilt for https://fedoraproject.org/wiki/Fedora_31_Mass_Rebuild + +* Sun Feb 03 2019 Fedora Release Engineering - 1.1.1-3 +- Rebuilt for https://fedoraproject.org/wiki/Fedora_30_Mass_Rebuild + +* Sat Jul 14 2018 Fedora Release Engineering - 1.1.1-2 +- Rebuilt for https://fedoraproject.org/wiki/Fedora_29_Mass_Rebuild + +* Tue Feb 20 2018 Robert Scheck - 1.1.1-1 +- Upgrade to 1.1.1 + +* Mon Feb 19 2018 Robert Scheck - 1.1.0-1 +- Upgrade to 1.1.0 + +* Fri Feb 09 2018 Fedora Release Engineering - 1.0.3-10 +- Rebuilt for https://fedoraproject.org/wiki/Fedora_28_Mass_Rebuild + +* Thu Aug 03 2017 Fedora Release Engineering - 1.0.3-9 +- Rebuilt for https://fedoraproject.org/wiki/Fedora_27_Binutils_Mass_Rebuild + +* Thu Jul 27 2017 Fedora Release Engineering - 1.0.3-8 +- Rebuilt for https://fedoraproject.org/wiki/Fedora_27_Mass_Rebuild + +* Sat Feb 11 2017 Fedora Release Engineering - 1.0.3-7 +- Rebuilt for https://fedoraproject.org/wiki/Fedora_26_Mass_Rebuild + +* Wed Apr 06 2016 Robert Scheck - 1.0.3-6 +- Build with ext4 support for RHEL 5 (#862934, thanks to Mike Swanson) + +* Fri Feb 05 2016 Fedora Release Engineering - 1.0.3-5 +- Rebuilt for https://fedoraproject.org/wiki/Fedora_24_Mass_Rebuild + * Fri Jun 19 2015 Fedora Release Engineering - 1.0.3-4 - Rebuilt for https://fedoraproject.org/wiki/Fedora_23_Mass_Rebuild