Delta ISOs: Difference between revisions

Revision as of 10:04, 20 July 2011

A delta ISO is a file that contains the differences between two ISO files, and can be used to convert one into the other. It makes use of delta RPMs between RPM files in the old and new ISOs, and so is only useful if these ISOs mainly consist of RPM files (as is the case for Fedora install images, but not live images).

If you like delta RPMs, you will like delta ISOs
Using delta ISOs saves bandwidth and time.

System Requirements

Fedora

xz compression change in Fedora 15
If you want to use delta ISOs for F15 or above on a system running F14 or below, see this on how to either build executables, or download prebuilt executables, to use in place of those in the native deltaiso package (which will not work on F14 or below).

Fedora 11 or later: RPM packages in Fedora 12 and later use xz compression (RPMs in older versions use gzip compression). In order to either create or use delta ISOs between ISOs containing xz-compressed RPMs, Fedora 11 or later is required. (Fedora 10 or below does not work because there is not a deltarpm package with xz support.)
In Fedora 11, the deltarpm package must be installed, and it should be the updated version (deltarpm-3.5-0.4.20090913git.fc11.1), not the deltarpm-3.4-16.fc11 release version that does not contain xz support.
In Fedora 12 or later, the deltaiso package must be installed. (In Fedora 11, delta ISO support is contained in the deltarpm package, and there is no separate deltaiso package.)

RHEL/CentOS

RHEL/CentOS 4 or later. In RHEL/CentOS 4 and 5, the EPEL repository must be enabled.
In RHEL/CentOS 4, the deltarpm package must be installed. Note that the available version (deltarpm-3.4) does not include xz support which is required for working with delta ISOs between recent versions of Fedora (12 or later).
In RHEL/CentOS 5 or later, the deltaiso package must be installed. (In RHEL/CentOS 4, deltaiso support is contained in the deltarpm package, and there is no separate deltaiso package.)

Using Delta ISOs

The applydeltaiso command is used. The syntax is:

applydeltaiso oldiso deltaiso newiso

If oldiso is on a mounted CD/DVD disc, the following also works, but runs more slowly due to the optical drive's greater access time:

applydeltaiso /dev/dvd deltaiso newiso

Alternatively, the rawread script (download) can be used to read the disc image into a file, as follows:

rawread /dev/dvd > oldiso

This can be done while the delta ISO is downloading, and the resulting ISO file can be verified (both in terms of integrity, and to make sure the correct image is being used for oldiso). When the download is finished, using applydeltaiso on the ISO file will save time compared to using the optical disc.

Creating Delta ISOs

The makedeltaiso command is used. The syntax is

makedeltaiso oldiso newiso deltaiso

Here, unlike the applydeltaiso command, oldiso should always refer to an ISO file, never a CD/DVD disc (RHBZ #569499). If necessary, the rawread script (download) can be used to read a CD/DVD disc image into an ISO file.

If the delta ISO is intended for a large audience, then run and time the applydeltaiso command and verify that newiso is correctly generated. There are two reasons for this.

Telling users the estimated run time for applydeltaiso lets them determine whether the download time saved by using a delta ISO is likely to be greater than the time required to run applydeltaiso.
Around the time of xz compression changes, certain delta ISOs may be nonfunctional as a result of not all RPMs in newiso using the same compression. Hence the delta ISO should be checked. When applydeltaiso finishes running, there should be a message similar to this:

iso successfully re-created, md5sum: f90d7a6d19a2cc5428a95892d5e2ca84

The md5sum is that of newiso, which is stored in the delta ISO for later verification. On the other hand, a failed reconstruction shows this message:

md5sum mismatch, iso is corrupt

and in this case the delta ISO should not be used.

External Links

@@ Line 1: / Line 1: @@
-A Delta ISO (deltaiso) is a file that contains the differences between two ISO files, and can be used to convert one into the other. It makes use of DeltaRPMs (deltarpm) between RPM files in the old and new ISOs, and so is only useful if these ISOs mainly consist of RPM files (as is the case for Fedora install images, but not live images).
+A delta ISO is a file that contains the differences between two ISO files, and can be used to convert one into the other. It makes use of delta RPMs between RPM files in the old and new ISOs, and so is only useful if these ISOs mainly consist of RPM files (as is the case for Fedora install images, but not live images).
-{{admon/tip|If you like DeltaRPMs, you will like Delta ISOs|Using deltaisos saves bandwidth and time.}}
+{{admon/tip|If you like delta RPMs, you will like delta ISOs|Using delta ISOs saves bandwidth and time.}}
 == System Requirements ==
@@ Line 7: / Line 7: @@
 === Fedora ===
-{{admon/important|xz compression change in Fedora 15|If you want to use deltaisos for F15 or above on a system running F14 or below, see [http://lists.fedoraproject.org/pipermail/test/2011-April/098585.html this] on how to either build executables, or download prebuilt executables, to use in place of those in the native deltaiso package (which will not work on F14 or below).}}
+{{admon/important|xz compression change in Fedora 15|If you want to use delta ISOs for F15 or above on a system running F14 or below, see [http://lists.fedoraproject.org/pipermail/test/2011-April/098585.html this] on how to either build executables, or download prebuilt executables, to use in place of those in the native <code>deltaiso</code> package (which will not work on F14 or below).}}
-* '''Fedora 11 or later''': RPM packages in Fedora 12 and later use xz compression (RPMs in older versions use gzip compression).  In order to either create or use deltaisos between ISOs containing xz-compressed RPMs, Fedora 11 or later is required. (Fedora 10 or below does ''not'' work because there is not a <code>deltarpm</code> package with xz support.)
+* '''Fedora 11 or later''': RPM packages in Fedora 12 and later use xz compression (RPMs in older versions use gzip compression).  In order to either create or use delta ISOs between ISOs containing xz-compressed RPMs, Fedora 11 or later is required. (Fedora 10 or below does ''not'' work because there is not a <code>deltarpm</code> package with xz support.)
 * In Fedora 11, the <code>deltarpm</code> package must be installed, and it should be the updated version (<code>deltarpm-3.5-0.4.20090913git.fc11.1</code>), not the <code>deltarpm-3.4-16.fc11</code> release version that does not contain xz support.
-* In Fedora 12 or later, the <code>deltaiso</code> package must be installed.  (In Fedora 11, <code>deltaiso</code> support is contained in the <code>deltarpm</code> package, and there is no separate <code>deltaiso</code> package.)
+* In Fedora 12 or later, the <code>deltaiso</code> package must be installed.  (In Fedora 11, delta ISO support is contained in the <code>deltarpm</code> package, and there is no separate <code>deltaiso</code> package.)
 === RHEL/CentOS ===
-* '''RHEL/CentOS 4 or later with the [[EPEL]] repository enabled''': The necessary packages for  <code>deltaiso</code> support in RHEL/CentOS 4 or 5 are available in the [[EPEL]] repository.
+* '''RHEL/CentOS 4 or later'''. In RHEL/CentOS 4 and 5, the [[EPEL]] repository must be enabled.
-* In RHEL/CentOS 4, the <code>deltarpm</code> package must be installed.  Note that the available version (<code>deltarpm-3.4</code>) does not include xz support which is required for working with deltaisos between recent versions of Fedora (12 or later).
+* In RHEL/CentOS 4, the <code>deltarpm</code> package must be installed.  Note that the available version (<code>deltarpm-3.4</code>) does not include xz support which is required for working with delta ISOs between recent versions of Fedora (12 or later).
-* In RHEL/CentOS 5, the <code>deltaiso</code> package must be installed.  (In RHEL/CentOS 4, <code>deltaiso</code> support is contained in the <code>deltarpm</code> package, and there is no separate <code>deltaiso</code> package.)
+* In RHEL/CentOS 5 or later, the <code>deltaiso</code> package must be installed.  (In RHEL/CentOS 4, <code>deltaiso</code> support is contained in the <code>deltarpm</code> package, and there is no separate <code>deltaiso</code> package.)
 == Using Delta ISOs ==
@@ Line 33: / Line 33: @@
 <pre>rawread /dev/dvd > oldiso</pre>
-This can be done while the deltaiso is downloading, and the resulting ISO file can be verified (both in terms of integrity, and to make sure the correct image is being used for <code>oldiso</code>).  When the download is finished, using <code>applydeltaiso</code> on the ISO file will save time compared to using the optical disc.
+This can be done while the delta ISO is downloading, and the resulting ISO file can be verified (both in terms of integrity, and to make sure the correct image is being used for <code>oldiso</code>).  When the download is finished, using <code>applydeltaiso</code> on the ISO file will save time compared to using the optical disc.
 == Creating Delta ISOs ==
@@ Line 43: / Line 43: @@
 Here, unlike the <code>applydeltaiso</code> command, <code>oldiso</code> should always refer to an ISO file, never a CD/DVD disc ({{bz|569499}}).  If necessary, the [http://www.troubleshooters.com/linux/coasterless.htm#rawread rawread script] ([https://fedoraproject.org/wiki/File:Rawread.sh download]) can be used to read a CD/DVD disc image into an ISO file.
-If the deltaiso is intended for a large audience, then run and time the <code>applydeltaiso</code> command and verify that <code>newiso</code> is correctly generated.  There are two reasons for this.
+If the delta ISO is intended for a large audience, then run and time the <code>applydeltaiso</code> command and verify that <code>newiso</code> is correctly generated.  There are two reasons for this.
-# Telling users the estimated run time for <code>applydeltaiso</code> lets them determine whether the download time saved by using a deltaiso is likely to be greater than the time required to run <code>applydeltaiso</code>.
+# Telling users the estimated run time for <code>applydeltaiso</code> lets them determine whether the download time saved by using a delta ISO is likely to be greater than the time required to run <code>applydeltaiso</code>.
-# Around the time of <code>xz</code> compression changes, certain deltaisos may be nonfunctional as a result of not all RPMs in <code>newiso</code> using the same compression. To be sure the deltaiso should be checked. When <code>applydeltaiso</code> finishes running, there should be a message similar to this:
+# Around the time of <code>xz</code> compression changes, certain delta ISOs may be nonfunctional as a result of not all RPMs in <code>newiso</code> using the same compression. Hence the delta ISO should be checked. When <code>applydeltaiso</code> finishes running, there should be a message similar to this:
 <pre>iso successfully re-created, md5sum: f90d7a6d19a2cc5428a95892d5e2ca84</pre>
-The md5sum is that of <code>newiso</code>, which is stored in the deltaiso for later verification.  On the other hand, a failed reconstruction shows this message:
+The md5sum is that of <code>newiso</code>, which is stored in the delta ISO for later verification.  On the other hand, a failed reconstruction shows this message:
 <pre>md5sum mismatch, iso is corrupt</pre>
-and in this case the deltaiso should not be used.
+and in this case the delta ISO should not be used.
 == External Links ==

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