Introducing bmaptool as an alternative to dd

content/blog/bmaptool-iso.md

@@ -0,0 +1,118 @@
+---
+title: "Bmaptool: A simpler way to copy ISOs"
+date: 2023-01-18T11:08:20-05:00
+draft: false
+tags: []
+math: false
+---
+
+Bmaptool is a project created by Intel for creating and copying data using block maps. It's meant to be a simpler, faster, and more reliable tool than `dd`.
+
+From their [GitHub page](https://github.com/intel/bmap-tools):
+
+> - Faster. Depending on various factors, like write speed, image size, how full is the image, and so on, `bmaptool` was 5-7 times faster than `dd` in the Tizen IVI project.
+> - Integrity. `bmaptool` verifies data integrity while flashing, which means that possible data corruptions will be noticed immediately.
+> - Usability. `bmaptool` can read images directly from the remote server, so users do not have to download images and save them locally.
+> - Protects user's data. Unlike `dd`, if you make a mistake and specify a wrong block device name, `bmaptool` will less likely destroy your data because it has protection mechanisms which, for example, prevent `bmaptool` from writing to a mounted block device.
+
+It comes with two commands **create** and **copy**. Create generates the block maps which isn't required to use the application. However, having a bmap will speed up the copying process. The syntax of the copy command is the following
+
+```bash
+sudo bmaptool copy SRC DST
+```
+
+Let's say that I want to flash the latest Ubuntu ISO to a USB stick located at `/dev/sdX`. As the third bullet point claims, I can easily use the URL as SRC and since we don't have a bmap, we'll have to specify that with the flag `--nobmap`.
+
+```bash
+sudo bmaptool copy --nobmap https://releases.ubuntu.com/22.04.1/ubuntu-22.04.1-desktop-amd64.iso /dev/sdX
+```
+
+Example run on my desktop:
+
+ ```
+ bmaptool: info: no bmap given, copy entire image to '/dev/sdX'
+ /
+ bmaptool: info: synchronizing '/dev/sdX'
+ bmaptool: info: copying time: 3m 7.3s, copying speed 19.5 MiB/sec
+ ```
+
+Now if we have the ISO downloaded on our computer, we can take the time to create a bmap for it.
+
+```bash
+sudo bmaptool create ubuntu-22.04.1-desktop-amd64.iso > ubuntu-22.04.1-desktop-amd64.bmap
+```
+
+A bmap file is a human readable XML file that shows the block map and the checksums for each block.
+
+```xml
+<?xml version="1.0" ?>
+<!-- This file contains the block map for an image file, which is basically
+     a list of useful (mapped) block numbers in the image file. In other words,
+     it lists only those blocks which contain data (boot sector, partition
+     table, file-system metadata, files, directories, extents, etc). These
+     blocks have to be copied to the target device. The other blocks do not
+     contain any useful data and do not have to be copied to the target
+     device.
+
+     The block map an optimization which allows to copy or flash the image to
+     the image quicker than copying of flashing the entire image. This is
+     because with bmap less data is copied: <MappedBlocksCount> blocks instead
+     of <BlocksCount> blocks.
+
+     Besides the machine-readable data, this file contains useful commentaries
+     which contain human-readable information like image size, percentage of
+     mapped data, etc.
+
+     The 'version' attribute is the block map file format version in the
+     'major.minor' format. The version major number is increased whenever an
+     incompatible block map format change is made. The minor number changes
+     in case of minor backward-compatible changes. -->
+
+<bmap version="2.0">
+    <!-- Image size in bytes: 3.6 GiB -->
+    <ImageSize> 3826831360 </ImageSize>
+
+    <!-- Size of a block in bytes -->
+    <BlockSize> 4096 </BlockSize>
+
+    <!-- Count of blocks in the image file -->
+    <BlocksCount> 934285 </BlocksCount>
+
+    <!-- Count of mapped blocks: 3.6 GiB or 100.0%   -->
+    <MappedBlocksCount> 934285 </MappedBlocksCount>
+
+    <!-- Type of checksum used in this file -->
+    <ChecksumType> sha256 </ChecksumType>
+
+    <!-- The checksum of this bmap file. When it is calculated, the value of
+         the checksum has be zero (all ASCII "0" symbols).  -->
+    <BmapFileChecksum> e69f56b4cf11a26fba8700bc66a443a20f667d0d0fe1c2d8028715ac060c402d </BmapFileChecksum>
+
+    <!-- The block map which consists of elements which may either be a
+         range of blocks or a single block. The 'chksum' attribute
+         (if present) is the checksum of this blocks range. -->
+    <BlockMap>
+        <Range chksum="c396e956a9f52c418397867d1ea5c0cf1a99a49dcf648b086d2fb762330cc88d"> 0-934284 </Range>
+    </BlockMap>
+</bmap>
+```
+
+Once we have generated the bmap, we can copy the ISO to the device.
+
+```bash
+sudo bmaptool copy ubuntu-22.04.1-desktop-amd64.iso /dev/sdX
+```
+
+Example run on my desktop:
+
+```
+bmaptool: info: discovered bmap file 'ubuntu-22.04.1-desktop-amd64.bmap'
+bmaptool: info: block map format version 2.0
+bmaptool: info: 934285 blocks of size 4096 (3.6 GiB), mapped 934285 blocks (3.6 GiB or 100.0%)
+bmaptool: info: copying image 'ubuntu-22.04.1-desktop-amd64.iso' to block device '/dev/sdX' using bmap file 'ubuntu-22.04.1-desktop-amd64.bmap'
+bmaptool: info: 100% copied
+bmaptool: info: synchronizing '/dev/sdX'
+bmaptool: info: copying time: 2m 49.2s, copying speed 21.6 MiB/sec
+```
+
+Recall that the `bmap` generation isn't necessary, as you can pass in the `--nobmap` flag.

content/blog/robustdd.md

@@ -1,11 +1,13 @@
 ---
-title: "Robustdd"
+title: "Robustly copying ISOs using dd"
 date: 2019-09-27T22:45:56-04:00
 draft: false
 tags: [ "Linux" ]
 medium_enabled: true
 ---
 
+**Note:** [Currently I favor using `bmaptool`](/blog/bmaptool-iso)
+
 This blog post is going to assume that we're writing to `/dev/sdX`. Please change this to whatever disk you're actually trying to write to. I bear no responsibility if you accidentally write to your OS drives.
 
 Make sure the disk you wish to write to is unmounted.