From 66c7f4cb944aea255f52fcb598c876b951879154 Mon Sep 17 00:00:00 2001
From: Johannes Stoelp <johannes.stoelp@gmail.com>
Date: Sun, 13 Apr 2025 21:31:18 +0200
Subject: dd: initial notes

---
 src/cli/dd.md | 46 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 46 insertions(+)
 create mode 100644 src/cli/dd.md

(limited to 'src/cli/dd.md')

diff --git a/src/cli/dd.md b/src/cli/dd.md
new file mode 100644
index 0000000..709cfa0
--- /dev/null
+++ b/src/cli/dd.md
@@ -0,0 +1,46 @@
+# dd(1)
+
+Copy data `block-wise`.
+
+```
+dd [opts]
+    if=<path>         input file to read (stdin in case not specified)
+    of=<path>         oputput file to write
+    status=progress   show progress while copying
+    bs=<bytes>        block size
+    count=<n>         copy only <n> blocks
+    skip=<n>          skip <n> blocks in input (seek input)
+    seek=<n>          skip <n> blocks in oputput (seek output)
+    conv=<conv>
+         notrunc      dont truncate output file
+         excl         fail if output already exists
+         nocreat      fail if output does not exists
+```
+
+## Example: bootstick
+
+```bash
+dd bs=4M if=<iso> of=<blkdev> oflag=sync status=progress
+```
+
+## Example: patch file in place
+
+```bash
+# Create a 1024 bytes file filled with zeros.
+dd if=/dev/zero of=disk bs=512 count=2
+
+# Overwrite 4 bytes starting at byte 0.
+printf "aaaa" | dd of=disk bs=1 seek=0 conv=notrunc
+
+# Overwrite 4 bytes starting at byte 512.
+printf "bbbb" | dd of=disk bs=1 seek=512 conv=notrunc
+
+hexdump disk
+# 0000000 6161 6161 0000 0000 0000 0000 0000 0000
+# 0000010 0000 0000 0000 0000 0000 0000 0000 0000
+# *
+# 0000200 6262 6262 0000 0000 0000 0000 0000 0000
+# 0000210 0000 0000 0000 0000 0000 0000 0000 0000
+# *
+# 0000400
+```
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