From 221054c481e81d0b393a90f248180874d64b90e1 Mon Sep 17 00:00:00 2001
From: Michele Cereda <cereda.michele@gmail.com>
Date: Sun, 24 Jul 2022 20:13:11 +0200
Subject: [PATCH] Added system shared folders and file deduplication section

---
 knowledge base/synology dsm.md | 60 ++++++++++++++++++++++++++--------
 1 file changed, 47 insertions(+), 13 deletions(-)

diff --git a/knowledge base/synology dsm.md b/knowledge base/synology dsm.md
index 22e966d..6783d5e 100644
--- a/knowledge base/synology dsm.md	
+++ b/knowledge base/synology dsm.md	
@@ -1,5 +1,21 @@
 # Synology DiskStation Manager
 
+## System's shared folders
+
+Automatically created by services or packages.
+
+Cannot be changed/removed manually if their creator is still active or installed.
+
+```text
+/volumeX
+├── docker      # data container for the Docker service, created by it upon installation
+├── homes       # all users' home directories, created by the SSH service upon activation
+├── music       # created by the Media Server package upon installation
+├── NetBackup   # created by the rsync service upon activation
+├── photo       # created by the Media Server package upon installation
+└── video       # created by the Media Server package upon installation
+```
+
 ## Rsync
 
 Requirements:
@@ -14,17 +30,19 @@ Examples:
 
 ```sh
 # From a shared folder on a NAS to a local one.
+# Use the SSH port defined in the NAS settings.
 rsync \
-  --archive --hard-links \
-  --append-verify --partial \
-  --progress --verbose \
-  --compress --no-motd \
-  --exclude "@*" --exclude "#*" \
   "user@nas:/volume1/shared_folder/" \
   "path/to/local/folder/" \
+  --archive --copy-links --protect-args \
+  --acls --xattrs --fake-super \
+  --partial --append-verify --sparse \
+  --progress -vv --no-inc-recursive \
+  --compress --no-motd --rsh='ssh -p12345' \
+  --exclude "@eaDir" --exclude "#recycle" \
   --delete --dry-run
 
-# Sync all snapshotted data to a folder
+# Sync all snapshotted data to a folder.
 find /volume1/@sharesnap/shared_folder \
   -maxdepth 1 -mindepth 1 \
   -type d
@@ -52,20 +70,36 @@ Gotchas:
      > /dev/mapper/cachedev_0 on /volume1/Data/#snapshot type btrfs (ro,nodev,relatime,ssd,synoacl,space_cache=v2,auto_reclaim_space,metadata_ratio=50,block_group_cache_tree,subvolid=266,subvol=/@syno/@sharesnap/Data)
      > ```
 
-## Deduplicate blocks in a volume
+## Data deduplication
 
 Requirements:
 
-1. `docker` needs to be installed from the package manager, as it is simpler to run a container than installing `duperemove` and all its dependencies on the machine
-1. the container needs to be run in privileged mode (`--privileged`) due to its actions on the disk
+1. `docker` needs to be installed from the package manager, as it is simpler (and safer?) to run a container than installing `duperemove` or `jdupes` and all their dependencies on the machine
+
+### Remove duplicated files with jdupes
+
+Examples:
+
+```sh
+# `sudo` is only needed if the user has no privileges to run `docker` commands.
+sudo docker run \
+  -it --init \
+  -v "/volume/shared_folder1:/data1" \
+  -v "/volume/shared_folder2:/data2" \
+  ghcr.io/jbruchon/jdupes:latest \
+    -drOZ \
+    -X 'nostr:@eaDir' -X 'nostr:#recycle' \
+    "/data1" "/data2"
+```
+
+### Deduplicate blocks in a volume with duperemove
 
 Gotchas:
 
+1. `duperemove`'s container needs to be run in privileged mode (`--privileged`) due to it taking actions on the disk
 1. the container might fail on very large datasets, usually due to Out Of Memory (OOM) issues; to avoid this:
-
-   1. offload the hashes from RAM using a hash file (`--hashfile "/volume1/NetBackup/duperemove.tmp"`)
-   1. use smaller datasets where possible, like a shared folder and just one of its snapshots instead of all of them
-
+   - offload the hashes from RAM using a hash file (`--hashfile "/volume1/NetBackup/duperemove.tmp"`)
+   - use smaller datasets where possible, like a shared folder and just one of its snapshots instead of all of them
 1. `duperemove` can dedupe blocks only if acting on folders in a _rw_ mount; when deduplicating snapshots, use their _rw_ mount path `/@syno/@sharesnap/shared_folder` instead of their _ro_ version `/volumeN/shared_folder/#snapshot`
 
 Examples: