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I have been using snapraid since circa 2015 for my main first past redundancy. I have a second home server used as a backup server that weekly backs up using restic.

The main snapraid commands I use are: sudo snapraid sync to sync the files that have changes since last sync. I usually do this weekly, manually. sudo snapraid scrub to check the parity of the array, usually the oldest files first. I usually do this weekly, manually. sudo snapraid status to check the status of the array. I usually do this weekly, manually. sudo snapraid touch to add sub-second time granularity to the files that improves snapraid usage. I usually do this weekly, if reported as requried by status, manually. sudo snapraid smart to check the smart status of the array drives (does not report on nvme drives). I usually do this weekly, manually. Really for information only.

Snapraid allows files and directories that have been deleted since the last sync to be recovered.

snapraid diff –test-fmt path
snapraid diff –test-fmt disk This will let you know the data disk from snapraids array perspective

Snapraid does not expect you to provide the absolute file system path when fixing files.

snapraid fix -m This will recreate any deleted file in the entire array
snapraid fix -m -d d1 This will recreate any deleted file on data disk d1
snapraid fix -m -f Example/ This will recreate the contents of any folder named Example anywhere in the array
snapraid check -m -f Example/ -v If you are unsure what will happen you can replace fix with check above and add -v with this. Snapraid will then tell you that there is a problem with each of the files matching the filter or that they are ok.

The main snapraid configuration file /etc/snapraid.conf

Install Snapraid on Linux

Some good references are Setting up SnapRAID on Ubuntu to Create a Flexible Home Media Fileserver and How to install and configure SnapRAID on Ubuntu Server

apt-get install gcc git make -y
 
cd 
wget https://github.com/amadvance/snapraid/releases/download/v12.3/snapraid-12.3.tar.gz
tar xzvf snapraid-12.3.tar.gz
cd snapraid-12.3/
./configure
make
make check
make install
cd ..
cp ~/snapraid-12.3/snapraid.conf.example /etc/snapraid.conf
cd ..
 
rm -rf snapraid*

My main server configuration files, /etc/snapraid.conf

I probably should check this configuration file against the latest version example. My current operating version is 12.0 (2021/12) the latest version is 12.4 (2025/01), there looks to be mainly some minor optimisations and bug fixes.

# Example configuration for snapraid

# Defines the file to use as parity storage
# It must NOT be in a data disk
# Format: "parity FILE [,FILE] ..."
parity /media/disk3/snapraid.parity

# Defines the files to use as additional parity storage.
# If specified, they enable the multiple failures protection
# from two to six level of parity.
# To enable, uncomment one parity file for each level of extra
# protection required. Start from 2-parity, and follow in order.
# It must NOT be in a data disk
# Format: "X-parity FILE [,FILE] ..."
#2-parity /mnt/diskq/snapraid.2-parity
#3-parity /mnt/diskr/snapraid.3-parity
#4-parity /mnt/disks/snapraid.4-parity
#5-parity /mnt/diskt/snapraid.5-parity
#6-parity /mnt/disku/snapraid.6-parity

# Defines the files to use as content list
# You can use multiple specification to store more copies
# You must have least one copy for each parity file plus one. Some more don't hurt
# They can be in the disks used for data, parity or boot,
# but each file must be in a different disk
# Format: "content FILE"
content /home/snapraid.content
content /media/disk1/snapraid.content
content /media/disk2/snapraid.content

# Defines the data disks to use
# The name and mount point association is relevant for parity, do not change it
# WARNING: Adding here your /home, /var or /tmp disks is NOT a good idea!
# SnapRAID is better suited for files that rarely changes!
# Format: "data DISK_NAME DISK_MOUNT_POINT"
data d1 /home/shared
data d2 /media/disk1/
data d3 /media/disk2/

# Excludes hidden files and directories (uncomment to enable).
#nohidden

# Defines files and directories to exclude
# Remember that all the paths are relative at the mount points
# Format: "exclude FILE"
# Format: "exclude DIR/"
# Format: "exclude /PATH/FILE"
# Format: "exclude /PATH/DIR/"
exclude *.unrecoverable
exclude /tmp/
exclude /lost+found/
exclude /.Trash-0/
exclude /*.vhdx
exclude .thumbs.db
exclude /VMs/
exclude /home/shared/www/html/logs/
exclude logs/
exclude log/
#exclude .config/
exclude .cache/
exclude /home/baumkp/.vnc/
exclude .log

# Defines the block size in kibi bytes (1024 bytes) (uncomment to enable).
# WARNING: Changing this value is for experts only!
# Default value is 256 -> 256 kibi bytes -> 262144 bytes
# Format: "blocksize SIZE_IN_KiB"
#blocksize 256

# Defines the hash size in bytes (uncomment to enable).
# WARNING: Changing this value is for experts only!
# Default value is 16 -> 128 bits
# Format: "hashsize SIZE_IN_BYTES"
#hashsize 16

# Automatically save the state when syncing after the specified amount
# of GB processed (uncomment to enable).
# This option is useful to avoid to restart from scratch long 'sync'
# commands interrupted by a machine crash.
# It also improves the recovering if a disk break during a 'sync'.
# Default value is 0, meaning disabled.
# Format: "autosave SIZE_IN_GB"
autosave 100

# Defines the pooling directory where the virtual view of the disk
# array is created using the "pool" command (uncomment to enable).
# The files are not really copied here, but just linked using
# symbolic links.
# This directory must be outside the array.
# Format: "pool DIR"
#pool /pool

# Defines a custom smartctl command to obtain the SMART attributes
# for each disk. This may be required for RAID controllers and for
# some USB disk that cannot be autodetected.
# In the specified options, the "%s" string is replaced by the device name.
# Refers at the smartmontools documentation about the possible options:
# RAID -> https://www.smartmontools.org/wiki/Supported_RAID-Controllers
# USB -> https://www.smartmontools.org/wiki/Supported_USB-Devices
#smartctl d1 -d sat %s
#smartctl d2 -d usbjmicron %s
#smartctl parity -d areca,1/1 /dev/sg0
#smartctl 2-parity -d areca,2/1 /dev/sg0

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