Rsync

# Debian/Ubuntu
sudo apt install rsync

# Fedora/RHEL
sudo dnf install rsync

# Arch Linux
sudo pacman -S rsync

rsync [options] <source> <destination>

rsync -av /path/to/source/ /path/to/destination/

rsync -avz /path/to/source/ <user>@<host>:/path/to/destination/

rsync -avz <user>@<host>:/path/to/source/ /path/to/destination/

rsync -av --delete /path/to/source/ /path/to/destination/

# Source: /data/ contains file1.txt, file2.txt

# WITH trailing slash: files end up at /backup/file1.txt, /backup/file2.txt
rsync -av /data/ /backup/

# WITHOUT trailing slash: files end up at /backup/data/file1.txt, /backup/data/file2.txt
rsync -av /data /backup/

rsync -avz -e ssh /path/to/source/ <user>@<host>:/path/to/destination/

rsync -avz -e "ssh -p <port> -i /path/to/key" /data/ <user>@<host>:/backup/

# Generate key pair (if not already existing)
ssh-keygen -t ed25519 -f ~/.ssh/id_rsync -N ""

# Copy public key to remote host
ssh-copy-id -i ~/.ssh/id_rsync.pub <user>@<host>

# Test
rsync -avz -e "ssh -i ~/.ssh/id_rsync" /data/ <user>@<host>:/backup/

command="rsync --server --sender -logDtprze.iLsfxCIvu . /allowed/path/",restrict ssh-ed25519 AAAA... rsync@client

# Limit to 5 MiB/s
rsync -avz --bwlimit=5120 /data/ <user>@<host>:/backup/

# Limit to 1 MiB/s
rsync -avz --bwlimit=1024 /data/ <user>@<host>:/backup/

#!/bin/bash
HOUR=$(date +%H)
if [ "$HOUR" -ge 8 ] && [ "$HOUR" -lt 18 ]; then
    BWLIMIT="--bwlimit=2048"   # 2 MiB/s during business hours
else
    BWLIMIT=""                  # Unlimited at night
fi
rsync -avz $BWLIMIT /data/ backup@server:/backup/

rsync -av --exclude='*.tmp' --exclude='.cache' --exclude='node_modules' /data/ /backup/

*.tmp
*.swp
*~
.cache/
.thumbnails/
__pycache__/
node_modules/
.git/
/proc/
/sys/
/dev/
/tmp/
/run/

rsync -av --exclude-from='/etc/rsync/excludes.txt' /data/ /backup/

rsync -av --include='*.conf' --include='*/' --exclude='*' /etc/ /backup/etc/

rsync -avc /data/ /backup/

# Global settings
uid = nobody
gid = nogroup
use chroot = yes
max connections = 10
log file = /var/log/rsyncd.log
pid file = /var/run/rsyncd.pid

# Module definitions
[backups]
    path = /srv/backups
    comment = Backup storage
    read only = no
    auth users = backup
    secrets file = /etc/rsyncd.secrets
    hosts allow = 192.0.2.0/24 198.51.100.0/24
    hosts deny = *

[public]
    path = /srv/public
    comment = Public files
    read only = yes

backup:<your-password>

chmod 600 /etc/rsyncd.secrets

# Systemd
sudo systemctl enable --now rsync

# Or manually
rsync --daemon --config=/etc/rsyncd.conf

# List modules on a daemon
rsync rsync://<host>/

# Pull from a daemon module
rsync -avz rsync://backup@<host>/backups/ /local/backup/

# Push to a daemon module
rsync -avz /data/ rsync://backup@<host>/backups/

# With password file (for automation)
echo "<your-password>" > ~/.rsync-password
chmod 600 ~/.rsync-password
rsync -avz --password-file=~/.rsync-password /data/ rsync://backup@<host>/backups/

# Daily backup at 2:00 AM
0 2 * * * /usr/bin/rsync -avz --delete --log-file=/var/log/rsync-backup.log /data/ backup@server:/backup/

# Weekly full sync on Sunday at 3:00 AM
0 3 * * 0 /usr/bin/rsync -avc --delete /data/ /backup/

[Unit]
Description=Rsync backup
Wants=network-online.target
After=network-online.target

[Service]
Type=oneshot
Nice=19
IOSchedulingClass=idle
ExecStart=/usr/bin/rsync -avz --delete --log-file=/var/log/rsync-backup.log /data/ backup@server:/backup/

[Unit]
Description=Run rsync backup daily

[Timer]
OnCalendar=*-*-* 02:00:00
Persistent=true
RandomizedDelaySec=30m

[Install]
WantedBy=timers.target

sudo systemctl daemon-reload
sudo systemctl enable --now rsync-backup.timer

# Debian/Ubuntu
sudo apt install inotify-tools

# Arch Linux
sudo pacman -S inotify-tools

#!/bin/bash
SOURCE="/path/to/source/"
DESTINATION="<user>@<host>:/path/to/destination/"
LOGFILE="/var/log/rsync-inotify.log"

inotifywait -m -r -e modify,create,delete,move --format '%w%f' "${SOURCE}" | while read file; do
    echo "$(date): Change detected: ${file}" >> "${LOGFILE}"
    rsync -avz --delete "${SOURCE}" "${DESTINATION}" >> "${LOGFILE}" 2>&1
done

#!/bin/bash
SOURCE="/path/to/source/"
DESTINATION="<user>@<host>:/path/to/destination/"
LOGFILE="/var/log/rsync-inotify.log"
DEBOUNCE=5  # seconds

inotifywait -m -r -e modify,create,delete,move --format '%w%f' "${SOURCE}" | while read file; do
    # Kill any pending sync, reset the timer
    if [ -n "${SYNC_PID}" ] && kill -0 "${SYNC_PID}" 2>/dev/null; then
        kill "${SYNC_PID}" 2>/dev/null
    fi
    (
        sleep ${DEBOUNCE}
        echo "$(date): Syncing after change to ${file}" >> "${LOGFILE}"
        rsync -avz --delete "${SOURCE}" "${DESTINATION}" >> "${LOGFILE}" 2>&1
    ) &
    SYNC_PID=$!
done

[Unit]
Description=Real-time rsync via inotify
After=network-online.target

[Service]
Type=simple
ExecStart=/usr/local/bin/rsync-inotify.sh
Restart=always
RestartSec=10

[Install]
WantedBy=multi-user.target

# Check current limit
cat /proc/sys/fs/inotify/max_user_watches

# Increase temporarily
echo 524288 | sudo tee /proc/sys/fs/inotify/max_user_watches

# Persist in /etc/sysctl.d/90-inotify.conf
fs.inotify.max_user_watches = 524288