RSync only if filesystem is mounted

Question

I want to setup a cron job to rsync a remote system to a backup partition, something like:

bash -c 'rsync -avz --delete --exclude=proc --exclude=sys root@remote1:/ /mnt/remote1/'

I would like to be able to "set it and forget it" but what if /mnt/remote1 becomes unmounted? (After a reboot or something) I'd like to error out if /mnt/remote1 isn't mounted, rather than filling up the local filesystem.

Edit:
Here is what I came up with for a script, cleanup improvements appreciated (especially for the empty then ... else, I couldn't leave them empty or bash errors)

#!/bin/bash

DATA=data
ERROR="0"

if cut -d' ' -f2 /proc/mounts | grep -q "^/mnt/$1\$"; then
    ERROR=0
else
    if mount /dev/vg/$1 /mnt/$1; then
        ERROR=0
    else
        ERROR=$?
        echo "Can't backup $1, /mnt/$1 could not be mounted: $ERROR"
    fi
fi

if [ "$ERROR" = "0" ]; then
    if cut -d' ' -f2 /proc/mounts | grep -q "^/mnt/$1/$DATA\$"; then
        ERROR=0
    else
        if mount /dev/vg/$1$DATA /mnt/$1/data; then
            ERROR=0
        else
            ERROR=$?
            echo "Can't backup $1, /mnt/$1/data could not be mounted."
        fi
    fi
fi

if [ "$ERROR" = "0" ]; then
    rsync -aqz --delete --numeric-ids --exclude=proc --exclude=sys \
        root@$1.domain:/ /mnt/$1/
    RETVAL=$?
    echo "Backup of $1 completed, return value of rsync: $RETVAL"
fi

Answer 1

if cut -d' ' -f2 /proc/mounts | grep '^/mnt/remote1$' >/dev/null; then
    rsync -avz ...
fi

Get the list of mounted partitions from /proc/mounts, only match /mnt/remote1 (and if it is mounted, send grep's output to /dev/null), then run your rsync job.

Recent greps have a -q option that you can use instead of sending the output to /dev/null.

Answer 2

mountpoint seems to be the best solution to this: it returns 0 if a path is a mount point:

#!/bin/bash
if [[ `mountpoint -q /path` ]]; then
    echo "filesystem mounted"
else
    echo "filesystem not mounted"
fi

Found at LinuxQuestions.

Answer 3

A quick google led me to this bash script that can check if a filesystem is mounted. It seems that grepping the output of df or mount is the way to go:

if df |grep -q '/mnt/mountpoint$'
    then
        echo "Found mount point, running task"
        # Do some stuff
    else
        echo "Aborted because the disk is not mounted"
        # Do some error correcting stuff
        exit -1
fi

Answer 4

1. Copy and paste the script below to a file (e.g. backup.sh).
2. Make the script executable (e.g. chmod +x backup.sh)
3. Call the script as root with the format backup.sh [username (for rsync)] [backup source device] [backup source location] [backup target device] [backup target location]

!!!ATTENTION!!! Don't execute the script as root user without understanding the code!

I think there's nothing to explain. The code is straightforward and well documented.

#!/bin/bash

##
## COMMAND USAGE: backup.sh [username] [backup source device] [backup source location] [backup target device] [backup target location]
##
## for example: sudo /home/manu/bin/backup.sh "manu" "/media/disk1" "/media/disk1/." "/media/disk2" "/media/disk2"
##

##
## VARIABLES
##

# execute as user
USER="$1"

# Set source location
BACKUP_SOURCE_DEV="$2"
BACKUP_SOURCE="$3"

# Set target location
BACKUP_TARGET_DEV="$4"
BACKUP_TARGET="$5"

# Log file
LOG_FILE="/var/log/backup_script.log"

##
## SCRIPT
##

function end() {
    echo -e "###########################################################################\
#########################################################################\n\n" >> "$LOG_FILE"
    exit $1
}

# Check that the log file exists
if [ ! -e "$LOG_FILE" ]; then
        touch "$LOG_FILE"
    chown $USER "$LOG_FILE"
fi

# Check if backup source device is mounted
if ! mountpoint "$BACKUP_SOURCE_DEV"; then
        echo "$(date "+%Y-%m-%d %k:%M:%S") - ERROR: Backup source device is not mounted!" >> "$LOG_FILE"
    end 1
fi

# Check that source dir exists and is readable.
if [ ! -r  "$BACKUP_SOURCE" ]; then
        echo "$(date "+%Y-%m-%d %k:%M:%S") - ERROR: Unable to read source dir." >> "$LOG_FILE"
        echo "$(date "+%Y-%m-%d %k:%M:%S") - ERROR: Unable to sync." >> "$LOG_FILE"
    end 1
fi

# Check that target dir exists and is writable.
if [ ! -w  "$BACKUP_TARGET" ]; then
        echo "$(date "+%Y-%m-%d %k:%M:%S") - ERROR: Unable to write to target dir." >> "$LOG_FILE"
        echo "$(date "+%Y-%m-%d %k:%M:%S") - ERROR: Unable to sync." >> "$LOG_FILE"
    end 1
fi

# Check if the drive is mounted
if ! mountpoint "$BACKUP_TARGET_DEV"; then
        echo "$(date "+%Y-%m-%d %k:%M:%S") - WARNING: Backup device needs mounting!" >> "$LOG_FILE"

        # If not, mount the drive
        if mount "$BACKUP_TARGET_DEV" > /dev/null 2>&1 || /bin/false; then
                echo "$(date "+%Y-%m-%d %k:%M:%S") - Backup device mounted." >> "$LOG_FILE"
        else
                echo "$(date "+%Y-%m-%d %k:%M:%S") - ERROR: Unable to mount backup device." >> "$LOG_FILE"
                echo "$(date "+%Y-%m-%d %k:%M:%S") - ERROR: Unable to sync." >> "$LOG_FILE"
        end 1
        fi
fi

# Start entry in the log
echo "$(date "+%Y-%m-%d %k:%M:%S") - Sync started." >> "$LOG_FILE"

# Start sync
su -c "rsync -ayhEAX --progress --delete-after --inplace --compress-level=0 --log-file=\"$LOG_FILE\" \"$BACKUP_SOURCE\" \"$BACKUP_TARGET\"" $USER
echo "" >> "$LOG_FILE"

# Unmount the drive so it does not accidentally get damaged or wiped
if umount "$BACKUP_TARGET_DEV" > /dev/null 2>&1 || /bin/false; then
    echo "$(date "+%Y-%m-%d %k:%M:%S") - Backup device unmounted." >> "$LOG_FILE"
else
    echo "$(date "+%Y-%m-%d %k:%M:%S") - WARNING: Backup device could not be unmounted." >> "$LOG_FILE"
fi

# Exit successfully
end 0

Answer 5

I am skimming This but I would think you would rather rsync -e ssh and setup the keys to accept the account.