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

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 2

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 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