Reinstall rEFInd on an imac

[George Wren]

Hi. I'd like to try an reinstall rEFInd on an imac, original install no longer loads. Can I just reinstall it or is it better to uninstall the original first? How can I tell if the original install components are even still there?
Any advice or questions would be appreciated, thanks!

[joevt]

If it's still installed, then you just need to rebless it with the bless command. If you installed it to an HFS+ partition with ownhfs, then it will be listed in the Startup Disk preferences panel. If not, then it's probably on an EFI partition. EFI partitions are not mounted automatically by the Finder but you can mount them manually. I use the following script to mount all EFI partitions.

mountpartition() {
    local mounttype=$1
    local slice=$2
    local volume=$3
    local mountpoint=$(mount | sed -n -E "/\/dev\/$slice on (.*) \(.*/s//\1/p")
    if [ -z $mountpoint ]; then
        i=0
        local startmountpoint="/Volumes/$volume"
        mountpoint="$startmountpoint"
        while [ -d "$mountpoint" ]; do
            ((i++))
            mountpoint="$startmountpoint$i"
        done
    fi
    if [ ! -d "$mountpoint" ]; then
        sudo mkdir "$mountpoint" 2> /dev/null
        sudo mount$mounttype "/dev/$slice" "$mountpoint"
    fi
    echo -n "$mountpoint"
}

getvolumename () {
    local slice="$1"
    eval "$(diskutil info -plist /dev/$slice | plutil -p - | sed -nE '/^ *"VolumeName" => (.*)/s//echo \1/p')"
}


mountEFIpartitions () {
    IFS=$'\n'
    local diskinfo=""
    for diskinfo in $(diskutil list | sed -nE '/^ *[0-9]+: +EFI (.*[^ ]) +[0-9.]+ [^ ]?B +(disk[0-9]+s[0-9]+)$/s//\1_\2/p'); do
        local slice="${diskinfo##*_}"
        local volume="$(getvolumename $slice)"
        mountpartition "_msdos" "$slice" "$volume" > /dev/null
    done
}

mountEFIpartitions