Find filesystem of an unmounted partition from a script

Question

I'm writing a custom automated install using AIF (Arch Installation Framework), and I need to find the filesystem on a partition given a partition.

So far I have this:

grok_partitions () {
    local partitions=
    for label in `ls /dev/disk/by-label | grep "Arch"`
    do
        if [ $label == "Arch" ]
        then
            mount_point="/"
        else
            IFS="-" read base mount <<< "${label}"
            mount_point="/${mount}"
        fi

        local partition=$(readlink -f /dev/disk/by-label/${label})
        local part_no=$(echo ${partition} | grep -Po '\d+')
        local fs=$(parted -mls | grep "^${part_no}" | cut -d: -f5)
        partitions+="${partition} raw ${label} ${fs};yes;${mount_point};target;no_opts;${label};no_params\n"
    done

    # do the swap
    if [ -e /dev/disk/by-label/swap ]
    then
        local partition=$(readlink -f /dev/disk/by-label/swap)
        partitions+="$partition raw swap swap;yes;no_mountpoint;target;no_opts;swap;no_params"
    else
        # if there's no labeled swap, use the first one we find
        local partition=$(fdisk -l | grep -m1 swap | awk '{ print $1 }')
        if [ ! -e $partition ]
        then
            echo "No swap detected. Giving up."
            exit 1
        fi
        partitions+="$partition raw no_label swap;yes;no_mountpoint;target;no_opts;no_label;no_params"
    fi

    echo -n ${partitions}
}

This worked fine on my machine with only one hard drive, but it failed (obviously) when running in my VM running on a LiveCD (the LiveCD was being picked up as another drive, /dev/sr0).

I've thought of a couple of hacks I could try:

• mount $partition; grep $partition /etc/mtab | awk ...
• use parted -mls, but pull out the partition I care about with clever scripting, then parse as I already do in the scriptt

Is there a better, simpler way of doing this? I already have the partitions I'm interested in, and I only need to find their filesystems (as well as find available swap).

Answer 1

I think I found the answer: blkid

From the man page:

The blkid program is the command-line interface to working with the libblkid(3) library. It can determine the type of content (e.g. filesystem or swap) that a block device holds, and also attributes (tokens, NAME=value pairs) from the content metadata (e.g. LABEL or UUID fields).

Apparently it prints the device name along with the filesystem type (along with some other useful information). To get a list of all devices with their types:

blkid | sed 's!\(.*\):.*TYPE="\(.*\)".*!\1: \2!'

To find all /dev/sd*/ devices, just add in a grep:

blkid | grep "/dev/sd.*" | sed 's!\(.*\):.*TYPE="\(.*\)".*!\1: \2!'

Then just cut or awk to get what you need.

Answer 2

file -s /path/to/device will identify the filesystem on a disk/partition/slice.

A la:

[root@node2 ~]# file -s /dev/mapper/VolGroup00-LogVol00
/dev/mapper/VolGroup00-LogVol00: Linux rev 1.0 ext3 filesystem data (needs journa recovery) (large files)
[root@node2 ~]# file -s /dev/mapper/coraid--pool-coraid--lv1 
/dev/mapper/coraid--pool-coraid--lv1: Linux GFS2 Filesystem (blocksize 4096, lockproto lock_dlm)
[root@node2 ~]# file -s /dev/mapper/coraid--pool-coraid--lv2 
/dev/mapper/coraid--pool-coraid--lv2: SGI XFS filesystem data (blksz 4096, inosz 256, v2 dirs)

at least, on Linux it does.

Answer 3

Show only the block device's TYPE tag, and only output its value:

blkid -s TYPE -o value "$device"

Example:

$ blkid -s TYPE -o value /dev/mapper/vg_svelte-home 
btrfs

Answer 4

A secondary option that works with many filesystems and has the benefit of working even with filesystems that have damaged structures is testdisk. (You can run sudo apt install testdisk to install it on Debian-based systems.)

Script it to return just the filesystem type like this:

$ testdisk /list "$path_to_partition" | awk '$1 == "P" {print $2}'