04-24-2016
Multiple filesystems DO NOT coexist on a partition.
Hadoop either creates a file on an underlying UNIX filesystem and uses UNIX system calls to allocate blocks to that file, read blocks from the file, write blocks to the file, etc; or it creates a HDFS filesystem on a block special UNIX file and/or character special UNIX file that is a partition where no UNIX filesystem is allocated (and still uses UNIX read and write system calls to read and write HDFS blocks to that underlying UNIX file). The fact that the data written to that file is treated as a filesystem by Hadoop and may contain many files that Hadoop serves to users of the HDFS stored (entirely or partially) inside that UNIX file is invisible to the underlying UNIX system.
This User Gave Thanks to Don Cragun For This Post:
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FINDFS(8) System Administration FINDFS(8)
NAME
findfs - find a filesystem by label or UUID
SYNOPSIS
findfs NAME=value
DESCRIPTION
findfs will search the block devices in the system looking for a filesystem or partition with specified tag. The currently supported tags
are:
LABEL=<label>
Specifies filesystem label.
UUID=<uuid>
Specifies filesystem UUID.
PARTUUID=<uuid>
Specifies partition UUID. This partition identifier is supported for example for GUID Partition Table (GPT) partition tables.
PARTLABEL=<label>
Specifies partition label (name). The partition labels are supported for example for GUID Partition Table (GPT) or MAC partition
tables.
If the filesystem or partition is found, the device name will be printed on stdout.
The complete overview about filesystems and partitions you can get for example by
lsblk --fs
partx --show <disk>
blkid
EXIT STATUS
0 success
1 label or uuid cannot be found
2 usage error, wrong number of arguments or unknown option
AUTHOR
findfs was originally written by Theodore Ts'o <tytso@mit.edu> and re-written for the util-linux package by Karel Zak <kzak@redhat.com>.
ENVIRONMENT
LIBBLKID_DEBUG=all
enables libblkid debug output.
SEE ALSO
blkid(8), lsblk(8), partx(8)
AVAILABILITY
The findfs command is part of the util-linux package and is available from Linux Kernel Archive <https://www.kernel.org/pub/linux/utils
/util-linux/>.
util-linux March 2014 FINDFS(8)