@@ -27,6 +27,8 @@ btrfs \- control a btrfs filesystem
.PP
\fBbtrfs\fP \fBfilesystem label\fP\fI <dev> [newlabel]\fP
.PP
+\fBbtrfs\fP \fBfilesystem df\fP\fI [-k] \fIpath [path..]\fR\fP
+.PP
\fBbtrfs\fP \fBsubvolume find-new\fP\fI <subvolume> <last_gen>\fP
.PP
\fBbtrfs\fP \fBfilesystem balance\fP\fI <path> \fP
@@ -214,6 +216,104 @@ NOTE: Currently there are the following limitations:
- the filesystem should not have more than one device.
.TP
+\fBfilesystem df\fP [-k] \fIpath [path..]\fR
+
+Show space usage information for a mount point.
+
+\fIOptions\fP
+
+\fB-k\fP Set KB (1024 bytes) as unit
+
+\fIUsage information\fP
+
+.\"
+.\" this section is extract from
+.\" http://en.wikipedia.org/wiki/Btrfs#Chunk_and_device_trees
+The disk(s) of a btrfs filesystem are divided into chunks of 256 MB or more.
+Chunks may be mirrored or striped across multiple devices, depending by
+the allocation policy.
+The mirroring/striping arrangement is transparent to the rest of the
+file system, which simply sees the single, logical address space that
+chunks are mapped into.
+Chunks are allocated on demand. In the default allocation policy
+the data chunks are not duplicated and the metadata chunks
+are duplicated. This default can be changed during the filesystem
+creation, and in general the chunks allocation policy may change
+during the filesystem life.
+
+Depending by the allocation policy a chunk may require a space on
+the disk greater than the logical space that it provides. E.g.
+a chunk DUPlicated or with a RAID1/RAID10 level
+requires a space on the disk
+two times greater than the logical space provided.
+Different RAID levels
+have a different ratio disk-usage / logical space offered.
+
+Normally the file contents are stored in the Data chunks; however
+small files (which fit into a btree leaf) are stored in the
+metadata chunks. So the computation of the \fIfree space\fP
+and \fIused space\fP
+is complex: depending by the file size different
+allocation policies are used.
+
+The command \fBbtrfs filesystem df\fP is used to query the status
+of the chunks, how many space on the disk(s) are used by the chunks,
+how many space are available in the chunks, and an estimation of the free
+space of the filesystem.
+The output of the command \fBbtrfs filesystem df\fP shows:
+
+.RS
+.IP \fBDisk\ size\fP
+the total size of the disks which compose the filesystem.
+
+.IP \fBDisk\ allocated\fP\ or\ \fBSize_(disk)\fP
+the size of the area of the disks used by the chunks.
+
+.IP \fBDisk\ unallocated\fP
+the size of the area of the disks which is free (i.e.
+the differences of the values above).
+
+.IP \fBLogical\ size\fP\ or\ \fBSize_(logical)\fP
+the available logical space of chunk.
+
+.IP \fBUsed\fP
+the portion of the logical space used by the file and metadata.
+
+.IP \fBFree\ (estimated)\fP
+the estimated free space available. The evaluation
+cannot be rigorous because it depends by the allocation policy (DUP,Single,
+RAID1...) of the metadata and data chunks. If every chunks is stored as
+"Single" the sum of the \fBfree (estimated)\fP space and the \fBused\fP
+space is equal to the \fBdisk size\fP.
+Otherwise if all the chunk are mirrored (raid1 or raid10) or duplicated
+the sum of the \fBfree (estimated)\fP space and the \fBused\fP space is
+half of the \fBdisk size\fP. Normally the \fBfree (estimated)\fP is between
+these two limits.
+
+.IP \fBData\ to\ disk\ ratio\fP
+the ratio betwen the \fBlogical size\fP and the \fBdisk allocated\fP.
+
+.IP \fBMode\fP
+the kind of allocation policy used by the chunk (e.g. DUPlicated,
+RAID1, RAID10, Single....)
+
+.IP \fBType\fP
+the kind of chunk (Data, Metdata, System...)
+
+.RE
+.RS
+\fINOTE\fP
+
+When a chunk is allocated, its disk-area is used and its allocation
+policy is fixed.
+A rebalance operation could rearrange the chunks, moving data in the chunks
+and resizing the allocated chunks. This causes the change of all the values
+discussed above, with the exception of the \fBused\fP and
+\fBdisk size\fP values.
+
+.RE
+.TP
+
\fBfilesystem show\fR [--all-devices|<uuid>|<label>]\fR
Show the btrfs filesystem with some additional info. If no \fIUUID\fP or
\fIlabel\fP is passed, \fBbtrfs\fR show info of all the btrfs filesystem.
From: Goffredo Baroncelli <kreijack@inwind.it> --- man/btrfs.8.in | 100 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 100 insertions(+)