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Show First 20 Lines • Show All 2,259 Lines • ▼ Show 20 Lines	<para>When <command>ls .zfs/snapshot</command> was issued, the
others. Copying files or directories from this hidden		others. Copying files or directories from this hidden
<filename>.zfs/snapshot</filename> is simple enough. Trying		<filename>.zfs/snapshot</filename> is simple enough. Trying
it the other way around results in this error:</para>		it the other way around results in this error:</para>

<screen>&prompt.root; <userinput>cp <replaceable>/etc/rc.conf</replaceable> /var/tmp/.zfs/snapshot/<replaceable>after_cp/</replaceable></userinput>		<screen>&prompt.root; <userinput>cp <replaceable>/etc/rc.conf</replaceable> /var/tmp/.zfs/snapshot/<replaceable>after_cp/</replaceable></userinput>
cp: /var/tmp/.zfs/snapshot/after_cp/rc.conf: Read-only file system</screen>		cp: /var/tmp/.zfs/snapshot/after_cp/rc.conf: Read-only file system</screen>

<para>The error reminds the user that snapshots are read-only		<para>The error reminds the user that snapshots are read-only
and can not be changed after creation. No files can be		and cannot be changed after creation. No files can be
		wblockUnsubmitted Done Inline Actions Not your fault, but the "no files can be" is just unpleasant. Better: Files cannot be wblock: Not your fault, but the "no files can be" is just unpleasant. Better: ```Files cannot be```
copied into or removed from snapshot directories because		copied into or removed from snapshot directories because
that would change the state of the dataset they		that would change the state of the dataset they
represent.</para>		represent.</para>

<para>Snapshots consume space based on how much the parent		<para>Snapshots consume space based on how much the parent
file system has changed since the time of the snapshot. The		file system has changed since the time of the snapshot. The
<literal>written</literal> property of a snapshot tracks how		<literal>written</literal> property of a snapshot tracks how
much space is being used by the snapshot.</para>		much space is being used by the snapshot.</para>
Show All 33 Lines	used:</para>
<screen>&prompt.root; <userinput>zfs list -rt all <replaceable>camino/home/joe</replaceable></userinput>		<screen>&prompt.root; <userinput>zfs list -rt all <replaceable>camino/home/joe</replaceable></userinput>
NAME USED AVAIL REFER MOUNTPOINT		NAME USED AVAIL REFER MOUNTPOINT
camino/home/joe 108K 1.3G 87K /usr/home/joe		camino/home/joe 108K 1.3G 87K /usr/home/joe
camino/home/joe@plans 21K - 85.5K -		camino/home/joe@plans 21K - 85.5K -
camino/home/joe@backup 0K - 87K -</screen>		camino/home/joe@backup 0K - 87K -</screen>

<para>A typical use for clones is to experiment with a specific		<para>A typical use for clones is to experiment with a specific
dataset while keeping the snapshot around to fall back to in		dataset while keeping the snapshot around to fall back to in
case something goes wrong. Since snapshots can not be		case something goes wrong. Since snapshots cannot be
changed, a read/write clone of a snapshot is created. After		changed, a read/write clone of a snapshot is created. After
the desired result is achieved in the clone, the clone can be		the desired result is achieved in the clone, the clone can be
promoted to a dataset and the old file system removed. This		promoted to a dataset and the old file system removed. This
is not strictly necessary, as the clone and dataset can		is not strictly necessary, as the clone and dataset can
coexist without problems.</para>		coexist without problems.</para>

<screen>&prompt.root; <userinput>zfs clone <replaceable>camino/home/joe</replaceable>@<replaceable>backup</replaceable> <replaceable>camino/home/joenew</replaceable></userinput>		<screen>&prompt.root; <userinput>zfs clone <replaceable>camino/home/joe</replaceable>@<replaceable>backup</replaceable> <replaceable>camino/home/joenew</replaceable></userinput>
&prompt.root; <userinput>ls /usr/home/joe*</userinput>		&prompt.root; <userinput>ls /usr/home/joe*</userinput>
▲ Show 20 Lines • Show All 105 Lines • ▼ Show 20 Lines	mypool@backup1 0 - 43.6M -</screen>
<para>Now that a snapshot exists, <command>zfs send</command>		<para>Now that a snapshot exists, <command>zfs send</command>
can be used to create a stream representing the contents of		can be used to create a stream representing the contents of
the snapshot. This stream can be stored as a file or received		the snapshot. This stream can be stored as a file or received
by another pool. The stream is written to standard output,		by another pool. The stream is written to standard output,
but must be redirected to a file or pipe or an error is		but must be redirected to a file or pipe or an error is
produced:</para>		produced:</para>

<screen>&prompt.root; <userinput>zfs send <replaceable>mypool</replaceable>@<replaceable>backup1</replaceable></userinput>		<screen>&prompt.root; <userinput>zfs send <replaceable>mypool</replaceable>@<replaceable>backup1</replaceable></userinput>
Error: Stream can not be written to a terminal.		Error: Stream cannot be written to a terminal.
		wblockUnsubmitted Done Inline Actions This is output from a command and should not be changed. Or rather, changed in the source, but not here. wblock: This is output from a command and should not be changed. Or rather, changed in the source, but…
You must redirect standard output.</screen>		You must redirect standard output.</screen>

<para>To back up a dataset with <command>zfs send</command>,		<para>To back up a dataset with <command>zfs send</command>,
redirect to a file located on the mounted backup pool. Ensure		redirect to a file located on the mounted backup pool. Ensure
that the pool has enough free space to accommodate the size of		that the pool has enough free space to accommodate the size of
the snapshot being sent, which means all of the data contained		the snapshot being sent, which means all of the data contained
in the snapshot, not just the changes from the previous		in the snapshot, not just the changes from the previous
snapshot.</para>		snapshot.</para>
▲ Show 20 Lines • Show All 1,007 Lines • ▼ Show 20 Lines	<para><acronym>ZFS</acronym> is a fundamentally different file
system because it is more than just a file system.		system because it is more than just a file system.
<acronym>ZFS</acronym> combines the roles of file system and		<acronym>ZFS</acronym> combines the roles of file system and
volume manager, enabling additional storage devices to be added		volume manager, enabling additional storage devices to be added
to a live system and having the new space available on all of		to a live system and having the new space available on all of
the existing file systems in that pool immediately. By		the existing file systems in that pool immediately. By
combining the traditionally separate roles,		combining the traditionally separate roles,
<acronym>ZFS</acronym> is able to overcome previous limitations		<acronym>ZFS</acronym> is able to overcome previous limitations
that prevented <acronym>RAID</acronym> groups being able to		that prevented <acronym>RAID</acronym> groups being able to
grow. Each top level device in a zpool is called a		grow. Each top level device in a pool is called a
<emphasis>vdev</emphasis>, which can be a simple disk or a		<emphasis>vdev</emphasis>, which can be a simple disk or a
<acronym>RAID</acronym> transformation such as a mirror or		<acronym>RAID</acronym> transformation such as a mirror or
<acronym>RAID-Z</acronym> array. <acronym>ZFS</acronym> file		<acronym>RAID-Z</acronym> array. <acronym>ZFS</acronym> file
systems (called <emphasis>datasets</emphasis>) each have access		systems (called <emphasis>datasets</emphasis>) each have access
to the combined free space of the entire pool. As blocks are		to the combined free space of the entire pool. As blocks are
allocated from the pool, the space available to each file system		allocated from the pool, the space available to each file system
decreases. This approach avoids the common pitfall with		decreases. This approach avoids the common pitfall with
extensive partitioning where free space becomes fragmented		extensive partitioning where free space becomes fragmented
across the partitions.</para>		across the partitions.</para>

<informaltable pgwide="1">		<informaltable pgwide="1">
<tgroup cols="2">		<tgroup cols="2">
<tbody valign="top">		<tbody valign="top">
<row>		<row>
<entry xml:id="zfs-term-zpool">zpool</entry>		<entry xml:id="zfs-term-pool">pool</entry>
		wblockUnsubmitted Done Inline Actions The ID change is okay, but it is important to build the document to make sure that xrefs to the previous name aren't broken. wblock: The ID change is okay, but it is important to build the document to make sure that xrefs to the…
		sd_beastie.ioAuthorUnsubmitted Not Done Inline Actions xref checked by full build. sd_beastie.io: xref checked by full build.

<entry>A storage <emphasis>pool</emphasis> is the most		<entry>A storage <emphasis>pool</emphasis> is the most
basic building block of <acronym>ZFS</acronym>. A pool		basic building block of <acronym>ZFS</acronym>. A pool
is made up of one or more vdevs, the underlying devices		is made up of one or more vdevs, the underlying devices
that store the data. A pool is then used to create one		that store the data. A pool is then used to create one
or more file systems (datasets) or block devices		or more file systems (datasets) or block devices
(volumes). These datasets and volumes share the pool of		(volumes). These datasets and volumes share the pool of
remaining free space. Each pool is uniquely identified		remaining free space. Each pool is uniquely identified
▲ Show 20 Lines • Show All 41 Lines • ▼ Show 20 Lines	<tbody valign="top">

<listitem>		<listitem>
<para		<para
xml:id="zfs-term-vdev-file"><emphasis>File</emphasis>		xml:id="zfs-term-vdev-file"><emphasis>File</emphasis>
- In addition to disks, <acronym>ZFS</acronym>		- In addition to disks, <acronym>ZFS</acronym>
pools can be backed by regular files, this is		pools can be backed by regular files, this is
especially useful for testing and experimentation.		especially useful for testing and experimentation.
Use the full path to the file as the device path		Use the full path to the file as the device path
in the zpool create command. All vdevs must be		in the &man.zpool.8; create command. All vdevs
		wblockUnsubmitted Done Inline Actions Better to use <command> here rather than the man reference: in <command>zpool create</command>. All vdevs wblock: Better to use <command> here rather than the man reference: ```in <command>zpool…
at least 128 MB in size.</para>		must be at least 128 MB in size.</para>
		wblockUnsubmitted Done Inline Actions Moving the "must be" to this line is a whitespace-only change, and should not be mixed with a content change. But the suggestion for the previous line makes that unnecessary anyway. wblock: Moving the "must be" to this line is a whitespace-only change, and should not be mixed with a…
		sd_beastie.ioAuthorUnsubmitted Done Inline Actions This still ends up being on the next line b/c of the command start and end tags. sd_beastie.io: This still ends up being on the next line b/c of the command start and end tags.
		wblockUnsubmitted Done Inline Actions No, wrapping that line is a whitespace-only change. So you have to break the formatting rules while making the content change: in <command>zpool create</command>. All vdevs must be at least 128 MB in size.</para> That too-long line will be fixed in the followup whitespace-only commit. wblock: No, wrapping that line is a whitespace-only change. So you have to break the formatting rules…
		sd_beastie.ioAuthorUnsubmitted Not Done Inline Actions Got it. sd_beastie.io: Got it.
</listitem>		</listitem>

<listitem>		<listitem>
<para		<para
xml:id="zfs-term-vdev-mirror"><emphasis>Mirror</emphasis>		xml:id="zfs-term-vdev-mirror"><emphasis>Mirror</emphasis>
- When creating a mirror, specify the		- When creating a mirror, specify the
<literal>mirror</literal> keyword followed by the		<literal>mirror</literal> keyword followed by the
list of member devices for the mirror. A mirror		list of member devices for the mirror. A mirror
▲ Show 20 Lines • Show All 89 Lines • ▼ Show 20 Lines	<listitem>
mirrored, but <acronym>RAID-Z</acronym> is not		mirrored, but <acronym>RAID-Z</acronym> is not
supported. If multiple log devices are used,		supported. If multiple log devices are used,
writes will be load balanced across them.</para>		writes will be load balanced across them.</para>
</listitem>		</listitem>

<listitem>		<listitem>
<para		<para
xml:id="zfs-term-vdev-cache"><emphasis>Cache</emphasis>		xml:id="zfs-term-vdev-cache"><emphasis>Cache</emphasis>
- Adding a cache vdev to a zpool will add the		- Adding a cache vdev to a pool will add the
storage of the cache to the <link		storage of the cache to the <link
linkend="zfs-term-l2arc"><acronym>L2ARC</acronym></link>.		linkend="zfs-term-l2arc"><acronym>L2ARC</acronym></link>.
Cache devices cannot be mirrored. Since a cache		Cache devices cannot be mirrored. Since a cache
device only stores additional copies of existing		device only stores additional copies of existing
data, there is no risk of data loss.</para>		data, there is no risk of data loss.</para>
</listitem>		</listitem>
</itemizedlist></entry>		</itemizedlist></entry>
</row>		</row>
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