Silence some igor warnings by wrapping overlong lines.
Also, add an extra space after a sentence stop in a few places. Some indentations in this file are still not perfect, but I focused on lines that were to long primarily to keep the diff small. No content changes.
This commit is contained in:
Benedict Reuschling
parent
03050dbbfe
commit
9d88ddc81d
Notes:
svn2git
2020-12-08 03:00:23 +00:00
svn path=/head/; revision=40546
1 changed files with 251 additions and 223 deletions
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@ -70,79 +70,84 @@
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<releaseinfo>$FreeBSD$</releaseinfo>
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<abstract>
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<para>This article covers the use of solid state disk devices in &os;
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to create embedded systems.</para>
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<para>This article covers the use of solid state disk devices in
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&os; to create embedded systems.</para>
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<para>Embedded systems have the advantage of increased stability due to
|
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the lack of integral moving parts (hard drives). Account must be
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taken, however, for the generally low disk space available in the
|
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system and the durability of the storage medium.</para>
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<para>Embedded systems have the advantage of increased stability
|
||||
due to the lack of integral moving parts (hard drives).
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Account must be taken, however, for the generally low disk
|
||||
space available in the system and the durability of the
|
||||
storage medium.</para>
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|
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<para>Specific topics to be covered include the types and attributes of
|
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solid state media suitable for disk use in &os;, kernel options
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that are of interest in such an environment, the
|
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<filename>rc.initdiskless</filename> mechanisms that automate the
|
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initialization of such systems and the need for read-only filesystems,
|
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and building filesystems from scratch. The article will conclude
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with some general strategies for small and read-only &os;
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environments.</para>
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<para>Specific topics to be covered include the types and
|
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attributes of solid state media suitable for disk use in &os;,
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kernel options that are of interest in such an environment,
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the <filename>rc.initdiskless</filename> mechanisms that
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automate the initialization of such systems and the need for
|
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read-only filesystems, and building filesystems from scratch.
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The article will conclude with some general strategies for
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small and read-only &os; environments.</para>
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</abstract>
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</articleinfo>
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<sect1 id="intro">
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<title>Solid State Disk Devices</title>
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<para>The scope of this article will be limited to solid state disk
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devices made from flash memory. Flash memory is a solid state memory
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(no moving parts) that is non-volatile (the memory maintains data even
|
||||
after all power sources have been disconnected). Flash memory can
|
||||
withstand tremendous physical shock and is reasonably fast (the flash
|
||||
memory solutions covered in this article are slightly slower than a EIDE
|
||||
hard disk for write operations, and much faster for read operations).
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One very important aspect of flash memory, the ramifications of which
|
||||
will be discussed later in this article, is that each sector has a
|
||||
limited rewrite capacity. You can only write, erase, and write again to
|
||||
a sector of flash memory a certain number of times before the sector
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||||
becomes permanently unusable. Although many flash memory products
|
||||
automatically map bad blocks, and although some even distribute write
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||||
operations evenly throughout the unit, the fact remains that there
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exists a limit to the amount of writing that can be done to the device.
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Competitive units have between 1,000,000 and 10,000,000 writes per
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sector in their specification. This figure varies due to the
|
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temperature of the environment.</para>
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<para>The scope of this article will be limited to solid state
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disk devices made from flash memory. Flash memory is a solid
|
||||
state memory (no moving parts) that is non-volatile (the memory
|
||||
maintains data even after all power sources have been
|
||||
disconnected). Flash memory can withstand tremendous physical
|
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shock and is reasonably fast (the flash memory solutions covered
|
||||
in this article are slightly slower than a EIDE hard disk for
|
||||
write operations, and much faster for read operations). One
|
||||
very important aspect of flash memory, the ramifications of
|
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which will be discussed later in this article, is that each
|
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sector has a limited rewrite capacity. You can only write,
|
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erase, and write again to a sector of flash memory a certain
|
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number of times before the sector becomes permanently unusable.
|
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Although many flash memory products automatically map bad
|
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blocks, and although some even distribute write operations
|
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evenly throughout the unit, the fact remains that there exists a
|
||||
limit to the amount of writing that can be done to the device.
|
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Competitive units have between 1,000,000 and 10,000,000 writes
|
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per sector in their specification. This figure varies due to
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the temperature of the environment.</para>
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|
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<para>Specifically, we will be discussing ATA compatible compact-flash
|
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units, which are quite popular as storage media for digital
|
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cameras. Of particular interest is the fact that they pin out directly
|
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to the IDE bus and are compatible with the ATA command set. Therefore,
|
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with a very simple and low-cost adaptor, these devices can be attached
|
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directly to an IDE bus in a computer. Once implemented in this manner,
|
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operating systems such as &os; see the device as a normal hard disk
|
||||
(albeit small).</para>
|
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<para>Specifically, we will be discussing ATA compatible
|
||||
compact-flash units, which are quite popular as storage media
|
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for digital cameras. Of particular interest is the fact that
|
||||
they pin out directly to the IDE bus and are compatible with the
|
||||
ATA command set. Therefore, with a very simple and low-cost
|
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adaptor, these devices can be attached directly to an IDE bus in
|
||||
a computer. Once implemented in this manner, operating systems
|
||||
such as &os; see the device as a normal hard disk (albeit
|
||||
small).</para>
|
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|
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<para>Other solid state disk solutions do exist, but their expense,
|
||||
obscurity, and relative unease of use places them beyond the scope of
|
||||
this article.</para>
|
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<para>Other solid state disk solutions do exist, but their
|
||||
expense, obscurity, and relative unease of use places them
|
||||
beyond the scope of this article.</para>
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</sect1>
|
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|
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<sect1 id="kernel">
|
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<title>Kernel Options</title>
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|
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<para>A few kernel options are of specific interest to those creating
|
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an embedded &os; system.</para>
|
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<para>A few kernel options are of specific interest to those
|
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creating an embedded &os; system.</para>
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|
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<para>All embedded &os; systems that use flash memory as system
|
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disk will be interested in memory disks and memory filesystems. Because
|
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of the limited number of writes that can be done to flash memory, the
|
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disk and the filesystems on the disk will most likely be mounted
|
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read-only. In this environment, filesystems such as
|
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<filename>/tmp</filename> and <filename>/var</filename> are mounted as
|
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memory filesystems to allow the system to create logs and update
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counters and temporary files. Memory filesystems are a critical
|
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component to a successful solid state &os; implementation.</para>
|
||||
disk will be interested in memory disks and memory filesystems.
|
||||
Because of the limited number of writes that can be done to
|
||||
flash memory, the disk and the filesystems on the disk will most
|
||||
likely be mounted read-only. In this environment, filesystems
|
||||
such as <filename>/tmp</filename> and <filename>/var</filename>
|
||||
are mounted as memory filesystems to allow the system to create
|
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logs and update counters and temporary files. Memory
|
||||
filesystems are a critical component to a successful solid state
|
||||
&os; implementation.</para>
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|
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<para>You should make sure the following lines exist in your kernel
|
||||
configuration file:</para>
|
||||
<para>You should make sure the following lines exist in your
|
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kernel configuration file:</para>
|
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|
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<programlisting>options MFS # Memory Filesystem
|
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options MD_ROOT # md device usable as a potential root device
|
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@ -150,58 +155,63 @@ pseudo-device md # memory disk</programlisting>
|
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</sect1>
|
||||
|
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<sect1 id="ro-fs">
|
||||
<title>The <literal>rc</literal> Subsystem and Read-Only Filesystems</title>
|
||||
<title>The <literal>rc</literal> Subsystem and Read-Only
|
||||
Filesystems</title>
|
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|
||||
<para>The post-boot initialization of an embedded &os; system is
|
||||
controlled by <filename>/etc/rc.initdiskless</filename>.</para>
|
||||
|
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<para><filename>/etc/rc.d/var</filename> mounts <filename>/var</filename>
|
||||
as a memory filesystem, makes a configurable list of directories in
|
||||
<filename>/var</filename> with the &man.mkdir.1; command, and
|
||||
changes modes on some of those directories. In the execution of
|
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<para><filename>/etc/rc.d/var</filename> mounts
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<filename>/var</filename> as a memory filesystem, makes a
|
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configurable list of directories in <filename>/var</filename>
|
||||
with the &man.mkdir.1; command, and changes modes on some of
|
||||
those directories. In the execution of
|
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<filename>/etc/rc.d/var</filename>, one other
|
||||
<filename>rc.conf</filename> variable comes into play –
|
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<literal>varsize</literal>. The <filename>/etc/rc.d/var</filename>
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file creates a <filename>/var</filename> partition based on the value of
|
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<literal>varsize</literal>. The
|
||||
<filename>/etc/rc.d/var</filename> file creates a
|
||||
<filename>/var</filename> partition based on the value of
|
||||
this variable in <filename>rc.conf</filename>:</para>
|
||||
|
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<programlisting>varsize=8192</programlisting>
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|
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<para>Remember that this value is in sectors by default.</para>
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|
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<para>The fact that <filename>/var</filename>
|
||||
is a read-write filesystem is an important
|
||||
distinction, as the <filename>/</filename> partition (and any other
|
||||
partitions you may have on your flash media) should be mounted
|
||||
read-only. Remember that in <xref linkend="intro"/> we detailed the
|
||||
limitations of flash memory - specifically the limited write capability.
|
||||
The importance of not mounting filesystems on flash media read-write,
|
||||
and the importance of not using a swap file, cannot be overstated. A
|
||||
swap file on a busy system can burn through a piece of flash media in
|
||||
less than one year. Heavy logging or temporary file creation and
|
||||
destruction can do the same. Therefore, in addition to removing the
|
||||
<para>The fact that <filename>/var</filename> is a read-write
|
||||
filesystem is an important distinction, as the
|
||||
<filename>/</filename> partition (and any other partitions you
|
||||
may have on your flash media) should be mounted read-only.
|
||||
Remember that in <xref linkend="intro"/> we detailed the
|
||||
limitations of flash memory - specifically the limited write
|
||||
capability. The importance of not mounting filesystems on flash
|
||||
media read-write, and the importance of not using a swap file,
|
||||
cannot be overstated. A swap file on a busy system can burn
|
||||
through a piece of flash media in less than one year. Heavy
|
||||
logging or temporary file creation and destruction can do the
|
||||
same. Therefore, in addition to removing the
|
||||
<literal>swap</literal> entry from your
|
||||
<filename>/etc/fstab</filename> file, you should also change the Options
|
||||
field for each filesystem to <literal>ro</literal> as follows:</para>
|
||||
<filename>/etc/fstab</filename> file, you should also change the
|
||||
Options field for each filesystem to <literal>ro</literal> as
|
||||
follows:</para>
|
||||
|
||||
<programlisting># Device Mountpoint FStype Options Dump Pass#
|
||||
/dev/ad0s1a / ufs ro 1 1</programlisting>
|
||||
|
||||
<para>A few applications in the average system will immediately begin to
|
||||
fail as a result of this change. For instance, cron
|
||||
<para>A few applications in the average system will immediately
|
||||
begin to fail as a result of this change. For instance, cron
|
||||
will not run properly as a result of missing cron tabs in the
|
||||
<filename>/var</filename> created by
|
||||
<filename>/etc/rc.d/var</filename>, and syslog and dhcp will
|
||||
encounter problems as well as a result of the read-only filesystem and
|
||||
missing items in the <filename>/var</filename> that
|
||||
<filename>/etc/rc.d/var</filename> has created. These are only
|
||||
temporary problems though, and are addressed, along with solutions to
|
||||
the execution of other common software packages in
|
||||
encounter problems as well as a result of the read-only
|
||||
filesystem and missing items in the <filename>/var</filename>
|
||||
that <filename>/etc/rc.d/var</filename> has created. These are
|
||||
only temporary problems though, and are addressed, along with
|
||||
solutions to the execution of other common software packages in
|
||||
<xref linkend="strategies"/>.</para>
|
||||
|
||||
<para>An important thing to remember is that a filesystem that was mounted
|
||||
read-only with <filename>/etc/fstab</filename> can be made read-write at
|
||||
any time by issuing the command:</para>
|
||||
<para>An important thing to remember is that a filesystem that was
|
||||
mounted read-only with <filename>/etc/fstab</filename> can be
|
||||
made read-write at any time by issuing the command:</para>
|
||||
|
||||
<screen>&prompt.root; <userinput>/sbin/mount -uw <replaceable>partition</replaceable></userinput></screen>
|
||||
|
||||
|
|
@ -213,73 +223,79 @@ pseudo-device md # memory disk</programlisting>
|
|||
<sect1>
|
||||
<title>Building a File System From Scratch</title>
|
||||
|
||||
<para>Because ATA compatible compact-flash cards are seen by &os; as
|
||||
normal IDE hard drives, you could
|
||||
theoretically install &os; from the network using the kern and
|
||||
mfsroot floppies or from a CD.</para>
|
||||
<para>Because ATA compatible compact-flash cards are seen by &os;
|
||||
as normal IDE hard drives, you could theoretically install &os;
|
||||
from the network using the kern and mfsroot floppies or from a
|
||||
CD.</para>
|
||||
|
||||
<para>However, even a small installation of &os; using normal
|
||||
installation procedures can produce a system in size of greater than 200
|
||||
megabytes. Because most people will be using smaller flash memory
|
||||
devices (128 megabytes is considered fairly large - 32 or even 16
|
||||
megabytes is common) an installation using normal mechanisms is not
|
||||
possible—there is simply not enough disk space for even the
|
||||
smallest of conventional installations.</para>
|
||||
installation procedures can produce a system in size of greater
|
||||
than 200 megabytes. Because most people will be using smaller
|
||||
flash memory devices (128 megabytes is considered fairly large -
|
||||
32 or even 16 megabytes is common) an installation using normal
|
||||
mechanisms is not possible—there is simply not enough disk
|
||||
space for even the smallest of conventional
|
||||
installations.</para>
|
||||
|
||||
<para>The easiest way to overcome this space limitation is to install
|
||||
&os; using conventional means to a normal hard disk. After the
|
||||
installation is complete, pare down the operating system to a size that
|
||||
will fit onto your flash media, then tar the entire filesystem. The
|
||||
following steps will guide you through the process of preparing a piece
|
||||
of flash memory for your tarred filesystem. Remember, because a normal
|
||||
installation is not being performed, operations such as partitioning,
|
||||
labeling, file-system creation, etc. need to be performed by hand. In
|
||||
addition to the kern and mfsroot floppy disks, you will also need to use
|
||||
the fixit floppy.</para>
|
||||
<para>The easiest way to overcome this space limitation is to
|
||||
install &os; using conventional means to a normal hard disk.
|
||||
After the installation is complete, pare down the operating
|
||||
system to a size that will fit onto your flash media, then tar
|
||||
the entire filesystem. The following steps will guide you
|
||||
through the process of preparing a piece of flash memory for
|
||||
your tarred filesystem. Remember, because a normal installation
|
||||
is not being performed, operations such as partitioning,
|
||||
labeling, file-system creation, etc. need to be performed by
|
||||
hand. In addition to the kern and mfsroot floppy disks, you
|
||||
will also need to use the fixit floppy.</para>
|
||||
|
||||
<procedure>
|
||||
<step>
|
||||
<title>Partitioning your flash media device</title>
|
||||
|
||||
<para>After booting with the kern and mfsroot floppies, choose
|
||||
<literal>custom</literal> from the installation menu. In the custom
|
||||
installation menu, choose <literal>partition</literal>. In the
|
||||
partition menu, you should delete all existing partitions using the
|
||||
<keycap>d</keycap> key. After deleting all existing partitions,
|
||||
create a partition using the <keycap>c</keycap> key and accept the
|
||||
default value for the size of the partition. When asked for the
|
||||
type of the partition, make sure the value is set to
|
||||
<literal>165</literal>. Now write this partition table to the disk
|
||||
by pressing the <keycap>w</keycap> key (this is a hidden option on
|
||||
this screen). If you are using an ATA compatible compact
|
||||
flash card, you should choose the &os; Boot Manager. Now press
|
||||
the <keycap>q</keycap> key to quit the partition menu. You will be
|
||||
shown the boot manager menu once more - repeat the choice you made
|
||||
earlier.</para>
|
||||
<literal>custom</literal> from the installation menu. In
|
||||
the custom installation menu, choose
|
||||
<literal>partition</literal>. In the partition menu, you
|
||||
should delete all existing partitions using the
|
||||
<keycap>d</keycap> key. After deleting all existing
|
||||
partitions, create a partition using the <keycap>c</keycap>
|
||||
key and accept the default value for the size of the
|
||||
partition. When asked for the type of the partition, make
|
||||
sure the value is set to <literal>165</literal>. Now write
|
||||
this partition table to the disk by pressing the
|
||||
<keycap>w</keycap> key (this is a hidden option on this
|
||||
screen). If you are using an ATA compatible compact flash
|
||||
card, you should choose the &os; Boot Manager. Now press
|
||||
the <keycap>q</keycap> key to quit the partition menu. You
|
||||
will be shown the boot manager menu once more - repeat the
|
||||
choice you made earlier.</para>
|
||||
</step>
|
||||
|
||||
<step>
|
||||
<title>Creating filesystems on your flash memory device</title>
|
||||
<title>Creating filesystems on your flash memory
|
||||
device</title>
|
||||
|
||||
<para>Exit the custom installation menu, and from the main
|
||||
installation menu choose the <literal>fixit</literal> option. After
|
||||
entering the fixit environment, enter the following command:</para>
|
||||
installation menu choose the <literal>fixit</literal>
|
||||
option. After entering the fixit environment, enter the
|
||||
following command:</para>
|
||||
|
||||
<screen>&prompt.root; <userinput>disklabel -e /dev/ad0c</userinput></screen>
|
||||
|
||||
<para>At this point you will have entered the vi editor under the
|
||||
auspices of the disklabel command. Next, you need to add
|
||||
an <literal>a:</literal> line at the end of the file. This
|
||||
<literal>a:</literal> line should look like:</para>
|
||||
<para>At this point you will have entered the vi editor under
|
||||
the auspices of the disklabel command. Next, you need to
|
||||
add an <literal>a:</literal> line at the end of the file.
|
||||
This <literal>a:</literal> line should look like:</para>
|
||||
|
||||
<programlisting>a: <replaceable>123456</replaceable> 0 4.2BSD 0 0</programlisting>
|
||||
|
||||
<para>Where <replaceable>123456</replaceable> is a number that is
|
||||
exactly the same as the number in the existing <literal>c:</literal>
|
||||
entry for size. Basically you are duplicating the existing
|
||||
<literal>c:</literal> line as an <literal>a:</literal> line, making
|
||||
sure that fstype is <literal>4.2BSD</literal>. Save the file and
|
||||
exit.</para>
|
||||
<para>Where <replaceable>123456</replaceable> is a number that
|
||||
is exactly the same as the number in the existing
|
||||
<literal>c:</literal> entry for size. Basically you are
|
||||
duplicating the existing <literal>c:</literal> line as an
|
||||
<literal>a:</literal> line, making sure that fstype is
|
||||
<literal>4.2BSD</literal>. Save the file and exit.</para>
|
||||
|
||||
<screen>&prompt.root; <userinput>disklabel -B -r /dev/ad0c</userinput>
|
||||
&prompt.root; <userinput>newfs /dev/ad0a</userinput></screen>
|
||||
|
|
@ -292,22 +308,24 @@ pseudo-device md # memory disk</programlisting>
|
|||
|
||||
<screen>&prompt.root; <userinput>mount /dev/ad0a /flash</userinput></screen>
|
||||
|
||||
<para>Bring this machine up on the network so we may transfer our tar
|
||||
file and explode it onto our flash media filesystem. One example of
|
||||
how to do this is:</para>
|
||||
<para>Bring this machine up on the network so we may transfer
|
||||
our tar file and explode it onto our flash media filesystem.
|
||||
One example of how to do this is:</para>
|
||||
|
||||
<screen>&prompt.root; <userinput>ifconfig xl0 192.168.0.10 netmask 255.255.255.0</userinput>
|
||||
&prompt.root; <userinput>route add default 192.168.0.1</userinput></screen>
|
||||
|
||||
<para>Now that the machine is on the network, transfer your tar file.
|
||||
You may be faced with a bit of a dilemma at this point - if your
|
||||
flash memory part is 128 megabytes, for instance, and your tar file
|
||||
is larger than 64 megabytes, you cannot have your tar file on the
|
||||
flash media at the same time as you explode it - you will run out of
|
||||
space. One solution to this problem, if you are using FTP, is to
|
||||
untar the file while it is transferred over FTP. If you perform
|
||||
your transfer in this manner, you will never have the tar file and
|
||||
the tar contents on your disk at the same time:</para>
|
||||
<para>Now that the machine is on the network, transfer your
|
||||
tar file. You may be faced with a bit of a dilemma at this
|
||||
point - if your flash memory part is 128 megabytes, for
|
||||
instance, and your tar file is larger than 64 megabytes, you
|
||||
cannot have your tar file on the flash media at the same
|
||||
time as you explode it - you will run out of
|
||||
space. One solution to this problem, if you are using FTP,
|
||||
is to untar the file while it is transferred over FTP. If
|
||||
you perform your transfer in this manner, you will never
|
||||
have the tar file and the tar contents on your disk at the
|
||||
same time:</para>
|
||||
|
||||
<screen><prompt>ftp></prompt> <userinput>get tarfile.tar "| tar xvf -"</userinput></screen>
|
||||
|
||||
|
|
@ -316,70 +334,74 @@ pseudo-device md # memory disk</programlisting>
|
|||
|
||||
<screen><prompt>ftp></prompt> <userinput>get tarfile.tar "| zcat | tar xvf -"</userinput></screen>
|
||||
|
||||
<para>After the contents of your tarred filesystem are on your flash
|
||||
memory filesystem, you can unmount the flash memory and
|
||||
reboot:</para>
|
||||
<para>After the contents of your tarred filesystem are on your
|
||||
flash memory filesystem, you can unmount the flash memory
|
||||
and reboot:</para>
|
||||
|
||||
<screen>&prompt.root; <userinput>cd /</userinput>
|
||||
&prompt.root; <userinput>umount /flash</userinput>
|
||||
&prompt.root; <userinput>exit</userinput></screen>
|
||||
|
||||
<para>Assuming that you configured your filesystem correctly when it
|
||||
was built on the normal hard disk (with your filesystems mounted
|
||||
read-only, and with the necessary options compiled into the kernel)
|
||||
you should now be successfully booting your &os; embedded
|
||||
system.</para>
|
||||
<para>Assuming that you configured your filesystem correctly
|
||||
when it was built on the normal hard disk (with your
|
||||
filesystems mounted read-only, and with the necessary
|
||||
options compiled into the kernel) you should now be
|
||||
successfully booting your &os; embedded system.</para>
|
||||
</step>
|
||||
</procedure>
|
||||
</sect1>
|
||||
|
||||
<sect1 id="strategies">
|
||||
<title>System Strategies for Small and Read Only Environments</title>
|
||||
<title>System Strategies for Small and Read Only
|
||||
Environments</title>
|
||||
|
||||
<para>In <xref linkend="ro-fs"/>, it was pointed out that the
|
||||
<filename>/var</filename> filesystem constructed by
|
||||
<filename>/etc/rc.d/var</filename> and the presence of a read-only
|
||||
root filesystem causes problems with many common software packages used
|
||||
with &os;. In this article, suggestions for successfully running
|
||||
cron, syslog, ports installations, and the Apache web server will be
|
||||
provided.</para>
|
||||
<filename>/etc/rc.d/var</filename> and the presence of a
|
||||
read-only root filesystem causes problems with many common
|
||||
software packages used with &os;. In this article, suggestions
|
||||
for successfully running cron, syslog, ports installations, and
|
||||
the Apache web server will be provided.</para>
|
||||
|
||||
<sect2>
|
||||
<title>cron</title>
|
||||
|
||||
<para>Upon boot, <filename class="directory">/var</filename> gets
|
||||
populated by <filename>/etc/rc.d/var</filename> using the list from
|
||||
<filename>/etc/mtree/BSD.var.dist</filename>, so the <filename
|
||||
class="directory">cron</filename>, <filename
|
||||
class="directory">cron/tabs</filename>, <filename
|
||||
class="directory">at</filename>, and a few other standard
|
||||
<para>Upon boot, <filename class="directory">/var</filename>
|
||||
gets populated by <filename>/etc/rc.d/var</filename> using the
|
||||
list from <filename>/etc/mtree/BSD.var.dist</filename>, so the
|
||||
<filename class="directory">cron</filename>, <filename
|
||||
class="directory">cron/tabs</filename>, <filename
|
||||
class="directory">at</filename>, and a few other standard
|
||||
directories get created.</para>
|
||||
|
||||
<para>However, this does not solve the problem of maintaining cron
|
||||
tabs across reboots. When the system reboots, the
|
||||
<filename>/var</filename> filesystem that is in memory will disappear
|
||||
and any cron tabs you may have had in it will also disappear.
|
||||
Therefore, one solution would be to create cron tabs for the users
|
||||
that need them, mount your <filename>/</filename> filesystem as
|
||||
read-write and copy those cron tabs to somewhere safe, like
|
||||
<para>However, this does not solve the problem of maintaining
|
||||
cron tabs across reboots. When the system reboots, the
|
||||
<filename>/var</filename> filesystem that is in memory will
|
||||
disappear and any cron tabs you may have had in it will also
|
||||
disappear. Therefore, one solution would be to create cron
|
||||
tabs for the users that need them, mount your
|
||||
<filename>/</filename> filesystem as read-write and copy those
|
||||
cron tabs to somewhere safe, like
|
||||
<filename>/etc/tabs</filename>, then add a line to the end of
|
||||
<filename>/etc/rc.initdiskless</filename> that copies those crontabs into
|
||||
<filename>/var/cron/tabs</filename> after that directory has been
|
||||
created during system initialization. You may also need to add a line
|
||||
that changes modes and permissions on the directories you create and
|
||||
the files you copy with <filename>/etc/rc.initdiskless</filename>.</para>
|
||||
<filename>/etc/rc.initdiskless</filename> that copies those
|
||||
crontabs into <filename>/var/cron/tabs</filename> after that
|
||||
directory has been created during system initialization. You
|
||||
may also need to add a line that changes modes and permissions
|
||||
on the directories you create and the files you copy with
|
||||
<filename>/etc/rc.initdiskless</filename>.</para>
|
||||
</sect2>
|
||||
|
||||
<sect2>
|
||||
<title>syslog</title>
|
||||
|
||||
<para><filename>syslog.conf</filename> specifies the locations of
|
||||
certain log files that exist in <filename>/var/log</filename>. These
|
||||
files are not created by <filename>/etc/rc.d/var</filename> upon
|
||||
system initialization. Therefore, somewhere in
|
||||
<filename>/etc/rc.d/var</filename>, after the section that creates
|
||||
the directories in <filename>/var</filename>, you will need to add
|
||||
something like this:</para>
|
||||
<para><filename>syslog.conf</filename> specifies the locations
|
||||
of certain log files that exist in
|
||||
<filename>/var/log</filename>. These files are not created by
|
||||
<filename>/etc/rc.d/var</filename> upon system initialization.
|
||||
Therefore, somewhere in <filename>/etc/rc.d/var</filename>,
|
||||
after the section that creates the directories in
|
||||
<filename>/var</filename>, you will need to add something like
|
||||
this:</para>
|
||||
|
||||
<screen>&prompt.root; <userinput>touch /var/log/security /var/log/maillog /var/log/cron /var/log/messages</userinput>
|
||||
&prompt.root; <userinput>chmod 0644 /var/log/*</userinput></screen>
|
||||
|
|
@ -388,27 +410,30 @@ pseudo-device md # memory disk</programlisting>
|
|||
<sect2>
|
||||
<title>Ports Installation</title>
|
||||
|
||||
<para>Before discussing the changes necessary to successfully use the
|
||||
ports tree, a reminder is necessary regarding the read-only nature of
|
||||
your filesystems on the flash media. Since they are read-only, you
|
||||
will need to temporarily mount them read-write using the mount syntax
|
||||
shown in <xref linkend="ro-fs"/>. You should always remount those
|
||||
<para>Before discussing the changes necessary to successfully
|
||||
use the ports tree, a reminder is necessary regarding the
|
||||
read-only nature of your filesystems on the flash media.
|
||||
Since they are read-only, you will need to temporarily mount
|
||||
them read-write using the mount syntax shown in <xref
|
||||
linkend="ro-fs"/>. You should always remount those
|
||||
filesystems read-only when you are done with any maintenance -
|
||||
unnecessary writes to the flash media could considerably shorten its
|
||||
lifespan.</para>
|
||||
unnecessary writes to the flash media could considerably
|
||||
shorten its lifespan.</para>
|
||||
|
||||
<para>To make it possible to enter a ports directory and successfully
|
||||
run <command>make</command> <maketarget>install</maketarget>,
|
||||
we must create a packages directory on
|
||||
a non-memory filesystem that will keep track of our packages across
|
||||
reboots. Because it is necessary to mount your filesystems as
|
||||
read-write for the installation of a package anyway, it is sensible to
|
||||
assume that an area on the flash media can also be used for package
|
||||
<para>To make it possible to enter a ports directory and
|
||||
successfully run
|
||||
<command>make</command> <maketarget>install</maketarget>, we
|
||||
must create a packages directory on a non-memory filesystem
|
||||
that will keep track of our packages across reboots. Because
|
||||
it is necessary to mount your filesystems as read-write for
|
||||
the installation of a package anyway, it is sensible to assume
|
||||
that an area on the flash media can also be used for package
|
||||
information to be written to.</para>
|
||||
|
||||
<para>First, create a package database directory. This is normally in
|
||||
<filename>/var/db/pkg</filename>, but we cannot place it there as it
|
||||
will disappear every time the system is booted.</para>
|
||||
<para>First, create a package database directory. This is
|
||||
normally in <filename>/var/db/pkg</filename>, but we cannot
|
||||
place it there as it will disappear every time the system is
|
||||
booted.</para>
|
||||
|
||||
<screen>&prompt.root; <userinput>mkdir /etc/pkg</userinput></screen>
|
||||
|
||||
|
|
@ -418,12 +443,13 @@ pseudo-device md # memory disk</programlisting>
|
|||
|
||||
<screen>&prompt.root; <userinput>ln -s /etc/pkg /var/db/pkg</userinput></screen>
|
||||
|
||||
<para>Now, any time that you mount your filesystems as read-write and
|
||||
install a package, the <command>make</command> <maketarget>install</maketarget> will work,
|
||||
and package information
|
||||
will be written successfully to <filename>/etc/pkg</filename> (because
|
||||
the filesystem will, at that time, be mounted read-write) which will
|
||||
always be available to the operating system as
|
||||
<para>Now, any time that you mount your filesystems as
|
||||
read-write and install a package, the
|
||||
<command>make</command> <maketarget>install</maketarget> will
|
||||
work, and package information will be written successfully to
|
||||
<filename>/etc/pkg</filename> (because the filesystem will, at
|
||||
that time, be mounted read-write) which will always be
|
||||
available to the operating system as
|
||||
<filename>/var/db/pkg</filename>.</para>
|
||||
</sect2>
|
||||
|
||||
|
|
@ -431,40 +457,42 @@ pseudo-device md # memory disk</programlisting>
|
|||
<title>Apache Web Server</title>
|
||||
|
||||
<note>
|
||||
<para>The steps in this section are only necessary if Apache is
|
||||
set up to write its pid or log information outside of
|
||||
<para>The steps in this section are only necessary if Apache
|
||||
is set up to write its pid or log information outside of
|
||||
<filename class="directory">/var</filename>. By default,
|
||||
Apache keeps its pid file in <filename
|
||||
class="directory">/var/run/httpd.pid</filename> and its log
|
||||
files in <filename class="directory">/var/log</filename>.</para>
|
||||
class="directory">/var/run/httpd.pid</filename> and its
|
||||
log files in <filename
|
||||
class="directory">/var/log</filename>.</para>
|
||||
</note>
|
||||
|
||||
<para>It is now assumed that Apache keeps its log files in a
|
||||
directory <filename
|
||||
class="directory"><replaceable>apache_log_dir</replaceable></filename>
|
||||
class="directory"><replaceable>apache_log_dir</replaceable></filename>
|
||||
outside of <filename class="directory">/var</filename>.
|
||||
When this directory lives on a read-only filesystem, Apache will
|
||||
not be able to save any log files, and may have problems working.
|
||||
If so, it is necessary to add a new directory to the
|
||||
When this directory lives on a read-only filesystem, Apache
|
||||
will not be able to save any log files, and may have problems
|
||||
working. If so, it is necessary to add a new directory to the
|
||||
list of directories in <filename>/etc/rc.d/var</filename> to
|
||||
create in <filename>/var</filename>, and to link
|
||||
<filename class="directory"><replaceable>apache_log_dir</replaceable></filename> to
|
||||
<filename>/var/log/apache</filename>. It is also necessary to set
|
||||
permissions and ownership on this new directory.</para>
|
||||
<filename
|
||||
class="directory"><replaceable>apache_log_dir</replaceable></filename>
|
||||
to <filename>/var/log/apache</filename>. It is also necessary
|
||||
to set permissions and ownership on this new directory.</para>
|
||||
|
||||
<para>First, add the directory <literal>log/apache</literal> to the list
|
||||
of directories to be created in
|
||||
<para>First, add the directory <literal>log/apache</literal> to
|
||||
the list of directories to be created in
|
||||
<filename>/etc/rc.d/var</filename>.</para>
|
||||
|
||||
<para>Second, add these commands to
|
||||
<filename>/etc/rc.d/var</filename> after the directory creation
|
||||
section:</para>
|
||||
<filename>/etc/rc.d/var</filename> after the directory
|
||||
creation section:</para>
|
||||
|
||||
<screen>&prompt.root; <userinput>chmod 0774 /var/log/apache</userinput>
|
||||
&prompt.root; <userinput>chown nobody:nobody /var/log/apache</userinput></screen>
|
||||
|
||||
<para>Finally, remove the existing
|
||||
<filename class="directory"><replaceable>apache_log_dir</replaceable></filename>
|
||||
<para>Finally, remove the existing <filename
|
||||
class="directory"><replaceable>apache_log_dir</replaceable></filename>
|
||||
directory, and replace it with a link:</para>
|
||||
|
||||
<screen>&prompt.root; <userinput>rm -rf <filename class="directory"><replaceable>apache_log_dir</replaceable></filename></userinput>
|
||||
|
|
|
|||
Loading…
Reference in a new issue