mirror of
https://github.com/Zeckmathederg/glfs.git
synced 2025-01-24 06:52:14 +08:00
1350 lines
61 KiB
XML
1350 lines
61 KiB
XML
<?xml version="1.0" encoding="UTF-8"?>
|
|
<!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
|
|
"http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
|
|
<!ENTITY % general-entities SYSTEM "../../general.ent">
|
|
%general-entities;
|
|
]>
|
|
|
|
<sect1 id="unpacking">
|
|
<?dbhtml filename="notes-on-building.html"?>
|
|
|
|
|
|
<title>Notes on Building Software</title>
|
|
|
|
<para>Those people who have built an LFS system may be aware
|
|
of the general principles of downloading and unpacking software. Some
|
|
of that information is repeated here for those new to building
|
|
their own software.</para>
|
|
|
|
<para>Each set of installation instructions contains a URL from which you
|
|
can download the package. The patches; however, are stored on the LFS
|
|
servers and are available via HTTP. These are referenced as needed in the
|
|
installation instructions.</para>
|
|
|
|
<para>While you can keep the source files anywhere you like, we assume that
|
|
you have unpacked the package and changed into the directory created by the
|
|
unpacking process (the source directory). We also assume you have
|
|
uncompressed any required patches and they are in the directory
|
|
immediately above the source directory.</para>
|
|
|
|
<para>We can not emphasize strongly enough that you should start from a
|
|
<emphasis>clean source tree</emphasis> each time. This means that if
|
|
you have had an error during configuration or compilation, it's usually
|
|
best to delete the source tree and
|
|
re-unpack it <emphasis>before</emphasis> trying again. This obviously
|
|
doesn't apply if you're an advanced user used to hacking
|
|
<filename>Makefile</filename>s and C code, but if in doubt, start from a
|
|
clean tree.</para>
|
|
|
|
<sect2>
|
|
<title>Building Software as an Unprivileged (non-root) User</title>
|
|
|
|
<para>The golden rule of Unix System Administration is to use your
|
|
superpowers only when necessary. Hence, BLFS recommends that you
|
|
build software as an unprivileged user and only become the
|
|
<systemitem class='username'>root</systemitem> user when installing the
|
|
software. This philosophy is followed in all the packages in this book.
|
|
Unless otherwise specified, all instructions should be executed as an
|
|
unprivileged user. The book will advise you on instructions that need
|
|
<systemitem class='username'>root</systemitem> privileges.</para>
|
|
|
|
</sect2>
|
|
|
|
<sect2>
|
|
<title>Unpacking the Software</title>
|
|
|
|
<para>If a file is in <filename class='extension'>.tar</filename> format
|
|
and compressed, it is unpacked by running one of the following
|
|
commands:</para>
|
|
|
|
<screen><userinput>tar -xvf filename.tar.gz
|
|
tar -xvf filename.tgz
|
|
tar -xvf filename.tar.Z
|
|
tar -xvf filename.tar.bz2</userinput></screen>
|
|
|
|
<note>
|
|
<para>You may omit using the <option>v</option> parameter in the commands
|
|
shown above and below if you wish to suppress the verbose listing of all
|
|
the files in the archive as they are extracted. This can help speed up the
|
|
extraction as well as make any errors produced during the extraction
|
|
more obvious to you.</para>
|
|
</note>
|
|
|
|
<para>You can also use a slightly different method:</para>
|
|
|
|
<screen><userinput>bzcat filename.tar.bz2 | tar -xv</userinput></screen>
|
|
|
|
<para>
|
|
Finally, sometimes we have a compressed patch file in
|
|
<filename class='extension'>.patch.gz</filename> or
|
|
<filename class='extension'>.patch.bz2</filename> format.
|
|
The best way to apply the patch is piping the output of the
|
|
decompressor to the <command>patch</command> utility. For example:
|
|
</para>
|
|
|
|
<screen><userinput>gzip -cd ../patchname.patch.gz | patch -p1</userinput></screen>
|
|
|
|
<para>
|
|
Or for a patch compressed with <command>bzip2</command>:
|
|
</para>
|
|
|
|
<screen><userinput>bzcat ../patchname.patch.bz2 | patch -p1</userinput></screen>
|
|
|
|
</sect2>
|
|
|
|
<sect2>
|
|
<title>Verifying File Integrity</title>
|
|
|
|
<para>Generally, to verify that the downloaded file is complete,
|
|
many package maintainers also distribute md5sums of the files. To verify the
|
|
md5sum of the downloaded files, download both the file and the
|
|
corresponding md5sum file to the same directory (preferably from different
|
|
on-line locations), and (assuming <filename>file.md5sum</filename> is the
|
|
md5sum file downloaded) run the following command:</para>
|
|
|
|
<screen><userinput>md5sum -c file.md5sum</userinput></screen>
|
|
|
|
<para>If there are any errors, they will be reported. Note that the BLFS
|
|
book includes md5sums for all the source files also. To use the BLFS
|
|
supplied md5sums, you can create a <filename>file.md5sum</filename> (place
|
|
the md5sum data and the exact name of the downloaded file on the same
|
|
line of a file, separated by white space) and run the command shown above.
|
|
Alternately, simply run the command shown below and compare the output
|
|
to the md5sum data shown in the BLFS book.</para>
|
|
|
|
<screen><userinput>md5sum <replaceable><name_of_downloaded_file></replaceable></userinput></screen>
|
|
|
|
<para>MD5 is not cryptographically secure, so the md5sums are only
|
|
provided for detecting unmalicious changes to the file content. For
|
|
example, an error or truncation introduced during network transfer, or
|
|
a <quote>stealth</quote> update to the package from the upstream
|
|
(updating the content of a released tarball instead of making a new
|
|
release properly).</para>
|
|
|
|
<para>There is no <quote>100%</quote> secure way to make
|
|
sure the genuity of the source files. Assuming the upstream is managing
|
|
their website correctly (the private key is not leaked and the domain is
|
|
not hijacked), and the trust anchors have been set up correctly using
|
|
<xref linkend="make-ca"/> on the BLFS system, we can reasonably trust
|
|
download URLs to the upstream official website
|
|
<emphasis role="bold">with https protocol</emphasis>. Note that
|
|
BLFS book itself is published on a website with https, so you should
|
|
already have some confidence in https protocol or you wouldn't trust the
|
|
book content.</para>
|
|
|
|
<para>If the package is downloaded from an unofficial location (for
|
|
example a local mirror), checksums generated by cryptographically secure
|
|
digest algorithms (for example SHA256) can be used to verify the
|
|
genuity of the package. Download the checksum file from the upstream
|
|
<emphasis role="bold">official</emphasis> website (or somewhere
|
|
<emphasis role="bold">you can trust</emphasis>) and compare the
|
|
checksum of the package from unofficial location with it. For example,
|
|
SHA256 checksum can be checked with the command:</para>
|
|
|
|
<note>
|
|
<para>If the checksum and the package are downloaded from the same
|
|
untrusted location, you won't gain security enhancement by verifying
|
|
the package with the checksum. The attacker can fake the checksum as
|
|
well as compromising the package itself.</para>
|
|
</note>
|
|
|
|
<screen><userinput>sha256sum -c <replaceable>file</replaceable>.sha256sum</userinput></screen>
|
|
|
|
<para>If <xref linkend="gnupg2"/> is installed, you can also verify the
|
|
genuity of the package with a GPG signature. Import the upstream GPG
|
|
public key with:</para>
|
|
|
|
<screen><userinput>gpg --recv-key <replaceable>keyID</replaceable></userinput></screen>
|
|
|
|
<para><replaceable>keyID</replaceable> should be replaced with the key ID
|
|
from somewhere <emphasis role="bold">you can trust</emphasis> (for
|
|
example, copy it from the upstream official website using https). Now
|
|
you can verify the signature with:</para>
|
|
|
|
<screen><userinput>gpg --recv-key <replaceable>file</replaceable>.sig <replaceable>file</replaceable></userinput></screen>
|
|
|
|
<para>The advantage of <application>GnuPG</application> signature is,
|
|
once you imported a public key which can be trusted, you can download
|
|
both the package and its signature from the same unofficial location and
|
|
verify them with the public key. So you won't need to connect to the
|
|
official upstream website to retrieve a checksum for each new release.
|
|
You only need to update the public key if it's expired or revoked.
|
|
</para>
|
|
|
|
</sect2>
|
|
|
|
<sect2>
|
|
<title>Creating Log Files During Installation</title>
|
|
|
|
<para>For larger packages, it is convenient to create log files instead of
|
|
staring at the screen hoping to catch a particular error or warning. Log
|
|
files are also useful for debugging and keeping records. The following
|
|
command allows you to create an installation log. Replace
|
|
<replaceable><command></replaceable> with the command you intend to execute.</para>
|
|
|
|
<screen><userinput>( <replaceable><command></replaceable> 2>&1 | tee compile.log && exit $PIPESTATUS )</userinput></screen>
|
|
|
|
<para><option>2>&1</option> redirects error messages to the same
|
|
location as standard output. The <command>tee</command> command allows
|
|
viewing of the output while logging the results to a file. The parentheses
|
|
around the command run the entire command in a subshell and finally the
|
|
<command>exit $PIPESTATUS</command> command ensures the result of the
|
|
<replaceable><command></replaceable> is returned as the result and not the
|
|
result of the <command>tee</command> command.</para>
|
|
|
|
</sect2>
|
|
|
|
<sect2 id="parallel-builds" xreflabel="Using Multiple Processors">
|
|
<title>Using Multiple Processors</title>
|
|
|
|
<para>For many modern systems with multiple processors (or cores) the
|
|
compilation time for a package can be reduced by performing a "parallel
|
|
make" by either setting an environment variable or telling the make program
|
|
to simultaneously execute multiple jobs.</para>
|
|
|
|
<para>For instance, an Intel Core i9-13900K CPU contains 8 performance
|
|
(P) cores and 16 efficiency (E) cores, and the P cores support SMT
|
|
(Simultaneous MultiThreading, also known as
|
|
<quote>Hyper-Threading</quote>) so each P core can run two threads
|
|
simultaneously and the Linux kernel will treat each P core as two
|
|
logical cores. As the result, there are 32 logical cores in total.
|
|
To utilize all these logical cores running <command>make</command>, we
|
|
can set an environment variable to tell <command>make</command> to
|
|
run 32 jobs simultaneously:</para>
|
|
|
|
<screen><userinput>export MAKEFLAGS='-j32'</userinput></screen>
|
|
|
|
<para>or just building with:</para>
|
|
|
|
<screen><userinput>make -j32</userinput></screen>
|
|
|
|
<para>
|
|
If you have applied the optional <command>sed</command> when building
|
|
<application>ninja</application> in LFS, you can use:
|
|
</para>
|
|
|
|
<screen><userinput>export NINJAJOBS=32</userinput></screen>
|
|
|
|
<para>
|
|
when a package uses <command>ninja</command>, or just:
|
|
</para>
|
|
|
|
<screen><userinput>ninja -j32</userinput></screen>
|
|
|
|
<para>
|
|
If you are not sure about the number of logical cores, run the
|
|
<command>nproc</command> command.
|
|
</para>
|
|
|
|
<para>
|
|
For <command>make</command>, the default number of jobs is 1. But
|
|
for <command>ninja</command>, the default number of jobs is N + 2 if
|
|
the number of logical cores N is greater than 2; or N + 1 if
|
|
N is 1 or 2. The reason to use a number of jobs slightly greater
|
|
than the number of logical cores is keeping all logical
|
|
processors busy even if some jobs are performing I/O operations.
|
|
</para>
|
|
|
|
<para>
|
|
Note that the <option>-j</option> switches only limits the parallel
|
|
jobs started by <command>make</command> or <command>ninja</command>,
|
|
but each job may still spawn its own processes or threads. For
|
|
example, <command>ld.gold</command> will use multiple threads for
|
|
linking, and some tests of packages can spawn multiple threads for
|
|
testing thread safety properties. There is no generic way for the
|
|
building system to know the number of processes or threads spawned by
|
|
a job. So generally we should not consider the value passed with
|
|
<option>-j</option> a hard limit of the number of logical cores to
|
|
use. Read <xref linkend='build-in-cgroup'/> if you want to set such
|
|
a hard limit.
|
|
</para>
|
|
|
|
<para>Generally the number of processes should not exceed the number of
|
|
cores supported by the CPU too much. To list the processors on your
|
|
system, issue: <userinput>grep processor /proc/cpuinfo</userinput>.
|
|
</para>
|
|
|
|
<para>In some cases, using multiple processes may result in a race
|
|
condition where the success of the build depends on the order of the
|
|
commands run by the <command>make</command> program. For instance, if an
|
|
executable needs File A and File B, attempting to link the program before
|
|
one of the dependent components is available will result in a failure.
|
|
This condition usually arises because the upstream developer has not
|
|
properly designated all the prerequisites needed to accomplish a step in the
|
|
Makefile.</para>
|
|
|
|
<para>If this occurs, the best way to proceed is to drop back to a
|
|
single processor build. Adding <option>-j1</option> to a make command
|
|
will override the similar setting in the <envar>MAKEFLAGS</envar>
|
|
environment variable.</para>
|
|
|
|
<important>
|
|
<para>
|
|
Another problem may occur with modern CPU's, which have a lot of cores.
|
|
Each job started consumes memory, and if the sum of the needed
|
|
memory for each job exceeds the available memory, you may encounter
|
|
either an OOM (Out of Memory) kernel interrupt or intense swapping
|
|
that will slow the build beyond reasonable limits.
|
|
</para>
|
|
|
|
<para>
|
|
Some compilations with <command>g++</command> may consume up to 2.5 GB
|
|
of memory, so to be safe, you should restrict the number of jobs
|
|
to (Total Memory in GB)/2.5, at least for big packages such as LLVM,
|
|
WebKitGtk, QtWebEngine, or libreoffice.
|
|
</para>
|
|
</important>
|
|
</sect2>
|
|
|
|
<sect2 id="build-in-cgroup">
|
|
<title>Use Linux Control Group to Limit the Resource Usage</title>
|
|
|
|
<para>
|
|
Sometimes we want to limit the resource usage when we build a
|
|
package. For example, when we have 8 logical cores, we may want
|
|
to use only 6 cores for building the package and reserve another
|
|
2 cores for playing a movie. The Linux kernel provides a feature
|
|
called control groups (cgroup) for such a need.
|
|
</para>
|
|
|
|
<para>
|
|
Enable control group in the kernel configuration, then rebuild the
|
|
kernel and reboot if necessary:
|
|
</para>
|
|
|
|
<xi:include xmlns:xi="http://www.w3.org/2001/XInclude"
|
|
href="cgroup-kernel.xml"/>
|
|
|
|
<!-- We need cgroup2 mounted at /sys/fs/cgroup. It's done by
|
|
systemd itself in LFS systemd, mountvirtfs script in LFS sysv. -->
|
|
|
|
<para revision='systemd'>
|
|
Ensure <xref linkend='systemd'/> and <xref linkend='shadow'/> have
|
|
been rebuilt with <xref linkend='linux-pam'/> support (if you are
|
|
interacting via a SSH or graphical session, also ensure the
|
|
<xref linkend='openssh'/> server or the desktop manager has been
|
|
built with <xref linkend='linux-pam'/>). As the &root; user, create
|
|
a configuration file to allow resource control without &root;
|
|
privilege, and instruct <command>systemd</command> to reload the
|
|
configuration:
|
|
</para>
|
|
|
|
<screen revision="systemd" role="nodump"><userinput>mkdir -pv /etc/systemd/system/user@.service.d &&
|
|
cat > /etc/systemd/system/user@.service.d/delegate.conf << EOF &&
|
|
<literal>[Service]
|
|
Delegate=memory cpuset</literal>
|
|
systemctl daemon-reload</userinput></screen>
|
|
|
|
<para revision='systemd'>
|
|
Then logout and login again. Now to run <command>make -j5</command>
|
|
with the first 4 logical cores and 8 GB of system memory, issue:
|
|
</para>
|
|
|
|
<screen revision="systemd" role="nodump"><userinput>systemctl --user start dbus &&
|
|
systemd-run --user --pty --pipe --wait -G -d \
|
|
-p MemoryHigh=8G \
|
|
-p AllowedCPUs=0-3 \
|
|
make -j5</userinput></screen>
|
|
|
|
<para revision='sysv'>
|
|
Ensure <xref linkend='sudo'/> is installed. To run
|
|
<command>make -j5</command> with the first 4 logical cores and 8 GB
|
|
of system memory, issue:
|
|
</para>
|
|
|
|
<!-- "\EOF" because we expect $$ to be expanded by the "bash -e"
|
|
shell, not the current shell.
|
|
|
|
TODO: can we use elogind to delegate the controllers (like
|
|
systemd) to avoid relying on sudo? -->
|
|
<screen revision="sysv" role="nodump"><userinput>bash -e << \EOF
|
|
sudo mkdir /sys/fs/cgroup/$$
|
|
sudo sh -c \
|
|
"echo +memory +cpuset > /sys/fs/cgroup/cgroup.subtree_control"
|
|
sudo sh -c \
|
|
"echo 0-3 > /sys/fs/cgroup/$$/cpuset.cpus"
|
|
sudo sh -c \
|
|
"echo $(bc -e '8*2^30') > /sys/fs/cgroup/$$/memory.high"
|
|
(
|
|
sudo sh -c "echo $BASHPID > /sys/fs/cgroup/$$/cgroup.procs"
|
|
exec make -j5
|
|
)
|
|
sudo rmdir /sys/fs/cgroup/$$
|
|
EOF</userinput></screen>
|
|
|
|
<para>
|
|
With
|
|
<phrase revision='systemd'>
|
|
<parameter>MemoryHigh=8G</parameter>
|
|
</phrase>
|
|
<phrase revision='sysv'>
|
|
<literal>8589934592</literal> (the output of
|
|
<userinput>bc -e '8*2^30'</userinput>, 2^30 represents
|
|
2<superscript>30</superscript>, i.e. a Gigabyte) in the
|
|
<filename>memory.high</filename> entry
|
|
</phrase>, a soft limit of memory usage is set.
|
|
If the processes in the cgroup (<command>make</command> and all the
|
|
descendants of it) uses more than 8 GB of system memory in total,
|
|
the kernel will throttle down the processes and try to reclaim the
|
|
system memory from them. But they can still use more than 8 GB of
|
|
system memory. If you want to make a hard limit instead, replace
|
|
<phrase revision='systemd'>
|
|
<parameter>MemoryHigh</parameter> with
|
|
<parameter>MemoryMax</parameter>.
|
|
</phrase>
|
|
<phrase revision='sysv'>
|
|
<filename>memory.high</filename> with
|
|
<filename>memory.max</filename>.
|
|
</phrase>
|
|
But doing so will cause the processes killed if 8 GB is not enough
|
|
for them.
|
|
</para>
|
|
|
|
<para>
|
|
<phrase revision='systemd'>
|
|
<parameter>AllowedCPUs=0-3</parameter>
|
|
</phrase>
|
|
<phrase revision='sysv'>
|
|
<literal>0-3</literal> in the <filename>cpuset.cpus</filename>
|
|
entry
|
|
</phrase> makes the kernel only run the processes in the cgroup on
|
|
the logical cores with numbers 0, 1, 2, or 3. You may need to
|
|
adjust this setting based the mapping between the logical cores and the
|
|
physical cores. For example, with an Intel Core i9-13900K CPU,
|
|
the logical cores 0, 2, 4, ..., 14 are mapped to the first threads of
|
|
the eight physical P cores, the logical cores 1, 3, 5, ..., 15 are
|
|
mapped to the second threads of the physical P cores, and the logical
|
|
cores 16, 17, ..., 31 are mapped to the 16 physical E cores. So if
|
|
we want to use four threads from four different P cores, we need to
|
|
specify <literal>0,2,4,6</literal> instead of <literal>0-3</literal>.
|
|
Note that the other CPU models may use a different mapping scheme.
|
|
If you are not sure about the mapping between the logical cores
|
|
and the physical cores, run <command>grep -E '^processor|^core'
|
|
/proc/cpuinfo</command> which will output logical core IDs in the
|
|
<computeroutput>processor</computeroutput> lines, and physical core
|
|
IDs in the <computeroutput>core id</computeroutput> lines.
|
|
</para>
|
|
|
|
<para>
|
|
When the <command>nproc</command> or <command>ninja</command> command
|
|
runs in a cgroup, it will use the number of logical cores assigned to
|
|
the cgroup as the <quote>system logical core count</quote>. For
|
|
example, in a cgroup with logical cores 0-3 assigned,
|
|
<command>nproc</command> will print
|
|
<computeroutput>4</computeroutput>, and <command>ninja</command>
|
|
will run 6 (4 + 2) jobs simultaneously if no <option>-j</option>
|
|
setting is explicitly given.
|
|
</para>
|
|
|
|
<para revision="systemd">
|
|
Read the man pages <ulink role='man'
|
|
url='&man;systemd-run.1'>systemd-run(1)</ulink> and
|
|
<ulink role='man'
|
|
url='&man;systemd.resource-control.5'>systemd.resource-control(5)</ulink>
|
|
for the detailed explanation of parameters in the command.
|
|
</para>
|
|
|
|
<para revision="sysv">
|
|
Read the <filename>Documentation/admin-guide/cgroup-v2.rst</filename>
|
|
file in the Linux kernel source tree for the detailed explanation of
|
|
<systemitem class="filesystem">cgroup2</systemitem> pseudo file
|
|
system entries referred in the command.
|
|
</para>
|
|
|
|
</sect2>
|
|
|
|
<sect2 id="automating-builds" xreflabel="Automated Building Procedures">
|
|
<title>Automated Building Procedures</title>
|
|
|
|
<para>There are times when automating the building of a package can come in
|
|
handy. Everyone has their own reasons for wanting to automate building,
|
|
and everyone goes about it in their own way. Creating
|
|
<filename>Makefile</filename>s, <application>Bash</application> scripts,
|
|
<application>Perl</application> scripts or simply a list of commands used
|
|
to cut and paste are just some of the methods you can use to automate
|
|
building BLFS packages. Detailing how and providing examples of the many
|
|
ways you can automate the building of packages is beyond the scope of this
|
|
section. This section will expose you to using file redirection and the
|
|
<command>yes</command> command to help provide ideas on how to automate
|
|
your builds.</para>
|
|
|
|
<bridgehead renderas="sect3">File Redirection to Automate Input</bridgehead>
|
|
|
|
<para>You will find times throughout your BLFS journey when you will come
|
|
across a package that has a command prompting you for information. This
|
|
information might be configuration details, a directory path, or a response
|
|
to a license agreement. This can present a challenge to automate the
|
|
building of that package. Occasionally, you will be prompted for different
|
|
information in a series of questions. One method to automate this type of
|
|
scenario requires putting the desired responses in a file and using
|
|
redirection so that the program uses the data in the file as the answers to
|
|
the questions.</para>
|
|
<!-- outdated
|
|
<para>Building the <application>CUPS</application> package is a good
|
|
example of how redirecting a file as input to prompts can help you automate
|
|
the build. If you run the test suite, you are asked to respond to a series
|
|
of questions regarding the type of test to run and if you have any
|
|
auxiliary programs the test can use. You can create a file with your
|
|
responses, one response per line, and use a command similar to the
|
|
one shown below to automate running the test suite:</para>
|
|
|
|
<screen><userinput>make check < ../cups-1.1.23-testsuite_parms</userinput></screen>
|
|
-->
|
|
<para>This effectively makes the test suite use the responses in the file
|
|
as the input to the questions. Occasionally you may end up doing a bit of
|
|
trial and error determining the exact format of your input file for some
|
|
things, but once figured out and documented you can use this to automate
|
|
building the package.</para>
|
|
|
|
<bridgehead renderas="sect3">Using <command>yes</command> to Automate
|
|
Input</bridgehead>
|
|
|
|
<para>Sometimes you will only need to provide one response, or provide the
|
|
same response to many prompts. For these instances, the
|
|
<command>yes</command> command works really well. The
|
|
<command>yes</command> command can be used to provide a response (the same
|
|
one) to one or more instances of questions. It can be used to simulate
|
|
pressing just the <keycap>Enter</keycap> key, entering the
|
|
<keycap>Y</keycap> key or entering a string of text. Perhaps the easiest
|
|
way to show its use is in an example.</para>
|
|
|
|
<para>First, create a short <application>Bash</application> script by
|
|
entering the following commands:</para>
|
|
|
|
<screen><userinput>cat > blfs-yes-test1 << "EOF"
|
|
<literal>#!/bin/bash
|
|
|
|
echo -n -e "\n\nPlease type something (or nothing) and press Enter ---> "
|
|
|
|
read A_STRING
|
|
|
|
if test "$A_STRING" = ""; then A_STRING="Just the Enter key was pressed"
|
|
else A_STRING="You entered '$A_STRING'"
|
|
fi
|
|
|
|
echo -e "\n\n$A_STRING\n\n"</literal>
|
|
EOF
|
|
chmod 755 blfs-yes-test1</userinput></screen>
|
|
|
|
<para>Now run the script by issuing <command>./blfs-yes-test1</command> from
|
|
the command line. It will wait for a response, which can be anything (or
|
|
nothing) followed by the <keycap>Enter</keycap> key. After entering
|
|
something, the result will be echoed to the screen. Now use the
|
|
<command>yes</command> command to automate the entering of a
|
|
response:</para>
|
|
|
|
<screen><userinput>yes | ./blfs-yes-test1</userinput></screen>
|
|
|
|
<para>Notice that piping <command>yes</command> by itself to the script
|
|
results in <keycap>y</keycap> being passed to the script. Now try it with a
|
|
string of text:</para>
|
|
|
|
<screen><userinput>yes 'This is some text' | ./blfs-yes-test1</userinput></screen>
|
|
|
|
<para>The exact string was used as the response to the script. Finally,
|
|
try it using an empty (null) string:</para>
|
|
|
|
<screen><userinput>yes '' | ./blfs-yes-test1</userinput></screen>
|
|
|
|
<para>Notice this results in passing just the press of the
|
|
<keycap>Enter</keycap> key to the script. This is useful for times when the
|
|
default answer to the prompt is sufficient. This syntax is used in the
|
|
<xref linkend="net-tools-automate-example"/> instructions to accept all the
|
|
defaults to the many prompts during the configuration step. You may now
|
|
remove the test script, if desired.</para>
|
|
|
|
<bridgehead renderas="sect3">File Redirection to Automate Output</bridgehead>
|
|
|
|
<para>In order to automate the building of some packages, especially those
|
|
that require you to read a license agreement one page at a time, requires
|
|
using a method that avoids having to press a key to display each page.
|
|
Redirecting the output to a file can be used in these instances to assist
|
|
with the automation. The previous section on this page touched on creating
|
|
log files of the build output. The redirection method shown there used the
|
|
<command>tee</command> command to redirect output to a file while also
|
|
displaying the output to the screen. Here, the output will only be sent to
|
|
a file.</para>
|
|
|
|
<para>Again, the easiest way to demonstrate the technique is to show an
|
|
example. First, issue the command:</para>
|
|
|
|
<screen><userinput>ls -l /usr/bin | less</userinput></screen>
|
|
|
|
<para>Of course, you'll be required to view the output one page at a time
|
|
because the <command>less</command> filter was used. Now try the same
|
|
command, but this time redirect the output to a file. The special file
|
|
<filename>/dev/null</filename> can be used instead of the filename shown,
|
|
but you will have no log file to examine:</para>
|
|
|
|
<screen><userinput>ls -l /usr/bin | less > redirect_test.log 2>&1</userinput></screen>
|
|
|
|
<para>Notice that this time the command immediately returned to the shell
|
|
prompt without having to page through the output. You may now remove the
|
|
log file.</para>
|
|
|
|
<para>The last example will use the <command>yes</command> command in
|
|
combination with output redirection to bypass having to page through the
|
|
output and then provide a <keycap>y</keycap> to a prompt. This technique
|
|
could be used in instances when otherwise you would have to page through
|
|
the output of a file (such as a license agreement) and then answer the
|
|
question of <quote>do you accept the above?</quote>. For this example,
|
|
another short <application>Bash</application> script is required:</para>
|
|
|
|
<screen><userinput>cat > blfs-yes-test2 << "EOF"
|
|
<literal>#!/bin/bash
|
|
|
|
ls -l /usr/bin | less
|
|
|
|
echo -n -e "\n\nDid you enjoy reading this? (y,n) "
|
|
|
|
read A_STRING
|
|
|
|
if test "$A_STRING" = "y"; then A_STRING="You entered the 'y' key"
|
|
else A_STRING="You did NOT enter the 'y' key"
|
|
fi
|
|
|
|
echo -e "\n\n$A_STRING\n\n"</literal>
|
|
EOF
|
|
chmod 755 blfs-yes-test2</userinput></screen>
|
|
|
|
<para>This script can be used to simulate a program that requires you to
|
|
read a license agreement, then respond appropriately to accept the
|
|
agreement before the program will install anything. First, run the script
|
|
without any automation techniques by issuing
|
|
<command>./blfs-yes-test2</command>.</para>
|
|
|
|
<para>Now issue the following command which uses two automation techniques,
|
|
making it suitable for use in an automated build script:</para>
|
|
|
|
<screen><userinput>yes | ./blfs-yes-test2 > blfs-yes-test2.log 2>&1</userinput></screen>
|
|
|
|
<para>If desired, issue <command>tail blfs-yes-test2.log</command> to see
|
|
the end of the paged output, and confirmation that <keycap>y</keycap> was
|
|
passed through to the script. Once satisfied that it works as it should,
|
|
you may remove the script and log file.</para>
|
|
|
|
<para>Finally, keep in mind that there are many ways to automate and/or
|
|
script the build commands. There is not a single <quote>correct</quote> way
|
|
to do it. Your imagination is the only limit.</para>
|
|
|
|
</sect2>
|
|
|
|
<sect2>
|
|
<title>Dependencies</title>
|
|
|
|
<para>For each package described, BLFS lists the known dependencies.
|
|
These are listed under several headings, whose meaning is as follows:</para>
|
|
|
|
<itemizedlist>
|
|
<listitem>
|
|
<para><emphasis>Required</emphasis> means that the target package
|
|
cannot be correctly built without the dependency having first been
|
|
installed, except if the dependency is said to be
|
|
<quote>runtime</quote>, which means the target package can be built but
|
|
cannot function without it.</para>
|
|
<para>
|
|
Note that a target package can start to <quote>function</quote>
|
|
in many subtle ways: an installed configuration file can make the
|
|
init system, cron daemon, or bus daemon to run a program
|
|
automatically; another package using the target package as an
|
|
dependency can run a program from the target package in the
|
|
building system; and the configuration sections in the BLFS book
|
|
may also run a program from a just installed package. So if
|
|
you are installing the target package without a
|
|
<emphasis>Required (runtime)</emphasis> dependency installed,
|
|
You should install the dependency as soon as possible after the
|
|
installation of the target package.
|
|
</para>
|
|
</listitem>
|
|
<listitem>
|
|
<para><emphasis>Recommended</emphasis> means that BLFS strongly
|
|
suggests this package is installed first (except if said to be
|
|
<quote>runtime</quote>, see below) for a clean and trouble-free
|
|
build, that won't have issues either during the build process, or at
|
|
run-time. The instructions in the book assume these packages are
|
|
installed. Some changes or workarounds may be required if these
|
|
packages are not installed. If a recommended dependency is said
|
|
to be <quote>runtime</quote>, it means that BLFS strongly suggests
|
|
that this dependency is installed before using the package, for
|
|
getting full functionality.</para>
|
|
</listitem>
|
|
<listitem>
|
|
<para><emphasis>Optional</emphasis> means that this package might be
|
|
installed for added functionality. Often BLFS will describe the
|
|
dependency to explain the added functionality that will result.
|
|
An optional dependency may be automatically pick up by the target
|
|
package if the dependency is installed, but another some optional
|
|
dependency may also need additional configuration options to enable
|
|
them when the target package is built. Such additional options are
|
|
often documented in the BLFS book. If an optional dependency is
|
|
said to be <quote>runtime</quote>, it means you may install
|
|
the dependency after installing the target package to support some
|
|
optional features of the target package if you need these
|
|
features.</para>
|
|
<para>An optional dependency may be out of BLFS. If you need such
|
|
an <emphasis>external</emphasis> optional dependency for some
|
|
features you need, read <xref linkend='beyond'/> for the general
|
|
hint about installing an out-of-BLFS package.</para>
|
|
</listitem>
|
|
</itemizedlist>
|
|
|
|
</sect2>
|
|
|
|
<sect2 id="package_updates">
|
|
<title>Using the Most Current Package Sources</title>
|
|
|
|
<para>On occasion you may run into a situation in the book when a package
|
|
will not build or work properly. Though the Editors attempt to ensure
|
|
that every package in the book builds and works properly, sometimes a
|
|
package has been overlooked or was not tested with this particular version
|
|
of BLFS.</para>
|
|
|
|
<para>If you discover that a package will not build or work properly, you
|
|
should see if there is a more current version of the package. Typically
|
|
this means you go to the maintainer's web site and download the most current
|
|
tarball and attempt to build the package. If you cannot determine the
|
|
maintainer's web site by looking at the download URLs, use Google and query
|
|
the package's name. For example, in the Google search bar type:
|
|
'package_name download' (omit the quotes) or something similar. Sometimes
|
|
typing: 'package_name home page' will result in you finding the
|
|
maintainer's web site.</para>
|
|
|
|
</sect2>
|
|
|
|
<sect2 id="stripping">
|
|
<title>Stripping One More Time</title>
|
|
|
|
<para>
|
|
In LFS, stripping of debugging symbols and unneeded symbol table
|
|
entries was discussed a couple of times. When building BLFS packages,
|
|
there are generally no special instructions that discuss stripping
|
|
again. Stripping can be done while installing a package, or
|
|
afterwards.
|
|
</para>
|
|
|
|
<bridgehead renderas="sect3" id="stripping-install">Stripping while Installing a Package</bridgehead>
|
|
|
|
<para>
|
|
There are several ways to strip executables installed by a
|
|
package. They depend on the build system used (see below <link
|
|
linkend="buildsystems">the section about build systems</link>),
|
|
so only some
|
|
generalities can be listed here:
|
|
</para>
|
|
|
|
<note>
|
|
<para>
|
|
The following methods using the feature of a building system
|
|
(autotools, meson, or cmake) will not strip static libraries if any
|
|
is installed. Fortunately there are not too many static libraries
|
|
in BLFS, and a static library can always be stripped safely by
|
|
running <command>strip --strip-unneeded</command> on it manually.
|
|
</para>
|
|
</note>
|
|
|
|
<itemizedlist>
|
|
<listitem>
|
|
<para>
|
|
The packages using autotools usually have an
|
|
<parameter>install-strip</parameter> target in their generated
|
|
<filename>Makefile</filename> files. So installing stripped
|
|
executables is just a matter of using
|
|
<command>make install-strip</command> instead of
|
|
<command>make install</command>.
|
|
</para>
|
|
</listitem>
|
|
<listitem>
|
|
<para>
|
|
The packages using the meson build system can accept
|
|
<parameter>-Dstrip=true</parameter> when running
|
|
<command>meson</command>. If you've forgot to add this option
|
|
running the <command>meson</command>, you can also run
|
|
<command>meson install --strip</command> instead of
|
|
<command>ninja install</command>.
|
|
</para>
|
|
</listitem>
|
|
<listitem>
|
|
<para>
|
|
<command>cmake</command> generates
|
|
<parameter>install/strip</parameter> targets for both the
|
|
<parameter>Unix Makefiles</parameter> and
|
|
<parameter>Ninja</parameter> generators (the default is
|
|
<parameter>Unix Makefiles</parameter> on linux). So just run
|
|
<command>make install/strip</command> or
|
|
<command>ninja install/strip</command> instead of the
|
|
<command>install</command> counterparts.
|
|
</para>
|
|
</listitem>
|
|
<listitem>
|
|
<para>
|
|
Removing (or not generating) debug symbols can also be
|
|
achieved by removing the
|
|
<parameter>-g<something></parameter> options
|
|
in C/C++ calls. How to do that is very specific for each
|
|
package. And, it does not remove unneeded symbol table entries.
|
|
So it will not be explained in detail here. See also below
|
|
the paragraphs about optimization.
|
|
</para>
|
|
</listitem>
|
|
</itemizedlist>
|
|
|
|
<bridgehead renderas="sect3" id="stripping-installed">Stripping Installed Executables</bridgehead>
|
|
|
|
<para>
|
|
The <command>strip</command> utility changes files in place, which may
|
|
break anything using it if it is loaded in memory. Note that if a file is
|
|
in use but just removed from the disk (i.e. not overwritten nor
|
|
modified), this is not a problem since the kernel can use
|
|
<quote>deleted</quote> files. Look at <filename>/proc/*/maps</filename>
|
|
and it is likely that you'll see some <emphasis>(deleted)</emphasis>
|
|
entries. The <command>mv</command> just removes the destination file from
|
|
the directory but does not touch its content, so that it satisfies the
|
|
condition for the kernel to use the old (deleted) file.
|
|
But this approach can detach hard links into duplicated copies,
|
|
causing a bloat which is obviously unwanted as we are stripping to
|
|
reduce system size. If two files in a same file system share the
|
|
same inode number, they are hard links to each other and we should
|
|
reconstruct the link. The script below is just an example.
|
|
It should be run as the &root; user:
|
|
</para>
|
|
|
|
<screen><userinput>cat > /usr/sbin/strip-all.sh << "EOF"
|
|
<literal>#!/usr/bin/bash
|
|
|
|
if [ $EUID -ne 0 ]; then
|
|
echo "Need to be root"
|
|
exit 1
|
|
fi
|
|
|
|
last_fs_inode=
|
|
last_file=
|
|
|
|
{ find /usr/lib -type f -name '*.so*' ! -name '*dbg'
|
|
find /usr/lib -type f -name '*.a'
|
|
find /usr/{bin,sbin,libexec} -type f
|
|
} | xargs stat -c '%m %i %n' | sort | while read fs inode file; do
|
|
if ! readelf -h $file >/dev/null 2>&1; then continue; fi
|
|
if file $file | grep --quiet --invert-match 'not stripped'; then continue; fi
|
|
|
|
if [ "$fs $inode" = "$last_fs_inode" ]; then
|
|
ln -f $last_file $file;
|
|
continue;
|
|
fi
|
|
|
|
cp --preserve $file ${file}.tmp
|
|
strip --strip-unneeded ${file}.tmp
|
|
mv ${file}.tmp $file
|
|
|
|
last_fs_inode="$fs $inode"
|
|
last_file=$file
|
|
done</literal>
|
|
EOF
|
|
chmod 744 /usr/sbin/strip-all.sh</userinput></screen>
|
|
|
|
<para>
|
|
If you install programs in other directories such as <filename
|
|
class="directory">/opt</filename> or <filename
|
|
class="directory">/usr/local</filename>, you may want to strip the files
|
|
there too. Just add other directories to scan in the compound list of
|
|
<command>find</command> commands between the braces.
|
|
</para>
|
|
|
|
<para>
|
|
For more information on stripping, see <ulink
|
|
url="https://www.technovelty.org/linux/stripping-shared-libraries.html"/>.
|
|
</para>
|
|
|
|
</sect2>
|
|
|
|
<!--
|
|
<sect2 id="libtool">
|
|
<title>Libtool files</title>
|
|
|
|
<para>
|
|
One of the side effects of packages that use Autotools, including
|
|
libtool, is that they create many files with an .la extension. These
|
|
files are not needed in an LFS environment. If there are conflicts with
|
|
pkgconfig entries, they can actually prevent successful builds. You
|
|
may want to consider removing these files periodically:
|
|
</para>
|
|
|
|
<screen><userinput>find /lib /usr/lib -not -path "*Image*" -a -name \*.la -delete</userinput></screen>
|
|
|
|
<para>
|
|
The above command removes all .la files with the exception of those that
|
|
have <quote>Image</quote> or <quote>openldap</quote> as a part of the
|
|
path. These .la files are used by the ImageMagick and openldap programs,
|
|
respectively. There may be other exceptions by packages not in BLFS.
|
|
</para>
|
|
|
|
</sect2>
|
|
-->
|
|
<sect2 id="buildsystems">
|
|
<title>Working with different build systems</title>
|
|
|
|
<para>
|
|
There are now three different build systems in common use for
|
|
converting C or C++ source code into compiled programs or
|
|
libraries and their details (particularly, finding out about available
|
|
options and their default values) differ. It may be easiest to understand
|
|
the issues caused by some choices (typically slow execution or
|
|
unexpected use of, or omission of, optimizations) by starting with
|
|
the <envar>CFLAGS</envar>, <envar>CXXFLAGS</envar>, and
|
|
<envar>LDFLAGS</envar> environment variables. There are also some
|
|
programs which use Rust.
|
|
</para>
|
|
|
|
<para>
|
|
Most LFS and BLFS builders are probably aware of the basics of
|
|
<envar>CFLAGS</envar> and <envar>CXXFLAGS</envar> for altering how a
|
|
program is compiled. Typically, some form of optimization is used by
|
|
upstream developers (<option>-O2</option> or <option>-O3</option>),
|
|
sometimes with the creation of debug symbols (<option>-g</option>),
|
|
as defaults.
|
|
</para>
|
|
|
|
<para>
|
|
If there are contradictory flags (e.g. multiple different
|
|
<option>-O</option> values),
|
|
the <emphasis>last</emphasis> value will be used. Sometimes this means
|
|
that flags specified in environment variables will be picked up before
|
|
values hardcoded in the Makefile, and therefore ignored. For example,
|
|
where a user specifies <option>-O2</option> and that is followed by
|
|
<option>-O3</option> the build will use <option>-O3</option>.
|
|
</para>
|
|
|
|
<para>
|
|
There are various other things which can be passed in CFLAGS or
|
|
CXXFLAGS, such as allowing using the instruction set extensions
|
|
available with a specific microarchitecture (e.g.
|
|
<option>-march=amdfam10</option> or <option>-march=native</option>),
|
|
tune the generated code for a specific microarchitecture (e. g.
|
|
<option>-mtune=tigerlake</option> or <option>-mtune=native</option>,
|
|
if <option>-mtune=</option> is not used, the microarchitecture from
|
|
<option>-march=</option> setting will be used), or specifying a
|
|
specific standard for C or C++ (<option>-std=c++17</option> for
|
|
example). But one thing which has now come to light is that
|
|
programmers might include debug assertions in their code, expecting
|
|
them to be disabled in releases by using <option>-DNDEBUG</option>.
|
|
Specifically, if <xref linkend="mesa"/> is built with these
|
|
assertions enabled, some activities such as loading levels of games
|
|
can take extremely long times, even on high-class video cards.
|
|
</para>
|
|
|
|
<bridgehead renderas="sect3" id="autotools-info">Autotools with Make</bridgehead>
|
|
|
|
<para>
|
|
This combination is often described as <quote>CMMI</quote>
|
|
(configure, make, make install) and is used here to also cover
|
|
the few packages which have a configure script that is not
|
|
generated by autotools.
|
|
</para>
|
|
|
|
<para>
|
|
Sometimes running <command>./configure --help</command> will produce
|
|
useful options about switches which might be used. At other times,
|
|
after looking at the output from configure you may need to look
|
|
at the details of the script to find out what it was actually searching
|
|
for.
|
|
</para>
|
|
|
|
<para>
|
|
Many configure scripts will pick up any CFLAGS or CXXFLAGS from the
|
|
environment, but CMMI packages vary about how these will be mixed with
|
|
any flags which would otherwise be used (<emphasis>variously</emphasis>:
|
|
ignored, used to replace the programmer's suggestion, used before the
|
|
programmer's suggestion, or used after the programmer's suggestion).
|
|
</para>
|
|
|
|
<para>
|
|
In most CMMI packages, running <command>make</command> will list
|
|
each command and run it, interspersed with any warnings. But some
|
|
packages try to be <quote>silent</quote> and only show which file
|
|
they are compiling or linking instead of showing the command line.
|
|
If you need to inspect the command, either because of an error, or
|
|
just to see what options and flags are being used, adding
|
|
<option>V=1</option> to the make invocation may help.
|
|
</para>
|
|
|
|
<bridgehead renderas="sect3" id="cmake-info">CMake</bridgehead>
|
|
|
|
<para>
|
|
CMake works in a very different way, and it has two backends which
|
|
can be used on BLFS: <command>make</command> and
|
|
<command>ninja</command>. The default backend is make, but
|
|
ninja can be faster on large packages with multiple processors. To
|
|
use ninja, specify <option>-G Ninja</option> in the cmake command.
|
|
However, there are some packages which create fatal errors in their
|
|
ninja files but build successfully using the default of Unix
|
|
Makefiles.
|
|
</para>
|
|
|
|
<para>
|
|
The hardest part of using CMake is knowing what options you might wish
|
|
to specify. The only way to get a list of what the package knows about
|
|
is to run <command>cmake -LAH</command> and look at the output for that
|
|
default configuration.
|
|
</para>
|
|
|
|
<para>
|
|
Perhaps the most-important thing about CMake is that it has a variety
|
|
of CMAKE_BUILD_TYPE values, and these affect the flags. The default
|
|
is that this is not set and no flags are generated. Any
|
|
<envar>CFLAGS</envar> or <envar>CXXFLAGS</envar> in the environment
|
|
will be used. If the programmer has coded any debug assertions,
|
|
those will be enabled unless -DNDEBUG is used. The following
|
|
CMAKE_BUILD_TYPE values will generate the flags shown, and these
|
|
will come <emphasis>after</emphasis> any flags in the environment
|
|
and therefore take precedence.
|
|
</para>
|
|
|
|
<informaltable align="center">
|
|
<tgroup cols="2">
|
|
<colspec colnum="1" align="center"/>
|
|
<colspec colnum="2" align="center"/>
|
|
<thead>
|
|
<row><entry>Value</entry><entry>Flags</entry></row>
|
|
</thead>
|
|
<tbody>
|
|
<row>
|
|
<entry>Debug</entry><entry><option>-g</option></entry>
|
|
</row>
|
|
<row>
|
|
<entry>Release</entry><entry><option>-O3 -DNDEBUG</option></entry>
|
|
</row>
|
|
<row>
|
|
<entry>RelWithDebInfo</entry><entry><option>-O2 -g -DNDEBUG</option></entry>
|
|
</row>
|
|
<row>
|
|
<entry>MinSizeRel</entry><entry><option>-Os -DNDEBUG</option></entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</informaltable>
|
|
|
|
<para>
|
|
CMake tries to produce quiet builds. To see the details of the commands
|
|
which are being run, use <command>make VERBOSE=1</command> or
|
|
<command>ninja -v</command>.
|
|
</para>
|
|
|
|
<para>
|
|
By default, CMake treats file installation differently from the other
|
|
build systems: if a file already exists and is not newer than a file
|
|
that would overwrite it, then the file is not installed. This may be
|
|
a problem if a user wants to record which file belongs to a package,
|
|
either using <envar>LD_PRELOAD</envar>, or by listing files newer
|
|
than a timestamp. The default can be changed by setting the variable
|
|
<envar>CMAKE_INSTALL_ALWAYS</envar> to 1 in the
|
|
<emphasis>environment</emphasis>, for example by
|
|
<command>export</command>'ing it.
|
|
</para>
|
|
|
|
<bridgehead renderas="sect3" id="meson-info">Meson</bridgehead>
|
|
|
|
<para>
|
|
Meson has some similarities to CMake, but many differences. To get
|
|
details of the defines that you may wish to change you can look at
|
|
<filename>meson_options.txt</filename> which is usually in the
|
|
top-level directory.
|
|
</para>
|
|
|
|
<para>
|
|
If you have already configured the package by running
|
|
<command>meson</command> and now wish to change one or more settings,
|
|
you can either remove the build directory, recreate it, and use the
|
|
altered options, or within the build directory run <command>meson
|
|
configure</command>, e.g. to set an option:
|
|
</para>
|
|
|
|
<screen><userinput>meson configure -D<some_option>=true</userinput></screen>
|
|
|
|
<para>
|
|
If you do that, the file <filename>meson-private/cmd_line.txt</filename>
|
|
will show the <emphasis>last</emphasis> commands which were used.
|
|
</para>
|
|
|
|
<para>
|
|
Meson provides the following buildtype values, and the flags they enable
|
|
come <emphasis>after</emphasis> any flags supplied in the environment and
|
|
therefore take precedence.
|
|
</para>
|
|
|
|
<itemizedlist>
|
|
<listitem>
|
|
<para>plain : no added flags. This is for distributors to supply their
|
|
own <envar>CFLAGS</envar>, <envar>CXXFLAGS</envar> and
|
|
<envar>LDFLAGS</envar>. There is no obvious reason to use
|
|
this in BLFS.</para>
|
|
</listitem>
|
|
<listitem>
|
|
<para>debug : <option>-g</option> - this is the default if
|
|
nothing is specified in either <filename>meson.build</filename>
|
|
or the command line. However it results large and slow binaries,
|
|
so we should override it in BLFS.</para>
|
|
</listitem>
|
|
<listitem>
|
|
<para>debugoptimized : <option>-O2 -g</option> - this is the
|
|
default specified in <filename>meson.build</filename> of some
|
|
packages.</para>
|
|
</listitem>
|
|
<listitem>
|
|
<para>release : <option>-O3</option> (occasionally a package will
|
|
force <option>-O2</option> here) - this is the buildtype we use
|
|
for most packages with Meson build system in BLFS.</para>
|
|
</listitem>
|
|
</itemizedlist>
|
|
|
|
<!-- From https://mesonbuild.com/Builtin-options.html#core-options:
|
|
b_ndebug: Default value = false, Possible values are
|
|
true, false, if-release. Some packages sets it to if-release
|
|
so we mistakenly believed if-release had been the default. -->
|
|
<para>
|
|
The <option>-DNDEBUG</option> flag is implied by the release
|
|
buildtype for some packages (for example <xref linkend='mesa'/>).
|
|
It can also be provided explicitly by passing
|
|
<option>-Db_ndebug=true</option>.
|
|
</para>
|
|
|
|
<para>
|
|
To see the details of the commands which are being run in a package using
|
|
meson, use <command>ninja -v</command>.
|
|
</para>
|
|
|
|
<bridgehead renderas="sect3" id="rust-info">Rustc and Cargo</bridgehead>
|
|
|
|
<para>
|
|
Most released rustc programs are provided as crates (source tarballs)
|
|
which will query a server to check current versions of dependencies
|
|
and then download them as necessary. These packages are built using
|
|
<command>cargo --release</command>. In theory, you can manipulate the
|
|
RUSTFLAGS to change the optimize-level (default for
|
|
<option>--release</option> is 3, i. e.
|
|
<option>-Copt-level=3</option>, like <option>-O3</option>) or to
|
|
force it to build for the machine it is being compiled on, using
|
|
<option>-Ctarget-cpu=native</option> but in practice this seems to
|
|
make no significant difference.
|
|
</para>
|
|
|
|
<para>
|
|
If you are compiling a standalone Rust program (as an unpackaged
|
|
<filename class='extension'>.rs</filename> file) by running
|
|
<command>rustc</command> directly, you should specify
|
|
<option>-O</option> (the abbreviation of
|
|
<option>-Copt-level=2</option>) or <option>-Copt-level=3</option>
|
|
otherwise it will do an unoptimized compile and run
|
|
<emphasis>much</emphasis> slower. If are compiling the program
|
|
for debugging it, replace the <option>-O</option> or
|
|
<option>-Copt-level=</option> options with <option>-g</option> to
|
|
produce an unoptimized program with debug info.
|
|
</para>
|
|
|
|
<para>
|
|
Like <command>ninja</command>, by default <command>cargo</command>
|
|
uses all logical cores. This can often be worked around,
|
|
either by exporting
|
|
<envar>CARGO_BUILD_JOBS=<replaceable><N></replaceable></envar>
|
|
or passing
|
|
<option>--jobs <replaceable><N></replaceable></option> to
|
|
<command>cargo</command>.
|
|
For compiling rustc itself, specifying
|
|
<option>--jobs <replaceable><N></replaceable></option> for
|
|
invocations of <command>x.py</command>
|
|
(together with the <envar>CARGO_BUILD_JOBS</envar> environment
|
|
variable, which looks like a <quote>belt and braces</quote>
|
|
approach but seems to be necessary) mostly works. The exception is
|
|
running the tests when building rustc, some of them will
|
|
nevertheless use all online CPUs, at least as of rustc-1.42.0.
|
|
</para>
|
|
|
|
</sect2>
|
|
|
|
<sect2 id="optimizations">
|
|
<title>Optimizing the build</title>
|
|
|
|
<para>
|
|
Many people will prefer to optimize compiles as they see fit, by providing
|
|
<envar>CFLAGS</envar> or <envar>CXXFLAGS</envar>. For an
|
|
introduction to the options available with gcc and g++ see <ulink
|
|
url="https://gcc.gnu.org/onlinedocs/gcc-&gcc-version;/gcc/Optimize-Options.html"/>.
|
|
The same content can be also found in <command>info gcc</command>.
|
|
</para>
|
|
|
|
<para>
|
|
Some packages default to <option>-O2 -g</option>, others to
|
|
<option>-O3 -g</option>, and if <envar>CFLAGS</envar> or
|
|
<envar>CXXFLAGS</envar> are supplied they might be added to the
|
|
package's defaults, replace the package's defaults, or even be
|
|
ignored. There are details on some desktop packages which were
|
|
mostly current in April 2019 at
|
|
<ulink url="https://www.linuxfromscratch.org/~ken/tuning/"/> - in
|
|
particular, <filename>README.txt</filename>,
|
|
<filename>tuning-1-packages-and-notes.txt</filename>, and
|
|
<filename>tuning-notes-2B.txt</filename>. The particular thing to
|
|
remember is that if you want to try some of the more interesting
|
|
flags you may need to force verbose builds to confirm what is being
|
|
used.
|
|
</para>
|
|
|
|
<para>
|
|
Clearly, if you are optimizing your own program you can spend time to
|
|
profile it and perhaps recode some of it if it is too slow. But for
|
|
building a whole system that approach is impractical. In general,
|
|
<option>-O3</option> usually produces faster programs than
|
|
<option>-O2</option>. Specifying
|
|
<option>-march=native</option> is also beneficial, but means that
|
|
you cannot move the binaries to an incompatible machine - this can
|
|
also apply to newer machines, not just to older machines. For
|
|
example programs compiled for <literal>amdfam10</literal> run on
|
|
old Phenoms, Kaveris, and Ryzens : but programs compiled for a
|
|
Kaveri will not run on a Ryzen because certain op-codes are not
|
|
present. Similarly, if you build for a Haswell not everything will
|
|
run on a SandyBridge.
|
|
</para>
|
|
|
|
<note>
|
|
<para>
|
|
Be careful that the name of a <option>-march</option> setting
|
|
does not always match the baseline of the microarchitecture
|
|
with the same name. For example, the Skylake-based Intel Celeron
|
|
processors do not support AVX at all, but
|
|
<option>-march=skylake</option> assumes AVX and even AVX2.
|
|
</para>
|
|
</note>
|
|
|
|
<para>
|
|
When a shared library is built by GCC, a feature named
|
|
<quote>semantic interposition</quote> is enabled by default. When
|
|
the shared library refers to a symbol name with external linkage
|
|
and default visibility, if the symbol exists in both the shared
|
|
library and the main executable, semantic interposition guarantees
|
|
the symbol in the main executable is always used. This feature
|
|
was invented in an attempt to make the behavior of linking a shared
|
|
library and linking a static library as similar as possible. Today
|
|
only a small number of packages still depend on semantic
|
|
interposition, but the feature is still on by the default of GCC,
|
|
causing many optimizations disabled for shared libraries because
|
|
they conflict with semantic interposition. The
|
|
<option>-fno-semantic-interposition</option> option can be passed
|
|
to <command>gcc</command> or <command>g++</command> to disable
|
|
semantic interposition and enable more optimizations for shared
|
|
libraries. This option is used as the default of some packages
|
|
(for example <xref linkend='python3'/>), and it's also the default
|
|
of Clang.
|
|
</para>
|
|
|
|
<para>
|
|
There are also various other options which some people claim are
|
|
beneficial. At worst, you get to recompile and test, and then
|
|
discover that in your usage the options do not provide a benefit.
|
|
</para>
|
|
|
|
<para>
|
|
If building Perl or Python modules,
|
|
in general the <envar>CFLAGS</envar> and <envar>CXXFLAGS</envar>
|
|
used are those which were used by those <quote>parent</quote>
|
|
packages.
|
|
</para>
|
|
|
|
<para>
|
|
For <envar>LDFLAGS</envar>, there are three options can be used
|
|
for optimization. They are quite safe to use and the building
|
|
system of some packages use some of these options as the default.
|
|
</para>
|
|
|
|
<para>
|
|
With <option>-Wl,-O1</option>, the linker will
|
|
optimize the hash table to speed up the dynamic linking.
|
|
Note that <option>-Wl,-O1</option> is completely unrelated to the
|
|
compiler optimization flag <option>-O1</option>.
|
|
</para>
|
|
|
|
<para>
|
|
With <option>-Wl,--as-needed</option>, the linker will disregard
|
|
unnecessary <option>-l<replaceable>foo</replaceable></option> options
|
|
from the command line, i. e. the shared library <systemitem
|
|
class='library'>lib<replaceable>foo</replaceable></systemitem>
|
|
will only be linked if a symbol in <systemitem
|
|
class='library'>lib<replaceable>foo</replaceable></systemitem> is
|
|
really referred from the executable or shared library being linked.
|
|
This can sometimes mitigate the <quote>excessive dependencies to
|
|
shared libraries</quote> issues caused by
|
|
<application>libtool</application>.
|
|
</para>
|
|
|
|
<para>
|
|
With <option>-Wl,-z,pack-relative-relocs</option>, the linker
|
|
generates a more compacted form of the relative relocation entries
|
|
for PIEs and shared libraries. It reduces the size of the linked
|
|
PIE or shared library, and speeds up the loading of the PIE or
|
|
shared library.
|
|
</para>
|
|
|
|
<para>
|
|
The <option>-Wl,</option> prefix is necessary because despite the
|
|
variable is named <envar>LDFLAGS</envar>, its content is actually
|
|
passed to <command>gcc</command> (or <command>g++</command>,
|
|
<command>clang</command>, etc.) during the link stage, not directly
|
|
passed to <command>ld</command>.
|
|
</para>
|
|
|
|
</sect2>
|
|
|
|
<sect2 id="hardening">
|
|
<title>Options for hardening the build</title>
|
|
|
|
<para>
|
|
Even on desktop systems, there are still a lot of exploitable
|
|
vulnerabilities. For many of these, the attack comes via javascript
|
|
in a browser. Often, a series of vulnerabilities are used to gain
|
|
access to data (or sometimes to pwn, i.e. own, the machine and
|
|
install rootkits). Most commercial distros will apply various
|
|
hardening measures.
|
|
</para>
|
|
|
|
<para>
|
|
In the past, there was Hardened LFS where gcc (a much older version)
|
|
was forced to use hardening (with options to turn some of it off on a
|
|
per-package basis). The current LFS and BLFS books are carrying
|
|
forward a part of its spirit by enabling PIE
|
|
(<option>-fPIE -pie</option>) and SSP
|
|
(<option>-fstack-protector-strong</option>) as the defaults
|
|
for GCC and clang. What is being covered here is different - first
|
|
you have to make sure that the package is indeed using your added
|
|
flags and not over-riding them.
|
|
</para>
|
|
|
|
<para>
|
|
For hardening options which are reasonably cheap, there is some
|
|
discussion in the 'tuning' link above (occasionally, one or more
|
|
of these options might be inappropriate for a package). These
|
|
options are <option>-D_FORTIFY_SOURCE=2</option>
|
|
(or <option>-D_FORTIFY_SOURCE=3</option> which is more secure but
|
|
with a larger performance overhead) and
|
|
(for C++) <option>-D_GLIBCXX_ASSERTIONS</option>. On modern
|
|
machines these should only have a little impact on how fast things
|
|
run, and often they will not be noticeable.
|
|
</para>
|
|
|
|
<para>
|
|
The main distros use much more, such as RELRO (Relocation Read Only)
|
|
and perhaps <option>-fstack-clash-protection</option>. You may also
|
|
encounter the so-called <quote>userspace retpoline</quote>
|
|
(<option>-mindirect-branch=thunk</option> etc.) which
|
|
is the equivalent of the spectre mitigations applied to the linux
|
|
kernel in late 2018. The kernel mitigations caused a lot of complaints
|
|
about lost performance, if you have a production server you might wish
|
|
to consider testing that, along with the other available options, to
|
|
see if performance is still sufficient.
|
|
</para>
|
|
|
|
<para>
|
|
Whilst gcc has many hardening options, clang/LLVM's strengths lie
|
|
elsewhere. Some options which gcc provides are said to be less effective
|
|
in clang/LLVM.
|
|
</para>
|
|
|
|
</sect2>
|
|
|
|
</sect1>
|