Linux From Scratch - Version 12.0

Chapter 8. Installing Basic System Software

8.5. Glibc-2.38

The Glibc package contains the main C library. This library provides the basic routines for allocating memory, searching directories, opening and closing files, reading and writing files, string handling, pattern matching, arithmetic, and so on.

Approximate build time: 11 SBU
Required disk space: 3.0 GB

8.5.1. Installation of Glibc

Some of the Glibc programs use the non-FHS compliant /var/db directory to store their runtime data. Apply the following patch to make such programs store their runtime data in the FHS-compliant locations: 

patch -Np1 -i ../glibc-2.38-fhs-1.patch

Now fix a regression causing the posix_memalign() function to be very slow in some conditions: 

patch -Np1 -i ../glibc-2.38-memalign_fix-1.patch

The Glibc documentation recommends building Glibc in a dedicated build directory: 

mkdir -v build
cd       build

Ensure that the ldconfig and sln utilities will be installed into /usr/sbin: 

echo "rootsbindir=/usr/sbin" > configparms

Prepare Glibc for compilation: 

../configure --prefix=/usr                            \
             --disable-werror                         \
             --enable-kernel=4.14                     \
             --enable-stack-protector=strong          \
             --with-headers=/usr/include              \
             libc_cv_slibdir=/usr/lib

The meaning of the configure options:

--disable-werror

This option disables the -Werror option passed to GCC. This is necessary for running the test suite.

--enable-kernel=4.14

This option tells the build system that this Glibc may be used with kernels as old as 4.14. This means generating workarounds in case a system call introduced in a later version cannot be used.

--enable-stack-protector=strong

This option increases system security by adding extra code to check for buffer overflows, such as stack smashing attacks.

--with-headers=/usr/include

This option tells the build system where to find the kernel API headers.

libc_cv_slibdir=/usr/lib

This variable sets the correct library for all systems. We do not want lib64 to be used.

Compile the package: 

make
[Important]

Important

In this section, the test suite for Glibc is considered critical. Do not skip it under any circumstance.

Generally a few tests do not pass. The test failures listed below are usually safe to ignore. 

make check

You may see some test failures. The Glibc test suite is somewhat dependent on the host system. A few failures out of over 5000 tests can generally be ignored. This is a list of the most common issues seen for recent versions of LFS:

  • io/tst-lchmod is known to fail in the LFS chroot environment.

  • The stdlib/tst-arc4random-thread test is known to fail if the host kernel is relatively old.

  • Some tests, for example nss/tst-nss-files-hosts-multi, are known to fail on relatively slow systems due to an internal timeout.

  • Additionally, some tests may fail with a relatively old CPU model or host kernel version.

Though it is a harmless message, the install stage of Glibc will complain about the absence of /etc/ld.so.conf. Prevent this warning with: 

touch /etc/ld.so.conf

Fix the Makefile to skip an outdated sanity check that fails with a modern Glibc configuration: 

sed '/test-installation/s@$(PERL)@echo not running@' -i ../Makefile

Install the package: 

make install

Fix a hardcoded path to the executable loader in the ldd script: 

sed '/RTLDLIST=/s@/usr@@g' -i /usr/bin/ldd

Install the configuration file and runtime directory for nscd: 

cp -v ../nscd/nscd.conf /etc/nscd.conf
mkdir -pv /var/cache/nscd

Next, install the locales that can make the system respond in a different language. None of these locales are required, but if some of them are missing, the test suites of some packages will skip important test cases.

Individual locales can be installed using the localedef program. E.g., the second localedef command below combines the /usr/share/i18n/locales/cs_CZ charset-independent locale definition with the /usr/share/i18n/charmaps/UTF-8.gz charmap definition and appends the result to the /usr/lib/locale/locale-archive file. The following instructions will install the minimum set of locales necessary for the optimal coverage of tests: 

mkdir -pv /usr/lib/locale
localedef -i POSIX -f UTF-8 C.UTF-8 2> /dev/null || true
localedef -i cs_CZ -f UTF-8 cs_CZ.UTF-8
localedef -i de_DE -f ISO-8859-1 de_DE
localedef -i de_DE@euro -f ISO-8859-15 de_DE@euro
localedef -i de_DE -f UTF-8 de_DE.UTF-8
localedef -i el_GR -f ISO-8859-7 el_GR
localedef -i en_GB -f ISO-8859-1 en_GB
localedef -i en_GB -f UTF-8 en_GB.UTF-8
localedef -i en_HK -f ISO-8859-1 en_HK
localedef -i en_PH -f ISO-8859-1 en_PH
localedef -i en_US -f ISO-8859-1 en_US
localedef -i en_US -f UTF-8 en_US.UTF-8
localedef -i es_ES -f ISO-8859-15 es_ES@euro
localedef -i es_MX -f ISO-8859-1 es_MX
localedef -i fa_IR -f UTF-8 fa_IR
localedef -i fr_FR -f ISO-8859-1 fr_FR
localedef -i fr_FR@euro -f ISO-8859-15 fr_FR@euro
localedef -i fr_FR -f UTF-8 fr_FR.UTF-8
localedef -i is_IS -f ISO-8859-1 is_IS
localedef -i is_IS -f UTF-8 is_IS.UTF-8
localedef -i it_IT -f ISO-8859-1 it_IT
localedef -i it_IT -f ISO-8859-15 it_IT@euro
localedef -i it_IT -f UTF-8 it_IT.UTF-8
localedef -i ja_JP -f EUC-JP ja_JP
localedef -i ja_JP -f SHIFT_JIS ja_JP.SJIS 2> /dev/null || true
localedef -i ja_JP -f UTF-8 ja_JP.UTF-8
localedef -i nl_NL@euro -f ISO-8859-15 nl_NL@euro
localedef -i ru_RU -f KOI8-R ru_RU.KOI8-R
localedef -i ru_RU -f UTF-8 ru_RU.UTF-8
localedef -i se_NO -f UTF-8 se_NO.UTF-8
localedef -i ta_IN -f UTF-8 ta_IN.UTF-8
localedef -i tr_TR -f UTF-8 tr_TR.UTF-8
localedef -i zh_CN -f GB18030 zh_CN.GB18030
localedef -i zh_HK -f BIG5-HKSCS zh_HK.BIG5-HKSCS
localedef -i zh_TW -f UTF-8 zh_TW.UTF-8

In addition, install the locale for your own country, language and character set.

Alternatively, install all the locales listed in the glibc-2.38/localedata/SUPPORTED file (it includes every locale listed above and many more) at once with the following time-consuming command: 

make localedata/install-locales

Then use the localedef command to create and install locales not listed in the glibc-2.38/localedata/SUPPORTED file when you need them. For instance, the following two locales are needed for some tests later in this chapter: 

localedef -i POSIX -f UTF-8 C.UTF-8 2> /dev/null || true
localedef -i ja_JP -f SHIFT_JIS ja_JP.SJIS 2> /dev/null || true
[Note]

Note

Glibc now uses libidn2 when resolving internationalized domain names. This is a run time dependency. If this capability is needed, the instructions for installing libidn2 are in the BLFS libidn2 page.

8.5.2. Configuring Glibc

8.5.2.1. Adding nsswitch.conf

The /etc/nsswitch.conf file needs to be created because the Glibc defaults do not work well in a networked environment.

Create a new file /etc/nsswitch.conf by running the following: 

cat > /etc/nsswitch.conf << "EOF"
# Begin /etc/nsswitch.conf

passwd: files
group: files
shadow: files

hosts: files dns
networks: files

protocols: files
services: files
ethers: files
rpc: files

# End /etc/nsswitch.conf
EOF

8.5.2.2. Adding Time Zone Data

Install and set up the time zone data with the following: 

tar -xf ../../tzdata2023c.tar.gz

ZONEINFO=/usr/share/zoneinfo
mkdir -pv $ZONEINFO/{posix,right}

for tz in etcetera southamerica northamerica europe africa antarctica  \
          asia australasia backward; do
    zic -L /dev/null   -d $ZONEINFO       ${tz}
    zic -L /dev/null   -d $ZONEINFO/posix ${tz}
    zic -L leapseconds -d $ZONEINFO/right ${tz}
done

cp -v zone.tab zone1970.tab iso3166.tab $ZONEINFO
zic -d $ZONEINFO -p America/New_York
unset ZONEINFO

The meaning of the zic commands:

zic -L /dev/null ...

This creates posix time zones without any leap seconds. It is conventional to put these in both zoneinfo and zoneinfo/posix. It is necessary to put the POSIX time zones in zoneinfo, otherwise various test suites will report errors. On an embedded system, where space is tight and you do not intend to ever update the time zones, you could save 1.9 MB by not using the posix directory, but some applications or test suites might produce some failures.

zic -L leapseconds ...

This creates right time zones, including leap seconds. On an embedded system, where space is tight and you do not intend to ever update the time zones, or care about the correct time, you could save 1.9MB by omitting the right directory.

zic ... -p ...

This creates the posixrules file. We use New York because POSIX requires the daylight savings time rules to be in accordance with US rules.

One way to determine the local time zone is to run the following script: 

tzselect

After answering a few questions about the location, the script will output the name of the time zone (e.g., America/Edmonton). There are also some other possible time zones listed in /usr/share/zoneinfo such as Canada/Eastern or EST5EDT that are not identified by the script but can be used.

Then create the /etc/localtime file by running: 

ln -sfv /usr/share/zoneinfo/<xxx> /etc/localtime

Replace <xxx> with the name of the time zone selected (e.g., Canada/Eastern).

8.5.2.3. Configuring the Dynamic Loader

By default, the dynamic loader (/lib/ld-linux.so.2) searches through /usr/lib for dynamic libraries that are needed by programs as they are run. However, if there are libraries in directories other than /usr/lib, these need to be added to the /etc/ld.so.conf file in order for the dynamic loader to find them. Two directories that are commonly known to contain additional libraries are /usr/local/lib and /opt/lib, so add those directories to the dynamic loader's search path.

Create a new file /etc/ld.so.conf by running the following: 

cat > /etc/ld.so.conf << "EOF"
# Begin /etc/ld.so.conf
/usr/local/lib
/opt/lib

EOF

If desired, the dynamic loader can also search a directory and include the contents of files found there. Generally the files in this include directory are one line specifying the desired library path. To add this capability run the following commands: 

cat >> /etc/ld.so.conf << "EOF"
# Add an include directory
include /etc/ld.so.conf.d/*.conf

EOF
mkdir -pv /etc/ld.so.conf.d

8.5.3. Contents of Glibc

Installed programs: gencat, getconf, getent, iconv, iconvconfig, ldconfig, ldd, lddlibc4, ld.so (symlink to ld-linux-x86-64.so.2 or ld-linux.so.2), locale, localedef, makedb, mtrace, nscd, pcprofiledump, pldd, sln, sotruss, sprof, tzselect, xtrace, zdump, and zic
Installed libraries: ld-linux-x86-64.so.2, ld-linux.so.2, libBrokenLocale.{a,so}, libanl.{a,so}, libc.{a,so}, libc_nonshared.a, libc_malloc_debug.so, libdl.{a,so.2}, libg.a, libm.{a,so}, libmcheck.a, libmemusage.so, libmvec.{a,so}, libnsl.so.1, libnss_compat.so, libnss_dns.so, libnss_files.so, libnss_hesiod.so, libpcprofile.so, libpthread.{a,so.0}, libresolv.{a,so}, librt.{a,so.1}, libthread_db.so, and libutil.{a,so.1}
Installed directories: /usr/include/arpa, /usr/include/bits, /usr/include/gnu, /usr/include/net, /usr/include/netash, /usr/include/netatalk, /usr/include/netax25, /usr/include/neteconet, /usr/include/netinet, /usr/include/netipx, /usr/include/netiucv, /usr/include/netpacket, /usr/include/netrom, /usr/include/netrose, /usr/include/nfs, /usr/include/protocols, /usr/include/rpc, /usr/include/sys, /usr/lib/audit, /usr/lib/gconv, /usr/lib/locale, /usr/libexec/getconf, /usr/share/i18n, /usr/share/zoneinfo, /var/cache/nscd, and /var/lib/nss_db

Short Descriptions

gencat

Generates message catalogues

getconf

Displays the system configuration values for file system specific variables

getent

Gets entries from an administrative database

iconv

Performs character set conversion

iconvconfig

Creates fastloading iconv module configuration files

ldconfig

Configures the dynamic linker runtime bindings

ldd

Reports which shared libraries are required by each given program or shared library

lddlibc4

Assists ldd with object files. It does not exist on newer architectures like x86_64

locale

Prints various information about the current locale

localedef

Compiles locale specifications

makedb

Creates a simple database from textual input

mtrace

Reads and interprets a memory trace file and displays a summary in human-readable format

nscd

A daemon that provides a cache for the most common name service requests

pcprofiledump

Dump information generated by PC profiling

pldd

Lists dynamic shared objects used by running processes

sln

A statically linked ln program

sotruss

Traces shared library procedure calls of a specified command

sprof

Reads and displays shared object profiling data

tzselect

Asks the user about the location of the system and reports the corresponding time zone description

xtrace

Traces the execution of a program by printing the currently executed function

zdump

The time zone dumper

zic

The time zone compiler

ld-*.so

The helper program for shared library executables

libBrokenLocale

Used internally by Glibc as a gross hack to get broken programs (e.g., some Motif applications) running. See comments in glibc-2.38/locale/broken_cur_max.c for more information

libanl

Dummy library containing no functions. Previously was the asynchronous name lookup library, whose functions are now in libc

libc

The main C library

libc_malloc_debug

Turns on memory allocation checking when preloaded

libdl

Dummy library containing no functions. Previously was the dynamic linking interface library, whose functions are now in libc

libg

Dummy library containing no functions. Previously was a runtime library for g++

libm

The mathematical library

libmvec

The vector math library, linked in as needed when libm is used

libmcheck

Turns on memory allocation checking when linked to

libmemusage

Used by memusage to help collect information about the memory usage of a program

libnsl

The network services library, now deprecated

libnss_*

The Name Service Switch modules, containing functions for resolving host names, user names, group names, aliases, services, protocols, etc. Loaded by libc according to the configuration in /etc/nsswitch.conf

libpcprofile

Can be preloaded to PC profile an executable

libpthread

Dummy library containing no functions. Previously contained functions providing most of the interfaces specified by the POSIX.1c Threads Extensions and the semaphore interfaces specified by the POSIX.1b Real-time Extensions, now the functions are in libc

libresolv

Contains functions for creating, sending, and interpreting packets to the Internet domain name servers

librt

Contains functions providing most of the interfaces specified by the POSIX.1b Real-time Extensions

libthread_db

Contains functions useful for building debuggers for multi-threaded programs

libutil

Dummy library containing no functions. Previously contained code for “standard” functions used in many different Unix utilities. These functions are now in libc