#### Linux From Scratch - Version 7.9

### Chapter 6. Installing Basic System Software

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# 6.9. Glibc-2.23

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: 16.4 SBU
Required disk space: 1.1 GB

## 6.9.1. Installation of Glibc

### Note

Some packages outside of LFS suggest installing GNU libiconv in order to translate data from one encoding to another. The project's home page (http://www.gnu.org/software/libiconv/) says “This library provides an `iconv()` implementation, for use on systems which don't have one, or whose implementation cannot convert from/to Unicode.” Glibc provides an `iconv()` implementation and can convert from/to Unicode, therefore libiconv is not required on an LFS system.

Some of the Glibc programs use non-FHS compilant `/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-2.23-fhs-1.patch

The Glibc build system is self-contained and will install perfectly, even though the compiler specs file and linker are still pointing at `/tools`. The specs and linker cannot be adjusted before the Glibc install because the Glibc autoconf tests would give false results and defeat the goal of achieving a clean build.

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

    mkdir -v build
    cd       build

Prepare Glibc for compilation:

    ../configure --prefix=/usr          \
                 --disable-profile      \
                 --enable-kernel=2.6.32 \
                 --enable-obsolete-rpc

Compile the package:

    make

### 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, but you can generally ignore any of the test failures listed below. Now test the build results:

    make check

You will probably see some test failures. The Glibc test suite is somewhat dependent on the host system. This is a list of the most common issues seen for this version of LFS:

- posix/tst-getaddrinfo4 and posix/tst-getaddrinfo5 will always fail due to not having the necessary networking applications when the tests are run.

- The rt/tst-cputimer1 and rt/tst-cpuclock2 tests have been known to fail. The reason is not completely understood, but indications are that minor timing issues can trigger these failures.

- The math tests sometimes fail when running on systems where the CPU is not a relatively new Intel or AMD processor.

- Other tests known to fail on some architectures are malloc/tst-malloc-usable and nptl/tst-cleanupx4.

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

Install the package:

    make install

Install the configuration file and runtime directory for nscd:

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

The locales that can make the system respond in a different language were not installed by the above command. None of the locales are required, but if some of them are missing, test suites of the future packages would skip important testcases.

Individual locales can be installed using the localedef program. E.g., the first 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 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 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_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 it_IT -f ISO-8859-1 it_IT
    localedef -i it_IT -f UTF-8 it_IT.UTF-8
    localedef -i ja_JP -f EUC-JP ja_JP
    localedef -i ru_RU -f KOI8-R ru_RU.KOI8-R
    localedef -i ru_RU -f UTF-8 ru_RU.UTF-8
    localedef -i tr_TR -f UTF-8 tr_TR.UTF-8
    localedef -i zh_CN -f GB18030 zh_CN.GB18030

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

Alternatively, install all locales listed in the `glibc-2.23/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-2.23/localedata/SUPPORTED` file in the unlikely case you need them.

## 6.9.2. Configuring Glibc

### 6.9.2.1. 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

### 6.9.2.2. Adding time zone data

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

    tar -xf ../../tzdata2016a.tar.gz

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

    for tz in etcetera southamerica northamerica europe africa antarctica  \
              asia australasia backward pacificnew systemv; do
        zic -L /dev/null   -d $ZONEINFO       -y "sh yearistype.sh" ${tz}
        zic -L /dev/null   -d $ZONEINFO/posix -y "sh yearistype.sh" ${tz}
        zic -L leapseconds -d $ZONEINFO/right -y "sh yearistype.sh" ${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 1.9MB 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:

    cp -v /usr/share/zoneinfo/<xxx> /etc/localtime

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

### 6.9.2.3. Configuring the Dynamic Loader

By default, the dynamic loader (`/lib/ld-linux.so.2`) searches through `/lib` and `/usr/lib` for dynamic libraries that are needed by programs as they are run. However, if there are libraries in directories other than `/lib` and `/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

## 6.9.3. Contents of Glibc

Installed programs: catchsegv, gencat, getconf, getent, iconv, iconvconfig, ldconfig, ldd, lddlibc4, locale, localedef, makedb, mtrace, nscd, pcprofiledump, pldd, rpcgen, sln, sotruss, sprof, tzselect, xtrace, zdump, and zic
Installed libraries: ld-2.23.so, libBrokenLocale.{a,so}, libSegFault.so, libanl.{a,so}, libc.{a,so}, libc_nonshared.a, libcidn.so, libcrypt.{a,so}, libdl.{a,so}, libg.a, libieee.a, libm.{a,so}, libmcheck.a, libmemusage.so, libnsl.{a,so}, libnss_compat.so, libnss_dns.so, libnss_files.so, libnss_hesiod.so, libnss_nis.so, libnss_nisplus.so, libpcprofile.so, libpthread.{a,so}, libpthread_nonshared.a, libresolv.{a,so}, librpcsvc.a, librt.{a,so}, libthread_db.so, and libutil.{a,so}
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/rpcsvc, /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

catchsegv | Can be used to create a stack trace when a program terminates with a segmentation fault
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
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 | Dumps information generated by PC profiling
pldd | Lists dynamic shared objects used by running processes
rpcgen | Generates C code to implement the Remote Procedure Call (RPC) protocol
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-2.23.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-2.23/locale/broken_cur_max.c` for more information
`libSegFault` | The segmentation fault signal handler, used by catchsegv
`libanl` | An asynchronous name lookup library
`libc` | The main C library
`libcidn` | Used internally by Glibc for handling internationalized domain names in the `getaddrinfo()` function
`libcrypt` | The cryptography library
`libdl` | The dynamic linking interface library
`libg` | Dummy library containing no functions. Previously was a runtime library for g++
`libieee` | Linking in this module forces error handling rules for math functions as defined by the Institute of Electrical and Electronic Engineers (IEEE). The default is POSIX.1 error handling
`libm` | The mathematical library
`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
`libnss` | The Name Service Switch libraries, containing functions for resolving host names, user names, group names, aliases, services, protocols, etc.
`libpcprofile` | Contains profiling functions used to track the amount of CPU time spent in specific source code lines
`libpthread` | The POSIX threads library
`libresolv` | Contains functions for creating, sending, and interpreting packets to the Internet domain name servers
`librpcsvc` | Contains functions providing miscellaneous RPC services
`librt` | Contains functions providing most of the interfaces specified by the POSIX.1b Realtime Extension
`libthread_db` | Contains functions useful for building debuggers for multi-threaded programs
`libutil` | Contains code for “standard” functions used in many different Unix utilities

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