8.5. Glibc-2.37

#### Linux From Scratch - Version 11.3-systemd

### Chapter 8. Installing Basic System Software

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# 8.5. Glibc-2.37

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: 2.9 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-2.37-fhs-1.patch

Fix a security issue identified upstream:

    sed '/width -=/s/workend - string/number_length/' \
        -i stdio-common/vfprintf-process-arg.c

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=3.2                      \
                 --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=3.2`

  This option tells the build system that this Glibc may be used with kernels as old as 3.2. 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

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.

- misc/tst-ttyname 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.

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 unneeded sanity check that fails in the LFS partial environment:

    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

Install the systemd support files for nscd:

    install -v -Dm644 ../nscd/nscd.tmpfiles /usr/lib/tmpfiles.d/nscd.conf
    install -v -Dm644 ../nscd/nscd.service /usr/lib/systemd/system/nscd.service

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-2.37/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-2.37/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

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 ../../tzdata2022g.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, libcrypt.{a,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-2.37/locale/broken_cur_max.c` for more information
`libanl` | An asynchronous name lookup library
`libc` | The main C library
`libc_malloc_debug` | Turns on memory allocation checking when preloaded
`libcrypt` | The cryptography library
`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.1b Realtime Extension, 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 Realtime Extension
`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`

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