8.5. Glibc-2.43

#### Linux From Scratch - Version r13.0-154-systemd

### Chapter 8. Installing Basic System Software

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# 8.5. Glibc-2.43

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: 12 SBU
Required disk space: 3.5 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-fhs-1.patch

Now add some fixes to address building and testing with Linux 7, and fix 5 security vulnerabilities found after the glibc-2.43 release:

    patch -Np1 -i ../glibc-2.43-upstream_fixes-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                \
                 --disable-nscd                  \
                 libc_cv_slibdir=/usr/lib        \
                 --enable-stack-protector=strong \
                 --enable-kernel=5.10

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=5.10`

  This option tells the build system that this Glibc may be used with kernels as old as 5.10. 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. Note that Glibc always explicitly overrides the default of GCC, so this option is still needed even though we've already specified `--enable-default-ssp` for GCC.

`--disable-nscd`

  Do not build the name service cache daemon which is no longer used.

`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 6000 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.

- Some tests, for example nss/tst-nss-files-hosts-multi and nptl/tst-thread-affinity* are known to fail due to a timeout (especially when the system is relatively slow and/or running the test suite with multiple parallel make jobs). These tests can be identified with:

      grep "Timed out" $(find -name \*.out)

  It's possible to re-run a single test with enlarged timeout with TIMEOUTFACTOR=`<factor>` make test t=`<test name>`. For example, TIMEOUTFACTOR=10 make test t=nss/tst-nss-files-hosts-multi will re-run nss/tst-nss-files-hosts-multi with ten times the original timeout.

- Additionally, some tests may fail with a relatively old CPU model (for example elf/tst-cpu-features-cpuinfo) or host kernel version (for example stdlib/tst-arc4random-thread), or with a host kernel newer than 7.1.3.

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

### Important

If upgrading Glibc to a new minor version (for example, from Glibc-2.36 to Glibc-2.43) on a running LFS system, you need to take some extra precautions to avoid breaking the system:

- Upgrading Glibc on a LFS system prior to 11.0 (exclusive) is not supported. Rebuild LFS if you are running such an old LFS system but you need a newer Glibc.

- If upgrading on a LFS system prior to 12.0 (exclusive), install Libxcrypt following Section 8.29, “Libxcrypt-4.5.2.” In addition to a normal Libxcrypt installation, you MUST follow the note in Libxcrypt section to install `libcrypt.so.1*` (replacing `libcrypt.so.1` from the prior Glibc installation).

- If upgrading on a LFS system prior to 12.1 (exclusive), remove the nscd program:

      rm -f /usr/sbin/nscd

  If this system (prior to LFS 12.1, exclusive) is based on Systemd, it's also needed to disable and stop the nscd service now:

      systemctl disable --now nscd

- Upgrade the kernel and reboot if it's older than 5.10 (check the current version with uname -r) or if you want to upgrade it anyway, following Section 10.3, “Linux-7.1.3.”

- Upgrade the kernel API headers if it's older than 5.10 (check the current version with cat /usr/include/linux/version.h) or if you want to upgrade it anyway, following Section 5.4, “Linux-7.1.3 API Headers” (but removing `$LFS` from the cp command).

- Perform a `DESTDIR` installation and upgrade the Glibc shared libraries on the system using one single install command:

      make DESTDIR=$PWD/dest install
      install -vm755 dest/usr/lib/*.so.* /usr/lib

It's imperative to strictly follow these steps above unless you completely understand what you are doing. Any unexpected deviation may render the system completely unusable. YOU ARE WARNED.

Then continue to run the make install command, the sed command against `/usr/bin/ldd`, and the commands to install the locales. Once they are finished, reboot the system immediately.

When the system has successfully rebooted, if you are running a LFS system prior to 12.0 (exclusive) where GCC was not built with the `--disable-fixincludes` option, move two GCC headers into a better location and remove the stale “fixed” copies of the Glibc headers:

    DIR=$(dirname $(gcc -print-libgcc-file-name))
    [ -e $DIR/include/limits.h ]    || mv $DIR/include{-fixed,}/limits.h
    [ -e $DIR/include/syslimits.h ] || mv $DIR/include{-fixed,}/syslimits.h
    rm -rfv $DIR/include-fixed/*
    unset DIR

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

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:

    localedef -i C -f UTF-8 C.UTF-8
    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 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-2.43/localedata/SUPPORTED` file (it includes every locale listed above and many more) at once with the following time-consuming command:

    make localedata/install-locales

### 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 systemd
    group: files systemd
    shadow: files systemd

    hosts: mymachines resolve [!UNAVAIL=return] files myhostname 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 ../../tzdata2026c.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 tz

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 saving 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, 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, 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
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-2.43/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`

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