The shared library xx. so cannot be found for software compilation in Linux.

The shared library xx. so cannot be found for software compilation in Linux.
When memcached is compiled, no libevent is reported. Therefore, download libevent, configure, make & make install, and reinstall memcache. Memcached is installed in the/usr/local/bin/directory by default. Run the command. /memcache-help error: [root @ localhost bin] #. /memcached. /memcached: error while loading shared libraries: libevent-2.0.so.5: cannot open shared object file: No such file or directory but the above clearly has installed libevent, it should be memcached not found. Find the installation path of libevent: [root @ localhost bin] # whereis libeventlibevent:/usr/local/lib/libevent. la/usr/local/lib/libevent. a/usr/local/lib/libevent. so we can see that it has been installed to:/usr/local/lib/libevent. so let's check the dependency of memcached:

[root@localhost bin]# ldd /usr/local/bin/memcached        linux-gate.so.1 =>  (0x00c8d000)        libevent-2.0.so.5 => not found        librt.so.1 => /lib/librt.so.1 (0x00720000)        libpthread.so.0 => /lib/libpthread.so.0 (0x006fc000)        libc.so.6 => /lib/libc.so.6 (0x00564000)        /lib/ld-linux.so.2 (0x0053e000)

 

The dependent libevent-2.0.so.5 found => not found. View how libevent looks for dependencies:

[root@localhost bin]# LD_DEBUG=libs ./memcached -v     10071:     find library=libevent-2.0.so.5 [0]; searching     10071:      search cache=/etc/ld.so.cache     10071:      search path=/lib/tls/i686/sse2:/lib/tls/i686:/lib/tls/sse2:/lib/tls:/lib/i686/sse2:/lib/i686:/lib/sse2:/lib:/usr/lib/tls/i686/sse2:/usr/lib/tls/i686:/usr/lib/tls/sse2:/usr/lib/tls:/usr/lib/i686/sse2:/usr/lib/i686:/usr/lib/sse2:/usr/lib               (system search path)     10071:       trying file=/lib/tls/i686/sse2/libevent-2.0.so.5     10071:       trying file=/lib/tls/i686/libevent-2.0.so.5     10071:       trying file=/lib/tls/sse2/libevent-2.0.so.5     10071:       trying file=/lib/tls/libevent-2.0.so.5     10071:       trying file=/lib/i686/sse2/libevent-2.0.so.5     10071:       trying file=/lib/i686/libevent-2.0.so.5     10071:       trying file=/lib/sse2/libevent-2.0.so.5     10071:       trying file=/lib/libevent-2.0.so.5     10071:       trying file=/usr/lib/tls/i686/sse2/libevent-2.0.so.5     10071:       trying file=/usr/lib/tls/i686/libevent-2.0.so.5     10071:       trying file=/usr/lib/tls/sse2/libevent-2.0.so.5     10071:       trying file=/usr/lib/tls/libevent-2.0.so.5     10071:       trying file=/usr/lib/i686/sse2/libevent-2.0.so.5     10071:       trying file=/usr/lib/i686/libevent-2.0.so.5     10071:       trying file=/usr/lib/sse2/libevent-2.0.so.5     10071:       trying file=/usr/lib/libevent-2.0.so.5

 

We can see: search path =/lib/tls/i686/sse2:/lib/tls/i686:/lib/tls/sse2:/lib/tls: /lib/i686/sse2:/lib/i686:/lib/sse2:/lib:/usr/lib/tls/i686/sse2:/usr/lib/tls/i686: /usr/lib/tls/sse2:/usr/lib/tls:/usr/lib/i686/sse2:/usr/lib/i686:/usr/lib/sse2: the/usr/lib (system search path) system looks for the lib path, which does not include:/usr/local/lib/. Therefore, it is easy to solve the problem. There are also multiple methods. 1) make a soft connection to any directory in the search path above: [root @ localhost bin] # ln-s/usr/local/lib/libevent. so/usr/lib/libevent-2.0.so.5 verification has been resolved:

[root@localhost bin]# memcached -helpmemcached 1.4.24-p <num>      TCP port number to listen on (default: 11211)-U <num>      UDP port number to listen on (default: 11211, 0 is off)-s <file>     UNIX socket path to listen on (disables network support)-A            enable ascii "shutdown" command-a <mask>     access mask for UNIX socket, in octal (default: 0700)-l <addr>     interface to listen on (default: INADDR_ANY, all addresses)              <addr> may be specified as host:port. If you don't specify              a port number, the value you specified with -p or -U is              used. You may specify multiple addresses separated by comma              or by using -l multiple times-d            run as a daemon-r            maximize core file limit-u <username> assume identity of <username> (only when run as root)-m <num>      max memory to use for items in megabytes (default: 64 MB)-M            return error on memory exhausted (rather than removing items)-c <num>      max simultaneous connections (default: 1024)-k            lock down all paged memory.  Note that there is a              limit on how much memory you may lock.  Trying to              allocate more than that would fail, so be sure you              set the limit correctly for the user you started              the daemon with (not for -u <username> user;              under sh this is done with 'ulimit -S -l NUM_KB').-v            verbose (print errors/warnings while in event loop)-vv           very verbose (also print client commands/reponses)-vvv          extremely verbose (also print internal state transitions)-h            print this help and exit-i            print memcached and libevent license-V            print version and exit-P <file>     save PID in <file>, only used with -d option-f <factor>   chunk size growth factor (default: 1.25)-n <bytes>    minimum space allocated for key+value+flags (default: 48)-L            Try to use large memory pages (if available). Increasing              the memory page size could reduce the number of TLB misses              and improve the performance. In order to get large pages              from the OS, memcached will allocate the total item-cache              in one large chunk.-D <char>     Use <char> as the delimiter between key prefixes and IDs.              This is used for per-prefix stats reporting. The default is              ":" (colon). If this option is specified, stats collection              is turned on automatically; if not, then it may be turned on              by sending the "stats detail on" command to the server.-t <num>      number of threads to use (default: 4)-R            Maximum number of requests per event, limits the number of              requests process for a given connection to prevent               starvation (default: 20)-C            Disable use of CAS-b            Set the backlog queue limit (default: 1024)-B            Binding protocol - one of ascii, binary, or auto (default)-I            Override the size of each slab page. Adjusts max item size              (default: 1mb, min: 1k, max: 128m)-F            Disable flush_all command-o            Comma separated list of extended or experimental options              - (EXPERIMENTAL) maxconns_fast: immediately close new                connections if over maxconns limit              - hashpower: An integer multiplier for how large the hash                table should be. Can be grown at runtime if not big enough.                Set this based on "STAT hash_power_level" before a                 restart.              - tail_repair_time: Time in seconds that indicates how long to wait before                forcefully taking over the LRU tail item whose refcount has leaked.                Disabled by default; dangerous option.              - hash_algorithm: The hash table algorithm                default is jenkins hash. options: jenkins, murmur3              - lru_crawler: Enable LRU Crawler background thread              - lru_crawler_sleep: Microseconds to sleep between items                default is 100.              - lru_crawler_tocrawl: Max items to crawl per slab per run                default is 0 (unlimited)              - lru_maintainer: Enable new LRU system + background thread              - hot_lru_pct: Pct of slab memory to reserve for hot lru.                (requires lru_maintainer)              - warm_lru_pct: Pct of slab memory to reserve for warm lru.                (requires lru_maintainer)              - expirezero_does_not_evict: Items set to not expire, will not evict.                (requires lru_maintainer)

 

No error is reported. 2) When compiling libevent, specify the relevant directory:

[root@localhost libevent]# ./configure --help`configure' configures this package to adapt to many kinds of systems.Usage: ./configure [OPTION]... [VAR=VALUE]...To assign environment variables (e.g., CC, CFLAGS...), specify them asVAR=VALUE.  See below for descriptions of some of the useful variables.Defaults for the options are specified in brackets.Configuration:  -h, --help              display this help and exit      --help=short        display options specific to this package      --help=recursive    display the short help of all the included packages  -V, --version           display version information and exit  -q, --quiet, --silent   do not print `checking ...' messages      --cache-file=FILE   cache test results in FILE [disabled]  -C, --config-cache      alias for `--cache-file=config.cache'  -n, --no-create         do not create output files      --srcdir=DIR        find the sources in DIR [configure dir or `..']Installation directories:  --prefix=PREFIX         install architecture-independent files in PREFIX                          [/usr/local]  --exec-prefix=EPREFIX   install architecture-dependent files in EPREFIX                          [PREFIX]By default, `make install' will install all the files in`/usr/local/bin', `/usr/local/lib' etc.  You can specifyan installation prefix other than `/usr/local' using `--prefix',for instance `--prefix=$HOME'.For better control, use the options below.Fine tuning of the installation directories:  --bindir=DIR            user executables [EPREFIX/bin]  --sbindir=DIR           system admin executables [EPREFIX/sbin]  --libexecdir=DIR        program executables [EPREFIX/libexec]  --sysconfdir=DIR        read-only single-machine data [PREFIX/etc]  --sharedstatedir=DIR    modifiable architecture-independent data [PREFIX/com]  --localstatedir=DIR     modifiable single-machine data [PREFIX/var]  --libdir=DIR            object code libraries [EPREFIX/lib]  --includedir=DIR        C header files [PREFIX/include]  --oldincludedir=DIR     C header files for non-gcc [/usr/include]  --datarootdir=DIR       read-only arch.-independent data root [PREFIX/share]  --datadir=DIR           read-only architecture-independent data [DATAROOTDIR]  --infodir=DIR           info documentation [DATAROOTDIR/info]  --localedir=DIR         locale-dependent data [DATAROOTDIR/locale]  --mandir=DIR            man documentation [DATAROOTDIR/man]  --docdir=DIR            documentation root [DATAROOTDIR/doc/PACKAGE]  --htmldir=DIR           html documentation [DOCDIR]  --dvidir=DIR            dvi documentation [DOCDIR]  --pdfdir=DIR            pdf documentation [DOCDIR]  --psdir=DIR             ps documentation [DOCDIR]Program names:  --program-prefix=PREFIX            prepend PREFIX to installed program names  --program-suffix=SUFFIX            append SUFFIX to installed program names  --program-transform-name=PROGRAM   run sed PROGRAM on installed program namesSystem types:  --build=BUILD     configure for building on BUILD [guessed]  --host=HOST       cross-compile to build programs to run on HOST [BUILD]Optional Features:  --disable-option-checking  ignore unrecognized --enable/--with options  --disable-FEATURE       do not include FEATURE (same as --enable-FEATURE=no)  --enable-FEATURE[=ARG]  include FEATURE [ARG=yes]  --enable-dependency-tracking                          do not reject slow dependency extractors  --disable-dependency-tracking                          speeds up one-time build  --enable-gcc-warnings   enable verbose warnings with GCC  --disable-thread-support                          disable support for threading  --disable-malloc-replacement                          disable support for replacing the memory mgt                          functions  --disable-openssl       disable support for openssl encryption  --disable-debug-mode    disable support for running in debug mode  --disable-libevent-install, disable installation of libevent  --disable-libevent-regress, skip regress in make check  --enable-function-sections, make static library allow smaller binaries with --gc-sections  --enable-shared[=PKGS]  build shared libraries [default=yes]  --enable-static[=PKGS]  build static libraries [default=yes]  --enable-fast-install[=PKGS]                          optimize for fast installation [default=yes]  --disable-libtool-lock  avoid locking (might break parallel builds)Optional Packages:  --with-PACKAGE[=ARG]    use PACKAGE [ARG=yes]  --without-PACKAGE       do not use PACKAGE (same as --with-PACKAGE=no)  --with-pic[=PKGS]       try to use only PIC/non-PIC objects [default=use                          both]  --with-gnu-ld           assume the C compiler uses GNU ld [default=no]  --with-sysroot=DIR Search for dependent libraries within DIR                        (or the compiler's sysroot if not specified).Some influential environment variables:  CC          C compiler command  CFLAGS      C compiler flags  LDFLAGS     linker flags, e.g. -L<lib dir> if you have libraries in a              nonstandard directory <lib dir>  LIBS        libraries to pass to the linker, e.g. -l<library>  CPPFLAGS    (Objective) C/C++ preprocessor flags, e.g. -I<include dir> if              you have headers in a nonstandard directory <include dir>  CPP         C preprocessorUse these variables to override the choices made by `configure' or to helpit to find libraries and programs with nonstandard names/locations.Report bugs to the package provider.Installation directories:  --prefix=PREFIX         install architecture-independent files in PREFIX                          [/usr/local]  --exec-prefix=EPREFIX   install architecture-dependent files in EPREFIX                          [PREFIX]By default, `make install' will install all the files in`/usr/local/bin', `/usr/local/lib' etc.  You can specifyan installation prefix other than `/usr/local' using `--prefix',for instance `--prefix=$HOME'.For better control, use the options below.Fine tuning of the installation directories:  --bindir=DIR            user executables [EPREFIX/bin]  --sbindir=DIR           system admin executables [EPREFIX/sbin]  --libexecdir=DIR        program executables [EPREFIX/libexec]  --sysconfdir=DIR        read-only single-machine data [PREFIX/etc]  --sharedstatedir=DIR    modifiable architecture-independent data [PREFIX/com]  --localstatedir=DIR     modifiable single-machine data [PREFIX/var]  --libdir=DIR            object code libraries [EPREFIX/lib]  --includedir=DIR        C header files [PREFIX/include]

 

So we can specify the path in configure as follows: [root @ localhost libevent] #. /configure -- libdir =/usr/lib3) modify the environment variable LD_LIBRARY_PATH and include/usr/local/lib. However, this method is generally not recommended (but there is a work und, For details, refer to 3> In the summary ). Summary: 1. How to handle some errors related to the shared library: 1> LD_DEBUG command: LD_DEBUG is an environment variable set by loader in glibc to facilitate debugging. By setting this environment variable, you can easily see the loader loading process.

[root@localhost libevent]# LD_DEBUG=help lsValid options for the LD_DEBUG environment variable are:  libs        display library search paths  reloc       display relocation processing  files       display progress for input file  symbols     display symbol table processing  bindings    display information about symbol binding  versions    display version dependencies  all         all previous options combined  statistics  display relocation statistics  unused      determined unused DSOs  help        display this help message and exitTo direct the debugging output into a file instead of standard outputa filename can be specified using the LD_DEBUG_OUTPUT environment variable.

 

All options of LD_DEBUG are listed above, and LD_DEBUG = libs is used above. You can use this command to obtain a lot of useful information. 2> ldd-print shared library dependencies print the output dependency library 3> LD_LIBRARY_PATH,/etc/ld. so. conf. d, ldconfig because the connector will go to the/etc/ld directory. so. conf. d. Find the directory for shared library configuration. Based on this principle, we can create a configuration file for/usr/local/lib, add to the directory list of the connector to find the Shared Library:

[root@localhost ld.so.conf.d]# pwd/etc/ld.so.conf.d[root@localhost ld.so.conf.d]# lskernel-2.6.32-504.el6.i686.conf  mysql-i386.conf  qt-i386.conf  xulrunner-32.conf[root@localhost ld.so.conf.d]# echo "/usr/local/lib" > usr_local_lib.conf[root@localhost ld.so.conf.d]# lltotal 20-r--r--r--. 1 root root 324 Oct 15  2014 kernel-2.6.32-504.el6.i686.conf-rw-r--r--. 1 root root  15 Feb 13  2014 mysql-i386.conf-rw-r--r--. 1 root root  20 Sep 24  2011 qt-i386.conf-rw-r--r--. 1 root root  15 Sep 13 08:51 usr_local_lib.conf-rw-r--r--. 1 root root  19 Oct 30  2013 xulrunner-32.conf[root@localhost ld.so.conf.d]# cat usr_local_lib.conf/usr/local/lib[root@localhost ld.so.conf.d]# ldconfig

 

In this case, the shared library in/usr/local/lib will be searched by the connector. After you modify the connector-related configuration, you must use the ldconfig command to update the library. Otherwise, you will still be unable to find the shared library. 2. how to find files and libraries: whereis-locate the binary, source, and manual page files for a command updatedb-update a database for locate-find files by name find command find-search for files in a directory hierarchy example: whereis libevent, updatedb, locate libevent,

find / -name libevent.*[root@localhost bin]# find /usr/local -name libevent.*/usr/local/redis-3.0.3/deps/hiredis/adapters/libevent.h/usr/local/src/libevent/libevent.pc.in/usr/local/src/libevent/libevent.pc/usr/local/lib/libevent.la/usr/local/lib/libevent.a/usr/local/lib/pkgconfig/libevent.pc/usr/local/lib/libevent.so[root@localhost bin]# find / -name libevent.so/usr/local/lib/libevent.so[root@localhost bin]# find / -name libevent.so*/usr/local/lib/libevent.so

 

The first parameter of the find command is the path/usr/local to be searched. The second parameter is the expression of the file name to be searched. You can use a regular expression to represent the file name to be searched. Find also has a common usage: execute a command on the found file: find. -name \*. lo-o-name \*. o | xargs rm-f (xargs-build and execute command lines from standard input) 3. before configure, you must view the configuration options in configure -- help.