Where things go when packages are installed?
/bin, /usr/bin, /usr/local/bin
Unix shell script is all about "executing a program". In general, program is designed to do a certain thing very well with versatile option switches. For example, "-l" switch for "/bin/ls". "Executing a program" is not limited to CLI or shell activity. In heart of Unix, a system is composed by a unit of "Process", which is a memory image of an executable program.
The executables are placed in many places. The standard locations are /bin, /usr/bin, and /usr/local/bin. Each are just conventions. For example, if we install firefox on a Linux system, usually it will be placed in /usr/bin/firefox. If someone decided to put it in /bin, that's okay. This doesn't break the system. The search path is defined in a shell variable called "PATH". Most programming languages will have similar config variable for searching. For example, Java has CLASSPATH and Golang has GOPATH. Python has PYTHONPATH, which will be prepended to sys.path list when an interpreter initiates. Unix PATH usually contains minimum "/bin" and "/usr/bin". There are also /sbin, /usr/sbin, and /usr/local/sbin. But, sbin directory is only for privileged purpose. Normal user might be able to execute this in read-only fashion.
Why so many "bin" (binary) directories? As a matter of fact, the distinction between these directories became blurred. For example, modern Fedora symlinks /bin to /usr/bin. But, let's visit what was the "intention" of each bin/ directories.
/bin
/bin is core executable of a unix operating system. The biggest role of /bin is to provide minimum binaries for boot and recovery mode. Therefore, the convention of /bin is part of "/" partition where boot is mounting. The binary files in this directory will be always available in whichever environment the process is in. The best example is /bin/ls. We can always assume that "ls" command is available in any situation. Usually, packages named binutils and coreutils will deploy binaries into /bin.
/usr/bin
/usr/bin is for distribution's binary files. When a distro organizes packages, the binaries part of OS distro will be placed into /usr/bin directory. So, from our first questions specific to my favorite editor Emacs, "yum install emacs" will place Emacs binary into /usr/bin as /usr/bin/emacs, and other parts (libraries, elisp files) into different directories, called /usr/lib. We will visit this soon.
/usr/local/bin
This directory is for local system. This directory is for any software which are not part of distro. For example, if we download a source code of tmux, patch something on our own for unknown feature, and install on the system, then most likely it will be placed into /usr/local/bin. The GNU build system assumes "--prefix" config to "/usr/local" if not specified. Doing so, we can distinguish tmux binary from our source compilation and distro installed tmux binary. The former binary will be /usr/local/bin/tmux, and the latter binary will be /usr/bin/tmux.
/lib, /usr/lib, and /usr/local/lib
We only handled /bin series. But an executable file commonly comes with multiple files for many reasons. /lib supports other files for an executable.
/lib directories are for supporting files for executables in /bin. Anything which makes executable file useful, but which is not executable by itself, will be placed in /lib series directory. The convention is, executable files for /bin will find libraries from /lib or /lib64. The same convention applies to /usr/bin searching /usr/lib or /usr/lib64. And, the same rule for /usr/local/bin.
To complete the conversation, let me mention more directories. There are even more important directories in Unix system.
The first level is the top level, which is '/'. For '/' level, /bin, /sbin/, and /lib are the main directories for binary files. As modern systems become 64 bit CPU, modern systems include /lib64 directory. We know /bin and /sbin. These are for executable files. /lib and /lib64 are library binary files, or linkable binary files. Most of them are C libraries, which other languages will stub-in with their libc interfacing. There are two important special directories, /etc and /var. In my opinion, /etc/ is named incorrect. /etc is one of the most important directory in the system, which contains all config files for the OS. These are mostly text files. /var is variable content directory. The most popular directory is /var/log, which contains system logs. /var contains mostly data files, either in plain text or binary format. /proc, /dev, /sys won't be covered here.
The next level is the /usr level. On this level, /usr/include, /usr/bin, /usr/sbin, /usr/lib, /usr/lib64, and /usr/share will be placed. We know /usr/bin and /usr/sbin. These are for executable files. /usr/lib and /usr/lib64 can be guessed from previous level. These are linkable C libraries. (Some are written in assembly, but both asm/c are ended up elf/elf64 kind of binary format, which are treated as the same way. ) /usr/include is where C header files are placed. /usr/share will have other stuff like man pages, fonts for Graphics system, etc.
The next level is /usr/local. This is similar to /usr level. /usr/local/include, /usr/local/bin, /usr/local/sbin, /usr/local/lib, /usr/local/lib64, /usr/local/share. They behave the same as /usr level, but these directories are from my local system installation, not from the distro.
Back to our question: Where things go?
At this point, we can dig a further detail about file layout laid by yum package manager. When we want to install mysql server, (thanks to Oracle, opensource group had to rename/fork mysql to mariadb), we issue "yum install mariadb-server" on RHEL or CentOS server. In Fedora system, dnf is used instead of yum. "dnf install mariadb-server".
To look what files were installed, we can use following command. "rpm -ql" will list files in a given package. As we can see, mysql server provided /etc config, /usr/bin/ executables including the MySQL server itself(/usr/bin/mysqld_safe), mysql libraries (*.so files) under /usr/lib64 directory, document and manpages under /usr/share, and /var/lib/mysql directory for run-variable (such as mysql.sock socket file), and logs in /var/log/mariadb.
$ rpm -ql mariadb-server
/etc/logrotate.d/mariadb
/etc/my.cnf.d/mariadb-server.cnf
/run/mariadb
/usr/bin/aria_chk
/usr/bin/aria_dump_log
/usr/bin/aria_ftdump
/usr/bin/aria_pack
/usr/bin/aria_read_log
/usr/bin/innochecksum
/usr/bin/mariadb-service-convert
/usr/bin/my_print_defaults
/usr/bin/myisam_ftdump
/usr/bin/myisamchk
/usr/bin/myisamlog
/usr/bin/myisampack
/usr/bin/mysql_install_db
/usr/bin/mysql_secure_installation
/usr/bin/mysql_tzinfo_to_sql
/usr/bin/mysqld_safe
/usr/bin/replace
/usr/bin/resolve_stack_dump
/usr/bin/resolveip
/usr/bin/wsrep_sst_common
/usr/bin/wsrep_sst_mariabackup
/usr/bin/wsrep_sst_mysqldump
/usr/bin/wsrep_sst_rsync
/usr/bin/wsrep_sst_rsync_wan
/usr/bin/wsrep_sst_xtrabackup
/usr/bin/wsrep_sst_xtrabackup-v2
/usr/lib/.build-id
/usr/lib/.build-id/07
/usr/lib/.build-id/07/69bc37f26a1a41c25db627ca6e741f3674283d
/usr/lib/.build-id/0d
/usr/lib/.build-id/0d/5e64382cb9d8547a4f39e7ecb6e9230c15d2a4
/usr/lib/.build-id/13
/usr/lib/.build-id/13/9d378f787c7458ed20cca0f08725a4b46d95d6
/usr/lib/.build-id/18
/usr/lib/.build-id/18/6a7a4263fdddaa04c6d56d8fc53bbadc0b222b
/usr/lib/.build-id/1a
/usr/lib/.build-id/1a/330e5f506700544e7e83f80a006fbea60f0b44
/usr/lib/.build-id/2a
/usr/lib/.build-id/2a/1c3ed5bbdcfa8f3c59a8b1b05deabbce96299d
/usr/lib/.build-id/2b
/usr/lib/.build-id/2b/4e76a3395d841de367654ab85a917279544eae
/usr/lib/.build-id/33
/usr/lib/.build-id/33/b4f714be5c7263f95fecefca2dd38310698abe
/usr/lib/.build-id/3c
/usr/lib/.build-id/3c/57f6bbf6229fec7b31309f410cfa59d7beb437
/usr/lib/.build-id/40
/usr/lib/.build-id/40/9a5555811260c669ea0b31a058f8d30f4efb16
/usr/lib/.build-id/44
/usr/lib/.build-id/44/82b8a2fb5bccca1933b4b8fa880ca073101afe
/usr/lib/.build-id/46
/usr/lib/.build-id/46/82dfb2855b2eb003064b83670d826fbde6e81b
/usr/lib/.build-id/47
/usr/lib/.build-id/47/90d0a4ca19e94d3e78ad02eeb05bc4089e6516
/usr/lib/.build-id/47/d6829933e751e57b260bc4d97967a31c087627
/usr/lib/.build-id/4d
/usr/lib/.build-id/4d/31eee35b4eee0d8227a1dafa9fadc288664e02
/usr/lib/.build-id/4e
/usr/lib/.build-id/4e/cc3b0a86f73a81a3e3d5830e77b502bed91d31
/usr/lib/.build-id/5d
/usr/lib/.build-id/5d/ac50185e31b8abc7c6f16327c3672bf26d88e4
/usr/lib/.build-id/6f
/usr/lib/.build-id/6f/2c3669f8fdace052898056be49ab6c71204d38
/usr/lib/.build-id/71
/usr/lib/.build-id/71/feb118b050b1cc5f0877c1baa52c1b2334a04d
/usr/lib/.build-id/7e
/usr/lib/.build-id/7e/4b4db940f84e46030047474fa1f41aec479005
/usr/lib/.build-id/80
/usr/lib/.build-id/80/566468a3aff5645b767a5e33c01b23f5dafff1
/usr/lib/.build-id/81
/usr/lib/.build-id/81/465a1473bca6964e37b113a65a36ba8e36b127
/usr/lib/.build-id/85
/usr/lib/.build-id/85/9c4e8b5a76fc8634e47fb6e1a29daf8852ae80
/usr/lib/.build-id/8c
/usr/lib/.build-id/8c/e93602c48bc7741dc2bdd55e951c3410acf828
/usr/lib/.build-id/92
/usr/lib/.build-id/92/af0abffd118bcf996c2c4e481ec1c4c6755887
/usr/lib/.build-id/98
/usr/lib/.build-id/98/111fa7869cde6147379b588e1498956107c978
/usr/lib/.build-id/99
/usr/lib/.build-id/99/1d896e56841cdc26a4e298a131bd52567d8a0d
/usr/lib/.build-id/99/f16a0e66d86dc25ea303fbed84c35e4adc2183
/usr/lib/.build-id/9a
/usr/lib/.build-id/9a/b2090934eb1d9bd032bb94d9098619e5cd1442
/usr/lib/.build-id/a0
/usr/lib/.build-id/a0/2bfc59270525407437f5bf547729ba373ba177
/usr/lib/.build-id/a1/9445b256e54f196a3829aac58bf4f49139ea15
/usr/lib/.build-id/a5
/usr/lib/.build-id/a5/9c430c85514065863c75479fe59da1c94a06f5
/usr/lib/.build-id/a6
/usr/lib/.build-id/a6/c8a9ef59973e71c7a29615e08c4e1fdd5b70e4
/usr/lib/.build-id/a9
/usr/lib/.build-id/a9/4e72d1427370d03a8e109a63b6e6140ce0ab18
/usr/lib/.build-id/a9/58baafa7fe7f982ad021ce48ee35bde00d8563
/usr/lib/.build-id/b7
/usr/lib/.build-id/b7/130c3f36369abcd1d75842fc4ebbece80e03fa
/usr/lib/.build-id/b7/753b47f584a4983191b630d200a334074b682e
/usr/lib/.build-id/cc
/usr/lib/.build-id/cc/87a3e8c2f36c89c280d2692062aae3411a542e
/usr/lib/.build-id/cc/d75921ce1f4dd7ac4b3ac66ca1c1cf2c609474
/usr/lib/.build-id/d0
/usr/lib/.build-id/d0/067e264e038dbb9c4d3bbee4ca72dd12903e57
/usr/lib/.build-id/d7
/usr/lib/.build-id/d7/b5038105ded94b48755e280d81555617958a1a
/usr/lib/.build-id/d7/ba029b8a789fcca13d63bdda97756101892879
/usr/lib/.build-id/dd
/usr/lib/.build-id/dd/078cf99fab7a9691a9a1a101b21cfc5a2ad29d
/usr/lib/.build-id/de
/usr/lib/.build-id/de/7ae341fae7425fb1b8978b2449f6e50d205ac2
/usr/lib/.build-id/e0
/usr/lib/.build-id/e0/9cb5aceb9840b18587045be3cf8ee3d77b452d
/usr/lib/.build-id/e2
/usr/lib/.build-id/e2/ec917cfe902b2fe429a888116bbed6b52cfcca
/usr/lib/.build-id/e5
/usr/lib/.build-id/e5/fe58c64cd71b7a2fcd04abe029645073fd1cc0
/usr/lib/.build-id/ef
/usr/lib/.build-id/ef/f1f5c65d204ca96466a4e233456a6b91e2fd89
/usr/lib/.build-id/f1
/usr/lib/.build-id/f1/b465d2f347bd8337da0ee4312435d4da89ad82
/usr/lib/.build-id/f1/fb93f74645872fdd9e36870cd0848f5df2f62c
/usr/lib/.build-id/f3
/usr/lib/.build-id/f3/8547cd11777ed1603839ed0d10c25033f95ba7
/usr/lib/.build-id/f5
/usr/lib/.build-id/f5/4fa57dad5a3e13acc200e9b4a8b0f7cded62f1
/usr/lib/.build-id/fb
/usr/lib/.build-id/fb/6af65f1e7ad9b6654a40a58f904541c49d0dee
/usr/lib/.build-id/fe
/usr/lib/.build-id/fe/890bedf4a0381a9ab37a38af7a4c1704f06452
/usr/lib/.build-id/ff
/usr/lib/.build-id/ff/c16ecade55664771bf1e11541a0aaee5ad73ac
/usr/lib/.build-id/ff/c1ae2e0dbf80dc1715863264d7c328c106a93c
/usr/lib/systemd/system/mariadb.service
/usr/lib/systemd/system/mariadb.service.d
/usr/lib/systemd/system/mariadb.service.d/tokudb.conf
/usr/lib/systemd/system/mariadb@.service
/usr/lib/systemd/system/mariadb@bootstrap.service.d
/usr/lib/systemd/system/mariadb@bootstrap.service.d/use_galera_new_cluster.conf
/usr/lib/sysusers.d/mariadb.conf
/usr/lib/tmpfiles.d/mariadb.conf
/usr/lib64/mariadb
/usr/lib64/mariadb/INFO_BIN
/usr/lib64/mariadb/INFO_SRC
/usr/lib64/mariadb/plugin
/usr/lib64/mariadb/plugin/adt_null.so
/usr/lib64/mariadb/plugin/auth_0x0100.so
/usr/lib64/mariadb/plugin/auth_ed25519.so
/usr/lib64/mariadb/plugin/auth_gssapi.so
/usr/lib64/mariadb/plugin/auth_pam.so
/usr/lib64/mariadb/plugin/auth_socket.so
/usr/lib64/mariadb/plugin/auth_test_plugin.so
/usr/lib64/mariadb/plugin/client_ed25519.so
/usr/lib64/mariadb/plugin/daemon_example.ini
/usr/lib64/mariadb/plugin/debug_key_management.so
/usr/lib64/mariadb/plugin/dialog_examples.so
/usr/lib64/mariadb/plugin/disks.so
/usr/lib64/mariadb/plugin/example_key_management.so
/usr/lib64/mariadb/plugin/file_key_management.so
/usr/lib64/mariadb/plugin/ha_example.so
/usr/lib64/mariadb/plugin/ha_federated.so
/usr/lib64/mariadb/plugin/ha_mroonga.so
/usr/lib64/mariadb/plugin/ha_spider.so
/usr/lib64/mariadb/plugin/ha_test_sql_discovery.so
/usr/lib64/mariadb/plugin/handlersocket.so
/usr/lib64/mariadb/plugin/libdaemon_example.so
/usr/lib64/mariadb/plugin/locales.so
/usr/lib64/mariadb/plugin/metadata_lock_info.so
/usr/lib64/mariadb/plugin/mypluglib.so
/usr/lib64/mariadb/plugin/qa_auth_client.so
/usr/lib64/mariadb/plugin/qa_auth_interface.so
/usr/lib64/mariadb/plugin/qa_auth_server.so
/usr/lib64/mariadb/plugin/query_cache_info.so
/usr/lib64/mariadb/plugin/query_response_time.so
/usr/lib64/mariadb/plugin/semisync_master.so
/usr/lib64/mariadb/plugin/semisync_slave.so
/usr/lib64/mariadb/plugin/server_audit.so
/usr/lib64/mariadb/plugin/simple_password_check.so
/usr/lib64/mariadb/plugin/sql_errlog.so
/usr/lib64/mariadb/plugin/wsrep_info.so
/usr/libexec/mysql-check-socket
/usr/libexec/mysql-check-upgrade
/usr/libexec/mysql-prepare-db-dir
/usr/libexec/mysql-scripts-common
/usr/libexec/mysqld
/usr/share/doc/mariadb-server
/usr/share/doc/mariadb-server/README.mysql-cnf
/usr/share/groonga-normalizer-mysql/README.md
/usr/share/groonga-normalizer-mysql/lgpl-2.0.txt
/usr/share/groonga/COPYING
/usr/share/groonga/README.md
/usr/share/man/man1/aria_chk.1.gz
/usr/share/man/man1/aria_dump_log.1.gz
/usr/share/man/man1/aria_ftdump.1.gz
/usr/share/man/man1/aria_pack.1.gz
/usr/share/man/man1/aria_read_log.1.gz
/usr/share/man/man1/galera_new_cluster.1.gz
/usr/share/man/man1/galera_recovery.1.gz
/usr/share/man/man1/innochecksum.1.gz
/usr/share/man/man1/mariadb-service-convert.1.gz
/usr/share/man/man1/my_print_defaults.1.gz
/usr/share/man/man1/myisam_ftdump.1.gz
/usr/share/man/man1/myisamchk.1.gz
/usr/share/man/man1/myisamlog.1.gz
/usr/share/man/man1/myisampack.1.gz
/usr/share/man/man1/mysql.server.1.gz
/usr/share/man/man1/mysql_install_db.1.gz
/usr/share/man/man1/mysql_secure_installation.1.gz
/usr/share/man/man1/mysql_tzinfo_to_sql.1.gz
/usr/share/man/man1/mysqld_safe.1.gz
/usr/share/man/man1/mysqld_safe_helper.1.gz
/usr/share/man/man1/replace.1.gz
/usr/share/man/man1/resolve_stack_dump.1.gz
/usr/share/man/man1/resolveip.1.gz
/usr/share/man/man1/wsrep_sst_common.1.gz
/usr/share/man/man1/wsrep_sst_mysqldump.1.gz
/usr/share/man/man1/wsrep_sst_rsync.1.gz
/usr/share/man/man1/wsrep_sst_xtrabackup-v2.1.gz
/usr/share/man/man1/wsrep_sst_xtrabackup.1.gz
/usr/share/man/man8/mysqld.8.gz
/usr/share/mariadb/fill_help_tables.sql
/usr/share/mariadb/install_spider.sql
/usr/share/mariadb/maria_add_gis_sp.sql
/usr/share/mariadb/maria_add_gis_sp_bootstrap.sql
/usr/share/mariadb/mroonga/AUTHORS
/usr/share/mariadb/mroonga/COPYING
/usr/share/mariadb/mroonga/install.sql
/usr/share/mariadb/mroonga/uninstall.sql
/usr/share/mariadb/my-huge.cnf
/usr/share/mariadb/my-innodb-heavy-4G.cnf
/usr/share/mariadb/my-large.cnf
/usr/share/mariadb/my-medium.cnf
/usr/share/mariadb/my-small.cnf
/usr/share/mariadb/mysql_performance_tables.sql
/usr/share/mariadb/mysql_system_tables.sql
/usr/share/mariadb/mysql_system_tables_data.sql
/usr/share/mariadb/mysql_test_data_timezone.sql
/usr/share/mariadb/mysql_to_mariadb.sql
/usr/share/mariadb/policy
/usr/share/mariadb/policy/selinux
/usr/share/mariadb/policy/selinux/README
/usr/share/mariadb/policy/selinux/mariadb-server.fc
/usr/share/mariadb/policy/selinux/mariadb-server.te
/usr/share/mariadb/policy/selinux/mariadb.pp
/usr/share/mariadb/policy/selinux/mariadb.te
/usr/share/mariadb/systemd/mariadb.service
/usr/share/mariadb/systemd/mariadb@.service
/usr/share/mariadb/wsrep.cnf
/usr/share/mariadb/wsrep_notify
/var/lib/mysql
/var/log/mariadb
/var/log/mariadb/mariadb.log
