RHEL / CentOS Linux install and activate Bash completion

Packages to install and enable Bash completion on CentOS/RHEL

You need to install two packages:

1. bash-completion: Programmable completion for Bash
2. bash-completion-extras : Additional programmable completions for Bash (only for CentOS/RHEL/Oracle/SL v7.x)

RHEL / CentOS Linux install and activate Bash completion

First, turn on the EPEL repo on a CentOS/RHEL version 6 (if you are using CentOS/RHEL 7.x, see this page to turn on EPEL repo) and type the following yum command to install bash-completion package:
# yum install bash-completion
OR
# yum install bash-completion bash-completion-extras
Sample outputs:

Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
 * base: ftp.iitm.ac.in
 * epel: ftp.cuhk.edu.hk
 * extras: ftp.iitm.ac.in
 * updates: ftp.iitm.ac.in
Resolving Dependencies
--> Running transaction check
---> Package bash-completion.noarch 1:2.1-6.el7 will be installed
---> Package bash-completion-extras.noarch 1:2.1-11.el7 will be installed
--> Finished Dependency Resolution
 
Dependencies Resolved
 
=======================================================================================================
 Package                            Arch               Version                  Repository        Size
=======================================================================================================
Installing:
 bash-completion                    noarch             1:2.1-6.el7              base              85 k
 bash-completion-extras             noarch             1:2.1-11.el7             epel             123 k
 
Transaction Summary
=======================================================================================================
Install  2 Packages
 
Total download size: 208 k
Installed size: 648 k
Is this ok [y/d/N]: y
Downloading packages:
(1/2): bash-completion-2.1-6.el7.noarch.rpm                                     |  85 kB  00:00:03     
(2/2): bash-completion-extras-2.1-11.el7.noarch.rpm                             | 123 kB  00:00:07     
-------------------------------------------------------------------------------------------------------
Total                                                                   26 kB/s | 208 kB  00:00:07     
Running transaction check
Running transaction test
Transaction test succeeded
Running transaction
  Installing : 1:bash-completion-2.1-6.el7.noarch                                                  1/2 
  Installing : 1:bash-completion-extras-2.1-11.el7.noarch                                          2/2 
  Verifying  : 1:bash-completion-extras-2.1-11.el7.noarch                                          1/2 
  Verifying  : 1:bash-completion-2.1-6.el7.noarch                                                  2/2 
 
Installed:
  bash-completion.noarch 1:2.1-6.el7             bash-completion-extras.noarch 1:2.1-11.el7            
 
Complete!

Fedora Linux user type the following dnf command:
$ sudo dnf install bash-completion

Related: How to install and enable Bash auto completion in Fedora Linux

How do I use bash Autocomplete feature?

Then exits a login shell / ssh session and log back in using the following command:
# logout
Open a terminal or log in using ssh:
$ ssh nixcraft@server1.cyberciti.biz
Alternatively, use the following command to source completion code for bash:
$ . /etc/bash_completion
OR
$ source /etc/bash_completion
For newer version try:
$ source /etc/profile.d/bash_completion.sh

Usage examples

You need to simply press [TAB] key. The syntax is:

command [TAB]
command arg[TAB][TAB]
man da[TAB]

rpm usage

Type the following command (type rpm -qi ph followed by [TAB]):

$ rpm -qi ph[TAB][TAB]
php         php-cli     php-common  php-devel   php-imap

yum usage

Type the following command:

$ yum [TAB][TAB]
--assumeyes        --enableplugin     list               search
--cacheonly        --enablerepo       makecache          --setopt
check              --errorlevel       --nogpgcheck       shell
check-update       --exclude          --noplugins        --showduplicates
clean              groupinfo          --obsoletes        --skip-broken
--color            groupinstall       provides           --tolerant
--config           grouplist          --quiet            update
--debuglevel       groupremove        --randomwait       upgrade
deplist            help               reinstall          --verbose
--disableexcludes  --help             --releasever       version
--disableplugin    history            remove             --version
--disablerepo      info               repolist           
distro-sync        install            resolvedep         
downgrade          --installroot      --rpmverbosity 

To search a package called lsof:
$ yum se[TAB] lsof
Or search and install on fly:

# yum in[TAB] ls[TAB]
lshell.noarch            lslk-debuginfo.x86_64    lsscsi-debuginfo.x86_64
lshw-gui.x86_64          lslk.x86_64              lsscsi.x86_64
lshw.x86_64              lsof-debuginfo.x86_64    lsyncd.x86_64

cryptsetup usage

Linux Unified Key Setup-on-disk-format (LUKS) allows you to encrypt whole disks and you can use cryptsetup command to mount or remount encrypted partition:
cryptsetup [TAB] luksOpen /dev/md[TAB]
Sample outputs:

Fig.01: cryptsetup on RHEL based system

A list of all commands supported by Autocomplete feature

Type the following command:
$ cd /etc/bash_completion.d
$ ls
Sample outputs:

autoconf       gpg2               ntpdate           shadow
automake       gzip               open-iscsi        smartctl
bash-builtins  iconv              openssl           sqlite3
bind-utils     iftop              perl              ssh
brctl          ifupdown           pkg-config        strace
bzip2          info               pm-utils          subscription-manager
chkconfig      ipmitool           postfix           tar
configure      iproute2           procps            tcpdump
coreutils      iptables           python            util-linux
cpio           lsof               quota-tools       wireless-tools
crontab        lvm                redefine_filedir  xmllint
cryptsetup     lzma               rfkill            xmlwf
dd             make               rpm               xz
dhclient       man                rsync             yum.bash
e2fsprogs      mdadm              scl.bash          yum-utils.bash
findutils      module-init-tools  service
getent         net-tools          sh

Conclusion

We explained how to install and use the bash-completion package under RHEL and CentOS Linux. For more info see this page.