Rulam comanda:
[root@centos-lvm ~]# nslookup
-bash: nslookup: command not found
[root@centos-lvm ~]#

Vedem ca programul nu este instalat sau nu este in path-ul nostru de programe

Ne vom asigura ca acesta chiar nu este instalat.

[root@centos-lvm ~]# nslookup
-bash: nslookup: command not found
[root@centos-lvm ~]# locate nslooup
[root@centos-lvm ~]#

Daca nu afiseaza nimic inseamna ca nslookup nu este instalat.

Ok, dar cum aflam din ce pachet software face parte comanda nslookup.
Vom folosi yum pentru a lista toate pachetele care ne ofera nslookup.

[root@centos-lvm ~]# yum provides */nslookup
Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
* base: mirrors.pidginhost.com
* epel: ftp.ines.lug.ro
* extras: mirrors.pidginhost.com
* updates: mirrors.pidginhost.com
1:bash-completion-extras-2.1-11.el7.noarch : Additional programmable completions for Bash
Repo : epel
Matched from:
Filename : /usr/share/bash-completion/completions/nslookup

32:bind-utils-9.9.4-37.el7.x86_64 : Utilities for querying DNS name servers
Repo : base
Matched from:
Filename : /usr/bin/nslookup

32:bind-utils-9.9.4-38.el7_3.x86_64 : Utilities for querying DNS name servers
Repo : updates
Matched from:
Filename : /usr/bin/nslookup

32:bind-utils-9.9.4-38.el7_3.1.x86_64 : Utilities for querying DNS name servers
Repo : updates
Matched from:
Filename : /usr/bin/nslookup

32:bind-utils-9.9.4-38.el7_3.2.x86_64 : Utilities for querying DNS name servers
Repo : updates
Matched from:
Filename : /usr/bin/nslookup

zsh-5.0.2-25.el7.x86_64 : Powerful interactive shell
Repo : base
Matched from:
Filename : /usr/share/zsh/5.0.2/functions/nslookup

zsh-5.0.2-25.el7_3.1.x86_64 : Powerful interactive shell
Repo : updates
Matched from:
Filename : /usr/share/zsh/5.0.2/functions/nslookup

[root@centos-lvm ~]#

Dupa cum putea observa sunt mai multe pachete care ofera nslookup.
Dar cum il alegem?
Pai comenzile Linux se ruleaza de obicei (daca sunt instalate dintr-un store) din calea /usr/bin/.
Putem vedea ca pachetul bind-utils va instala nslookup in calea care ne intereseaza.

Apoi instalam cu:
[root@centos-lvm ~]# yum install bind-utils

Gata