Installing Tomcat on Centos and Ubuntu
- Searching Java 8
# Create a Centos Machine
sudo yum update
sudo yum search jdk
sudo apt-get update
sudo apt-cache search jdk
- Repeat the same process to search for tomcat
sudo yum search tomcat
sudo apt-cache search tomcat
Findout Version of the Software to be installed
- Ubuntu: Also refer a article from here
sudo apt-cache madison <package-name>
- Exercise: Try installing older version of Jenkins on ubuntu
- Try doing the same exercise on centos
Uninstalling Software from Linux
- APT:
apt-get remove <package-name>
apt-get purge <package-name>
- YUM:
yum remove <package-name>
Important References
Users and Groups in Linux
- Linux is a multi-user OS
- Since multiple users are involved, managing permissions for user w.r.t any devices/folders etc.. is must to understand/
User-Creation
- To create user in linux we have useradd and adduser
- So lets try to create user1 and user2 in both centos and ubuntu.
# become root (sudo -i)
adduser user1
useradd user2
- Observe the contents of /etc/passwd
cat /etc/passwd
-
Centos Users
-
Ubuntu Users
-
Passwd file in /etc folders shows the username, userid, groupid, home directory and default prompt
-
Useradd command behavior
- Centos:
- Creates home directory
- Password is not set
- Ubuntu:
- Doesn’t create the home directory
- Password is not set
- Centos:
-
adduser command behavior
- Centos
- Creates home directory
- Password is not set
- Ubuntu:
- Creates home directory
- Password is set when user enters password as part of the user creation
- Centos
-
Whenever a user is created , a group with same name as user name will also be created
-
groups can be created using
groupadd
& deleted usinggroup del
-
To Set Password
passwd <username>
- To set basic permissions linux adopts numbering
- Read = 4
- Write = 2
- Exectue = 1
- Now navigate to /home and execute
ls -la /home and check the permissions
# Sample
total 28
drwxr-xr-x 2 test test 4096 Dec 23 02:32 test
drwxr-xr-x 5 ubuntu ubuntu 4096 Dec 23 02:37 ubuntu
drwxr-xr-x 8 jenkins jenkins 4096 Dec 26 02:53 jenkins
drwxr-xr-x 23 root root 4096 Dec 28 02:28 ..
drwxr-xr-x 2 user1 user1 4096 Dec 28 04:01 user1
drwxr-xr-x 2 root root 4096 Dec 28 04:12 user2
drwxr-xr-x 7 root root 4096 Dec 28 04:12 .
- Lets understand permissions, basic pattern is
d<User permission in rwx><group permission in rwx><others permission in rwx>
#sample
rw- => read write => 6
r-- => read 4
r-x => read execute => 5
rwx => read write execut => 7
- Changing permissions require numbering
- Whenver user is added a unique user id (uid) is created, when the user is deleted (userdel) the user name will be removed from /etc/passwd, but the uid will not be allocated to any other user
- The users created over here are local to the machine in which they are created.
- Exercise: Examine /etc/passwd file for Jenkins Master.