ORACLE DBA COMMANDS
1. USERADD :
useradd is a command in Linux that is used to add user accounts to your system. It makes changes to the following files:
- /etc/passwd
- /etc/shadow
- /etc/group
- /etc/gshadow
- creates a directory for new user in /home
[root@sdbt ~]# useradd tesdbuser [root@sdbt ~]# cat /etc/passwd root:x:0:0:root:/root:/bin/bash bin:x:1:1:bin:/bin:/sbin/nologin daemon:x:2:2:daemon:/sbin:/sbin/nologin adm:x:3:4:adm:/var/adm:/sbin/nologin lp:x:4:7:lp:/var/spool/lpd:/sbin/nologin sync:x:5:0:sync:/sbin:/bin/sync shutdown:x:6:0:shutdown:/sbin:/sbin/shutdown halt:x:7:0:halt:/sbin:/sbin/halt mail:x:8:12:mail:/var/spool/mail:/sbin/nologin smmsp:x:51:51::/var/spool/mqueue:/sbin/nologin tesdbuser:x:54322:54335::/home/tesdbuser:/bin/bash [root@sdbt ~]# cd /home [root@sdbt home]# ll total 4 drwx------. 3 tesdbuser 54331 92 Jun 29 16:44 krish drwx------. 22 oracle oinstall 4096 Oct 18 16:50 oracle drwx------. 3 pgbouncer pgbouncer 92 May 26 14:37 pgbouncer drwx------. 3 sdbt sdbt 78 Mar 1 2022 sdbt drwx------. 3 tesdbuser tesdbuser 92 Oct 20 17:46 tesdbuser
Creating user with comment :
[root@sdbt home]# useradd -c "this is a test user" test_user [root@sdbt home]# cat /etc/passwd|grep test_user test_user:x:54323:54336:this is a test user:/home/test_user:/bin/bash
Creating user with expiry date:
[root@sdbt home]# useradd -e 2023-11-30 test_user1 [root@sdbt home]# cat /etc/passwd|grep test_user1 test_user1:x:54324:54337::/home/test_user1:/bin/bash [root@sdbt home]# chage -l test_user1 Last password change : Oct 20, 2023 Password expires : never Password inactive : never Account expires : Nov 30, 2023 Minimum number of days between password change : 0 Maximum number of days between password change : 99999 Number of days of warning before password expires : 7
Creating user to a particular group:
[root@sdbt home]# useradd -g 0 test_user2 [root@sdbt home]# id test_user2 uid=54325(test_user2) gid=0(root) groups=0(root) [root@sdbt home]#
2. USERMOD :
usermod command or modify user is a command in Linux that is used to change the properties of a user in Linux through the command line.
After creating a user we have to sometimes change their attributes like password or login directory etc. so in order to do that we use the Usermod command.
usermod command needs to be executed only as a root user.
2.1 To add a comment for a user
[root@sdbt home]# usermod -c "this is test user" test_user2 [root@sdbt home]# cat /etc/passwd|grep test_user2 test_user2:x:54325:0:this is test user:/home/test_user2:/bin/bash
2.2 To change the expiry date of a user
[root@sdbt home]# usermod -e 2023-12-31 test_user2 [root@sdbt home]# chage -l test_user2 Last password change : Oct 20, 2023 Password expires : never Password inactive : never Account expires : Dec 31, 2023 Minimum number of days between password change : 0 Maximum number of days between password change : 99999 Number of days of warning before password expires : 7
2.3 To change user login name
[root@sdbt ~]# cat /etc/passwd|grep test_user2 test_user2:x:54325:0:this is test user:/home/test_user2:/bin/bash You have new mail in /var/spool/mail/root [root@sdbt ~]# usermod -l test_user3 test_user2 usermod: warning: /var/spool/mail/test_user2 not owned by test_user2 [root@sdbt ~]# cat /etc/passwd|grep test_user3 test_user3:x:54325:0:this is test user:/home/test_user2:/bin/bash [root@sdbt ~]#
3. USERDEL:
userdel command in Linux system is used to delete a user account and related files.
userdel -f: This option forces the removal of the specified user account. It doesn’t matter that the user is still logged in. It also forces the userdel to remove
the user’s home directory and mail spool, even if another user is using the same home directory or even if the mail spool is not owned by the specified user.
userdel -r: Whenever we are deleting a user using this option then the files in the user’s home directory will be removed along with the home directory itself and the user’s mail spool.
[root@sdbt ~]# cat /etc/passwd|grep test_user1 test_user1:x:54324:54337::/home/test_user1:/bin/bash [root@sdbt ~]# userdel -r test_user1 [root@sdbt ~]# cat /etc/passwd|grep test_user1 [root@sdbt ~]#
4. CHOWN -R:
This option is used to apply the changes recursively.
[root@sdbt ~]# cd tesdb [root@sdbt tesdb]# ll total 0 [root@sdbt tesdb]# touch test1 [root@sdbt tesdb]# ll total 0 -rw-r--r--. 1 root root 0 Oct 21 11:04 test1 [root@sdbt tesdb]# chown -R oracle:oinstall test1 [root@sdbt tesdb]# ll total 0 -rw-r--r--. 1 oracle oinstall 0 Oct 21 11:04 test1 [root@sdbt tesdb]#
5. CHGRP:
The `chgrp` command in Linux is used to change the group ownership of a file or directory.
Changing Group Ownership of a Single File
[root@sdbt ~]# ls -lrt|grep test_file -rw-r--r--. 1 root root 0 Oct 25 12:18 test_file [root@sdbt ~]# chgrp oinstall test_file [root@sdbt ~]# ls -lrt|grep test_file -rw-r--r--. 1 root oinstall 0 Oct 25 12:18 test_file [root@sdbt ~]#
Changing Group Ownership of Multiple Files
[root@sdbt tesdb]# ls -lrt total 0 -rw-r--r--. 1 oracle oinstall 0 Oct 21 11:04 test1 -rw-r--r--. 1 oracle oinstall 0 Oct 25 12:37 test2 [root@sdbt tesdb]# chgrp root test1 test2 [root@sdbt tesdb]# ls -lrt total 0 -rw-r--r--. 1 oracle root 0 Oct 21 11:04 test1 -rw-r--r--. 1 oracle root 0 Oct 25 12:37 test2 [root@sdbt tesdb]#
Using the groupname of a reference file
[root@sdbt tesdb]# ls -lrt total 0 -rw-r--r--. 1 oracle oinstall 0 Oct 21 11:04 test1 -rw-r--r--. 1 oracle oinstall 0 Oct 25 12:37 test2 -rw-r--r--. 1 root root 0 Oct 25 12:41 test3 [root@sdbt tesdb]# chgrp -R --reference=test3 test1 test2 [root@sdbt tesdb]# ls -lrt total 0 -rw-r--r--. 1 oracle root 0 Oct 21 11:04 test1 -rw-r--r--. 1 oracle root 0 Oct 25 12:37 test2 -rw-r--r--. 1 root root 0 Oct 25 12:41 test3 [root@sdbt tesdb]#
6. NETSTAT -PLUNT :
will show the Active Internet connections along with port number
[root@sdbt tesdb]# netstat -plunt Active Internet connections (only servers) Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name tcp 0 0 192.168.122.1:53 0.0.0.0:* LISTEN 1722/dnsmasq tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN 1132/sshd tcp 0 0 127.0.0.1:631 0.0.0.0:* LISTEN 1114/cupsd tcp 0 0 0.0.0.0:5432 0.0.0.0:* LISTEN 1146/postmaster tcp 0 0 127.0.0.1:25 0.0.0.0:* LISTEN 1838/sendmail: acce tcp 0 0 0.0.0.0:111 0.0.0.0:* LISTEN 667/rpcbind tcp6 0 0 :::22 :::* LISTEN 1132/sshd tcp6 0 0 ::1:631 :::* LISTEN 1114/cupsd tcp6 0 0 :::5432 :::* LISTEN 1146/postmaster tcp6 0 0 :::111 :::* LISTEN 667/rpcbind udp 0 0 192.168.122.1:53 0.0.0.0:* 1722/dnsmasq udp 0 0 0.0.0.0:67 0.0.0.0:* 1722/dnsmasq udp 0 0 0.0.0.0:111 0.0.0.0:* 667/rpcbind udp 0 0 0.0.0.0:5353 0.0.0.0:* 732/avahi-daemon: r udp 0 0 0.0.0.0:840 0.0.0.0:* 667/rpcbind udp 0 0 0.0.0.0:26548 0.0.0.0:* 732/avahi-daemon: r udp6 0 0 :::111 :::* 667/rpcbind udp6 0 0 :::840 :::* 667/rpcbind [root@sdbt tesdb]#
