Frequently Used Linux Commands for System & Oracle DBA Operations

As an Oracle DBA or Linux system administrator, we frequently perform operational tasks such as checking port usage, cleaning old files, troubleshooting network issues, and monitoring disk space.

This post documents commonly used Linux commands that are extremely helpful in day-to-day DBA activities, along with examples for better understanding.

1. How to Check Port Availability

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Using lsof

This command identifies which process is using a specific TCP port.

lsof -i tcp:8031

Sample Output:

java   24567 oracle  123u  IPv4  987654  TCP *:8031 (LISTEN)

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Using netstat

This command displays active network connections and listening ports.

netstat -putan | grep 8031

netstat -an |grep <Port_Number>

Sample Output:

tcp  0  0 0.0.0.0:8031  0.0.0.0:*  LISTEN  24567/java

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2. Renaming Multiple Characters in a File

This method is useful when you want to replace a specific word throughout a file.

Syntax

perl -pi -e 's/OLD_VALUE/NEW_VALUE/g' <FILE_NAME>

Example

perl -pi -e 's/DEV/TEST/g' initTEST.ora

This command replaces all occurrences of DEV with TEST in the file.

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3. Checking Connection Issues

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DNS Resolution Check

Used to verify hostname-to-IP resolution.

nslookup dbserver.example.com

Sample Output:

Name:    dbserver.example.com
Address: 10.x.x.x

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Oracle Listener Connectivity Check

tnsping ORCL

Sample Output:

OK (20 msec)

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4. Searching Multiple Parameters in a Single Command

Useful for validating applied Oracle patches.

$ORACLE_HOME/OPatch/opatch lsinventory | egrep -w 'PATCH1|PATCH2|PATCH3' | grep "applied on"

Sample Output:

Patch PATCH1 applied on Tue Jan 02 10:15:30 IST 2025

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5. Tar Command (Archive and Extract Files)

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Create Archive

tar -cvzf software_backup.tar.gz software_dir/

Sample Output:

software_dir/
software_dir/file1
software_dir/file2

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Extract Archive

tar -xvzf software_backup.tar.gz

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6. Nohup Command

The nohup command allows a process to continue running even after you log out.

nohup tar -cvf software_backup.tar.gz software_dir/ &

Sample Output:

[1] 23456
nohup: ignoring input and appending output to nohup.out

Monitor Running Jobs

jobs -l

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7. Deleting Old or Large Files

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List Files Older Than 5 Days

find . -type f -mtime +5

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Delete Files Older Than 5 Days

find . -type f -mtime +5 -exec rm -vf {} \;

Sample Output:

removed './old_log_01.log'
removed './old_log_02.log'

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8. Moving Old Files to Another Directory

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List Files Older Than 4 Days

find . -type f -mtime +4

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Move Files

find . -type f -mtime +4 -exec mv {} /backup/archive_dir/ \;

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9. Find Top Disk Space Consuming Files

du -sh * | sort -rh | head -n 5

Sample Output:

133G   request_01.req
104G   request_02.req
37G    request_03.req

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10. Network Connectivity Testing

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Using Netcat

nc -zv 10.x.x.x 1521

Sample Output:

Ncat: No route to host

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Using Telnet

telnet 10.x.x.x 1521

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Using Curl

curl -v telnet://10.x.x.x:1521

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11. Advanced find Command Examples

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Find Files Larger Than 1GB

find . -type f -size +1G

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Delete Log Files Older Than 7 Days

find . -name "*.log" -mtime +7 -exec rm -f {} \;

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Find Files Modified Today

find . -type f -mtime 0

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12. SCP Command (Secure Copy)

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Copy File to Remote Server

scp file_name user@remote_host:/remote/path/

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Copy Directory Recursively

scp -r source_dir user@remote_host:/remote/path/

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Copy File From Remote Server

scp user@remote_host:/remote/path/file_name /local/path/

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