Essential Linux Commands Every Backend Engineer Needs: Network, Process, and Server Resource Management

Network Management Commands

1. ping – network connectivity test

# Test basic connectivity (send 4 packets)
ping -c 4 api.example.com

# Continuous test (10 packets per second)
ping -i 0.1 -c 10 api.example.com

Use case: Verify network reachability. If ping fails, the problem is network‑level; if ping succeeds but the service is unreachable, investigate port or application configuration.

2. netstat – port and connection monitoring

# Show all listening ports
netstat -tuln

# Show a specific port (e.g., 8080)
netstat -tuln | grep :8080

# Show processes owning ports (most common)
netstat -tulnp

Use case: When an application reports "port already in use", use netstat -tulnp to locate the owning PID and decide whether to terminate the process or change the configuration.

3. curl – HTTP request testing

# Send a GET request
curl -v https://api.example.com/v1/data

# Send a POST request with JSON payload
curl -X POST -H "Content-Type: application/json" -d '{"key":"value"}' https://api.example.com/v1/data

# Save response to a file
curl -o response.json https://api.example.com/v1/data

Use case: Validate API endpoints during development or troubleshoot third‑party API calls in production.

4. traceroute – network path analysis

traceroute api.example.com

Use case: Identify bottleneck nodes when a service response is slow, distinguishing between local network problems and remote server issues.

5. ss – modern socket statistics (netstat replacement)

# Show all TCP connections
ss -tuln

# Show a specific port
ss -tuln | grep :8080

Use case: ss is faster than netstat and provides more detailed TCP state information.

Process Management Commands

1. ps – process snapshot

# List all processes (including other users)
ps aux

# Filter for a specific process
ps aux | grep java

# Show process hierarchy as a tree
ps axf

Use case: Confirm whether a service is running and view parent‑child relationships between processes.

2. top – real‑time system monitoring

top
# Inside the top UI:
#   P – sort by CPU
#   M – sort by memory
#   k – kill a process (enter PID)
#   q – quit

Use case: When a server becomes sluggish, use top to spot high‑CPU or high‑memory processes.

3. kill – terminate processes

# Terminate a specific PID
kill 12345

# Force kill if normal kill fails
kill -9 12345

# Kill by exact command line match
pkill -f "java -jar myapp.jar"

Use case: Quickly stop a misbehaving test service to free its port.

4. nohup & – run commands in background

# Run a long‑running job and ignore SIGHUP
nohup java -jar myapp.jar &

# List background jobs
jobs

# Bring a background job to the foreground
fg %1

Use case: Keep a task running after the SSH session is closed.

5. jps – Java process listing

# List all Java processes
jps

Use case: Verify that Java applications are up and running.

Server Resource Management Commands

1. df – disk space usage

# Human‑readable disk usage
df -h

Use case: Quickly check disk consumption when storage runs low.

2. du – directory size

# Human‑readable size of a directory
du -sh /var/log

# Find files larger than 100 MB
find / -type f -size +100M -exec ls -lh {} \;

Use case: Locate large directories with du -sh, then pinpoint individual large files with find.

3. free – memory usage

# Human‑readable memory summary
free -h

# Detailed memory usage in megabytes
free -m

Use case: Diagnose Java memory leaks and decide whether JVM parameters need adjustment.

4. vmstat – overall system performance

# Continuous stats, refreshed every second
vmstat 1

Use case: When overall performance degrades, vmstat shows CPU, memory, and I/O metrics to pinpoint the bottleneck.

5. iostat – I/O performance monitoring

# Detailed disk I/O statistics (3 samples, 1 s interval)
iostat -x 1 3

Use case: Identify disk I/O saturation when application read/write latency is high.

6. lsof – list open files

# Find process using a specific port
lsof -i :8080

# List processes that have opened a particular file
lsof /var/log/app.log

Use case: Before deleting a file that is in use, use lsof to see which processes hold it.

7. systemctl – service management

# Check service status
systemctl status nginx

# Restart a service
systemctl restart nginx

# Start a service
systemctl start nginx

Use case: Manage services such as Nginx or MySQL on a Linux server using standardized commands.