10 Essential Linux Sysadmin Hacks to Boost Efficiency

Efficient Linux system administrators can dramatically reduce routine task time with a handful of proven tricks.

Tip 1: Eject an Unresponsive DVD Drive

Identify the process holding the DVD device and terminate it:

# mount /media/cdrom # cd /media/cdrom # while [ 1 ]; do echo "All your drives are belong to us!"; sleep 30; done

In another terminal run:

# eject

If the device is busy, find the owning process:

# fuser /media/cdrom

Terminate it as root:

# fuser -k /media/cdrom

Then the drive can be ejected safely.

Tip 2: Recover a Frozen Console

When the terminal becomes garbled, use the reset command (not reboot or shutdown) to restore normal output without restarting the machine.

Tip 3: Collaborative Screen Sessions

Share a screen session between two users:

# su - david # ssh posh # screen -S foo

On the second machine, attach to the same session:

# screen -x foo

Detach with Ctrl‑A D and re‑attach later using screen -x foo.

Tip 4: Reset a Forgotten Root Password (CentOS example)

Reboot, interrupt GRUB, edit the kernel line, append 1 to start in single‑user mode, then run:

# passwd

After setting a new password, reboot the system.

Tip 5: Create an SSH Backdoor

Use a publicly reachable host ( blackbox.example.com) as a relay. On the internal server ( ginger) run:

# ssh -R 2222:localhost:22 [email protected]

Keep the session open, then from the external machine connect back:

# ssh [email protected]

From there forward the connection to the internal host:

# ssh -p 2222 root@localhost

Tip 6: Remote VNC via SSH Tunnels

Start a VNC server on ginger:

# vncserver -geometry 1024x768 -depth 24 :99

Forward the VNC port through the same relay host:

# ssh -R 5999:localhost:5999 [email protected] # ssh -L 5999:localhost:5999 [email protected] # vncviewer localhost:99

Windows users can achieve the same with PuTTY port‑forwarding.

Tip 7: Measure Network Bandwidth

Compile and run iperf on both nodes, then start a server:

# /home/bob/perf/bin/iperf -s -f M

On the client:

# /home/bob/perf/bin/iperf -c ginger -P 4 -f M -w 256k -t 60

Typical results show ~112 Mbit/s on a single NIC and up to ~220 Mbit/s when bonding two NICs.

Tip 8: Command‑Line Scripting for Automation

Generate a large /etc/hosts file:

# P=1; for i in $(seq -w 200); do echo "192.168.99.$P n$i"; P=$(expr $P + 1); done >>/etc/hosts

Check memory across a cluster via SSH:

# for num in $(seq -w 200); do ssh n$num free -m | grep Mem | awk '{print $2}'; done | sort | uniq

The pipeline uses free, grep, awk, sort, and uniq to reveal uniform or differing memory sizes.

Tip 9: Console Inspection

Read the virtual console device to see what a remote user typed:

# cat /dev/vcs1

This can be faster than accessing the machine physically.

Tip 10: Random System Information Gathering

Collect CPU details:

# cat /proc/cpuinfo

Count processors:

# cat /proc/cpuinfo | grep processor | wc -l

Check disk usage:

# df -h

Inspect BIOS with dmidecode and NIC firmware with ethtool -i eth0.

Conclusion

Learning from experienced command‑line users, sharing screen sessions, reading manual pages, and constantly solving problems are the best ways to become a more efficient Linux administrator and free up time for personal interests.

Source: IBM/developerWorks Link: http://www.ibm.com/developerworks/cn/linux/l-10sysadtips/index.html