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65 useful CLI tools for Linux system admins

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#1 OFFLINE   securitybreach


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Posted 08 December 2014 - 03:17 PM


System administrators (sysadmins) are responsible for day-to-day operations of production systems and services. One of the critical roles of sysadmins is to ensure that operational services are available round the clock. For that, they have to carefully plan backup policies, disaster management strategies, scheduled maintenance, security audits, etc. Like every other discipline, sysadmins have their tools of trade. Utilizing proper tools in the right case at the right time can help maintain the health of operating systems with minimal service interruptions and maximum uptime.

This article will present some of the most popular and useful CLI tools recommended for sysadmins in their day to day activities. If you would like to recommend any useful tool which is not listed here, don't forget to share it in the comment section.

Network Tools

1. ping: Check end-to-end connectivity (RTT delay, jitter, packet loss) of a remote host with ICMP echo/reply. Useful to check system status and reachability.
2. hping: Network scanning and testing tool that can generate ICMP/TCP/UDP ping packets. Often used for advanced port scanning, firewall testing, manual path MTU discovery and fragmentation testing.
3. traceroute: Discover a layer-3 forwarding path from a local host to a remote destination host with TTL-limited ICMP/UDP/TCP probe packets. Useful to troubleshoot network reachability and routing problems.
4. mtr: A variation of traceroute which characterizes per-hop packet loss/jitter with running statistics. Useful to characterize routing path delays.
5. netcat/socat: A swiss army knife of TCP/IP networking, allowing to read/write byte streams over TCP/UDP. Useful to troubleshoot firewall policies and service availability.
6. dig: DNS troubleshooting tool that can generate forward queries, reverse queries, find authoritative name servers, check CNAME, MX and other DNS records. Can be instructed to query a specific DNS server of your choosing.
7. nslookup: Another DNS checking/troubleshooting tool. Works with all DNS queries and records. Can query a particular DNS server.
8. dnsyo: A DNS testing tool which checks DNS propagation by performing DNS lookup from over a number of open resolvers located across 1,500 different networks around the world.
9. lsof: Show information about files (e.g., regular files, pipes or sockets) which are opened by processes. Useful to monitor processes or users in terms of their open network connections or opened files.
10. iftop: A ncurses-based TUI utility that can be used to monitor in real time bandwidth utilization and network connections for individual network interfaces. Useful to keep track of bandwidth hogging applications, users, destinations and ports.
11. netstat: A network statistics utility that can show status information and statistics about open network connections (TCP/UDP ports, IP addresses), routing tables, TX/RX traffic and protocols. Useful for network related diagnosis and performance tuning.
12. tcpdump: A popular packet sniffer tool based on libpcap packet capture library. Can define packet capturing filters in Berkeley Packet Filters format........

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