How to: Basic Bash Administration Tools On Linux (df, fdisk, top, free, iostat, ifconfig, sensors, stat, nmap, and netstat)
June 29, 2015 by Andrew Mora ( 6 ) under VPS Hosting
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Verified and Tested 02/26/15
Introduction
This tutorial is a brief rundown of the BASH shell commands and tools that come in handy for the Linux administrator. Focus more on tools for administration, as opposed to the basic usage of Linux-based Operating Systems. While this article is being written in the context of distros based on RHEL 4+ and Debian 6+, many of these commands may also be found on BSD, FreeBSD, any other Unix systems. Depending on your Operating system, each command’s flag may differ or may not exist for the respective Operating System.
In This Article
- Prerequisites
- Basic Bash Administration Tools
- Find out how much hard drive space I have left | Command: df
- List my available hard drives | Command: fdisk
- View my systems resources(running tasks, CPU utilization) | Command: top
- View my systems memory utilization | Command: free
- View my systems disk activity | Command: iostat
- View my network interfaces and IP's | Command: ifconfig
- View my hardware's temperature readings | Command: sensors
- Get permission level of a file/directory | Command: stat
- Find what ports are open on a remote/local host | Command: nmap
- Find out what ports my server is listening on | Command: netstat
Prerequisites
RHEL 4+ and Debian 6+ based Operating Systems, including CentOS and Ubuntu. If you do not have a server, you can start up a reliable Linux server from Atlantic.Net in under 30 seconds.
Basic Bash Administration Tools
I will be providing a Need coupled with the BASH command that can satisfy this need. Keep in mind that each command may have many more functions and command-line options available than the examples I’ll show below. I’ll be sticking to the basic commands that attain the bare minimum output you desire. I encourage all of you to read the manual page for each command.
I need to:
Find out how much hard drive space I have left | Command: df
# df -h Filesystem Size Used Avail Use% Mounted on /dev/sda1 79G 2.2G 73G 3% / tmpfs 939M 0 939M 0% /dev/shm
List my available hard drives | Command: fdisk
# fdisk -l Disk /dev/sda: 85.9 GB, 85899345920 bytes 255 heads, 63 sectors/track, 10443 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x00015f65 Device Boot Start End Blocks Id System /dev/sda1 1 10444 83884032+ 83 Linux
View my systems resources(running tasks, CPU utilization) | Command: top
# top
top - 10:44:56 up 101 days, 25 min, 1 user, load average: 0.00, 0.01, 0.00
Tasks: 99 total, 1 running, 98 sleeping, 0 stopped, 0 zombie
Cpu(s): 0.1%us, 0.0%sy, 0.0%ni, 99.8%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st
Mem: 1922380k total, 1627448k used, 294932k free, 164252k buffers
Swap: 0k total, 0k used, 0k free, 1267812k cached
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
8655 root 20 0 15032 1068 808 R 2.0 0.1 0:00.01 top
1 root 20 0 19232 1420 1140 S 0.0 0.1 0:35.85 init
2 root 20 0 0 0 0 S 0.0 0.0 0:00.00 kthreadd
3 root RT 0 0 0 0 S 0.0 0.0 0:02.20 migration/0
4 root 20 0 0 0 0 S 0.0 0.0 0:02.05 ksoftirqd/0
5 root RT 0 0 0 0 S 0.0 0.0 0:00.00 migration/0
6 root RT 0 0 0 0 S 0.0 0.0 0:20.04 watchdog/0
View my systems memory utilization | Command: free
# free -m
total used free shared buffers cached
Mem: 1877 1589 288 0 160 1238
-/+ buffers/cache: 190 1686
Swap: 0 0 0
View my systems disk activity | Command: iostat
# iostat 2
Linux 2.6.32-431.el6.x86_64 (nginxs) 05/11/2015 _x86_64_ (2 CPU)
avg-cpu: %user %nice %system %iowait %steal %idle
0.11 0.00 0.05 0.02 0.00 99.83
Device: tps Blk_read/s Blk_wrtn/s Blk_read Blk_wrtn
sda 0.54 0.10 35.16 863199 306833368
avg-cpu: %user %nice %system %iowait %steal %idle
1.00 0.00 0.25 0.25 0.00 98.50
Device: tps Blk_read/s Blk_wrtn/s Blk_read Blk_wrtn
sda 5.00 0.00 88.00 0 176
View my network interfaces and IP’s | Command: ifconfig
# ifconfig
eth0 Link encap:Ethernet HWaddr 00:00:D1:D0:61:AF
inet addr:209.208.xx.xxx Bcast:209.208.xx.xxx Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:6414823 errors:0 dropped:0 overruns:0 frame:0
TX packets:6864133 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:1325544537 (1.2 GiB) TX bytes:1155254908 (1.0 GiB)
eth1 Link encap:Ethernet HWaddr 00:00:0A:D0:61:AF
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:296071 errors:0 dropped:0 overruns:0 frame:0
TX packets:5 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:13464542 (12.8 MiB) TX bytes:398 (398.0 b)
lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
inet6 addr: ::1/128 Scope:Host
UP LOOPBACK RUNNING MTU:16436 Metric:1
RX packets:9813 errors:0 dropped:0 overruns:0 frame:0
TX packets:9813 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:775658 (757.4 KiB) TX bytes:775658 (757.4 KiB)
View my hardware’s temperature readings | Command: sensors
# sensors coretemp-isa-0000 Adapter: ISA adapter Core 0: +39.0°C (high = +76.0°C, crit = +100.0°C) coretemp-isa-0001 Adapter: ISA adapter Core 1: +39.0°C (high = +76.0°C, crit = +100.0°C) it8718-isa-0290 Adapter: ISA adapter in0: +1.07 V (min = +0.00 V, max = +4.08 V) in1: +1.92 V (min = +0.00 V, max = +4.08 V) in2: +3.31 V (min = +0.00 V, max = +4.08 V) in3: +2.91 V (min = +0.00 V, max = +4.08 V) in4: +0.34 V (min = +0.00 V, max = +2.10 V) in5: +4.08 V (min = +0.00 V, max = +4.08 V) ALARM in6: +4.08 V (min = +0.00 V, max = +4.08 V) ALARM in7: +3.15 V (min = +0.00 V, max = +4.08 V) Vbat: +3.25 V fan1: 1231 RPM (min = 0 RPM) fan2: 1268 RPM (min = 0 RPM) temp1: -55.0°C (low = +127.0°C, high = +127.0°C) sensor = thermistor temp2: -2.0°C (low = +127.0°C, high = +127.0°C) sensor = thermistor temp3: +20.0°C (low = +127.0°C, high = +127.0°C) sensor = thermal diode
Get permission level of a file/directory | Command: stat
# stat -c '%a' /home/testfile.txt 644
Find what ports are open on a remote/local host | Command: nmap
NOTE: You’ll likely have to install the nmap package from your YUM/APT package manager.
# nmap -p- localhost Starting Nmap 5.51 ( http://nmap.org ) at 2015-05-11 11:07 EDT Failed to find device eth1 which was referenced in /proc/net/route Nmap scan report for localhost (127.0.0.1) Host is up (0.000011s latency). Other addresses for localhost (not scanned): 127.0.0.1 Not shown: 65528 closed ports PORT STATE SERVICE 21/tcp open ftp 22/tcp open ssh 25/tcp open smtp 80/tcp open http 139/tcp open netbios-ssn 445/tcp open microsoft-ds 9000/tcp open cslistener Nmap done: 1 IP address (1 host up) scanned in 1.52 seconds
Find out what ports my server is listening on | Command: netstat
# netstat -tulnp Active Internet connections (only servers) Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name tcp 0 0 0.0.0.0:139 0.0.0.0:* LISTEN 5573/smbd tcp 0 0 0.0.0.0:80 0.0.0.0:* LISTEN 29209/nginx tcp 0 0 0.0.0.0:21 0.0.0.0:* LISTEN 3557/vsftpd tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN 18608/sshd tcp 0 0 127.0.0.1:25 0.0.0.0:* LISTEN 9400/master tcp 0 0 0.0.0.0:445 0.0.0.0:* LISTEN 5573/smbd tcp 0 0 127.0.0.1:9000 0.0.0.0:* LISTEN 28996/php-fpm tcp 0 0 :::139 :::* LISTEN 5573/smbd tcp 0 0 :::22 :::* LISTEN 18608/sshd tcp 0 0 ::1:25 :::* LISTEN 9400/master tcp 0 0 :::445 :::* LISTEN 5573/smbd udp 0 0 209.208.x.x:137 0.0.0.0:* 5592/nmbd udp 0 0 209.208.x.x:137 0.0.0.0:* 5592/nmbd udp 0 0 0.0.0.0:137 0.0.0.0:* 5592/nmbd udp 0 0 209.208.x.x:138 0.0.0.0:* 5592/nmbd udp 0 0 209.208.x.x:138 0.0.0.0:* 5592/nmbd udp 0 0 0.0.0.0:138 0.0.0.0:* 5592/nmbd udp 0 0 0.0.0.0:1194 0.0.0.0:* 12988/openvpn
Thank you for following along with this guide on Basic Bash Administration Tools. I hope you enjoyed this guide; please check back for more updates.
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