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The following tips help you troubleshoot hardware in Linux more quickly and easily. There are many different factors that can cause problems with Linux hardware; before you start trying to diagnose, it's wise to understand the most common problems and the ones most likely to find the cause.

Linux servers run mission-critical business applications in many different types of infrastructure, including physical machines, virtual machines, private clouds, public clouds, and hybrid clouds. It is important for Linux system administrators to understand how to manage the Linux hardware infrastructure, including software-defined features related to network and storage, Linux containers, and multiple tools on Linux servers.

It may take some time to troubleshoot and resolve hardware-related issues on Linux. Even experienced system administrators sometimes spend hours solving inexplicable hardware and software problems.

The following tips help you troubleshoot hardware in Linux more quickly and easily. There are many different factors that can cause problems with Linux hardware; before you start trying to diagnose, it's wise to understand the most common problems and the ones most likely to find the cause.

1. Quickly diagnose devices, modules, and drivers

The first step in troubleshooting is usually to display a list of hardware installed on the Linux server. You can use the ls command to get hardware details, such as lspci, lsblk, lscpu, and lsscsi. For example, this is the output of the lsblk command:

# lsblkNAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINTxvda 202:0 0 50G 0 disk ├─ xvda1 202:1 0 1M 0 part └─ xvda2 202:2 0 50G 0 part / xvdb 202:16 0 20G 0 disk └─ xvdb1 202:17 0 20G 0 part

If the ls command does not show any errors, use the initialization process (such as systemd) to check the health of the Linux server. Systemd is the most popular initialization process that starts user space and controls multiple system processes. For example, this is the output of the systemctl status command:

# systemctl status ● bastion.f347.internal State: running Jobs: 0 queued Failed: 0 units Since: Wed 2018-11-28 01:29:05 UTC 2 days ago CGroup: / ├─ 1 / usr/lib/systemd/systemd-- switched-root-- system-- deserialize 21 ├─ kubepods.slice │ ├─ kubepods-pod3881728a_f2af_11e8_af77_06af52f87498.slice │ │ │ └─ 23860 / opt/bridge/bin/bridge-- public-dir=/opt/bridge/static-- Config=/var/console-config/console-c │ │ └─ docker-a4433f0d523c7e5bc772ee4db1861e4fa56c4e63a2d48f6bc831458c2ce9fd2d.scope │ │ └─ 23639 / usr/bin/pod2. Delve into multiple logs

Dmesg allows you to figure out the errors and warnings in the latest information about the kernel. For example, this is the output of the dmesg | more command:

# dmesg | more.... [1539.027419] IPv6: ADDRCONF (NETDEV_UP): eth0: link is not ready [1539.042726] IPv6: ADDRCONF (NETDEV_UP): veth71f37018: link is not ready [1539.048706] IPv6: ADDRCONF (NETDEV_CHANGE): veth71f37018: link becomes ready [1539.055034] IPv6: ADDRCONF (NETDEV_CHANGE): eth0: link becomes ready [1539.098550] device veth71f37018 entered promiscuous mode [1541.450207] device veth71f37018 left promiscuous mode [1542.493266] SELinux: mount invalid. Same superblock, different security settings for (dev mqueue, type mqueue) [9965.292788] SELinux: mount invalid. Same superblock, different security settings for (dev mqueue, type mqueue) [9965.449401] IPv6: ADDRCONF (NETDEV_UP): eth0: link is not ready [9965.462738] IPv6: ADDRCONF (NETDEV_UP): vetheacc333c: link is not ready [9965.468942] IPv6: ADDRCONF (NETDEV_CHANGE): vetheacc333c: link becomes ready....

You can also check all the Linux system logs in the / var/log/messages file to find errors related to specific problems. If you make changes to the hardware, such as mounting additional disks or adding Ethernet network cards, it is necessary to keep a close eye on the information in real time through the tail command. For example, this is the output of the tail-f / var/log/messages command:

# tail-f / var/log/messagesDec 1 13:20:33 bastion dnsmasq [30201]: using nameserver 127.0.0.1 °53 for domain in-addr.arpaDec 1 13:20:33 bastion dnsmasq [30201]: using nameserver 127.0.0.1 °53 for domain cluster.localDec 1 13:21:03 bastion dnsmasq [30201]: setting upstream servers from DBusDec 1 13:21:03 bastion dnsmasq [30201]: using nameserver 192.199.0.2#53Dec 1 13:21:03 bastion dnsmasq [30201]: Using nameserver 127.0.0.1#53 for domain in-addr.arpaDec 1 13:21:03 bastion dnsmasq [30201]: using nameserver 127.0.0.1#53 for domain cluster.localDec 1 13:21:33 bastion dnsmasq [30201]: setting upstream servers from DBusDec 1 13:21:33 bastion dnsmasq [30201]: using nameserver 192.199.0.2#53Dec 1 13:21:33 bastion dnsmasq [30201]: using nameserver 127.0.0.1#53 for domain in-addr.arpaDec 1 13:21 : 33 bastion dnsmasq [30201]: using nameserver 127.0.0.1#53 for domain cluster.local3. Analyze network function

You may have thousands of cloud native applications serving business services in a complex network environment; these may include virtualization, multi-cloud, and hybrid clouds. This means that you should analyze whether the network connection is working properly, which is part of troubleshooting. Practical commands for analyzing network functions in Linux servers include ip addr, traceroute, nslookup, dig, ping, and so on. For example, this is the output of the ip addr show command:

# ip addr show1:lo: mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000 link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 inet 127.0.0.1/8 scope host lo valid_lft forever preferred_lft forever inet6:: 1/128 scope host valid_lft forever preferred_lft forever2:eth0: mtu 9001 qdisc mq state UP group default qlen 1000 link/ether 06:af:52:f8:74:98 brd Ff:ff:ff:ff:ff:ff inet 192.199.0.169/24 brd 192.199.0.255 scope global noprefixroute dynamic eth0 valid_lft 3096sec preferred_lft 3096sec inet6 fe80::4af:52ff:fef8:7498/64 scope link valid_lft forever preferred_lft forever3:docker0: mtu 1500 qdisc noqueue state DOWN group default link/ether 02:42:67:fb:1a:a2 brd ff:ff:ff:ff:ff:ff inet 172.17.0. 1/16 scope global docker0 valid_lft forever preferred_lft forever inet6 fe80::42:67ff:fefb:1aa2/64 scope link valid_lft forever preferred_lft forever.... Concluding remarks

Linux hardware troubleshooting requires a solid knowledge of how to use powerful command-line tools and interpret system logs. You should also know how to diagnose kernel space, where you can find the root causes of many hardware problems. Keep in mind that hardware problems in Linux can be caused by many different aspects, including devices, modules, drivers, BIOS, networking, and even legacy hardware failures.

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