5 more basic UNIX commands for troubleshooting for a Windows Guy

Recalling another blog this week, 5 CentOS commands for basic troubleshooting for a Windows guy, I had wanted to cover few more UNIX commands. These commands had come in handy recently and in the past.

1. w, for who is logged in to system? Simply type: w

Example of output:

USER     TTY      FROM              LOGIN@   IDLE   JCPU   PCPU WHAT

root     pts/0    garzafx               14:05    0.00s  0.12s  0.00s w

Administering applications requiring UNIX user logons, this command had offered a quick view of the folks being displaced with service restarts or system restarts (i.e. Init 0,1,6 or reboot).

2. man, for help from the manual. If you had needed to get assistance on a command, simply remember, type man followed by what you are looking for! Syntax had followed this example;

man man or man ip a

Example of output:

[root@localhost ~]# man man

man(1)                                                                  man(1)


man – format and display the on-line manual pages


man  [-acdfFhkKtwW]  [–path]  [-m system] [-p string] [-C config_file]

[-M pathlist] [-P pager] [-B browser] [-H htmlpager] [-S  section_list]

[section] name …


man formats and displays the on-line manual pages.  If you specify sec-

tion, man only looks in that section of the manual.  name  is  normally

the  name of the manual page, which is typically the name of a command,

function, or file.  However, if name contains  a  slash  (/)  then  man

interprets  it  as a file specification, so that you can do man ./foo.5

or even man /cd/foo/bar.1.gz.

3. cp, for copying files. With UNIX configuration files of all sorts, this command had provided quick CYA measure worthy of mentioning. The syntax that UNIX had followed:

cp oldfile.txt newfile.txt

4. mv, for renaming files. Some applications had recreated configuration files on restart. Keeping it simple for this scenario, I had suggested a move in one command;

mv oldfile.txt newfile.txt

5. pf -ef | grep –I, for searching system wide. This command had required a lot of exposition maybe; however, in avoiding verbosity and any confusion, I had thought useful mentioning just the syntax. This piped command had come up multiple times in my travels from AIX to CentOS. Years ago, I had witnessed this command shopping for crash dump files (i.e. core files). The most recent occasion had occurred with hunting down NetworkManager service.

Example of output:

[root@localhost network-scripts]# ps -ef | grep -i network

root      1454     1  0 09:34 ?        00:00:00 NetworkManager –pidfile=/var/run/NetworkManager/NetworkManager.pid

If you had remembered other commands worth mentioning, chime in. Hopefully with your next system administrative crisis with UNIX gremlins, this post had provided some guide to navigating the waters of cli.


Read More:

Download Centos 6.4 
CentOS (Wikipedia)

5 CentOS commands for basic troubleshooting for a Windows guy

Recently in configuring a third party application on CentOS, I had made some interesting notes in troubleshooting an issue on Unix. Before starting, I had understood navigating around some general commands like LS, LS –L, PWD, TOP on Solaris 9.x, ESX 5.x and Ubuntu 12.x. with a touch of VI. The work this week had helped transpose some logic in search of my CentOS Gremlin.

1. List running services at boot: chkconfig –list

In Microsoft Windows, many IT folks had launched msconfig or the registry to get a quick rundown of suspects to knife during boot. To get a list of those in CentOS, that command had been:

chkconfig –list

This command had generated a print screen of services being off or on. In my case, I had needed to stop a service.

2. Stop a service at boot: chkconfig service (on/off)

In Windows, some people had leveraged the GUI with the snap-in services.msc, unchecked a box in msconfig, or set value to 0 in the registry. Here the handy command had followed this syntax: chkconfig service on or chkconfig service off.


chkconfig NetworkManager off

NOTE: This disables network configuration service for desktops


chkconfig iptables off

NOTE: This disables the firewall

3. List running network configuration: ip a

In the M$ world, developers had made this accessible via the run command: ncpl.cpa or ipconfig /all. On the CentOS platform, to get a quick rundown of network interfaces, I had entered the following command:

ip a


[root@localhost network-scripts]# ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 16436 qdisc noqueue state UNKNOWN
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet scope host lo
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP qlen 1000
link/ether 00:19:b9:b6:90:06 brd ff:ff:ff:ff:ff:ff
inet brd scope global eth0
inet6 fe80::219:b9ff:feb6:9006/64 scope link
valid_lft forever preferred_lft forever
3: eth1: <BROADCAST,MULTICAST> mtu 1500 qdisc mq state DOWN qlen 1000
link/ether 00:19:b9:b6:90:08 brd ff:ff:ff:ff:ff:ff
4: eth1.0100@eth1: <BROADCAST,MULTICAST,M-DOWN> mtu 1500 qdisc noqueue state DOWN
link/ether 00:19:b9:b6:90:08 brd ff:ff:ff:ff:ff:ff

4. Print the routing table: netstat –rn

Sometimes in Windows, it had been important to understand the default gateway and destination for all traffic. In my case the last line entry had a misconfigured gateway.


[root@localhost network-scripts]# netstat –rn
Kernel IP routing table
Destination     Gateway         Genmask         Flags   MSS Window  irtt Iface   U         0 0          0 eth0     U         0 0          0 eth0     U         0 0          0 eth1         UG        0 0          0 eth0

5. Restarting a service: service ServiceName (stop/start/restart)

In my adventure, I had three different services requiring some manual control (i.e. NetworkManager, MySQL, network). The one exception with a different name had a different service name, MySQL with MySQLD.


service network restart

Shutting down loopback interface:                          [  OK  ]

Bringing up loopback interface:                            [  OK  ]

Bringing up interface eth0:                                [  OK  ]

Bringing up interface eth1:                                [  OK  ]

So with those commands in hand and some editing of some network configuration files, I had fixed the issue preventing an application from completing initialization. Hopefully, some of this explanation had illuminated possibilities on a starting point for working with CentOS. The more light one had saught, the less Gremlins you’ll see.


Read More:

Download Centos 6.4 
CentOS (Wikipedia)

Adding secure connectivity for remote administration of CentOS with NX Server

Having been part of IT, there had always been adventure around the next key stroke, call or email. This go around, I had wanted to take a few minutes to document some steps in getting remote connectivity to work on a flavor of Unix, CentOS. Now let me contrast this by saying, Unix’s strong suit had always been the level of customization. The question had been knowing which pieces to squeeze together for certain administrative task. On that note, here had been the steps for getting remote connectivity setup up for an install of NXServer on CentOS below.


Before proceeding, a target system had required an install of  CentOS (6.x) with all the default settings. I had performed the following steps on server and Windows 7 desktop.

  1. Logged on to CentOS server locally.
  2. Elevated permissions in terminal by typing, su
  3. Entered password  (i.e. root password, etc..)
  4. Entered, yum install nx freenx
  5. Allowed the installation to complete.
  6. Switched directories with the following command, cd /etc/nxserver
  7. Modified configuration file with VI by entering in the following command, Vi node.conf
  8. Started data insert with vi by typing, I
  9. Located the following variable and set to 1, ENABLE_PASSDB_AUTHENTICATION=”1″
  10. Pressed the ESC key.
  11. Saved the file the follow key combination, :q 
  12. Added user enter to nx server with, nxserver –adduser packetfence
  13. Generated a client key type, cat /var/lib/nxserver/home/.ssh/client.id_dsa.key
  14. Copied the results into notepad for use on your desktop, Windows 7
  15. Launched Windows NX client on Windows.
  16. nx2
  17. Modified NX client from dialog box, clicking CONFIGURE.
  18. Clicked the GENERAL tab.
  19. Selected KEY.
  20. Pasted the key from #12 into the field.
  21. Selected KDE for session for desktop
  22. kde
  23. Saved changes and attempted to logon. It failed.
  24. Went to CentOS server, entered,  service sshd restart
  25. Then followed-up with the next command, chkconfig sshd on
  26. Important, chkconfig sshd on command ensuresd that the SSH service started on boot.
  27. Relaunched the NX client and attempt to connect.This time it connected successfully.
  28. Rebooted server and verified remote login again.


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