Posts Tagged ‘web interface’

Mount remote Linux SSHFS Filesystem harddisk on Windows Explorer SWISH SSHFS file mounter and a short evaluation on what is available to copy files to SSHFS from Windows PC

Monday, February 22nd, 2016

Reading Time: 6 minutes

swish-mount-and-copy-files-from-windows-to-linux-via-sshfs-mount

I'm forced to use Windows on my workbook and I found it really irritating, that I can't easily share files in a DropBox, Google Drive, MS OneDrive, Amazon Storage or other cloud-storage free remote service. etc.
I don't want to use DropBox like non self-hosted Data storage because I want to keep my data private and therefore the only and best option for me was to make possible share my Linux harddisk storage
dir remotely to the Windows notebook.

I didn't wanted to setup some complex environment such as Samba Share Server (which used to be often a common option to share file from Linux server to Windows), neither wanted to bother with  installing FTP service and bother with FTP clients, or configuring some other complex stuff such as WebDav – which BTW is an accepted and heavily used solution across corporate clients to access read / write files on a remote Linux servers.
Hence, I made a quick research what else besides could be used to easily share files and data from Windows PC / notebook to a home brew or professional hosting Linux server.

It turned out, there are few of softwares that gives a similar possibility for a home lan small network Linux / Windows hybrid network users such, here is few of the many:

  • SyncThingSyncthing is an open-source file synchronization client/server application, written in Go, implementing its own, equally free Block Exchange Protocol. The source code's content-management repository is hosted on GitHub

     

     

     

     

     

    syncthing-logo

  • OwnCloud – ownCloud provides universal access to your files via the web, your computer or your mobile devices

     

     

     

     

     

    owncloud-logo

  • Seafile – Seafile is a file hosting software system. Files are stored on a central server and can be synchronized with personal computers and mobile devices via the Seafile client. Files can also be accessed via the server's web interface


seafile-client-in-browser

I've checked all of them and give a quick try of Syncthing which is really easy to start, just download the binary launch it and configure it under https://Localhost:8385 URL from a browser on the Linux server.
Syncthing seemed to be nice and easy to configure solution to be able to Sync files between Server A (Windows) and Server B(Linux) and guess many would enjoy it, if you want to give it a try you can follow this short install syncthing article.
However what I didsliked in both SyncThing and OwnCloud and Seafile and all of the other Sync file solutions was, they only supported synchronization via web and didn't seemed to have a Windows Explorer integration and did required
the server to run more services, posing another security hole in the system as such third party softwares are not easily to update and maintain.

Because of that finally after rethinking about some other ways to copy files to a locally mounted Sync directory from the Linux server, I've decided to give SSHFS a try. Mounting SSHFS between two Linux / UNIX hosts is
quite easy task with SSHFS tool

In Windows however the only way I know to transfer files to Linux via SSHFS was with WinSCP client and other SCP clients as well as the experimental:

As well as few others such as ExpandDrive, Netdrive, Dokan SSHFS (mirrored for download here)
I should say that I first decided to try copying few dozen of Gigabyte movies, text, books etc. using WinSCP direct connection, but after getting a couple of timeouts I was tired of WinSCP and decided to look for better way to copy to remote Linux SSHFS.
However the best solution I found after a bit of extensive turned to be:

SWISH – Easy SFTP for Windows

Swish is very straight forward to configure compared to all of them you download the .exe which as of time of writting is at version 0.8.0 install on the PC and right in My Computer you will get a New Device called Swish next to your local and remote drives C:/ D:/ , USBs etc.

swish-new-device-to-appear-in-my-computer-to-mount-sshfs

As you see in below screenshot two new non-standard buttons will Appear in Windows Explorer that lets you configure SWISH

windows-mount-sshfs-swish-add-sftp-connection-button-screenshot

Next and final step before you have the SSHFS remote Linux filesystem visible on Windows Xp / 7 / 8 / 10 is to fill in remote Linux hostname address (or even better fill in IP to get rid of possible DNS issues), UserName (UserID) and Direcory to mount.

swish-new-fill-in-dialog-to-make-new-linux-sshfs-mount-directory-possible-on-windows

Then you will see the SSHFS moutned:

swish-sshfs-mounted-on-windows

You will be asked to accept the SSH host-key as it used to be unknown so far

swish-mount-sshfs-partition-on-windows-from-remote-linux-accept-key

That's it now you will see straight into Windows Explorer the remote Linux SSHFS mounted:

remote-sshfs-linux-filesystem-mounted-in-windows-explorer-with-swish

Once setupped a Swish connection to copy files directly to it you can use the Send to Embedded Windows dialog, as in below screenshot

swish-send-to-files-windows-screenshot

The only 3 problem with SWISH are:

1. It doesn't support Save password, so on every Windows PC reboot when you want to connect to remote Linux SSHFS, you will have to retype remote login user pass.
Fron security stand point this is not such a bad thing, but it is a bit irritating to everytime type the password without an option to save permanently.
The good thing here is you can use Launch Key Agent
as visible in above screenshot and set in Putty Key Agent your remote host SSH key so the passwordless login will work without any authentication at
all however, this might open a security hole if your Win PC gets infected by virus, which might delete something on remote mounted SSHFS filesystem so I personally prefer to retype password on every boot.

2. it is a bit slow so if you're planning to Transfer large amounts of Data as hundreds of megabytes, expect a very slow transfer rate, even in a Local  10Mbit Network to transfer 20 – 30 GB of data, it took me about 2-3 hours or so.
SWISH is not actively supported and it doesn't have new release since 20th of June 2013, but for the general work I need it is just perfect, as I don't tent to be Synchronizing Dozens of Gigabytes all the time between my notebook PC and the Linux server.

3. If you don't use the established mounted connection for a while or your computer goes to sleep mode after recovering your connection to remote Linux HDD if opened in Windows File Explorer will probably be dead and you will have to re-enable it.

For Mac OS X users who want to mount / attach remote directory from a Linux partitions should look in fuguA Mac OS X SFTP, SCP and SSH Frontend

I'll be glad to hear from people on other good ways to achieve same results as with SWISH but have a better copy speed while using SSHFS.

Howto install GeoTrust RapidSSL certificate on Debian Lenny / Squeeze / Wheezy Linux

Thursday, March 25th, 2010

Reading Time: 5 minutes
I faced the task of generating official Validated SSL Certificates by in mydaily duties as a System Administrator at cadiaholding.com . Though generating self-signedSSL certificate is comparatively easy task. It was a pain in the ass setting Apache version 2.2.9-10+lenny6to correctly serve pages through https:// protocol over openssl version 0.9.8g-15+lenny6.I’ll try to go through the whole process of Generating the certificate in order to help some other Debianusers out there to face less setbacks in such a simple task as installing a Trusted SSL Certificate issued(bought) by RapidSSL. Even though this article will mostly deal with SSL certificate issued by RapidSSL,it should be not a problem to apply this methodogy with Verisign or some of the other Geotrust issuedSecure Socket Layer certificates.

In generating the Validated certficate I used enom which is a domain name,ssl certificates, email and hosting company whole-saler.
Fron emon’s website after logging in and using the web interface, there are two major things required to fill inin order to issue your Trusted SSL certificate.

1. Fill in in a form a CSR file, this is usually generated on the Linux server using the openssl.
To issue the CSR file required by Enom use the following commands:

a. First we generate an DES3 RSA encrypted key which we will use next to generate the opeensl CSR file required by ENOM.
debian:~# /usr/bin/openssl genrsa -des3 -out www.domain.com.key 2048
Enter pass phrase for www.domain.com.key:

You’ll be required to fill in a pass-phrase that will be later be required to fill in before Apache servers starts or restarts,so make sure you fill something you either remember or you keep the password stored in a file.
You have to change also the www.domain.com.key in accordance with your domain name.
Now as we already have a proper generated DES3 RSA key afterwards it’s necessery to generate the CSR file with the openssl command line frontend.
So here is how:

debian:~# /usr/bin/openssl req -new -key /home/hipo/www.domain.com.key -out /home/hipo/www.domain.com.csr

Again in the above example change all the paths and file names as you wish.
It’s necessery that the end user fill in a number of questions related to the Certificate Signing Request.
Herein I’ll list what kind of prompts will emerge after executing the above command:

Enter pass phrase for /home/hipo/www.domain.com.key:
You are about to be asked to enter information that will be incorporated
into your certificate request.
What you are about to enter is what is called a Distinguished Name or a DN.
There are quite a few fields but you can leave some blank
For some fields there will be a default value,
If you enter '.', the field will be left blank.
-----
Country Name (2 letter code) [AU]:
State or Province Name (full name) [Some-State]:
Locality Name (eg, city) []:
Organization Name (eg, company) [Internet Widgits Pty Ltd]:
Organizational Unit Name (eg, section) []:
Common Name (eg, YOUR name) []:
Email Address []:
Please enter the following 'extra' attributes
to be sent with your certificate request
A challenge password []:
An optional company name []:

Note that you’ll hav eto fill in the pass phrase previously entered during the generation of the www.domain.com.key file.
In case if you’d like to read more thoroughly on the subject of howto create a Certificate Signing Request or (CSR) as we called it on multiple times, you can read About Certificate Signing Request (CSR) Generation Instructions – Apache SSL more in depth here

2. Hopefully following the above instructions you’ll now have a file named www.domain.csrJust open the www.domain.scr and copy paste it’s content to the ENOM website CSR * webform.

3. Further on select your Webserver type on Enom’s website:In our case we have to select Apache + ApacheSSL

4. What follows next is filling in your company contact information This is also required for proper certificate generation, you have to think twice before you fill in this data, take a note this can’t be changed later on without issuing a brand SSL new certificate.

Apart from the 3 major above requirements to fill in Enom there are some few more radio buttons to use to make some selections according to your personal preferences, however I won’t take time to dig in that and I’ll leave this to you.
After all the above is fulfilled you’ll have to submit your certificate details and choose an email address to which you will receive in a minute a RapidSSL Certificate Request Confirmation

Following a link from the email, will show you some basic information about the certificate about to be generated. That’s your final chance to cancel the issued Trusted Certificated.
If you’re absolutely sure the information about to enter the certificate is correct then you’ll have to follow a link and approve the certificate.

You’ll be informed that you’ll receive your certificate either through Certifier website (e.g. Enom’s website) or via another email.
I thought it’s more probable I receive it via email but anyways I was wrong. More thank 4 hours has passed since the certificate was issued and is available via Enom’s interface but I haven’t received nothing on my mail.
Therefore my friendly advice is to check about your brand new shiny Trusted Certificate on Emom’s website. I had mine ready in about 10 minutes after the CSR was issued.

Assuming that you’ve succesfully obtained the SSL Trusted certificate from RapidSSL what follows is setting up the certificate.
Initially I tried using documentation from RapidSSL website called Installing your SSL Certificate / Web Server Certificate / Secure Server Certificate from RapidSSL.com
I tried to configure one of my Virtualhost as shown in their example inserting in my /etc/apache/sites-available/www.domain.com file, few directives within the VirtualHost something like the shown below

SSLEngine on
# domain.com.crt cointains the Trusted SSL certificate generated and obtained by you from RapidSSL
SSLCertificateFile /etc/apache2/ssl/www.domain.com.crt
# www.domain.com.key contains the file used to generate the CSR file as described earlier in this post
SSLCertificateKeyFile /etc/apache2/ssl/www.domain.com.key

It is also possible insetad of using the SSLCertificateFile and SSLCertificateKeyFile directvies directives in Apache config to use:

 

Another alternative is to use

SSLCertificateFile /etc/ssl/certs/your-domain-name.crt
SSLCertificateKeyFile /etc/ssl/certs/your-domain-name.key
SSLCACertificateFile /etc/ssl/certs/gd_bundle.crt

The key file is the one generated earlier on the server and handed to the SSL regisrar, the files:

your-domain-name.crt and gd_bundle.crt files are provided by RapidSSL or from whatever SSL registrater the SSL was purchased.

After trying the above configuration and restarting apache with:

/etc/init.d/apache2 restart

Apache failed to start, it might be helpful to somebody out there the error I had in my apache error.log:
The error.log red the following:

[warn] RSA server certificate is a CA certificate (BasicConstraints: CA == TRUE !?)

After some 30 minutes or an hour of Googling on the error I came to the conclusion that the error is caused, becauseApache is supposed to work with .PEM files instead of the classical .CRT and .KEY files asnormally approached in most of the other Unix operating systems.

It took me a bit more of reading on the internet to find out that actually the .pem files so widely adopted in Debian simply contain both the www.domain.com.key file and the www.domain.com.crt key simply pasted one after another, this I also observed from the default Apache self-signed certificate that I believe comes with debian /etc/apache2/ssl/apache.pem .
So I copied both the content of my www.domain.com.key and www.domain.com.crt and store it in one file:
/etc/apache2/ssl/www.domain.com.pem

Also the following configuration:
SSLEngine on
SSLCertificateFile /etc/apache2/ssl/www.domain.com.pem

had to go in your
/etc/apache2/sites-enabled/www.domain.com

Last thing that’s left is to restart your Apache;

/etc/init.d/apache2 restart

Apache will prompt you for your certificate password entered by you during the www.domain.com.key generation. Type your password and with a bit of luck and hopefully with God’s help you’ll be having a Trusted Certificate on your webserver.

Last step is to check if the certificate is okay accessing your domain https://www.domain.com.

Well this is the end of the article, hope you enjoy.If you do please leave your comments, any corrections are also welcomed 🙂

Linux: Add routing from different class network A (192.168.1.x) to network B (192.168.10.x) with ip route command

Friday, July 12th, 2013

Reading Time: 2 minutes

adding routing from one network to other linux with ip route

I had a Linux router which does NAT for a local network located behind a CISCO router receiving internet via its WAN interface routing traffic  to Linux with IP 192.168.1.235. The Linux router has few network interfaces and routes traffic for networks; 192.168.1.0/24 and 192.168.10.0/24. Another Linux with IP 192.168.1.8 had to talk to 192.168.10.0/24 (because it was necessary to be able access  ISCO's router web interface accessible via a local network interface with IP (192.168.10.1). Access to 192.168.10.1 wasn't possible from 192.168.1.8 because routing on NAT-ting Linux (192.168.1.235) to 192.168.10.0/24 network was missing. To make 192.168.1.8 Linux communicate with 192.168.10.1,  had to add following routing rules with ip command on both the Linux with IP 192.168.1.235 and Linux host behind NAT (192.168.1.8).

1. On Server (192.168.1.235) run in root shell and add to /etc/rc.local

# /sbin/ip r add 192.168.10.0/24 via 192.168.1.235
And then copy paste same line before exit 0 in /etc/rc.local

Its good idea always to check routing, after adding anything new, here is mine:
 

# ip r show

192.168.5.0/24 dev eth0  proto kernel  scope link  src 192.168.5.1
192.168.4.0/24 dev eth0  proto kernel  scope link  src 192.168.4.1
192.168.3.0/24 dev eth0  proto kernel  scope link  src 192.168.3.1
192.168.2.0/24 dev eth0  proto kernel  scope link  src 192.168.2.1
192.168.1.0/24 dev eth0  proto kernel  scope link  src 192.168.1.235
192.168.0.0/24 dev eth0  proto kernel  scope link  src 192.168.0.1
192.168.10.0/24 dev eth1  proto kernel  scope link  src 192.168.10.2
default via 192.168.10.1 dev eth1 
 

2. And also on Second Linux host (192.168.1.8) 

# /sbin/ip r add 192.168.10.0/24 via 192.168.1.235
To make routing permanent again paste in /etc/rc.local before exit 0

After above rules, I can normally ping and access hosts on class C network 192.168.10.1-255  from 192.168.1.8.

Create Email Forwarding with Qmail Vpopmail using .qmail file

Tuesday, June 11th, 2013

Reading Time: < 1 minute

how to do forwarding on qmail with vpopmail qmail e mailbox screenshot logo

Even though Qmail is considered as obsolete email server lately and it lacks good systematical official documentation and requires a lot of "hacking" to make work. It is surely still the fastest and maybe securest mail server out there (if properly configured).
My Qmail uses Vpopmail (for Virtual Email hosting). Every now and them some client requires to add a new e-mail forwarding from E-mail mail@host.com to Email to mail1@host2.com. Though many like to use Web interface as QmailAdmin for adding the forward I still prefer do it via old fashioned way, by SSH-ing to qmail server host and manually creating .qmail file.

Location (of my Vpopmail) install is (/var/vpopmail), so (to add e-mail forwarding for sample mail – mail@host.com)  .qmail file needs to be created in dir /var/vpopmail/domains/host.com/mail/ with content:

/var/vpopmail/domains/host.com/mail/Maildir/
&mail@host1.com

qmail:~# echo '/var/vpopmail/domains/host.com/mail/Maildir/' > /var/vpopmail/domains/host.com/mail/.qmail

qmail:~# echo '&mail@host1.com' >> /var/vpopmail/domains/host.com/mail/.qmail

First file instructs, where to store a copy of received e-mail (copy is stored in Maildir of receipt e-mail).

In Second line is mail to which to forward. For forwarding to group of e-mails all e-mails has to be listed in .qmail, i.e.:

/var/vpopmail/domains/host.com/mail/Maildir/
&mail@host1.com
&mail1@host2.com
&mail3@host3.com

Finally to make just created .qmail file work peroperly user group permissions has to be fixed:

# chown -R vpopmail:vchkpw /var/vpopmail/domains/host.com/mail/Maildir/.qmail

How to set password on a mysql server with no password via mysql command line interface

Monday, March 28th, 2011

Reading Time: 2 minutes
Many Linux distributions’s offered MySQL server comes without a set default password, in practice you can freely login to the mysql server on a plain mysql server installation on Debian, Ubuntu or Fedora by simply issuing:

linux:~# mysql -u root
Enter password:

Pressing enter will straight let you in the mysql server. The same kind of behaviour is also probably true on BSD based and many other Unixes which have pre-installed or the option to install a new mysql server.

I remember in my past that I’ve even seen a productive mysql servers on a servers running CMS based websites which doesn’t have a root password set.

Some administrators doesn’t take the time to think about the implications of the no password mysql installation and therefore being in a hurry simply let the server without an administrator password.
This is very common for the most lame and uneducated ones. Many novice system administrators think that by installing a phpmyadmin and configuring a password on it’s web interface is equal to setting up the mysql server (daemon) a password.

Thus for all this the uneducated ones and for all those who already have noticed that their newly installed mysql server doesn’t have a password set I’ve decided to give an example how a new mysql server password can be set or how an existing mysql server pass can be changed to a new one

To make any password manipulations usually the mysql-client package does provide a very handy instrument called mysqladmin , mysqladmin has many possibilities among which is creating a new mysql server admin (root) password or changing a previously set mysql server password to a new one

1. Here is how you can set a new MySQL server password:

mysqladmin -u root 'password' YOURasddsaPASSWORDjqweHERE

2. If you need to change an already existing mysql password you need to provide just one more argument to mysqladmin:

mysqladmin -u root 'password' YOURasdfdsaNEWasddsaPASSWORD_HERE -pEnter password:

Whether the Enter password: field appears you will be required to fill in the original mysql server root password after which the password will be changed to the above string passed in to the mysqladmin command line ‘YOURasdfdsaNEWasddsaPASSWORD_HERE’

That’s all now you have either set a new password for the mysql server or have already changed your previous one.

How to suspend Cpanel user through ssh / Cpanel shell command to suspend users

Friday, August 5th, 2011

Reading Time: < 1 minute
One of the servers running Cpanel has been suspended today and the Data Center decided to completely bring down our server and gave us access to it only through rescue mode running linux livecd.

Thus I had no way to access the Cpanel web interface to suspend the “hacker” who by the way was running a number of instances of this old Romanian script kiddies brute force ssh scanner called sshscan .

Thanksfully Cpanel is equipped with a number of handy scripts for emergency situations in /scripts directory. These shell management scripts are awesome for situations like this one, where no web access is not avaiable.

To suspend the abuser / (abusive user ) I had to issue the command:

root@rescue [/]# /scripts/suspendacct abuse_user
Changing Shell to /bin/false...chsh: Unknown user context is not authorized to change the shell of abuse_user
Done
Locking Password...Locking password for user abuse_user.
passwd: Success
Done
Suspending mysql users
warn [suspendmysqlusers] abuse_user has no databases.
Notification => reports@santrex.net via EMAIL [level => 3]
Account previously suspended (password was locked).
/bin/df: `/proc/sys/fs/binfmt_misc': No such file or directory
Using Universal Quota Support (quota=0)
Suspended document root /home/abuse_user/public_html
Suspended document root /home/abuse_user/public_html/updateverificationonline.com
Using Universal Quota Support (quota=0)
Updating ftp passwords for abuse_user
Ftp password files updated.
Ftp vhost passwords synced
abuse_user's account has been suspended

That’s all now the user is suspended, so hopefully the DC will bring the server online in few minutes.

How to make wordpress Update Plugins prompt to permanently store password / Get rid of annoying updates wordpress prompt

Thursday, February 2nd, 2012

Reading Time: < 1 minute

I'm managing few wordpress installations which requires me to type in:
Hostname , FTP Username and FTP Password , every single time a plugin update is issued and I want to upgrade to the new version.
Below is a screenshot of this annoying behaviour:

How to get rid of update plugins wordpress username password prompt

As you can see in the above screenshot, there is no way through Update Plugins web interface to store the password permanently. Hence the only option to store it permanently is to manually edit wp-config.php (file located in wordpress docroot, e.g. /path/to/wordpress/wp-config.php , inside the file find the line:

define ('WPLANG', '');

Right after it put a code similar to:

define('FS_METHOD', 'ftpsockets');
define('FTP_BASE', '/path/to/wordpress/');
define('FTP_CONTENT_DIR', '/path/to/wordpress/wp-content/');
define('FTP_PLUGIN_DIR ', '/path/to/wordpress/wp-content/plugins/');
define('FTP_USER', 'Username');
define('FTP_PASS', 'Password');
define('FTP_HOST', 'localhost');

Change the above defines:
path/to/wordpress/ – with your wordpress location directory.
Username and Password – with your respective FTP username and password. The localhost

That's all, from now onwards the User/Password prompt will not appear anymore. Consider there is a security downside of storing the FTP User/Pass in wp-config.php , if someone is able to intrude the wordpress install and access the documentroot of the wordpress install he we'll be able to obtain the ftp user/pass and log in the server directly via FTP protocol.

Fix to Nagios is currently not checking for external commands

Wednesday, August 24th, 2011

Reading Time: < 1 minute
While I was deploying a new Nagios install to Monitor some Windows hosts I’ve came across the following error in Nagios’s web interface:

Sorry, but Nagios is currently not checking for external commands, so your command will not be committed!
Read the documentation for information on how to enable external commands...

This error is caused by an option configuration for /etc/nagios/nrpe.cfg (part of the nrpe-nagios-server Debian package.

The config variable in nrpe.cfg causing the error is check_external_command=0 , the fix comes to changing the variable to:

check_external_command=1

As well as restart the /etc/init.d/nagios-nrpe-server and /etc/init.d/nagios3 services:

debian:~# /etc/init.d/nagios3 restart
...
debian:~# /etc/init.d/nagios-nrpe-server
...

This changes has work out the error Sorry, but Nagios is currently not checking for external commands, so your command will not be committed! , however immediately after another kind of error appared in Nagios web interface when I tried to use the send Nagios commands button. The error was:

Error: Could not stat() command file '/var/lib/nagios3/rw/nagios.cmd'!

This error is due to a deb package, which seems to be affecting the current deb versions of Nagios shipped with Debian 6 Squeeze stable, as well as the Latest Ubuntu release 11.04.

Thanksfully there is a work around to the problem I found online, to fix it up I had to execute the commands:

debian:~# /etc/init.d/nagios3 stop debian:~# dpkg-statoverride --update --add nagios www-data 2710 /var/lib/nagios3/rw
debian:~# dpkg-statoverride --update --add nagios nagios 751 /var/lib/nagios3
debian:~# /etc/init.d/nagios3 start

And hooray Thanks God the error is gone 😉

How to auto restart CentOS Linux server with software watchdog (softdog) to reduce server downtime

Wednesday, August 10th, 2011

Reading Time: 3 minutesHow to auto restart centos with software watchdog daemon to mitigate server downtimes, watchdog linux artistic logo

I’m in charge of dozen of Linux servers these days and therefore am required to restart many of the servers with a support ticket (because many of the Data Centers where the servers are co-located does not have a web interface or IPKVM connected to the server for that purpose). Therefore the server restart requests in case of crash sometimes gets processed in few hours or in best case in at least half an hour.

I’m aware of the existence of Hardware Watchdog devices, which are capable to detect if a server is hanged and auto-restart it, however the servers I administrate does not have Hardware support for Watchdog timer.

Thanksfully there is a free software project called Watchdog which is easily configured and mitigates the terrible downtimes caused every now and then by a server crash and respective delays by tech support in Data Centers.

I’ve recently blogged on the topic of Debian Linux auto-restart in case of kernel panic , however now i had to conifgure watchdog on some dozen of CentOS Linux servers.

It appeared installation & configuration of Watchdog on CentOS is a piece of cake and comes to simply following few easy steps, which I’ll explain quickly in this post:

1. Install with yum watchdog to CentOS

[root@centos:/etc/init.d ]# yum install watchdog
...

2. Add to configuration a log file to log watchdog activities and location of the watchdog device

The quickest way to add this two is to use echo to append it in /etc/watchdog.conf:

[root@centos:/etc/init.d ]# echo 'file = /var/log/messages' >> /etc/watchdog.conf
echo 'watchdog-device = /dev/watchdog' >> /etc/watchdog.conf

3. Load the softdog kernel module to initialize the software watchdog via /dev/watchdog

[root@centos:/etc/init.d ]# /sbin/modprobe softdog

Initialization of softdog should be indicated by a line in dmesg kernel log like the one above:

[root@centos:/etc/init.d ]# dmesg |grep -i watchdog
Software Watchdog Timer: 0.07 initialized. soft_noboot=0 soft_margin=60 sec (nowayout= 0)

4. Include the softdog kernel module to load on CentOS boot up

This is necessery, because otherwise after reboot the softdog would not be auto initialized and without it being initialized, the watchdog daemon service could not function as it does automatically auto reboots the server if the /dev/watchdog disappears.

It’s better that the softdog module is not loaded via /etc/rc.local but the default CentOS methodology to load module from /etc/rc.module is used:

[root@centos:/etc/init.d ]# echo modprobe softdog >> /etc/rc.modules
[root@centos:/etc/init.d ]# chmod +x /etc/rc.modules

5. Start the watchdog daemon service

The succesful intialization of softdog in step 4, should have provided the system with /dev/watchdog, before proceeding with starting up the watchdog daemon it’s wise to first check if /dev/watchdog is existent on the system. Here is how:

[root@centos:/etc/init.d ]# ls -al /dev/watchdogcrw------- 1 root root 10, 130 Aug 10 14:03 /dev/watchdog

Being sure, that /dev/watchdog is there, I’ll start the watchdog service.

[root@centos:/etc/init.d ]# service watchdog restart
...

Very important note to make here is that you should never ever configure watchdog service to run on boot time with chkconfig. In other words the status from chkconfig for watchdog boot on all levels should be off like so:

[root@centos:/etc/init.d ]# chkconfig --list |grep -i watchdog
watchdog 0:off 1:off 2:off 3:off 4:off 5:off 6:off

Enabling the watchdog from the chkconfig will cause watchdog to automatically restart the system as it will probably start the watchdog daemon before the softdog module is initialized. As watchdog will be unable to read the /dev/watchdog it will though the system has hanged even though the system might be in a boot process. Therefore it will end up in an endless loops of reboots which can only be fixed in a linux single user mode!!! Once again BEWARE, never ever activate watchdog via chkconfig!

Next step to be absolutely sure that watchdog device is running it can be checked with normal ps command:

[root@centos:/etc/init.d ]# ps aux|grep -i watchdog
root@hosting1-fr [~]# ps axu|grep -i watch|grep -v greproot 18692 0.0 0.0 1816 1812 ? SNLs 14:03 0:00 /usr/sbin/watchdog
root 25225 0.0 0.0 0 0 ? ZN 17:25 0:00 [watchdog] <defunct>

You have probably noticed the defunct state of watchdog, consider that as absolutely normal, above output indicates that now watchdog is properly running on the host and waiting to auto reboot in case of sudden /dev/watchdog disappearance.

As a last step before, after being sure its initialized properly, it’s necessery to add watchdog to run on boot time via /etc/rc.local post init script, like so:

[root@centos:/etc/init.d ]# echo 'echo /sbin/service watchdog start' >> /etc/rc.local

Now enjoy, watchdog is up and running and will automatically restart the CentOS host 😉