nginx: error while loading shared libraries: libpcre.so.1

If you get below error while starting nginx

    error:

nginx/sbin/nginx: error while loading shared libraries: libpcre.so.1: cannot open shared object file: No such file or directory

nginx couldn’t find the library by itself.
Specify the path of libpcre.so.1 in LD_LIBRARY_PATH and nginx will work fine

How to do specify the path?

export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:<absolute-path-of-libpcre.so.1>

Transform A,B,…AA,AB,.. to 1,2,..27,28,..

NOTE: Below code is Python 3.

base = 26
def transform(row):
    res = []
    for field in [tmp.strip() for tmp in row.split(',')]:
        ival = 0
        power = 0
        for c in field[::-1]:
            ival += pow(base,power)*(ord(c)-ord('A')+1)
            power += 1
        res.append(ival)
    return res


print(transform("A, B, Z, AA, AB, AAA"))


Output:

[1, 2, 26, 27, 28, 703]

apachectl status – How to solve lynx: command not found

apachectl status” will not work if you don’t have lynx ; text-based web browser.

You realize that when you get below message while using the command.

Error
bin/apachectl: line 95: lynx: command not found

Install the lynx and tell it to Apache httpd, he will surely understand.

Download the lynx from here. Change your working directory to the extracted folder and run the command:

./configure --prefix=<path-to-install-lynx>
make
make install

During lynx installation, it may stop with an error:

configure: error: No curses header-files found

Run the below command before proceeding:

sudo yum search ncurses-devel

Now it’s time to tell httpd about lynx.

In apachectl file (either in bin or conf directory), change the line starting with LYNX=”lynx -dump” to LYNX=”<lynx-installed-path>/lynx -dump”

apachectl status will start working..

Apache httpd: APR not found; error while installation

During Apache httpd installation if you get below error, that means Apache Portable Run-time environment was not found or not installed.

checking for APR... no
configure: error: APR not found.  Please read the documentation.

and/or

checking for APR-util... no
configure: error: APR-util not found. Please read the documentation.

So install APR and APR-util and give httpd those paths. Httpd will be happy to run for you after that… 🙂

Go further if you want to know how to install APR.

You can download APR and APR-util from here.

Then extract those to separate folders.

First change to the extract APR directory and install it. (Tip: cd command to change directory)

sudo ./configure --prefix=<apr-path>

sudo make

sudo make install

So you have a working APR. Next is APR-util.

Change to the extract APR-Util directory and install it. (Tip: cd command to change directory)

sudo ./configure --prefix=<apr-util-path> --with-prefix=<apr-path>

sudo make

sudo make instal

Install zlib packages with the command (optional; you can turn this off at your will):

yum install zlib zlib-devel

Apart from APR and APR-Util, you may need to install pcre too. So download it from here first.

Change to the directory and use the below commands to install.

sudo ./configure --prefix=<pcre-path>

sudo make

sudo make install

Now lets make httpd understand that we have a working pcre, APR and APR-util.

./configure --enable-file-cache --enable-cache --enable-disk-cache --enable-mem-cache --enable-deflate --enable-expires --enable-headers --enable-usertrack --enable-cgi --enable-vhost-alias --enable-rewrite --enable-so --prefix=<httpd-path> --with-apr=<apr-path> --with-apr-util=<apr-util-path> --with-pcre=<pcre-path>

# Rest is history make make install

Change the Java (JVM) used by tomcat.

Enterprise systems will have different versions of Java installed in it. A system administrator may have to set up Tomcat to use a particular one out of it. By default Tomcat uses the OS default; ie. the one installed into OS path. So how can we make it run with another version of Java.

This is easily achieved using the below commands(Open a terminal and run the below commands, don’t close it.):

export JAVA_HOME=<path-to-java>

or

export JRE_HOME=<path-to-java>

Run the start-up script from the same terminal and you will see from the logs that Tomcat picked up the Java from the path you set.

Notes:

JRE_HOME is set to JAVA_HOME if not set. So setting any of these variables suffice.

Shared folder for Fedora VM in VirtualBox

Hi,

I found a little hard to setup a shared folder for my VMs. So thought of sharing it..

So, assuming you already have your host machine, VirtualBox installed on it and a VM running Fedora (any linux), there we go..

Highlight your VM in VirtualBox window.

Screen Shot 2015-03-17 at 3.40.41 pmYes, it is powered off. Bring up the settings window for the VM clicking the below icon.

Screen Shot 2015-03-17 at 3.41.02 pmChoose the “Shared Folders” tab and you will see the list of folders shared with VM.Screen Shot 2015-03-17 at 3.41.22 pmClick on the plus sign you see on the left side and you get another window like the one below.

Screen Shot 2015-03-17 at 3.41.44 pmYou may choose the folder of the host machine you want to share and tick the “Auto-mount” option. Click OK.

Screen Shot 2015-03-17 at 4.12.42 pm

The folder you chose to share is now visible and we are done with the VirtualBox settings. Click OK to come out of it.

Screen Shot 2015-03-17 at 4.13.05 pm

Now boot up the VM. We need to install a few packages in Fedora for this. You may use below command to install the same.

Screen Shot 2015-03-17 at 5.11.50 pmThis will install latest gcc and kernel-devel packages. Guest addition may get arrogant, at times and gives error that it can’t find a particular version of kernel-devel. I will explain how to solve that later.

Now we can install “Guest Addition”

Click on the “Devices” menu and select the below highlighted option.Screen Shot 2015-03-17 at 4.15.35 pmSome OS automatically run the autorun script from CD. Otherwise open a file-browser and open the CD contents. You will see “autorun.sh” file there. Drag and drop it to Terminal. It will first authenticate you and start installing “Guest Addition”.

Screen Shot 2015-03-17 at 4.59.33 pmScreen Shot 2015-03-17 at 4.53.26 pm

You will get below output 99% of the times and that means just a reboot and you have a host-folder available in VM.

Screen Shot 2015-03-17 at 5.26.14 pm

The shared folder will be auto-mounted in /media.

Screen Shot 2015-03-17 at 5.30.02 pmThe 1% I left earlier is the case when “Guest Addition” fails to install with an error about the kernel-devel version. You may get below screen in such cases.

Screen Shot 2015-03-17 at 4.54.16 pmIn such cases you get a command from the above output.

yum install kernel-devel-3.17.4-301.fc21.x86_64

Just run the below part out of it and do the “Guest Addition” installation again and you are good to go..

yum install kernel-devel-3.17.4

Now let me take you through another issue you may face. Your folder will get listed in /media. But you may not have permission to open it. In my case, “Shared” is the shared-folder. /media/sf_Shared is the path in VM where it is mounted.

ls /media/sf_Shared

The above command will give an output like this:Screen Shot 2015-03-18 at 9.48.20 pm

This is because of the difference of UID in host and VM machines.

Screen Shot 2015-03-18 at 9.24.30 pm

The easiest way to sort this out is to add the user account to vboxsf.

usermod -a -G vboxsf

I went for a reboot (of VM) after that and things worked well.

May be you want to do this too.

Create a link in your home directory to access the shared directory mounted in /media. Make sure your home directory does not have “Shared” folder already.

ln -s /media/sf_Shared ~/Shared

So now you may use ~/Shared as your window to the host-machine..

Clone vdi image (.vdi) without error

Clone vdi image (.vdi) without the UID error.

Use the below command via terminal.

VBoxManage clonevdi <ImageYouWantToCopy.vdi> <DestinationImage.vdi>

If you get below error, that means one of your VM is using the .vdi image. Shutdown that VM and run the command again.

VBoxManage: error: Failed to lock source media 'ImageYouWantToCopy.vdi'

VBoxManage: error: Details: code VBOX_E_INVALID_OBJECT_STATE (0x80bb0007), component Medium, interface IMedium, callee nsISupports

VBoxManage: error: Context: "CloneTo(dstDisk, ComSafeArrayAsInParam(l_variants), NULL, progress.asOutParam())" at line 740 of file VBoxManageDisk.cpp