How to Create a Debian Package

In my previous blog, I've described how to create an RPM package. This time, I'm going to show you how to create a Debian package. I'm going to use the same code that's used in RPM tutorial blog. Creating a Debian package can be pretty complicated if we have to do it manually. Luckily there are some helper scripts that can make our lives easier.

1. Install devscripts and debhelper

sudo apt-get install devscripts debhelper

2. Create a simple hello.cpp

#include <iostream>
using namespace std;

int main() {
    cout << "Hello World" << endl;
    return 0;
}

3. Create a Makefile

CC = g++ 
CCFLAGS = -g -Wall
SRC = hello.cpp
TARGET = hello

.PHONY: clean install

all: hello

install: $(TARGET)
    if [ -d ${DESTDIR} ]; then rm -rf ${DESTDIR}; fi
    mkdir -p ${DESTDIR}
    cp $(TARGET) ${DESTDIR} 

hello: 
    $(CC) $(CCFLAGS) -o $(TARGET) $(SRC)

clean:
    rm -rf $(TARGET)

4. In the directory where we created the above files, create a new debian directory

mkdir debian

5. Create a debian/changelog file

dch --create -v 0.1 --package hello

We can create this changelog file without using dch script, but the changelog file requires a particular format and the dch script can help to create a changelog template. The changelog file should look like this.

hello (0.1) UNRELEASED; urgency=low

  * Initial release. (Closes: #123)

 -- foo <foo@bar.com>  Thu, 01 Mar 2012 14:16:42 +0800

6. Create a debian/compat
The content of this file is very simple. It just contains a number 8. This file is used to tell debhelper to use compatibility helper version 8. The file should look like this.

8

7. Create a debian/control file
This control file is used to describe the source and binary package and other information. This control file also has a particular format. Take a note that there's a space after the Description field. This to tell that it's an extended description. The description and extended description should be different; otherwise lintian (a tool to check the correctness of files rquired to create Debian packages) will complain. The control file should look like this.

Source: hello
Maintainer: foo <foo@bar.com>
Section: misc
Priority: optional
Standards-Version: 3.9.1
Build-Depends: debhelper (>= 8)

Package: hello
Architecture: any
Depends: ${shlibs:Depends}, ${misc:Depends}
Description: say hello
 say hello world

8. Create a debian/rules file
This file is basically a Makefile.

#!/usr/bin/make -f
%:
    dh $@

override_dh_auto_install:
    $(MAKE) DESTDIR=$$(pwd)/debian/hello/usr/bin install

The override_dh_auto_install is required because in our example, we have a custom make install target.
9. Create a debian/copyright file
For this tutorial, just create an empty copyright file.
10. To summarize, we should've already created all these files

/home/foo/testdeb/hello/hello.cpp
                       /Makefile
                       /debian/control
                       /copyright
                       /changelog
                       /compat
                       /rules

11. Create a Debian package

debuild -uc -us

-uc means don't sign the .changes file
-us means don't sign the source package
For more information about the options, read man dpkg-buildpackage.

You should now see your source and Debian packages in /home/foo/testdeb

12. Install the newly created Debian package

sudo dpkg -i hello_0.1_i386.deb

13. Test if hello program was successfully installed

hello

You should see "Hello World" output
14. Remove the hello package

sudo dpkg -r hello

How to Create an RPM Package

In this blog, I'm going to teach you how to create an RPM package.

1. Create a simple hello.cpp

#include <iostream>
using namespace std;

int main() {
    cout << "Hello World" << endl;
    return 0;
}

2. Create a Makefile

CC = g++ 
CCFLAGS = -g -Wall
SRC = hello.cpp
TARGET = hello

.PHONY: clean install

all: hello

install: $(TARGET)
    if [ -d ${DESTDIR} ]; then rm -rf ${DESTDIR}; fi
    mkdir -p ${DESTDIR}
    cp $(TARGET) ${DESTDIR} 

hello: 
    $(CC) $(CCFLAGS) -o $(TARGET) $(SRC)

clean:
    rm -rf $(TARGET)

3. Put hello.cpp and the Makefile in a directory structure like this

/home/foobar/hello/Makefile
                  /hello.cpp

4. Create a tarball of hello project

cd /home/foobar
tar czvf hello-0.1.tar.gz hello/

5. Create an rpmbuild directory

mkdir -p /home/foobar/rpmbuild

6. Create BUILD  BUILDROOT  RPMS  SOURCES  SPECS  SRPMS directories inside the /home/foobar/rpmbuild directory
BUILD --> the source files are unpacked and compiled here
BUILDROOT --> files are installed here
RPMS --> binary RPMs are created here
SOURCES --> source tarballs
SPECS --> spec files
SRPMS --> source RPMs
7. Create a spec file in the /hom/foobar/rpmbuild/SPECS/hello.spec

Summary             : Hello World program
Name                : hello
Version             : 0.1 
Release             : 1%{?dist}
License             : GPLv3+
Source              : %{name}-%{version}.tar.gz

%description
A simple Hello World program

%prep
%setup -q -n %{name}

%build
make

%install
make install DESTDIR="%{buildroot}%{_bindir}"

%files
%{_bindir}/hello

%prep --> this stage calls %setup to unpack hello-0.1.tar.gz to /home/foobar/rpmbuild/BUILD/hello. %{name} is a macro variable that substitutes to hello

%build --> this stage calls "make" in the /home/foobar/rpmbuild/BUILD/hello to create a hello executable

%install --> this stage calls "make install" to install the files into /home/foobar/rpmbuild/BUILDROOT/usr/bin. %{buildroot} is a macro variable that substitutes to /home/foobar/rpmbuild/BUILDROOT. Make sure the Makefile supports DESTDIR argument

%files --> lists all the files to be installed. %{_bindir} is a macro variablesubstitutes to /usr/bin. In this example, only hello executable needs to be installed into /usr/bin

8. Build the source and binary RPMs

rpmbuild -ba /home/foobar/SPECS/hello.spec

-ba option means build all (prep, build, install)
The binary RPM will be created in /home/foobar/rpmbuild/RPMS
The source RPM will be created in /home/foobar/rpmbuild/SRPMS
9. Install the newly created binary RPM

sudo rpm -ivh hello-0.1-1.fc16.i686.rpm

10. Test if hello program was successfully installed

hello

You should see "Hello World" output
11. Remove the hello package

sudo rpm -e hello

SSH Login without Password

To login in SSH without password, we need to do the following:
1. Generate a key pair (private key and public key) in Server A

ssh-keygen -t rsa

2. Copy the public key from Server A to Server B.

scp id_rsa.pub testuser:[server_B_ip_address]:/home/testuser/.ssh

3. In Server B, add that public key into authorized_keys file.

cat id_rsa.pub >> authorized_keys

4. Verify it from Server A.

ssh testuser@[server_B_ip_address]

How to Setup NFS in Linux

Make sure we have the NFS (both client and server) package installed.
1. Edit /etc/exports

/home/myuser/share *rw(root_squash)

rw --> read write
ro --> read only
root_squash --> the remote root user is not allowed to have a root level access
no_root_squash --> the remote root user is allowed to have a root-level access
2. Verify it

showmount -e [nfs_server_address]

3. Open firewall port 2049
4. Restart the nfsserver deamon

/etc/init.d/nfsserver restart

5. Mount the remote export.

mount -t nfs [nfs_server_address]:/home/myuser/share nfs/

How to Setup Samba in Linux

Make sure we have the Samba package installed. For example, we want to share the /tmp directory in Linux so that we can access it from our Windows or from another Linux client (NFS is better for Linux to Linux file sharing), we need to do the following:
1. Edit /etc/samba.conf add the following lines

[tmp]
    comment = Test
    path = /tmp
    writable = Yes
    public = Yes

2. Add a Samba user.

smbpasswd -a sambauser

Enter the password.
3. We need to open firewall for the following ports:
- 137 (netbios-ns)
- 138 (netbios-dgm)
- 139 (netbios-ssn)
- 445 (microsoft-ds)
For more info, see /etc/services
3. Restart smb daemon.

/etc/init.d/smb restart

For Windows client to access the shared directory:
1. Go to Run and enter \\[ip_address]\tmp
2. Enter the Samba username and password.

For Linux client to access the shared directory:

mount -t cifs //172.16.242.129/tmp -o username=sambauser,password=password samba/

How to Setup DNS in Linux

To setup DNS in Linux, make sure we have BIND package installed.
1. Add these lines in /etc/resolv.conf

domain fw-geekycoder.com
nameserver 172.16.242.129

2. Add forward and reverse zones in /etc/named.conf

zone "fw-geekycoder" in {
    type master;
    file "master/fw-geekycoder.zone";
};

zone "242.16.172.in-addr.arpa" in {
    type master;
    file "master/242.16.172.zone";
};

3. As you we can see in step two, there are two zone files that need to be created.
In /var/lib/named/master/fw-geekycoder.zone file

$TTL 1W
@       IN SOA  ns1.fw-geekycoder.com. root.fw-geekycoder.com. (
                                2010191505      ; serial (d. adams)
                                2D              ; refresh
                                4H              ; retry
                                6W              ; expiry
                                1W )            ; minimum

fw-geekycoder.com.      IN NS           ns1.fw-geekycoder.com.
ns1                     IN A            172.16.242.129
www                     IN A            172.16.242.129
gateway                 IN A            172.16.242.2

In 242.16.172.zone file

$TTL 1W
@       IN SOA  ns1.fw-geekycoder.com. root.fw-geekycoder.com. (
                                2010191605      ; serial (d. adams)
                                2D              ; refresh
                                4H              ; retry
                                6W              ; expiry
                                1W )            ; minimum

129.242.16.172.in-addr.arpa.    IN NS           ns1.fw-geekycoder.com.
129                             IN PTR          ns1.fw-geekycoder.com.
129                             IN PTR          www.fw-geekycoder.com.
2                               IN PTR          gateway.fw-geekycoder.com.

4. Restart the named daemon.

/etc/init.d/named restart

Creating ISO Images

Creating ISO images in Linux is very straightforward.
If for example, we need to create an ISO image for a CD/DVD, we can use dd command.

dd if=/dev/cdrom of=cd.iso

If we need to create an ISO image out for a directory/file, we can use mkisofs command.

mkisofs -o ~/docs.iso -J -r -V MY_LABEL ~/Documents

To verify if the ISO image is correct, we need to mount that ISO image.

mount -t iso9660 -o loop /media

To umount:

umount /media

See man dd and mkisofs for more information on the above commands.

Setting Up Quota in Linux

Setting up a quota in Linux is easy.
1. Install quota.

In Ubuntu:

sudo apt-get install quota

In openSUSE:

sudo yast2 -i quota

2. Add usrquota and grpquota parameters to the mount options in the /etc/fstab, e.g.

/dev/sda2  /  ext4  acl,user_xattr,usrquota,grpquota 1 1

For file systems that support journaling, such as ext3 and ext4, we need to add additional options, e.g.

/dev/sda2 / ext4 acl,user_xattr,usrjquota=aquota.user,
grpjquota=aquota.group,jqfmt=vfsv0 1 1

3. Run quotacheck -amvug
This command is used to perform a scan in the file system for disk usage as well as to create aquota.group and aquota.user files. In our example, the aquota.group and aquota.user files are created in / directory.

4. Run edquota -u <username>
This command is used to set a quota for a particular user. The block here means how many blocks the user can use and the inode here means how many files the user can own.

5. Run repquota -av
This command is used to give a summary on the quotas.

Create, Modify, and Delete User in Linux

These steps require root privilege.

To create a new user:

useradd -m -c "User1" -s /bin/bash user1

The -m option will automatically create a user's home directory, i.e. /home/user1.
The -s option is to specify the user's default shell.

To modify an existing user:
Suppose we want to add an additional group newgroup to user1.
In Ubuntu,

usermod -a -G newgroup user1

In openSUSE

usermod -A newgroup user1

Be aware that, if you specify only with -G, you need to include the group that you wish to add as well as the groups that have already been added. That's why in Ubuntu, it has additional switch, which is -a to append the group and -A in openSUSE.

To delete an existing user:

userdel -r user1

Changing Default Editor in Linux

Some tools, such as visudo use nano editor by default. This is especially true in a distro like Ubuntu while openSUSE uses vi. As a vi user, I'm more comfortable editing a file using vi. To change it, add this line in the .bashrc.

export EDITOR=vim

Creating New Partition and File System in Linux

Creating a new partition and file system, a.k.a formatting in Windows world is very easy. We can do that in just few clicks (right click, format, and select the file system). Creating a new partition and file system in Linux, however, is not that easy. Here I'm gonna show you how to do it.

You need to run these steps as root.
1. Run 'fdisk '
Example:

# fdisk /dev/sdb

If you're creating a new partition in the first SATA/SCSI disk, the device name will be /dev/sda, if it's a second SATA/SCSI disk, it'll be /dev/sdb and so on. If the device is the first master IDE disk, it'll be /dev/hda and so on.
2. Choose n to add a new partition.
3. Choose e for extended or p for primary.
4. Accept the default values for first and last cylinder if you wish to partition the whole disk.
5. Choose w to write the table to disk.
If suppose you've created the first partition in the second SATA/SCSI disk, you should be able to see that /dev/sdb1 has been created in your file system.
6. The next step is to create a file system on that partition. The command is 'mkfs -t '
Example:

# mkfs -t ext4 /dev/sdb1

The here can be ext2, ext3, ext4, etc. The here should be /dev/sdb1 and NOT /dev/sdb.
7. The last step is to mount this partition. To do that, execute 'mount -t '
Example:

# mkdir -p /mnt/newdisk
# mount -t ext4 /mnt/newdisk

To see if your partition has been mounted successfully. Run 'mount' or 'cat /etc/mtab'.
To mount it permanently, you need to create a new entry in the /etc/fstab as shown below.

/dev/sdb1            /mnt/newdisk         ext4       acl,user_xattr        1 2

The value last second option 1 specifies whether or not the file system should be dumped. 1 means dump. 0 means don't dump.
The value last option 2 specifies the order in which fsck should check the file system at reboot. For root partition, it should be 1, other partitions should be 2.

Create ISO Images on Linux

Creating ISO images on Linux is very straightforward. Unlike in Windows, you don't need any additional tool to install. You just need to type this in your terminal.

dd if=/dev/cdrom of=image.iso

Most Linux distros nowadays have a graphical utility to let you mount the ISO image. If you prefer to do it in command line, here is how to do it.

mkdir -p /mnt/myimage
mount -o loop -t iso9660 cd.iso /mnt/myimage