Managing Shared SSL
SSL stands for “Secure Socket Layer” and you can use this feature to protect all data exchanged between your Web site and the client. Shared SSL is a means of secure Web server access without requiring users to purchase a digital key.
In this case, only one domain should have real SSL sertificate. We will call it Master SSL Domain. Other domains, which are set up to use Shared SSL will use its resources.
To choose the Master SSL Domain from the list of domains which have SSL support enabled, go to the Server > Shared SSL page. In order to do this, set the Enable shared SSL checkbox and choose, which domain you want to be the Master SSL Domain.
Shared Libraries
Shared libraries are units of code, such as glibc, which are used by a number of applications and services.
Applications utilizing a shared library typically load the shared code when the application is initialized, so any applications using the updated library must be halted and relaunched.
To determine which running applications link against a particular library, use the lsof command as in the following example:
This command returns a list of all the running programs which use TCP wrappers for host access control. Therefore, any program listed must be halted and relaunched if the tcp_wrappers package is updated.
The latest CentOS 5.3/RHEL 5.3 updates for openssh (openssh-4.3p2-36) introduce the dependency on the libfipscheck.so.1 library supplied by fipscheck-1.0.3-1 RPM, but this RPM is missing in default file system template for ssh.
Log in as root to your PPCPL box.
Open the /etc/virtualhosting/filelists/ssh.sh file using a text editor:
vi /etc/virtualhosting/filelists/ssh.sh
Make sure that the file looks like:
$RPM_BIN -q nss nspr > /dev/null 2>&1 && \
cat <<EOF
S,rpm:nss
S,rpm:nspr
EOF
Reference: http://parallels.com
Shared Memory Pages
To facilitate data sharing, you can create shared memory pages. Multiple processes can read and write to and from a common shared memory area. The kernel maintains and administers the shared memory areas and allows individual processes access to the shared area.
The special ipcs command allows you to view the current shared memory pages on the system. Here’s the output from a sample ipcs command.
root@dell:~# ipcs -u
—— Shared Memory Status ——–
segments allocated 6
pages allocated 576
pages resident 528
pages swapped 0
Swap performance: 0 attempts 0 successes
—— Semaphore Status ——–
used arrays = 0
allocated semaphores = 0
—— Messages: Status ——–
allocated queues = 0
used headers = 0
used space = 0 bytes
Each shared memory segment has an owner that created the segment. Each segment also has a standard Linux permissions setting that sets the availability of the segment for other users. The key value is used to allow other users to gain access to the shared memory segment.
-m shared memory segments
root@dell:~# ipcs -m
—— Shared Memory Segments ——–
key shmid owner perms bytes nattch status
0×00000000 327680 buddy 600 393216 2 dest
0×00000000 360449 buddy 600 393216 2 dest
0×00000000 262146 buddy 600 393216 2 dest
0×00000000 294915 buddy 600 393216 2 dest
0×00000000 393220 buddy 600 393216 2 dest
0×00000000 425989 buddy 600 393216 2 dest
Shared Memory?
Shared memory (SHM) is another method of interprocess communication (IPC) whereby 2 or more processes share a single chunk of memory to communicate. The shared memory system can also be used to set permissions on memory, allowing for things like malloc debuggers to be written.
Types of Shared memory available
Basically there are two different types of shared memory available for most flavors of UNIX. As you may have guessed, each of the two orignal ancestors of modern UNIX have their own implementation, altough almost all modern UNIX flavors implement both. The names of the respective implementations are System V IPC, and BSD mmap.
