Differences
This shows you the differences between two versions of the page.
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scgc:laboratoare:01 [2018/02/28 13:08] alexandru.carp |
scgc:laboratoare:01 [2021/10/27 14:07] (current) maria.mihailescu |
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| - | ====== Laboratory 01. DNS ====== | + | ====== Naming Services: DNS ====== |
| ===== Lab Setup ===== | ===== Lab Setup ===== | ||
| - | * We will be using two virtual machines in the [[http://cloud.curs.pub.ro/|faculty's cloud]]. | + | * We will be using two virtual machines in the [[http://cloud.grid.pub.ro/|faculty's cloud]]. |
| - | * When creating a virtual machine follow the steps in this [[https://cloud.curs.pub.ro/about/tutorial-for-students/|tutorial]]. | + | |
| * Create two VMs (one will be our DNS master server and one will be our DNS slave server) | * Create two VMs (one will be our DNS master server and one will be our DNS slave server) | ||
| * When creating a virtual machine in the Launch Instance window: | * When creating a virtual machine in the Launch Instance window: | ||
| * Select **Boot from image** in **Instance Boot Source** section | * Select **Boot from image** in **Instance Boot Source** section | ||
| - | * For the master VM select **Debian 8.6** in **Image Name** section | + | * For the master VM select **Debian 10.3** in **Image Name** section |
| * For the slave VM select **Centos 7** in **Image Name** section | * For the slave VM select **Centos 7** in **Image Name** section | ||
| + | * Select the **m1.small** flavor for both VMs. | ||
| * The usernames for connecting to the VMs are: | * The usernames for connecting to the VMs are: | ||
| - | * ''debian'' for **Debian 8.6** | + | * ''debian'' for **Debian 10.3** |
| * ''student'' for **CentOS 7** | * ''student'' for **CentOS 7** | ||
| * For ease of use we recommend adding entries in the ''/etc/hosts'' file corresponding to the slave and master VMs | * For ease of use we recommend adding entries in the ''/etc/hosts'' file corresponding to the slave and master VMs | ||
| Line 125: | Line 125: | ||
| It is noteworthy, that dig and host do not use ''/etc/nsswitch.conf'' for querying DNS servers and they do not use the system's DNS resolver, which is usually a library. We can see this from the following commands: | It is noteworthy, that dig and host do not use ''/etc/nsswitch.conf'' for querying DNS servers and they do not use the system's DNS resolver, which is usually a library. We can see this from the following commands: | ||
| <code> | <code> | ||
| - | root@master:~# strace -e open host acs.pub.ro | + | root@master:~# strace -e openat host acs.pub.ro |
| [...] | [...] | ||
| - | open("/etc/resolv.conf", O_RDONLY) = 6 | + | openat(AT_FDCWD, "/etc/resolv.conf", O_RDONLY) = 6 |
| acs.pub.ro has address 141.85.227.151 | acs.pub.ro has address 141.85.227.151 | ||
| acs.pub.ro mail is handled by 10 mx.acs.pub.ro. | acs.pub.ro mail is handled by 10 mx.acs.pub.ro. | ||
| [...] | [...] | ||
| - | root@master:~# strace -e open ping -c 1 acs.pub.ro | + | root@master:~# strace -e openat ping -c 1 acs.pub.ro |
| [...] | [...] | ||
| - | open("/etc/resolv.conf", O_RDONLY|O_CLOEXEC) = 4 | + | openat(AT_FDCWD, "/etc/resolv.conf", O_RDONLY|O_CLOEXEC) = 4 |
| - | open("/etc/resolv.conf", O_RDONLY|O_CLOEXEC) = 4 | + | openat(AT_FDCWD, "/etc/resolv.conf", O_RDONLY|O_CLOEXEC) = 4 |
| - | open("/etc/nsswitch.conf", O_RDONLY|O_CLOEXEC) = 4 | + | openat(AT_FDCWD, "/etc/nsswitch.conf", O_RDONLY|O_CLOEXEC) = 4 |
| [...] | [...] | ||
| - | open("/etc/host.conf", O_RDONLY|O_CLOEXEC) = 4 | + | openat(AT_FDCWD, "/etc/host.conf", O_RDONLY|O_CLOEXEC) = 4 |
| - | open("/etc/hosts", O_RDONLY|O_CLOEXEC) = 4 | + | openat(AT_FDCWD, "/etc/hosts", O_RDONLY|O_CLOEXEC) = 4 |
| - | open("/etc/ld.so.cache", O_RDONLY|O_CLOEXEC) = 4 | + | openat(AT_FDCWD, "/etc/ld.so.cache", O_RDONLY|O_CLOEXEC) = 4 |
| - | open("/lib/x86_64-linux-gnu/libnss_dns.so.2", O_RDONLY|O_CLOEXEC) = 4 | + | openat(AT_FDCWD, "/lib/x86_64-linux-gnu/libnss_dns.so.2", O_RDONLY|O_CLOEXEC) = 4 |
| - | open("/lib/x86_64-linux-gnu/libresolv.so.2", O_RDONLY|O_CLOEXEC) = 4 | + | openat(AT_FDCWD, "/lib/x86_64-linux-gnu/libresolv.so.2", O_RDONLY|O_CLOEXEC) = 4 |
| PING acs.pub.ro (141.85.227.151) 56(84) bytes of data. | PING acs.pub.ro (141.85.227.151) 56(84) bytes of data. | ||
| - | open("/etc/hosts", O_RDONLY|O_CLOEXEC) = 4 | + | openat(AT_FDCWD, "/etc/hosts", O_RDONLY|O_CLOEXEC) = 4 |
| 64 bytes from acs.pub.ro (141.85.227.151): icmp_seq=1 ttl=62 time=0.688 ms | 64 bytes from acs.pub.ro (141.85.227.151): icmp_seq=1 ttl=62 time=0.688 ms | ||
