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Senior software engineer
EnErgo* posted a topic in Προσφορά ΕργασίαςΜόνο για αυτούς που είχαν από τα δώδεκα τους 3 servers να τρέχουν, κρυμμένους στη ντουλάπα! C++ / Computer Vision / Asynchronous programming / Software architecture / Systematic testing Κατά τα άλλα… καλός προγραμματιστής με ευρεία γνώση και ενδιαφέρον. Το υπόβαθρο είναι λιγότερο σημαντικό από το ενδιαφέρον για βελτιστοποίηση / optimalisation, ενσωμάτωση / embedding, πρωτόκολλα επικοινωνίας / communication protocols, ασφάλεια κώδικα / code security, big data κλπ. Η εμπειρία με Linux, Scrum και ROS είναι προτέρημα. Ομαδικό πνεύμα και άριστα επικοινωνιακά προσόντα. Προσφέρεται: εξέλιξη και πρωτοπορία! https://www.en-ergo.nl/el/jobs/senior-software-engineer/
Why Is Microsoft Releasing SQL Server on Linux?Συμφωνω με την παρακατω παραγραφο, αν και πρεπει να διαβαστει ολο το αρθρο για να καταλαβεις το ακριβες νοημα. link ΝΚ
Getting Started with Linux
nkspeed posted a topic in ΕκπαίδευσηΈνας χρήσιμος οδηγός και ευκολοδιάβαστος για μια γρήγορη εισαγωγή στο linux. An Introduction to the Linux TerminalBasic Linux Navigation and File ManagementAn Introduction to Linux PermissionsAn Introduction to Linux I/O Redirection NK
Linux TCP/IP networking: net-tools vs. iproute2
nkspeed posted a topic in Λοιπά Θέματαεπειδη δεν υπαρχει linux section και το αρθρο ειναι πολυ καλο το ανεβαζω εδω. εξηγει γιατι οι δανομες σταματουν τη χρηση των net-tools (ifconfig, route, arp and netstat) και τα αντικαθιστουν με την iproute. εχει μαλιστα και παραδειγματα εντολων απο τα παλια εργαλεια στα νεα. περισσοτερα εδω Linux TCP/IP networking: net-tools vs. iproute2 Last updated on September 4, 2014Authored by Dan Nanni 13 Comments Many sysadmins still manage and troubleshoot various network configurations by using a combination of ifconfig, route, arp and netstat command-line tools, collectively known as net-tools. Originally rooted in the BSD TCP/IP toolkit, the net-tools was developed to configure network functionality of older Linux kernels. Its development in the Linux community so far has ceased since 2001. Some Linux distros such as Arch Linux and CentOS/RHEL 7 have already deprecated net-tools, and others are planning to do so in favor of iproute2. iproute2, which is another family of network configuration tools, emerged to replace the functionality of net-tools. While net-tools accesses and changes kernel network configurations via procfs (/proc) and ioctl system call, iproute2 communicates with the kernel via netlink socket interface. The /proc interface is known to be more heavyweight than netlink interface. Putting performance aside, the user interface of iproute2 is more intuitive than that of net-tools. For example, network resources (e.g., link, IP address, route, tunnel, etc.) are aptly defined with "object" abstraction, and you can manage different objects using consistant syntax. Most importantly, iproute2 has been under active development so far. If you are still using net-tools, it is time to switch to iproute2, especially if you want to catch up with the latest and greatest networking features of the Linux kernel. Chances are that there are many things you can do with iproute2, but cannot with net-tools, be it source-based routing, QoS, VLAN, bonding, bridges, etc. It's also worth noting that higher-level network configuration tools such as network manager depend on iproute2. For those who want to make the switch, here is a round-up of net-tools vs. iproute2 comparison. Show All Connected Network InterfacesThe following commands show a list of all available network interfaces (whether or not they are active). With net-tools: $ ifconfig -a With iproute2: $ ip link show Activate or Deactivate a Network InterfaceTo activate/deactivate a particular network interface, use these commands. With net-tools: $ sudo ifconfig eth1 up $ sudo ifconfig eth1 down With iproute2: $ sudo ip link set down eth1 $ sudo ip link set up eth1 Assign IPv4 address(es) to a Network InterfaceUse these commands to configure IPv4 addresses of a network interface. With net-tools: $ sudo ifconfig eth1 10.0.0.1/24 With iproute2: $ sudo ip addr add 10.0.0.1/24 dev eth1 Note that with iproute2, you can assign multiple IP addresses to an interface, which you cannot do with ifconfig. A workaround for this with ifconfig is to use IP aliases. $ sudo ip addr add 10.0.0.1/24 broadcast 10.0.0.255 dev eth1 $ sudo ip addr add 10.0.0.2/24 broadcast 10.0.0.255 dev eth1 $ sudo ip addr add 10.0.0.3/24 broadcast 10.0.0.255 dev eth1 Remove an IPv4 address from a Network InterfaceAs far as IP address removal is concerned, there is no proper way to remove an IPv4 address from a network interface with net-tools, other than assigning 0 to the interface. iproute2 can properly handle this. With net-tools: $ sudo ifconfig eth1 0 With iproute2: $ sudo ip addr del 10.0.0.1/24 dev eth1 Show IPv4 Address(es) of a Network InterfaceChecking IPv4 addresses of a particular network interface can be done as follows. With net-tools: $ ifconfig eth1 With iproute2: $ ip addr show dev eth1 Again, if there are multiple IP addresses assigned to an interface, iproute2 shows all of them, while net-tools shows only one IP address. Assign an IPv6 address to a Network InterfaceUse these commands to add IPv6 address(es) to a network interface. Both net-tools and iproute2 allow you to add multiple IPv6 addresses to an interface. With net-tools: $ sudo ifconfig eth1 inet6 add 2002:0db5:0:f102::1/64 $ sudo ifconfig eth1 inet6 add 2003:0db5:0:f102::1/64 With iproute2: $ sudo ip -6 addr add 2002:0db5:0:f102::1/64 dev eth1 $ sudo ip -6 addr add 2003:0db5:0:f102::1/64 dev eth1 Show IPv6 address(es) of a Network InterfaceDisplaying IPv6 addresses of a particular network interface can be done as follows. Both net-tools and iproute2 can show all assigned IPv6 addresses. With net-tools: $ ifconfig eth1 With iproute2: $ ip -6 addr show dev eth1 Remove an IPv6 address from a Network InterfaceUse these commands to remove any unnecessary IPv6 address from an interface. With net-tools: $ sudo ifconfig eth1 inet6 del 2002:0db5:0:f102::1/64 With iproute2: $ sudo ip -6 addr del 2002:0db5:0:f102::1/64 dev eth1 Change the MAC Address of a Network InterfaceTo spoof the MAC address of a network interface, use the commands below. Note that before changing the MAC address, you need to deactivate the interface first. With net-tools: $ sudo ifconfig eth1 hw ether 08:00:27:75:2a:66 With iproute2: $ sudo ip link set dev eth1 address 08:00:27:75:2a:67 View the IP Routing Tablenet-tools has two options for showing the kernel's IP routing table: route or netstat. With iproute2, use ip route command. With net-tools: $ route -n $ netstat -rn With iproute2: $ ip route show Add or Modify a Default RouteHere are the commands to add or modify a default route in the kernel's IP routing table. Note that with net-tools, modifying a default route can be achieved by adding a new default route, and then removing an old default route. With iproute2, use ip route replace command. With net-tools: $ sudo route add default gw 192.168.1.2 eth0 $ sudo route del default gw 192.168.1.1 eth0 With iproute2: $ sudo ip route add default via 192.168.1.2 dev eth0 $ sudo ip route replace default via 192.168.1.2 dev eth0 Add or Remove a Static RouteA static routing can be added or removed with the following commands. With net-tools: $ sudo route add -net 172.16.32.0/24 gw 192.168.1.1 dev eth0 $ sudo route del -net 172.16.32.0/24 With iproute2: $ sudo ip route add 172.16.32.0/24 via 192.168.1.1 dev eth0 $ sudo ip route del 172.16.32.0/24 View Socket StatisticsHere are the commands to check socket statistics (e.g., active/listening TCP/UDP sockets). With net-tools: $ netstat $ netstat -l With iproute2: $ ss $ ss -l View the ARP TableYou can display the kernel's ARP table with these commands. With net-tools: $ arp -an With iproute2: $ ip neigh Add or Remove a Static ARP EntryAdding or removing a static ARP entry in the local ARP table is done as follows. With net-tools: $ sudo arp -s 192.168.1.100 00:0c:29:c0:5a:ef $ sudo arp -d 192.168.1.100 With iproute2: $ sudo ip neigh add 192.168.1.100 lladdr 00:0c:29:c0:5a:ef dev eth0 $ sudo ip neigh del 192.168.1.100 dev eth0 Add, Remove or View Multicast AddressesTo configure or view multicast addresses on a network interface, use the commands below. With net-tools: $ sudo ipmaddr add 33:44:00:00:00:01 dev eth0 $ sudo ipmaddr del 33:44:00:00:00:01 dev eth0 $ ipmaddr show dev eth0 $ netstat -g With iproute2: $ sudo ip maddr add 33:44:00:00:00:01 dev eth0 $ sudo ip maddr del 33:44:00:00:00:01 dev eth0 $ ip maddr list dev eth0
Problem with Hyper-V VSS daemon after upgrading CentOS 6.5 to the latest 6.6
ankso posted a blog entry in dead:beef::1Hello, Before some days CentOS team released a new version with number 6.6. After some upgrades and lab tests in the infrastructure I found some problems with the backing up procedure from the DPM and generally with the VSS. To be more specific when you try to take a backup from a CentOS 6.6 upgraded image from CentOS 6.5 with Hyper-V Backup Essentials installed (the module/package which was till 6.5 responsible for the VSS backup on Linux VMs) you are getting freeze the VM (hang) with kernel panic errors on the /var/log/messages file. So the only thing you can do is to hard reset your VM in order to be operational. The thing is that after the hard reset of your VM you will still can't take backup with VSS enabled. The one way to don't mess with this thing is to go on your Hyper-V Manager -> Virtual Machine settings and uncheck the Backup on the Integration Services configuration. The second way to avoid all this thing and use operational the VSS, please follow the below instructions: 1. You have to remove your integration services so you can install again the new released package for CentOS 6.6 (hyperv-daemons) which includes the Online backup ability without any problem rpm -e microsoft-hyper-v kmod-microsoft-hyper-v When uninstall complete please reboot your VM. 2. After the reboot please login on your VM and install the hyperv-daemons package (if you are not root run it with sudo in front of the command below) yum install hyperv-daemons When install complete please reboot your VM. Even after the above instructions completed and the VM is working fine, when you try to backup your VM you will get some errors on your remote console of hang_task_timeout_secs and inside the /var/log/messages file that the Hyper-V VSS: VSS: freeze of /boot: Permission denied. After a contact with Microsoft and some other on Technet the workaround is below. These problems occurs because of the SELINUX is not disable and be more specific it doesn't allow the hyper-v vss daemon to run. To workaround it please do the following: 1. Disable SELINUX 1.1 vi /etc/selinux/config1.2 disable SELINUX1.3 press ESC1.4 :wq1.5 reboot 2. If you are having strictly policy and for some reason you are using the SELINUX firewall module, run the following command in order to give rights on the hyper-v vss daemon to run on your CentOS semanage permissive -a hypervvssd_t If you get an error "command not found" is because you have to install the python policy core utilities that SELINUX uses. Run the following command in order to install them: yum install policycoreutils-python These things above have been tested on Windows Server Hyper-V 2012 R2 and DPM 2012 R2 UR3 and works without any problem (for now) Please, bofore do anything on your production Virtual Machines please test it on your infrastructure too because some things might not be the same or not fitting with the guide above. If you have any additional informations please comment. Have a nice day.