we want to test the network on all Linux machines  after all machines and switches configured to MTU=9000  the reason for that is because inconsistent MTU configuration can cause huge problem  so in our hadoop cluster we have ~50 machines and also switches that configured also  what are the Linux CLI that can approve that all linux / switches configured with MTU=9000  as all know ifconfig -a , show the MTU value  but we want to test it on each machine that MTU is real working
121929
We have some Red Hat servers, cluster servers for a mabri cluster.  A few questions:   Which Linux command prints the current MTU value? We have not yet configured MTU in the ifcfg file) What is the default MTU value (assuming that we installed the Red Hat machine from an ISO image) In which cases do we need to use high MTU values and what is the maximum value? What is the formula to calculate the MTU?
104887
I have 3 old computers lying around right now running a P2 at 800 MHz(?), Intel Mobile 1.6 GHz, AMD Athlon XP 2000+ at 1.66 GHz, and (might not use this) P4 at 2.7 GHz, all with 512 MB Ram, and am considering clustering them together for fun/knowledge. They would be running an undecided version of linux, preferably ubuntu based.   The issue is what I want to use it for: general computing and occasional video encoding. By general computing I mean day to day tasks. However I'm not sure if every program started by a single X session is going to exist on the same machine, defeating the purpose of such a system. Will programs be split up or exist on one machine?  Second, assuming this is running 100baseT ethernet (not sure if the PCI slot itself could handle Gigabit), would the speed of having a program exist over the network be an issue? It seems that the constant asking of various things in RAM would be quite slow.  And before you say "buy another computer!", that's not the point of this question. I'm asking would it be usable, not necessarily practical. And yes I know, this is going to be extreamly power consuming.
98476
I have bought an Alfa AWUS036NH and I think I have set it up properly but when I type ifconfig while running Kali Linux, there is no device showing an IPv4 address.   Output:  eth0: flags=4163&lt;UP,BROADCAST,RUNNING,MULTICAST&gt;  mtu 1500         inet 10.0.2.15  netmask 255.255.255.0  broadcast 10.0.2.255         inet6 fe80::a00:27ff:fef0:7ead  prefixlen 64  scopeid 0x20&lt;link&gt;         ether 08:00:27:f0:7e:ad  txqueuelen 1000  (Ethernet)         RX packets 2057987  bytes 1965468395 (1.8 GiB)         RX errors 0  dropped 0  overruns 0  frame 0         TX packets 743272  bytes 114166643 (108.8 MiB)         TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0  lo: flags=73&lt;UP,LOOPBACK,RUNNING&gt;  mtu 65536         inet 127.0.0.1  netmask 255.0.0.0         inet6 ::1  prefixlen 128  scopeid 0x10&lt;host&gt;         loop  txqueuelen 1000  (Local Loopback)         RX packets 1198257  bytes 1736573576 (1.6 GiB)         RX errors 0  dropped 0  overruns 0  frame 0         TX packets 1198257  bytes 1736573576 (1.6 GiB)         TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0  wlan0mon: flags=4163&lt;UP,BROADCAST,RUNNING,MULTICAST&gt;  mtu 1500         unspec 00-11-22-33-44-55-30-3A-00-00-00-00-00-00-00-00  txqueuelen 1000  (UNSPEC)         RX packets 0  bytes 0 (0.0 B)         RX errors 0  dropped 0  overruns 0  frame 0         TX packets 0  bytes 0 (0.0 B)         TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0
43370
we need to add disks on more then 100 redhat machines,  therefore we need to update also the /etc/fstab on each machine  the problem is that some machines configured with UUID and other with ordinary dev in fstab  so I want to make a bash script that will identify the fstab configuration as the following   in case fstab configured with UUID add new UUID lines for each additional disk in case fstab configured with ordinary dev then add new dev lines for each additional disk   so my question is - what is the best approach to identify what configured in fstab  UUID or ordinary dev ?  remark - not include the OS , we talk here only on additional disks in HW machines   here is example of linux machine with UUID conf in fstab  /dev/mapper/vg00-loov_root /                    xfs     defaults      00  UUID=7de1dc5c-b605-4a6f-bdf1-f1e869f6ffb9 /boot                   xfs      defaults        0 0 /dev/mapper/vg00-loov_var /var                    xfs     defaults       00  /dev/mapper/vg00-loov_swap swap                    swap    defaults      00  UUID="fcb73644-4ad3-4b19-85f8-dbb9ed53a871"   /data/sdb                        ext4 defaults,noatime 0 0 UUID="5f56c1d6-266f-4ea2-a8f7-df06f08e01c0"   /data/sdc                        ext4 defaults,noatime 0 0 UUID="4c908671-4045-41e8-a396-a5198978e3ac"   /data/sdd                        ext4 defaults,noatime 0 0 UUID="d44fe62a-72dc-4674-91ac-5a1962797e22"   /data/sde                        ext4 defaults,noatime 0 0 UUID="ee3d8fa8-e000-4abb-a26c-da99499e630c"   /data/sdf                        ext4 defaults,noatime 0 0 UUID="61e9e16f-eb49-4c97-aaf0-0ed2dc3f3007"   /data/sdg                        ext4 defaults,noatime 0 0 UUID="ada12394-0e0b-4657-a148-d85548d7bc75"   /data/sdh                        ext4 defaults,noatime 0 0
2113
So, let's say your server had 6 healthy hard drives.  A drive fails (will not mount/detect, drops out of raid with errors) or is failing (SMART getting worse, etc).  You need to swap out the bad drive.  When you open the case you see.. six identical hard drives.  How can you tell which one is no longer healthy/mounting/functioning?  System would be linux, most likely ubuntu server, using at most simple software RAID.  The hard drives would be SATA and connected directly to the motherboard. (no raid controller)   I don't want to randomly disconnect drives until I pick the correct one.  The drives all appear identical to me; I imagine there is some common way to identify which drive is which that I am unaware of.  Does anyone have any pointers/tips/best practices?  Thanks!  EDIT: I had wanted this to be 'generalized' in a hand-wavy sort of way, but it just came off as 'incomplete' and 'horrible'.  My bad!
49281
Does anyone know how shared access (multiple Initiators) to a single iSCSI target is supposed to work.  I have got it semi-working with Linux (CentOS-7) target and Win 2012 server / Win Hyper-V 2012 R2 Initiators.  Problem is each instance seems to get it's own version of the NTFS partition.  The reason for doing this is so that I can have my virtual machine files hosted on the remote iSCSI target and migrate the actual running virtual machines between servers.  Without sharing the iSCSI target I cannot see any way of doing this.
107540
I have a mixed network with mostly Windows machines, a Mac, and a few Linux boxes.  There is no DNS or WINS server, and adding one is outside of my control.  If I put a clean install of 10.04 desktop on a computer, then all other machines on the network can get to that machine by hostname just fine.    However, if I put 10.04 server on the same computer, then the other machines can only get to it by IP address.  The hostname does not resolve.  What do I need to do on the server so that all the other machines on the network can get to it?
83186
Often times I will ssh into a new client's box to make changes to their website configuration without knowing much about the server configuration. I have seen a few ways to get information about the system you're using, but are there some standard commands to tell me what version of Unix/Linux I'm on and basic system information (like if it is a 64-bit system or not), and that sort of thing?  Basically, if you just logged into a box and didn't know anything about it, what things would you check out and what commands would you use to do it?
30776
I'm still kinda new to linux and my understanding was I could let multiple people (at the most me + two more) use my pc at the same time. If this is indeed the case, how do I?
123692
I run a small academic research group and we have 4 workstations and one server, all running Ubuntu. I would like to have login credentials that are shared across all workstations and the server, so I can issue a userid once, and the user could sit down at any workstation and login. Nominally, the filesystem would be shared so that the user could have their files/desktop environment at any workstation. Is there any way to set up such a environment?
60991
we want to verify if raid1 is configured on out linux machine  so we found the answer on -   but from the output -  how we can be sure that raid1 is configured?  and how to understand it from the command: dmesg | grep raid  when non raid , and when raid1 is configured ?
122504
I've been banging my head against for wall for a while with this one.  I want to SSH into a set of machines and check whether they are available (accepting connections and not being used). I have created a small script, tssh, which does just that:  #!/bin/bash  host=$1 timeout=${2:-1}  ssh -qo "ConnectTimeout $timeout" $host "[ \`who | cut -f1 | wc -l \` -eq 0 ] &amp;&amp; exit 0 || exit 1"   This script works correctly. Returning 255 if there was a connection problem, 1 if the machine is busy and 0 if everything is good. If anyone knows a better way to do this please let me know.  So next I try and call tssh on my set of machines using a while read loop, and this is where it all goes wrong. The loop exits as soon as tssh returns 0 and never completes the full set.   while read nu ; do tssh "MYBOXES$nu" ; done &lt; &lt;(ruby -e '(0..20).each { |i| puts i }')   At first I thought this was a subshell problem but apparently not. Any help, along with comments on style/content, would be much appreciated! I know I'm going to kick myself when I find out why...
70793
I've just cloned a computer () and I want to make sure it will be OK on the same network as the original.   I've changed the host name back to what it was pre cloning, so there won't be duplicates on the network, but I want to make sure I make any other necessary fixes before I put the computers running Ubuntu 12.04, on the same network. Is there anything else I need to do before I link them back up?
116034
I have linux redhat machine version 6.5  I reboot machine and work as single user mode ,   then I set the network on eth0 with default gw address   /etc/sysconfig/network-script/ifcfg-eth0   but from some reason dg address not appears from netstat -rn after service network restart  my question - can we set default gw address and start network when we in single user mode ?
96565
It is my understanding that the main difference between a network hub and a network switch is that the hub always sends out all packets to all (other?) hosts while the switch is smart about it and keeps track of which port belongs to which MAC address via MAC address tables and whatnot. If a packet is addressed to a host which is connected to the switch but have never sent or received anything, the switch acts like a hub would. But every subsequent packet addressed to that host is not broadcast to the other hosts but forwarded only to that specific host. Please correct me if I got something wrong. Does a network bridge in Linux act like a hub would, or like a switch?
82600
I think this is kernel dependent and probably will change over time depending on the kernel a release uses, correct me if wrong  I'd like to know two things for all the currently supported Ubuntu releases:  How many maximum CPUs can Ubuntu handle (by default) at the same time with a standard desktop kernel? Is that count different from a server kernel and 32bit/64bit systems?  Where can I find that information on my system?
106062
I'm trying to configure a ubuntu server network. [Edit] My ifconfig: lo: flags=73&lt;UP,LOOPBACK,RUNNING&gt; mtu 65536 inet 127.0.0.1 netmask 255.0.0.0 inet6 ::1 prefixlen 128 scopeid 0x10&lt;host&gt; loop txqueuelen 1000 (Loopback Local) RX packets 352 bytes 26160 (26.1KB) RX erors 0 dropped 0 overruns 0 frame 0 TX packets 352 bytes 26160 (26.1KB) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0  I edited the /etc/network/interfaces file and here is how it is: auto lo auto eth0 iface eth0 inet static address 192.168.15.141 netmask 255.255.255.0 gateway 192.168.15.1  I'm trying to restart the server and I'm using: sudo ifdown --exclude=lo -a &amp;&amp; sudo ifup --exclude=lo -a  This command is an answer from this link:  And I'm getting the following error: Cannot find device &quot;eth0&quot; Failed to bring up eth0.  I'm pretty lay in configuring a server, so I have no idea what's going on. Can someone help me please?