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Thread: ubuntu server disconnection issue

  1. #1
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    ubuntu server disconnection issue

    Hello,
    I set up a web server based on ubuntu a while ago. I had initially set it up under ubuntu desktop, but as the problem persisted I switched to ubuntu server (the latest LTS version, everything is up to date with apt).
    The server disconnects randomly from the internet (it's connected via ethernet). I can't even see it on my box's configuration page. I only have ports 80 and 443 open on my box and I have set up a dmz on the server from my box. I am currently with red by sfr (a French operator) with a NB6VAC-FXC-r1 box and a NB6VAC-MAIN-R4.0.45d program version. I have only installed the nextcloud package on the server using snap (I had previously configured owncloud). I've also set up a static local IP address for the server on my box's control panel.
    Is this a server configuration problem? Server security? Or the box itself?
    Have a nice day.
    PS: I'm French, sorry in advance if my English is bad...

  2. #2
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    Re: ubuntu server disconnection issue

    Less discussion. More facts. Run commands to show what you think the issues are. Please show the exact, full, command AND the output from it. Wrap both in forum code-tags.

    I'm confused about a DMZ for a system hosted at a provider. That doesn't make any sense. Those systems are already on the public internet and don't generally have any firewall rules, unless you added some to the system. The only firewall rules I've seen in my VPS hosts are that SMTP traffic was blocked, until I asked them to unblock it. Besides that, it was open to the world until I set up some ipset block rules to keep the nastiest parts of the internet away.

    Also "latest LTS" isn't clear. Exactly, which release? lsb_release -d will tell us. "Latest" is never specific enough, since we don't know what YOU believe.
    Last edited by TheFu; 4 Weeks Ago at 05:26 PM.

  3. #3
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    Re: ubuntu server disconnection issue

    Quote Originally Posted by eraknix View Post
    server disconnects randomly from the internet
    What does this mean? What objective facts, tools and reasoning did you use to come to this conclusion?

  4. #4
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    Re: ubuntu server disconnection issue

    Hello,
    Thank you for your answers. I may have misspoken, but the machine is at my home and I host the server there. The lsb_release -d command gave "Ubuntu 24.04 LTS". I know it's not connected because I can't access it via ssh even on the local network (it's not even connected to the local network any more). On my internet box page, it is not displayed, it is only when I physically restart it that it reconnects.
    What commands would you like me to run?
    Thanks again.

  5. #5
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    Re: ubuntu server disconnection issue

    Perhaps another device on the local network shares an IP address? Are you using DHCP or static assignments?

    "sudo tcpdump -qni any arp" would reveal such a common problem.

  6. #6
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    Re: ubuntu server disconnection issue

    Please use forum code tags to post the exact commands and output.

    I don't care which commands you run. What commands do you believe you should run to prove your statements? ssh is very high up a software stack. Perhaps if you started lower and checked for basic connectivity, basic network services, and check bi-directionally (from outside the host and inside the host)?

    These forums are full of posts where people claim they don't have connectivity. What commands did the helpers ask them to run? Have you run those? What were the EXACT results? <---- this is another hint to show your work.

    BTW, this question comes up so often that I wrote a blog article about it in 2013 - https://blog.jdpfu.com/2013/03/01/li...101-networking . That's one way to go, but there are almost always 50 different solutions to any Unix problem.

    I'll be gone for a while, perhaps until Monday. My LUG is meeting in a few minutes and life does get in the way for all of us.

  7. #7
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    Re: ubuntu server disconnection issue

    Quote Originally Posted by currentshaft View Post
    Perhaps another device on the local network shares an IP address? Are you using DHCP or static assignments?

    "sudo tcpdump -qni any arp" would reveal such a common problem.
    Way to jump to step 45 of troubleshooting this type of issue. There are so many much more likely problems to check first before throwing someone into tcpdump.

  8. #8
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    Re: ubuntu server disconnection issue

    Thanks for your answers, I'm going to follow the advice on the site when the server stops working, the problem is that I don't know when..., just the
    Code:
    dmesg |grep eth[0-9]
    command didn't do anything, even with sudo.
    Have a nice day.

  9. #9
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    Re: ubuntu server disconnection issue

    It is important to do things in the correct order and share the results - IN THAT ORDER.

  10. #10
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    Re: ubuntu server disconnection issue

    Ok, for the command
    Code:
    ip addr
    :
    Code:
    1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
        inet 127.0.0.1/8 scope host lo
           valid_lft forever preferred_lft forever
        inet6 ::1/128 scope host noprefixroute
           valid_lft forever preferred_lft forever
    2: eno1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP group default qlen 1000
        link/ether 30:9c:23:ac:99:96 brd ff:ff:ff:ff:ff:ff
        altname enp33s0
        inet 192.168.1.87/24 metric 100 brd 192.168.1.255 scope global dynamic eno1
           valid_lft 70635sec preferred_lft 70635sec
        inet6 fe80::329c:23ff:feac:9996/64 scope link
           valid_lft forever preferred_lft forever
    for
    Code:
    route -n
    :
    Code:
    Kernel IP routing table
    Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
    0.0.0.0         192.168.1.1     0.0.0.0         UG    100    0        0 eno1
    192.168.1.0     0.0.0.0         255.255.255.0   U     100    0        0 eno1
    192.168.1.1     0.0.0.0         255.255.255.255 UH    100    0        0 eno1
    all the pings tests went well. (It's normal because there is no problem now)
    For
    Code:
    dmesg |grep eth[0-9]
    :
    Code:
    dmesg: read kernel buffer failed: Operation not permitted
    and with sudo, nothing happens.
    For
    Code:
    sudo lshw -C network
    :
    Code:
    *-network
           description: Ethernet interface
           product: I211 Gigabit Network Connection
           vendor: Intel Corporation
           physical id: 0
           bus info: pci@0000:21:00.0
           logical name: eno1
           version: 03
           serial: 30:9c:23:ac:99:96
           size: 1Gbit/s
           capacity: 1Gbit/s
           width: 32 bits
           clock: 33MHz
           capabilities: pm msi msix pciexpress bus_master cap_list ethernet physical tp 10bt 10bt-fd 100bt 100bt-fd 1000bt-fd autonegotiation
           configuration: autonegotiation=on broadcast=yes driver=igb driverversion=6.8.0-35-generic duplex=full firmware=0. 6-2 ip=192.168.1.87 latency=0 link=yes multicast=yes port=twisted pair speed=1Gbit/s
           resources: irq:25 memory:fc900000-fc91ffff ioport:f000(size=32) memory:fc920000-fc923fff
    For
    Code:
    ifconfig -a
    :
    Code:
    eno1: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
            inet 192.168.1.87  netmask 255.255.255.0  broadcast 192.168.1.255
            inet6 fe80::329c:23ff:feac:9996  prefixlen 64  scopeid 0x20<link>
            ether 30:9c:23:ac:99:96  txqueuelen 1000  (Ethernet)
            RX packets 5094979  bytes 7634868115 (7.6 GB)
            RX errors 0  dropped 9398  overruns 0  frame 0
            TX packets 931656  bytes 63270606 (63.2 MB)
            TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0
            device memory 0xfc900000-fc91ffff
    
    
    lo: flags=73<UP,LOOPBACK,RUNNING>  mtu 65536
            inet 127.0.0.1  netmask 255.0.0.0
            inet6 ::1  prefixlen 128  scopeid 0x10<host>
            loop  txqueuelen 1000  (Local Loopback)
            RX packets 19087  bytes 10049009 (10.0 MB)
            RX errors 0  dropped 0  overruns 0  frame 0
            TX packets 19087  bytes 10049009 (10.0 MB)
            TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0
    For
    Code:
    more /etc/resolv.conf
    :
    Code:
    # This is /run/systemd/resolve/stub-resolv.conf managed by man:systemd-resolved(8).
    # Do not edit.
    #
    # This file might be symlinked as /etc/resolv.conf. If you're looking at
    # /etc/resolv.conf and seeing this text, you have followed the symlink.
    #
    # This is a dynamic resolv.conf file for connecting local clients to the
    # internal DNS stub resolver of systemd-resolved. This file lists all
    # configured search domains.
    #
    # Run "resolvectl status" to see details about the uplink DNS servers
    # currently in use.
    #
    # Third party programs should typically not access this file directly, but only
    # through the symlink at /etc/resolv.conf. To manage man:resolv.conf(5) in a
    # different way, replace this symlink by a static file or a different symlink.
    #
    # See man:systemd-resolved.service(8) for details about the supported modes of
    # operation for /etc/resolv.conf.
    
    
    nameserver 127.0.0.53
    options edns0 trust-ad
    search .
    and finally for
    Code:
    route
    :
    Code:
    Kernel IP routing table
    Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
    default         box             0.0.0.0         UG    100    0        0 eno1
    192.168.1.0     0.0.0.0         255.255.255.0   U     100    0        0 eno1
    box             0.0.0.0         255.255.255.255 UH    100    0        0 eno1
    For the pings, it doesn't reach 192.168.1.0, I don't know if it's normal or not.

    Thanks again.

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