Discuss August 2020

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95 participants
66 discussions

Dumb Centos 8 DNF mirror question...
by Tom Bishop 14 Aug '20

14 Aug '20

I have several Centos 8 machines that I update and every now and again I will go through and update all of them and one of them will get a slow mirror, like downloading the kernel at 50kb etc. With the newer version I am unable to figure out how to force it to update the mirror list and hopefully change to a faster mirror. I have searched but must not be using the right verbiage since I am unable to find the easy solution to dump the mirrors and re-select. Thanks :)

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After update to 8 (2004) ... system is unbootable - UEFI Secure boot
by Leon Fauster 13 Aug '20

13 Aug '20

Hi all, I updated a Dell XPS laptop from CentOS 8.1 (1911) to 8.2 (2004). Installed kernels are kernel-4.18.0-147.5.1.el8_1.x86_64 kernel-4.18.0-147.8.1.el8_1.x86_64 kernel-4.18.0-193.6.3.el8_2.x86_64 Unfortunately I can not boot into the latest kernel-4.18.0-193.6.3.el8_2.x86_64. After grub2 screen I only see following line: EFI stub: UEFI Secure Boot is enabled Booting into the older kernel is still possible. The above line appears and after that the normal kernel output scrolls over the screen (rhgb quiet disabled). Is the new kernel correctly signed? What can I do? -- Thanks Leon

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kvm & external snapshots
by Gregory P. Ennis 13 Aug '20

13 Aug '20

Everyone, I am trying to create external snapshots of a kvm guest machine and have not been able to do so. In accordance with : https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/7/ht… I have used the command line : snapshot-create-as --diskspec vda,snapshot=external,file=/u4/guest/MaBa- clone/test.snap.img--domain MaBa-clone --name MaBa-clone_snap --description "Snap before 9Aug2020" This command line gives me the error : error: unsupported configuration: disk 'vda' must use snapshot mode 'internal' Is it possible to perform an external snapshot of a kvm guest? Greg Ennis

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[Sharing] CentOS 8.2 (2004) Linux Server is Compatible with Dell PowerEdge R640 1U Server
by Turritopsis Dohrnii Teo En Ming 13 Aug '20

13 Aug '20

Subject: [Sharing] CentOS 8.2 (2004) Linux Server is Compatible with Dell PowerEdge R640 1U Server Good day from Singapore, I have just installed CentOS 8.2 (2004) Linux Server on Dell PowerEdge R640 1U Server for "Donald Trump and Xi Jinping Investment Company LLP" (fictitious/fictional company name used) in Singapore on 11 August 2020 Tuesday. I can confirm that CentOS 8.2 (2004) is compatible with Dell PowerEdge R640. The hardware specifications of Dell PowerEdge R640 are: (1) Processor: Intel Xeon Silver 4210R CPU @ 2.40 GHz (10 cores, 20 threads) (2) 128 GB DDR4-2400 RAM (8 pieces of 16 GB RAM, all 8 slots filled up) (3) PERC H740P Mini RAID Controller (4) 2 units of 960 GB SATA 6 Gbps SSD in RAID 1 configuration (5) Network Ports: 4 x 1 GbE 2 x 10 GbE + 2 x 1 GbE Just sharing only. -- -----BEGIN EMAIL SIGNATURE----- The Gospel for all Targeted Individuals (TIs): [The New York Times] Microwave Weapons Are Prime Suspect in Ills of U.S. Embassy Workers Link: https://www.nytimes.com/2018/09/01/science/sonic-attack-cuba-microwave.html ******************************************************************************************** Singaporean Mr. Turritopsis Dohrnii Teo En Ming's Academic Qualifications as at 14 Feb 2019 and refugee seeking attempts at the United Nations Refugee Agency Bangkok (21 Mar 2017), in Taiwan (5 Aug 2019) and Australia (25 Dec 2019 to 9 Jan 2020): [1] https://tdtemcerts.wordpress.com/ [2] https://tdtemcerts.blogspot.sg/ [3] https://www.scribd.com/user/270125049/Teo-En-Ming -----END EMAIL SIGNATURE-----

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Testing
by Turritopsis Dohrnii Teo En Ming 13 Aug '20

13 Aug '20

Testing

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Docker swarm service misconfigured in FirewallD / CentOS 7
by Nicolas Kovacs 13 Aug '20

13 Aug '20

Hi, I'm currently fiddling with Docker Swarm on three sandbox servers running CentOS 7. Unfortunately I couldn't get even the most basic configuration running. After some experimenting and investigating, it turns out there's a problem with FirewallD. Here's what I did first on every single node. # firewall-cmd --permanent --add-service=docker-swarm # firewall-cmd --reload I launched a simple web service like this: # docker service create --name web -p 80:80 nginx My three nodes appear correctly with 'docker node ls'. >From here, I should be able to open the Nginx default web page in a web browser using any node's hostname. But nothing happens. No page is loaded. On a whim, I turned off FirewallD, and suddenly everything worked as expected. Now here's the list of ports that have to be open on every single node for Docker Swarm to work: * 2376/tcp * 2377/tcp * 7946/tcp * 7946/udp * 4789/udp And here's what docker-swarm.xml looks like under CentOS 7: # cat /usr/lib/firewalld/services/docker-swarm.xml <?xml version="1.0" encoding="utf-8"?> <service> <short>Docker integrated swarm mode</short> <description>Natively managed cluster of Docker Engines (>=1.12.0), where you deploy services.</description> <port port="2377" protocol="tcp"/> <port port="7946" protocol="tcp"/> <port port="7946" protocol="udp"/> <port port="4789" protocol="udp"/> <protocol value="esp"/> </service> So it looks like TCP port 2376 was forgotten in that service definition. I opened it up manually on every node: # firewall-cmd --permanent --add-port=2376/tcp # firewall-cmd --reload And now Docker Swarm works correctly. Cheers from the sunny South of France, Niki Kovacs -- Microlinux - Solutions informatiques durables 7, place de l'église - 30730 Montpezat Site : https://www.microlinux.fr Blog : https://blog.microlinux.fr Mail : info(a)microlinux.fr Tél. : 04 66 63 10 32 Mob. : 06 51 80 12 12

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NFSroot over wifi in CentOS 7 - graceful shutdown problem
by Dmitry E. Mikhailov 13 Aug '20

13 Aug '20

Hi, I've got a task to have a small number of laptops netboot Linux over WiFi. The kernel is loaded off the USB stick of cource, it's off topic for now. The WPA-supplicant daemon is started early by dracut off initrd. It works. Mostly. The problem is that upon shutdown systemd terminates all the processes FIRST and unmounts filesystems NEXT. Guess what? Upon termination, wpa-supplicant brings the wireless interface down and the system hangs being unable to unmount now-defunct NFSroot. There were some discussions regarding similar matter and there's even the RH Errata: https://access.redhat.com/errata/RHBA-2018:2447 But I'm woking on a fully updated CentOS Linux release 7.8.2003 and nevertheless I've got the problem. I don't have rights to see the BZ. https://bugzilla.redhat.com/show_bug.cgi?id=1593649 I'm deciding to use a quick and dirty hack to do a totally ungraceful shutdown/reboot: https://unix.stackexchange.com/questions/533307/systemd-fails-to-umount-man… Any better ideas? Best regards, Dmitry Mikhailov.

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Install OpenVAS on CentOS Linux release 8.2.2004 (Core)
by Kaushal Shriyan 12 Aug '20

12 Aug '20

Hi, I am running CentOS Linux release 8.2.2004 (Core). Are there any instructions to install OpenVAS for CentOS Linux release 8.2.2004 (Core)? Thanks in advance and I look forward to hearing from you. Best Regards, Kaushal

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Re: [CentOS] systemd syslog.target
by ctcard 11 Aug '20

11 Aug '20

Thanks Simon,I think my question got a bit lost amongst all the grub issues - does anyone else have information about whether any references to syslog.target in systemd unit files can be removed?ChrisSent from Samsung Mobile on O2 -------- Original message -------- From: Simon Matter via CentOS <centos(a)centos.org> Date: 31/07/2020 10:02 (GMT+00:00) To: CentOS mailing list <centos(a)centos.org> Subject: Re: [CentOS] systemd syslog.target Hi,>> I've noticed that there are several systemd unit files in CentOS 7 and 8> with the optionAfter=syslog.targetin the [Unit] section, but since systemd> version 198 syslog.target has not existed.I deduce from this that> "After=syslog.target" is ignored by systemd and can therefore be removed.> Is this correct? I am writing some systemd unit files for our own services> which previously used init.d scripts, so I want to ensure I'm not causing> problems by omitting "After=syslog.target"ChrisSent from Samsung Mobile on> O2Interesting, there is really no syslog.target on either CentOS 7 or 8. Butif a service needs classic syslog, shouldn't it have another After=instead?Simon_______________________________________________CentOS mailing listCentOS@centos.orghttps://lists.centos.org/mailman/listinfo/centos

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Docker container isolation not working in CentOS 7
by Nicolas Kovacs 10 Aug '20

10 Aug '20

Hi, I've decided to use these summer holidays to wrap my head around Docker and its quirks. Spent the last couple weeks working through a Udemy tutorial and a thick book about Docker, and I have Docker CE installed on two machines: * my workstation running OpenSUSE Leap 15.1 * a public sandbox server running CentOS 7 I'm currently fiddling with custom networks and container isolation, and it looks like I discovered a bug or at least an inconsistency in CentOS. Maybe the gurus among you have an explanation for this. Sorry if this is a bit long, but I try to be as clear as possible. OpenSUSE Leap 15.1 ------------------ For demonstration purposes on how things *should* be, I'm starting two Nginx containers named "webserver1" and "webserver2": $ docker run -dit --name webserver1 nginx $ docker run -dit --name webserver2 nginx These two containers have the respective 172.17.0.2 and 172.17.0.3 IP addresses: $ docker network inspect bridge | grep -i ipv4address "IPv4Address": "172.17.0.2/16", "IPv4Address": "172.17.0.3/16", The "webserver1" container has the 172.17.0.2 IP address: $ docker exec -it webserver1 hostname -I 172.17.0.2 Since "webserver1" and "webserver2" are both on the "bridge" network, they can communicate with each other: $ docker exec -it webserver1 curl -m 5 http://172.17.0.3 <!DOCTYPE html> <html> <head> <title>Welcome to nginx!</title> ... Now I'm creating the custom "blog" network: $ docker network create blog $ docker network ls NETWORK ID NAME DRIVER SCOPE e02e6fc654c6 blog bridge local 3ea6f28134ba bridge bridge local 8d2b8dfe5352 host host local 0bd337e274c2 none null local I'm starting a third container named "webserver3" and assign it to the new "blog" network: $ docker run -dit --name webserver3 --network blog nginx This new container is in a whole new network segment: $ docker network inspect blog | grep -i ipv4address "IPv4Address": "172.20.0.2/16", As is to be expected, it can't communicate with the other two containers: $ docker exec -it webserver3 curl -m 5 http://172.17.0.2 curl: (28) Connection timed out after 5001 milliseconds $ docker exec -it webserver3 curl -m 5 http://172.17.0.3 curl: (28) Connection timed out after 5001 milliseconds So far so good. CentOS 7 -------- Now let's repeat the exact same experiment on a server running CentOS 7. First, create two containers on the default "bridge" network and check if they can communicate with each other: $ docker run -dit --name webserver1 nginx $ docker run -dit --name webserver2 nginx $ docker network inspect bridge | grep -i ipv4address "IPv4Address": "172.17.0.3/16", "IPv4Address": "172.17.0.2/16", $ docker exec -it webserver1 hostname -I 172.17.0.2 $ docker exec -it webserver1 curl -m 5 http://172.17.0.3 <!DOCTYPE html> <html> <head> <title>Welcome to nginx!</title> ... Now create a custom "blog" network and start a third container assigned to that network: $ docker network create blog $ docker network ls | grep blog 0571c80fef1b blog bridge local $ docker run -dit --name webserver3 --network blog nginx $ docker network inspect blog | grep -i ipv4address "IPv4Address": "172.19.0.2/16", $ docker exec -it webserver3 hostname -I 172.19.0.2 Now IN THEORY "webserver3" shouldn't be able to communicate with the "webserver1" and "webserver2" containers. But here's what happens IN PRACTICE (and only on CentOS 7): $ docker exec -it webserver3 curl -m 5 http://172.17.0.2 <!DOCTYPE html> <html> <head> <title>Welcome to nginx!</title> ... $ docker exec -it webserver3 curl -m 5 http://172.17.0.3 <!DOCTYPE html> <html> <head> <title>Welcome to nginx!</title> ... As far as I'm concerned, it looks like a bug, it walks like a bug and it quacks like a bug. Any remarks and/or suggestions? Cheers from the sunny South of France, Niki -- Microlinux - Solutions informatiques durables 7, place de l'église - 30730 Montpezat Site : https://www.microlinux.fr Blog : https://blog.microlinux.fr Mail : info(a)microlinux.fr Tél. : 04 66 63 10 32 Mob. : 06 51 80 12 12

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Discuss August 2020