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mkfs.fat Device or resource busy
by Michael Hennebry 25 May '20

25 May '20

I'm trying to format a 16 GB SD card to FAT32. Either it won't find the device or it gives me the titular error message. mkfs.fat /dev/sdc I have tried "ejecting" the drive and reinserting the card. I have tried inserting another card, checking to insure that I could see its file, ejecting that card and inserting the target card. If I do not umount it, busy, if I don't, not found. What is the incantation for formatting an SD card. BTW I am using Centos 7 and a USB adapter. -- Michael hennebry(a)web.cs.ndsu.NoDak.edu "Sorry but your password must contain an uppercase letter, a number, a haiku, a gang sign, a heiroglyph, and the blood of a virgin." -- someeecards

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authconfig vs authselect
by Leon Fauster 24 May '20

24 May '20

I had the habit to use authconfig --passalgo=sha512 --update but in EL8 its not supported anymore. The authselect-compat package is installed (and it says "not supported anymore and have no effect). Whats the equivalent call using the new tool "authselect"? -- Thanks Leon

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Re: [CentOS] ether-wake
by Rich Greenwood 23 May '20

23 May '20

Some switch hardware can generate the packets directly, negating the need for a box on every VLAN. Meraki hardware can do it, but you have to go through the dashboard so automating it isn't currently possible. Here is some documentation on forwarding WoL on catalyst 3750 switches from Cisco: https://www.cisco.com/c/en/us/support/docs/switches/catalyst-3750-series-sw… -- Rich Greenwood Network Engineer Shasta County Office of Education 530-225-0161

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External Array Data Migration
by Xinhuan Zheng 23 May '20

23 May '20

Dear All, Below question has been puzzled me for a while, and don’t know if anyone has experienced such puzzle: You have an external array attached to a physical hardware. The operating system is CentOS 5. The file system is created on top of LVM on external array & mounted. The CentOS 5 can see the array controller, and manage all LVM configuration, etc. There is data stored in that external array. At some point, you want to upgrade the operating system to higher version, CentOS 7. Is there a fast way to migrate the external array data volume to new hardware with CentOS 7 without doing machine-to-machine rsync the whole external array data volume? In another words, can I detach external array from old hardware, and attach it to new hardware, then re-configure LVM, so new operating system can recognize the external array file system? Thanks, - Xinhuan

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Re: [CentOS] How to Load Custom CentOS 7 Image
by Xinhuan Zheng 21 May '20

21 May '20

Dear All, > It seems like kickstart is what you are looking for.? > Is this what you were trying to do? Yes, kickstart is what I’m looking for. Let me detail my provisioning process: * Provision a VM with standard CentOS 7 NetInstall ISO & my post script. The file system is created on top of LVM * Export entire VM as custom ISO image to be loaded into physical hardware * Kickstart physical hardware using above exported custom image & different grub/isolinux configuration Although I could just use the same CentOS 7 NetInstall ISO & run all my post script to the physical HW, it may take a few hours, since post script is long, and I wonder if above process will speed up, since the VM has everything needed. If that process isn’t feasible, then I’ll just do the same thing for physical hardware. Thanks, - Xinhuan

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how does autofs deal with stuck NFS mounts and suspending to RAM?
by hw 21 May '20

21 May '20

Hi, after trying sshfs to mount a remote file system on a server with the result that sshfs will sooner or later get stuck and require a reboot of the client, I'm fed up with it and am looking for alternatives. So next I would like to use NFS over a VPN connection instead. To minimize the instances of the NFS mount getting stuck, it might be helpful to use autofs. What happens when the mount is stuck because the connection is down and autofs figures the idle timeout has expired and tries to unmount the remote file system? What happens when I put the client to sleep by suspending to RAM? Will autofs automatically unmount first, or will the server have to deal with a client that has apparently gone away and might re-appear later in unexpected ways? Is there a way to tell NFS to retry an operation _now_ after the connection went down and came back, rather than having to wait for a possibly rather long time? Is there a better alternative for mounting remote file systems over unreliable connections?

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Re: [CentOS] How to Load Custom CentOS 7 Image
by Xinhuan Zheng 20 May '20

20 May '20

Dear Earl Ramirez, >I created a custom ISO a couple of years ago [0], you can use it as >your base of one of the following links[1-4], should be sufficient to >get you started. >[0] https://github.com/EarlRamirez/snipeit_iso In above github project, in https://github.com/EarlRamirez/snipeit_iso/blob/master/isolinux/grub.conf file, there is ‘@‘ symbol for splashimage, and for kernel, @KERNELPATH@, @ROOT@, etc. Will those be replaced by actual values? Where do actual values come from? How does actual values substitute those variables? Thanks again, - Xinhuan

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Transparent Squid and FirewallD : fine-tuning question
by Nicolas Kovacs 19 May '20

19 May '20

Hi, I just setup a very basic HTTP proxy with Squid on a router running CentOS 7. Up until early 2020 I've been using a bone-headed shell script with iptables to configure my firewall. But I decided to follow advice from a few gurus on this list, and I've since moved my configurations to FirewallD, which works nicely. There's one configuration left to tackle, that's port redirection for the Squid proxy server. Which also works fine, though I'd like to figure out a little detail. Here goes. My router has two network interfaces, which I've aptly named WAN and LAN in the NetworkManager configuration: $ nmcli con show NAME UUID TYPE DEVICE WAN 9574b606-8f6d-3edc-95ad-8165df0f3fce ethernet enp2s0 LAN c726b168-1fcd-4dc5-a01d-8ad8a1ba38ee ethernet enp3s1 Squid is acting as a transparent proxy server: $ sudo grep http_port /etc/squid/squid.conf http_port 3128 transparent In my firewall configuration, all requests to port 80 (HTTP) are redirected to port 3128: $ sudo firewall-cmd --permanent --add-forward-port=port=80:proto=tcp:toport=3128:toaddr=192.168.3.1 $ sudo firewall-cmd --reload $ sudo firewall-cmd --list-all internal (active) target: default icmp-block-inversion: no interfaces: enp3s1 sources: services: dhcp dns http squid ssh ports: protocols: masquerade: no forward-ports: port=80:proto=tcp:toport=3128:toaddr=192.168.3.1 source-ports: icmp-blocks: rich rules: In the current state, this configuration works as expected. When a client desktop in the 192.168.3.0/24 network browses HTTP sites on the web, it appears in the Squid log on the server in /var/log/squid/access.log. And here comes the question. How can I redirect all HTTP requests to port 3128 EXCEPT THOSE THAT ARE DIRECTLY AIMED AT THE PROXY SERVER? Here's the thing. The proxy server (amandine.sandbox.lan) is also running httpd to display a static information page for the local network. Now client desktops can access http://amandine.sandbox.lan in a web browser just fine. But this still goes through the proxy, and I'd like these requests to rather be handled directly. In iptables syntax this would vaguely look like this: $ iptables -A PREROUTING -t nat -i 192.168.3.1 -p tcp \ ! -d 192.168.3.1 --dport 80 -j REDIRECT --to-port 3128 How can I translate the "! -d 192.168.3.1" part into some FirewallD-specific syntax ? Cheers from the sunny South of France, Niki -- Microlinux - Solutions informatiques durables 7, place de l'église - 30730 Montpezat Site : https://www.microlinux.fr Mail : info(a)microlinux.fr Tél. : 04 66 63 10 32 Mob. : 06 51 80 12 12

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Centos8.1 Plymouthd crash 913: ply_event_loop_watch_for_timeout: Assertion `seconds > 0.0' failed.
by LAHAYE Olivier 18 May '20

18 May '20

Hi, I’m running a special initrd generated for SystemImager with a special dracut module that relies on plyouth scripted theme. It works perfectly on CentOS-6, CentOS-7, OpenSUSE-42.3, Fedora-29 (not tested later) and used to work on CentOS-8.0 Since CentOS-8.1 was released, IT chrashes with the following error: Plymouthd crash 913: ply_event_loop_watch_for_timeout: Assertion `seconds > 0.0' failed. I’m running quemu 5.0.0 with tianocore UEFI bios on MacOS (using accel=none or accel=hvf) (Bug also occurs with standard 256k bios) When I strace, I see multiple reasons but I can’t tell wich one is fatal. 1/ plymouthd reads /etc/Plymouth/plymouthd.conf (ok), then tries to read them from /var/run/plymouth/themes/<themename> instead of /usr/share/plymouth/themes/<themename>/ . As it fails it tries to read /var/run/plymouth/plymouthd.defaults (fails) then /usr/share/plymouth//plymouthd.defaults (ok) then it tries to read the theme /var/run/plymouth/themes/<themename>/<themename>.plymouth (fails) but never tries to read in from /usr/share/plymouth/themes/<themename>/<themename.plymouth> ??? It still continues 2/ After a few things, it tries to read /sys/devices/virtual/drm/ttm/uevent (ok) and the it tries to read /run/dev/data/+drm:ttm (fail). Is it expectable or does this means a problem like a missing udev rule or a boch driver bug or something else? 3/ Same as step 2 4/ Crash with @lymouthd: ply-event-loop.c:913: ply_event_loop_watch_for_timeout: Assertion `seconds > 0.0' failed. I’ve reported this in Centos-8.1 with no return and then RedHat-8.1 today. RedHat 8.1 bug report: https://bugzilla.redhat.com/show_bug.cgi?id=1836828 CentOS-8.1 bug report: https://bugs.centos.org/view.php?id=17140 Any idea where I could look for? More likely a plymouth bug or an udev missing rule or something else? (full dmesg and strace log in bug reports) Thanks a lot for any tips. PS: looking at google results, the only things I can find are very old bugs without resolution (not fixed and obsoleted due to new OS release) -- Olivier LAHAYE

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Live Patching Upgrade CentOS 7
by Xinhuan Zheng 18 May '20

18 May '20

Dear All, Does anyone know how to to live patching upgrade of CentOS 7 without rebuilding the whole boot volume? I have enough disk space in Boot volume. I don’t want to go through creating a new VM and install CentOS 7 patch release. Thanks, - Xinhuan

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