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CentOS and mdadm
by Nicolas Kovacs 01 Dec '20

01 Dec '20

Hi, I'm regularly using software RAID for my CentOS storage servers, either with RAID 1 or RAID 6 depending on the number of disks. Here's two questions about mdadm I've always been wondering about. 1. I'm not sure about the --metadata option. Let's say I want to create a simple RAID 1 setup, I'm usually doing it like this: # mdadm --create /dev/md/boot --level=1 --raid-devices=2 \ --metadata=1.2 /dev/sda1 /dev/sdb1 If anyone can explain the exact meaning of --metadata, I'd be grateful. Oh, and is it OK to use --metadata=1.2 in CentOS 7.x and 8.x ? 2. I'm regularly encountering the mdadm --misc option in various tutorials on the Internet. I looked it up in mdadm's manpage, but it doesn't seem to be documented. Any idea what this option does ? Cheers, 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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Physical position of swap partition on the disk
by Nicolas Kovacs 01 Dec '20

01 Dec '20

Hi, Here's a question to the fine-tuning gurus. Yesterday while installing a fresh CentOS server, I wondered how big of a deal the physical position of the swap partition on the disk is. Here's an example of a simple MBR partitioning scheme on a legacy BIOS machine with a 60 GB SSD: * /dev/sda1: 500 MB /boot ext2 * /dev/sda2: 4 GB swap * /dev/sda3: 55 GB / ext4 In the old (Slackware) days, I created the partitions manually using fdisk. Now when I do something similar in Anaconda, I have to reason in terms of mount points. So in a similar order I create the /boot partition, the swap partition and the root partition. What happens here is that Anaconda will always invert the root and swap partitions and put the swap partition at the end of the disk. So my setup looks like this: * /dev/sda1: 500 MB /boot ext2 * /dev/sda2: 55 GB / ext4 * /dev/sda3: 4 GB swap I'd be curious to know what's the reason behind this, and if this kind of configuration detail is really significant. Cheers, 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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Anaconda : MBR vs. GPT
by Nicolas Kovacs 28 Nov '20

28 Nov '20

Hi, I've always been a bit puzzled by the fact that Anaconda provides no option to manually create a partition table and specify if it's MBR or GPT. >From what I can tell - at least under CentOS 7.x - Anaconda will default to MBR, even if I specify a BIOS Boot partition. Maybe it switches automatically to GPT if the disk size requires it ( > 2 TB IIRC) though I don't have any corresponding hardware here to test it. Is this documented somewhere? Or is there a nifty little trick to tell Anaconda to prefer GPT partition tables? Cheers, 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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Emulate Ghost4Linux with standard Linux commands?
by Nicolas Kovacs 28 Nov '20

28 Nov '20

Hi, I'm currently trying to solve a tricky problem, and I don't even know if it's possible. Let me describe the situation with a practical example. In my office I have a sandbox PC for testing various setups that can't be tested in a virtual machine. I'm using this machine to test various setups with the Linux distributions I'm using, namely CentOS 7, CentOS 8 and OpenSUSE Leap 15. I have a series of Ghost images of these systems on a local FTP server, and I'm using G4L (Ghost4Linux) to transfer these images to and from the server. * https://sourceforge.net/projects/g4l/ On a side note, I take care of zeroing unused disk space in order to get relatively compact disk images like this: # dd if=/dev/zero of=/0bits bs=20M ; rm -f /0bits Besides my local sandbox machine, I also have a sandbox server in a datacenter, which I'm using for testing Internet-facing stuff. I'd like to be able to do something similar with this public machine, e. g. backup the whole disk content completely agnostic in terms of partitions and file systems and send it to a public FTP server. Unfortunately I can't boot G4L on this server, since I don't have physical access to the machine. The datacenter is about 700 km from where I can live. What I can do: fire up a rescue console via an administration web interface and boot a live Linux system, either Ubuntu 16.04 or 18.04. Now here's the question. From within my live system, how could I compress my system into a compact image and then send it to a distant FTP server? And once this is done, how could I get my image back from the server? 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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dnf via ansible fails if baseurl is used on CentOS 8
by Thomas Eriksson 26 Nov '20

26 Nov '20

Hi, I ran into an odd issue on CentOS 8, anyone seen this? When repos are configured to use baseurl instead of mirrorlist, the ansible dnf module fails. It is as if it is ignoring the baseurl configuration. #mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=BaseOS&infra=$infra baseurl=http://my.local.repo.server/$contentdir/$releasever/BaseOS/$basearch/os/ If trying to use the dnf module in ansible, dnf is still trying to find a mirror to use and fails. ansible test-build-0 -m dnf -a "name=zsh state=present" test-build-0 | FAILED! => { "changed": false, "msg": "Failed to download metadata for repo 'BaseOS': Cannot download repomd.xml: Cannot download repodata/repomd.xml: All mirrors were tried", "rc": 1, "results": [] } Using dnf locally from the command line works fine with baseurl If I re-configure with repos using mirrorlist again, ansible dnf works as expected. Just looking for ideas... /Thomas

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Replacing SW RAID-1 with SSD RAID-1
by Frank Bures 26 Nov '20

26 Nov '20

Hi, I want to replace my hard drives based SW RAID-1 with SSD's. What would be the recommended procedure? Can I just remove one drive, replace with SSD and rebuild, then repeat with the other drive? Thanks Frank -- <listfrank1(a)gmail.com>

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Xorg --configure
by Michael Hennebry 24 Nov '20

24 Nov '20

I'm currently running Centos 8 off an SD card. It, unlike F32, lets me use my monitor's full 1440 x 900. Both seem to use defaults and EDID, but F32 gets it wrong and saddles me with 640 x 480 when I can find the incantation to have it run at all. The configuration files and directories I can find are pretty much empty. How do I add --configure to the Xorg command line? 'Tis my understanding that would generate a configuration file that I could port to F32. -- 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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Update from 7 to 8
by Jerry Geis 24 Nov '20

24 Nov '20

I stumbled on this today. https://www.hostwinds.com/guide/upgrading-from-centos-7-to-8/ I understand the best is always a re-install.... But are these steps the next best thing to update from 7 to 8 ? Thanks, Jerry

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installing Centos 8 to an SD card
by Michael Hennebry 24 Nov '20

24 Nov '20

I'm trying to install Centos 8 from a CD burned with Centos-8-2-2004-x86_64-boot , to an SD card in a USB SD card reader. The installer appears not to notice the card reader. Doing a df from tty2 also provides no notice of the card reader. Can what I am trying to do be done? The card currently has a German Knoppix on it. I know from experience that my machine can boot from it. How do I make this happen? -- 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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Password manager for the command line ?
by Nicolas Kovacs 24 Nov '20

24 Nov '20

Hi, On my workstation and my laptop I'm using KeePassXC to store login credentials for my websites. The database is stored in my OwnCloud share, so it's synchronized between my two computers. Ideally I'd like to have something similar for my servers, but command-line driven. I know these tools exist but I haven't tested them yet. What I have in mind is a command-line password manager that stores the database in an encrypted database - like KeePassXC - and then I could eventually store this file in a private Gitlab repo to centralize it and access it from all my servers. Can you recommend any particular command line password manager ? Any recommendations / caveats for this kind of setup ? Cheers from the locked down 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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