Discuss April 2020

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90 participants
69 discussions

Upgraded to 7.10 from 6...
by mark 03 Apr '20

03 Apr '20

Let me start out by making clear I *LOATHE* gnome, ok? So I don't want to hear about it. What's happening is this: I did this: yum groupinstall "Development and Creative Workstation" yum groupinstall "KDE Plasma Workspaces" Now, when I go in graphical mode, I try to change to kde on login. Nope - minutes later, I can see a cursor, and a gray screen. Ditto on the "safe mode", and ditto on "gnome classic". What have I missed? mark

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IOMMU and kernel
by Georgios 03 Apr '20

03 Apr '20

Hi. Im trying to set intel_iommu=on on kernel parameters at grub but for some reason it doesnt work. I edit /etc/default/grub file and i add the parameter. then i run grub2-mkconfig -o /boot/efi/EFI/centos/grub.cfg and then i reboot. when i run virt-host-validate i get QEMU: Checking if IOMMU is enabled by kernel: WARN (IOMMU appears to be disabled in kernel. Add intel_iommu=on to kernel cmdline arguments) when i edit the grub menu durring boot and i put intel_iommu=on and the i run again virt-host-validate i get QEMU: Checking if IOMMU is enabled by kernel: PASS any ideas? I tried editing other variables like GRUB_TIMEOUT and it seems to me that changes are applied. Thanks in advance

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C8 and backup solution
by Alessandro Baggi 03 Apr '20

03 Apr '20

Hi list, I'm searching a valid backup system to perform backups of 3 server, one local and 2 remote, and 2 linux workstation. (this number could be higher in future). Currently I'm testing bacula, scripted rsync with hardlink and borgbackup on C8.1. Bacula works without any problem, well tested, solid but complex to configure. Tested on a single server (with volumes on disk) and a full backup of 810gb (~150000 files) took 6,30 hours (too much). I would run deduplication but 1. bacula on C8 is not compiled with aligned 2. bacula put attention on some possibile bad scenario where deduplication could be a problem in losing one block that could break many files with the same shared block. So deduplication is secure or I should be away from it? scripted rsync. Simple, through ssh protocol and private key. No agent required on target. I use file level deduplication using hardlinks. To perform compression and block deduplication I could use fs like zfs (not available from epel) or use something like stratis (I don't checked if it offer deduplication in this moment). Encryption could be performed on fs level. Using a scripted rsync is the simpler way but there is something that could be leaved out by me (or undiscovered error). Simple to restore. BorgBackup is another solution similar to rsync in some way. It works like rsync through ssh but while rsync simply sends data, borg run deduplication, compression and encryption on place. Why is similar rsync? Because I need another script to run borg. It is not a complete solution and it works on push method and not pull like with bacula or rsync. If I would manage all my server from a central backup server is a problem, so to accomplish this I should run the borg command from the central server on the target server that point back to the remote repository (located on the central server). There is another solution with borg: using sshfs but is 4 time slower (too much solwer). I have not so much experiences on backups and choosing the bad tool could be dangerous so I need some suggestion. What backup solution do you suggest for my scenario? Thank you in advance. Alessandro.

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Mounting CIFS shares on C8
by Patrick DERWAEL 03 Apr '20

03 Apr '20

Hi all, I'm tearing my hair off trying to understand the difference between C7 & C8 for mounting a cifs FS with fstab I'm building a Plex media server on C8 and duplicated the fstab entries over from my current C7 installation My data (music & movies) are on CIFS shares on a Synology NAS. The packages cifs-utils samba-client samba-common are installed, up to date etc... These are my current fstab entries on the C7 box //192.168.1.200/mp3 /home/plex/Musique cifs user=plex,pass=plex,ro,auto,vers=3.0 //192.168.1.200/videos /home/plex/Vidéos cifs user=plex,pass=plex,ro,auto,vers=3.0 On my C8: [root@plexvm etc]# cat fstab # # /etc/fstab # Created by anaconda on Fri Apr 3 14:02:23 2020 # # Accessible filesystems, by reference, are maintained under '/dev/disk/'. # See man pages fstab(5), findfs(8), mount(8) and/or blkid(8) for more info. # # After editing this file, run 'systemctl daemon-reload' to update systemd # units generated from this file. # /dev/mapper/cl_plexvm-root / xfs defaults 0 0 UUID=f7c4e0e2-703e-4e61-8d7a-0aa34f836b02 /boot ext4 defaults 1 2 /dev/mapper/cl_plexvm-swap swap swap defaults 0 0 //192.168.1.200/mp3 /home/plex/Musique cifs user=plex,pass=plex,workgroup=DERWAEL,ro,auto,vers=3.0 //192.168.1.200/videos /home/plex/Vidéos cifs user=plex,pass=plex,workgroup=DERWAEL,ro,auto,vers=3.0 //192.168.1.200/series /home/plex/Séries cifs user=plex,pass=plex,workgroup=DERWAEL,ro,auto,vers=3.0 [root@plexvm etc]# mount -a mount error(2): No such file or directory Refer to the mount.cifs(8) manual page (e.g. man mount.cifs) mount error(2): No such file or directory Refer to the mount.cifs(8) manual page (e.g. man mount.cifs) mount error(2): No such file or directory Refer to the mount.cifs(8) manual page (e.g. man mount.cifs) [root@plexvm etc]# Any pointer would be MUCH appreciated! Thanks -- Patrick Derwael Rue de la fontaine, 3 4210 Burdinne Tél:+32.(0)479.80.50.79

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Re: [CentOS] C8 and backup solution
by Alessandro Baggi 03 Apr '20

03 Apr '20

Il 02/04/20 21:14, Karl Vogel ha scritto: > [Replying privately because my messages aren't making it to the list] > >>> In a previous message, Alessandro Baggi said: > A> Bacula works without any problem, well tested, solid but complex to > A> configure. Tested on a single server (with volumes on disk) and a > A> full backup of 810gb (~150000 files) took 6,30 hours (too much). > > For a full backup, I'd use something like "scp -rp". Anything else > has overhead you don't need for the first copy. > > Also, pick a good cipher (-c) for the ssh/scp commands -- it can improve > your speed by an order of magnitude. Here's an example where I copy > my current directory to /tmp/bkup on my backup server: > > Running on: Linux x86_64 > Thu Apr 2 14:48:45 2020 > > me% scp -rp -c aes128-gcm(a)openssh.com -i $HOME/.ssh/bkuphost_ecdsa \ > . bkuphost:/tmp/bkup > > Authenticated to remote-host ([remote-ip]:22). > ansible-intro 100% 16KB 11.3MB/s 00:00 ETA > nextgov.xml 100% 27KB 21.9MB/s 00:00 ETA > building-VM-images 100% 1087 1.6MB/s 00:00 ETA > sort-array-of-hashes 100% 1660 2.5MB/s 00:00 ETA > ... > ex1 100% 910 1.9MB/s 00:00 ETA > sitemap.m4 100% 1241 2.3MB/s 00:00 ETA > contents 100% 3585 5.5MB/s 00:00 ETA > ini2site 100% 489 926.1KB/s 00:00 ETA > mkcontents 100% 1485 2.2MB/s 00:00 ETA > > Transferred: sent 6465548, received 11724 bytes, in 0.4 seconds > Bytes per second: sent 18002613.2, received 32644.2 > > Thu Apr 02 14:48:54 2020 > > A> scripted rsync. Simple, through ssh protocol and private key. No agent > A> required on target. I use file level deduplication using hardlinks. > > I avoid block-level deduplication as a general rule -- ZFS memory > use goes through the roof if you turn that on. > > rsync can do the hardlinks, but for me it's been much faster to create > a list of SHA1 hashes and use a perl script to link the duplicates. > I can send you the script if you're interested. > > This way, you're not relying on the network for anything other than the > copies; everything else takes place on the local or backup system. > > A> Using a scripted rsync is the simpler way but there is something that > A> could be leaved out by me (or undiscovered error). Simple to restore. > > I've never had a problem with rsync, and I've used it to back up Linux > workstations with ~600Gb or so. One caveat -- if you give it a really > big directory tree, it can get lost in the weeds. You might want to do > something like this: > > 1. Make your original backup using scp. > > 2. Get a complete list of file hashes on your production systems > using SHA1 or whatever you like. > > 3. Whenever you do a backup, get a (smaller) list of modified files > using something like "find ./something -newer /some/timestamp/file" > or just making a new list of file hashes and comparing that to the > original list. > > 4. Pass the list of modified files to rsync using the "--files-from" > option so it doesn't have to walk the entire tree again. > > Good luck! > > -- > Karl Vogel / vogelke(a)pobox.com / I don't speak for the USAF or my company > > The best setup is having a wife and a mistress. Each of them will assume > you're with the other, leaving you free to get some work done. > --programmer with serious work-life balance issues Hi Karl, thank you for your answer. I'm trying ssh scripted rsync using a faster cypher like you suggested and seems that transfer on 10GB is better of default selected cypher (129 sec vs 116 using aes128-gcm, I tested this multiple times). Now I will try to check on the entire dataset and see how much benefit I gain. Waiting that, what do you think about bacula as backup solution? Thank you in advance.

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CentOS 7 host with guests as bridge cannot access host
by Jerry Geis 02 Apr '20

02 Apr '20

I have CentOS 7 host. Two guests on bridge network setup by GUI and virt-manager. 1 CentOS 8 guest 1 Win 10 guest Both cannot access the host. They can other machines on the network. Guests can access the internet just not the host. I used virt-manager GUi to set up everything. Selected the eth0:macvtap and Bridge. I "desire" bridge network. If I select something else I get access to host - but of course machine is not on the main network. Thoughts ? Jerry

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Re: [CentOS] Versions in RHEL and CentOS
by Peter Kjellström 02 Apr '20

02 Apr '20

On Thu, 2 Apr 2020 11:10:23 +0530 Thomas Stephen Lee <lee.iitb(a)gmail.com> wrote: ... > /usr/bin/sensors > > from the lm_sensors package > > I had run > > sensors-detect --auto I had no idea people still used that package. Especially on a server. Per core temperatures in linux for Zen2 is done using (a very up to date kernel with its k10temp module). Alternatively one can look at: https://github.com/ocerman/zenpower.git I don't know if it works with the c8 kernel (but it does not work with the c7 one). But in the end. Why care about per core temperatures? Setup basic monitoring of the server using ipmi or whatever the vendor supports. /Peter K

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Cloud Image building (like CentOS is doing it)
by Nicolas Ghirlanda 02 Apr '20

02 Apr '20

Hello, I was not able to find information about how CentOS is building its Cloud Images. I know packer etc are able to do it, but I am interested in how CentOS is building its own images as we like to adapt that for our Openstack Cloud. thanks for any hints Nicolas

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centos 6 vs 7
by Divine Tanyingoh 02 Apr '20

02 Apr '20

Issue: After installing vms on vmware, I noticed a difference in behavior between centos 6 vs 7. On centos 6 I cannot ping the hostname and get a reply without first resolving in the /etc/hosts file by adding a new entry: 192.168.0.47 server1.example.com. But for centos 7 I am able to ping the hostname and get a reply even when I have not made any changes to the /etc/hosts file. Why is there this difference between centos 6 vs 7. Thank you for your assistance.

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Discuss April 2020