Caching NFS files with cachefilesd

A great tool for caching a network filesystem like NFS mounts is cachefilesd! It is easy to use it and a good deal of stats can be retrieved from the tool. More on how it works here https://www.kernel.org/doc/Documentation/filesystems/caching/fscache.txt

Here are quick steps to cache an NFS mounts (it works with NFS-Ganesha servers, too):

  1. Install the daemon tool cachefilesd
  2. Check the configuration file /etc/cachefilesd.conf. In most cases, no need to edit the file! Just check the disk limits if they are good.
  3. Start the cachefilesd daemon.
  4. Mount the network directories with “fsc” option. Umount and mount them all if they’ve been already mounted. The fsc is mandatory option to enable file cacheing of a network mount.
  5. Check stats to see if the file cching is working properly.

The example below is under CentOS 8, but it is almost the same in most Linux distributions.

STEP 1) Install the daemon tool cachefilesd

This is straight forward, just install it with the package manager:

[root@srv ~]# dnf install cachefilesd
Last metadata expiration check: 2:33:44 ago on Tue 08 Dec 2020 07:18:01 AM UTC.
Dependencies resolved.
=============================================================================================================================================================================================
 Package                                        Architecture                              Version                                            Repository                                 Size
=============================================================================================================================================================================================
Installing:
 cachefilesd                                    x86_64                                    0.10.10-4.el8                                      BaseOS                                     43 k

Transaction Summary
=============================================================================================================================================================================================
Install  1 Package

Total download size: 43 k
Installed size: 71 k
Is this ok [y/N]: y
Downloading Packages:
cachefilesd-0.10.10-4.el8.x86_64.rpm                                                                                                                         3.1 MB/s |  43 kB     00:00    
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Total                                                                                                                                                        2.8 MB/s |  43 kB     00:00     
Running transaction check
Transaction check succeeded.
Running transaction test
Transaction test succeeded.
Running transaction
  Preparing        :                                                                                                                                                                     1/1 
  Installing       : cachefilesd-0.10.10-4.el8.x86_64                                                                                                                                    1/1 
  Running scriptlet: cachefilesd-0.10.10-4.el8.x86_64                                                                                                                                    1/1 
  Verifying        : cachefilesd-0.10.10-4.el8.x86_64                                                                                                                                    1/1 

Installed:
  cachefilesd-0.10.10-4.el8.x86_64                                                                                                                                                           

Complete!

STEP 2) Check the configuration file and tune for your system.

In most cases, the defaults in /etc/cachefilesd.conf are good to start with:

dir /var/cache/fscache
tag mycache
brun 10%
bcull 7%
bstop 3%
frun 10%
fcull 7%
fstop 3%

# Assuming you're using SELinux with the default security policy included in
# this package
secctx system_u:system_r:cachefiles_kernel_t:s0

The directory where the cache will reside and the lines with the percentages are for disk space limitation. “brun 10%” means cache can runs freely till the disk space drops below 10%. “bcull 7%” – culling the cache when the free space drops below “7%” and more in the man page (or https://linux.die.net/man/5/cachefilesd.conf).
So if one maintains disk free space below 10% the configuration file should be edited.

STEP 3) Start the cachefilesd daemon.

And enable on boot to start automatically.

[root@srv ~]# systemctl start cachefilesd
[root@srv ~]# systemctl enable cachefilesd
Created symlink /etc/systemd/system/multi-user.target.wants/cachefilesd.service → /usr/lib/systemd/system/cachefilesd.service.
[root@srv ~]# systemctl status cachefilesd
● cachefilesd.service - Local network file caching management daemon
   Loaded: loaded (/usr/lib/systemd/system/cachefilesd.service; enabled; vendor preset: disabled)
   Active: active (running) since Tue 2020-12-08 10:01:24 UTC; 11s ago
 Main PID: 29786 (cachefilesd)
    Tasks: 1 (limit: 408616)
   Memory: 2.5M
   CGroup: /system.slice/cachefilesd.service
           └─29786 /usr/sbin/cachefilesd -n -f /etc/cachefilesd.conf

Dec 08 10:01:24 srv systemd[1]: Starting Local network file caching management daemon...
Dec 08 10:01:24 srv systemd[1]: Started Local network file caching management daemon.
Dec 08 10:01:24 srv cachefilesd[29786]: About to bind cache
Dec 08 10:01:24 srv cachefilesd[29786]: Bound cache
Dec 08 10:01:24 srv cachefilesd[29786]: Daemon Started

The status command shows the daemon cachefilesd is running. But does it cache?

STEP 4) Mount the network filesystems with option fsc

To make cachefilesd cache a network mount the option fsc must be included in the mount options. Remount may not work correctly, so to be sure a full umount/mount should be executed. Here is an example /etc/fstab file:

192.168.0.1:/mnt/storage /mnt/storage  nfs defaults,hard,intr,noexec,nosuid,_netdev,fsc,vers=4 0 0

And then mount with simple command:

mount /mnt/storage

Check whether the mounts if the FS cache is used. FSC must be “yes”.

[root@srv ~]# cat /proc/fs/nfsfs/volumes
NV SERVER   PORT DEV          FSID                              FSC
v4 c0a80001  801 0:41         d4098a2af096148:ec7560388cbe5b83  yes

There is a proc file for cache statistics:

[root@srv ~]# cat /proc/fs/fscache/stats
FS-Cache statistics
Cookies: idx=49 dat=4385599 spc=0
Objects: alc=43666 nal=0 avl=43666 ded=36002
ChkAux : non=0 ok=12289 upd=0 obs=761
Pages  : mrk=24915179 unc=24492585
Acquire: n=4385648 nul=0 noc=0 ok=4385648 nbf=0 oom=0
Lookups: n=43666 neg=31372 pos=12294 crt=31372 tmo=0
Invals : n=1 run=1
Updates: n=0 nul=0 run=1
Relinqs: n=4377930 nul=0 wcr=0 rtr=0
AttrChg: n=0 ok=0 nbf=0 oom=0 run=0
Allocs : n=0 ok=0 wt=0 nbf=0 int=0
Allocs : ops=0 owt=0 abt=0
Retrvls: n=751549 ok=716860 wt=21436 nod=34689 nbf=0 int=0 oom=0
Retrvls: ops=751549 owt=9158 abt=0
Stores : n=550412 ok=550412 agn=0 nbf=0 oom=0
Stores : ops=33238 run=583650 pgs=550412 rxd=550412 olm=0
VmScan : nos=23963352 gon=0 bsy=0 can=0 wt=0
Ops    : pend=9160 run=784788 enq=26874960 can=0 rej=0
Ops    : ini=1301962 dfr=265 rel=1301962 gc=265
CacheOp: alo=0 luo=0 luc=0 gro=0
CacheOp: inv=0 upo=0 dro=0 pto=0 atc=0 syn=0
CacheOp: rap=0 ras=0 alp=0 als=0 wrp=0 ucp=0 dsp=0
CacheEv: nsp=761 stl=0 rtr=0 cul=0

And here is the cache directory filled with files. If there are no files, the FS cache is not used, probably the mount is not mounted with FSC! Umount and mount the mounts again.

[root@srv ~]# find /var/cache/fscache|head -n 20
/var/cache/fscache
/var/cache/fscache/graveyard
/var/cache/fscache/cache
/var/cache/fscache/cache/@4a
/var/cache/fscache/cache/@4a/I03nfs
/var/cache/fscache/cache/@4a/I03nfs/@84
/var/cache/fscache/cache/@4a/I03nfs/@84/Jc0010800840000cG0400
/var/cache/fscache/cache/@4a/I03nfs/@84/Jc0010800840000cG0400/@68
/var/cache/fscache/cache/@4a/I03nfs/@84/Jc0010800840000cG0400/@68/J1100000000000Q0goaWH946iIn7oUMELrd80000000040000g00Kb000wFe000jt000oG3000000040000g000000000
/var/cache/fscache/cache/@4a/I03nfs/@84/Jc0010800840000cG0400/@68/J1100000000000Q0goaWH946iIn7oUMELrd80000000040000g00Kb000wFe000jt000oG3000000040000g000000000/@8b
/var/cache/fscache/cache/@4a/I03nfs/@84/Jc0010800840000cG0400/@68/J1100000000000Q0goaWH946iIn7oUMELrd80000000040000g00Kb000wFe000jt000oG3000000040000g000000000/@8b/EA0g00sg0200n8000000ixBMHyy9gdcUm_O8ewl7XMW1n8cXgyl60
/var/cache/fscache/cache/@4a/I03nfs/@84/Jc0010800840000cG0400/@68/J1100000000000Q0goaWH946iIn7oUMELrd80000000040000g00Kb000wFe000jt000oG3000000040000g000000000/@8b/EA0g00sg0200n8000000ixBMHyy9gdcUm_O8ewl7XZG2n84qfxl60
/var/cache/fscache/cache/@4a/I03nfs/@84/Jc0010800840000cG0400/@68/J1100000000000Q0goaWH946iIn7oUMELrd80000000040000g00Kb000wFe000jt000oG3000000040000g000000000/@8b/EA0g00sg0200n8000000ixBMHyy9gdcUm_O8ewl7XQM2n8IQ4El60
/var/cache/fscache/cache/@4a/I03nfs/@84/Jc0010800840000cG0400/@68/J1100000000000Q0goaWH946iIn7oUMELrd80000000040000g00Kb000wFe000jt000oG3000000040000g000000000/@8b/EA0g00sg0200n8000000ixBMHyy9gdcUm_O8ewl7XZO2n8Ms7kl60
/var/cache/fscache/cache/@4a/I03nfs/@84/Jc0010800840000cG0400/@68/J1100000000000Q0goaWH946iIn7oUMELrd80000000040000g00Kb000wFe000jt000oG3000000040000g000000000/@8b/EA0g00sg0200n8000000ixBMHyy9gdcUm_O8ewl7XvQ2n88dKgl60
/var/cache/fscache/cache/@4a/I03nfs/@84/Jc0010800840000cG0400/@68/J1100000000000Q0goaWH946iIn7oUMELrd80000000040000g00Kb000wFe000jt000oG3000000040000g000000000/@8b/EA0g00sg0200n8000000ixBMHyy9gdcUm_O8ewl7XV40o8cREC6b0
/var/cache/fscache/cache/@4a/I03nfs/@84/Jc0010800840000cG0400/@68/J1100000000000Q0goaWH946iIn7oUMELrd80000000040000g00Kb000wFe000jt000oG3000000040000g000000000/@8b/EA0g00sg0200n8000000ixBMHyy9gdcUm_O8ewl7X3Y1n8MHO_l60
/var/cache/fscache/cache/@4a/I03nfs/@84/Jc0010800840000cG0400/@68/J1100000000000Q0goaWH946iIn7oUMELrd80000000040000g00Kb000wFe000jt000oG3000000040000g000000000/@8b/EA0g00sg0200n8000000ixBMHyy9gdcUm_O8ewl7Xhkwn80f23zb0
/var/cache/fscache/cache/@4a/I03nfs/@84/Jc0010800840000cG0400/@68/J1100000000000Q0goaWH946iIn7oUMELrd80000000040000g00Kb000wFe000jt000oG3000000040000g000000000/@8b/EA0g00sg0200n8000000ixBMHyy9gdcUm_O8ewl7XEQ2n8IuAll60
/var/cache/fscache/cache/@4a/I03nfs/@84/Jc0010800840000cG0400/@68/J1100000000000Q0goaWH946iIn7oUMELrd80000000040000g00Kb000wFe000jt000oG3000000040000g000000000/@8b/EA0g00sg0200n8000000ixBMHyy9gdcUm_O8ewl7XoO2n8A7Bll60
[root@srv ~]# du -d 1 -h /var/cache/fscache
4.0K    /var/cache/fscache/graveyard
3.8G    /var/cache/fscache/cache
3.8G    /var/cache/fscache

There are 3.8G in the cache.

libelf was not found in the pkg-config search path

Building from source under CentOS the user may stumble on some compilation errors and most of them are for missing -devel packages. Here is such example with not so easy to find the name of a missing library:

[/tmp/netdata-libbpf-El77Ld/libbpf-0.0.9_netdata-1/src]# env CFLAGS=-fPIC CXXFLAGS= LDFLAGS= BUILD_STATIC_ONLY=y OBJDIR=build DESTDIR=.. make install 
Package libelf was not found in the pkg-config search path.
Perhaps you should add the directory containing `libelf.pc'
to the PKG_CONFIG_PATH environment variable
No package 'libelf' found
mkdir -p build/staticobjs
cc -I. -I../include -I../include/uapi -DCOMPAT_NEED_REALLOCARRAY -fPIC -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64   -c bpf.c -o build/staticobjs/bpf.o
cc -I. -I../include -I../include/uapi -DCOMPAT_NEED_REALLOCARRAY -fPIC -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64   -c btf.c -o build/staticobjs/btf.o
btf.c:17:18: fatal error: gelf.h: No such file or directory
 #include <gelf.h>
                  ^
compilation terminated.
make: *** [build/staticobjs/btf.o] Error 1
 FAILED   

The missing development library file is with the name: elfutils-libelf-devel. Installing the package with yum or dnf will resolve the above error:

yum install -y elfutils-libelf-devel

Or for CentOS 8 and newer Fedora versions:

dnf install -y elfutils-libelf-devel

removing the default kernel in CentOS 8 – remove elrepo kernel

Removing the default kernel aka the loaded kernel in CentOS 8 maybe challenging because the package is protected and cannot be removed by the yum or dnf.
Here is the case: an elrepo kernel-ml loaded and the dnf prints it cannot remove the package, because it is protected:

[root@srv ~]# dnf remove kernel-ml kernel-ml-core kernel-ml-modules
Error: 
 Problem: The operation would result in removing the following protected packages: kernel-ml-core
(try to add '--skip-broken' to skip uninstallable packages or '--nobest' to use not only best candidate packages)
[root@srv ~]# uname -a
Linux srv.localhost 5.10.4-1.el8.elrepo.x86_64 #1 SMP Tue Dec 29 11:04:23 EST 2020 x86_64 x86_64 x86_64 GNU/Linux
[root@srv ~]# grubby --default-kernel
/boot/vmlinuz-5.10.4-1.el8.elrepo.x86_64

The system is booted up with the kernel we are trying to remove, which is impossible.

The solution is to set a new default kernel and load it. Then dnf will be able to remove the first kernel.

For CentOS 7, just use the yum instead of dnf command.
Using grubby is really easy and straightforward:

STEP 1) List all installed and available to boot kernels

[root@srv ~]# grubby --info=ALL |grep ^kernel
kernel="/boot/vmlinuz-5.10.4-1.el8.elrepo.x86_64"
kernel="/boot/vmlinuz-4.18.0-259.el8.x86_64"
kernel="/boot/vmlinuz-4.18.0-257.el8.x86_64"
kernel="/boot/vmlinuz-0-rescue-45e12f0814fd4947b99cbdcb88950361"

STEP 2) Select the kernel to load the next time

[root@srv ~]# grubby --set-default "/boot/vmlinuz-4.18.0-259.el8.x86_64"
The default is /boot/loader/entries/45e12f0814fd4947b99cbdcb88950361-4.18.0-259.el8.x86_64.conf with index 1 and kernel /boot/vmlinuz-4.18.0-259.el8.x86_64

Keep on reading!

gitlab in podman cannot create unix sockets in glusterfs because of SELinux

Installing gitlab-ee (and gitlab-ce) under CentOS 7 with enabled SELinux (i.e. enforcing mode) looped endlessly the container in restarting the installation process! There were multiple errors for missing sockets in the podman logs of the gitlab container. Here are some of the errors:
Missing postgresql unix socket in “/var/opt/gitlab/postgresql”:

Recipe: gitlab::database_migrations
  * bash[migrate gitlab-rails database] action run
    [execute] rake aborted!
              PG::ConnectionBad: could not connect to server: No such file or directory
                Is the server running locally and accepting
                connections on Unix domain socket "/var/opt/gitlab/postgresql/.s.PGSQL.5432"?
              /opt/gitlab/embedded/service/gitlab-rails/lib/tasks/gitlab/db.rake:53:in `block (3 levels) in <top (required)>'
              /opt/gitlab/embedded/bin/bundle:23:in `load'
              /opt/gitlab/embedded/bin/bundle:23:in `<main>'
              Tasks: TOP => gitlab:db:configure
              (See full trace by running task with --trace)
    
    
    Error executing action `run` on resource 'bash[migrate gitlab-rails database]'
.....
.....
Running handlers:
There was an error running gitlab-ctl reconfigure:

bash[migrate gitlab-rails database] (gitlab::database_migrations line 55) had an error: Mixlib::ShellOut::ShellCommandFailed: Expected process to exit with [0], but received '1'
---- Begin output of "bash"  "/tmp/chef-script20200915-35-lemic5" ----
STDOUT: rake aborted!
PG::ConnectionBad: could not connect to server: No such file or directory
        Is the server running locally and accepting
        connections on Unix domain socket "/var/opt/gitlab/postgresql/.s.PGSQL.5432"?
/opt/gitlab/embedded/service/gitlab-rails/lib/tasks/gitlab/db.rake:53:in `block (3 levels) in <top (required)>'
/opt/gitlab/embedded/bin/bundle:23:in `load'
/opt/gitlab/embedded/bin/bundle:23:in `<main>'
Tasks: TOP => gitlab:db:configure
(See full trace by running task with --trace)
STDERR: 
---- End output of "bash"  "/tmp/chef-script20200915-35-lemic5" ----
Ran "bash"  "/tmp/chef-script20200915-35-lemic5" returned 1

Missing redis socket in

Running handlers:
There was an error running gitlab-ctl reconfigure:

redis_service[redis] (redis::enable line 19) had an error: RuntimeError: ruby_block[warn pending redis restart] (/opt/gitlab/embedded/cookbooks/cache/cookbooks/redis/resources/service.rb line 65) had an error: RuntimeError: Execution of the command `/opt/gitlab/embedded/bin/redis-cli -s /var/opt/gitlab/redis/redis.socket INFO` failed with a non-zero exit code (1)
stdout: 
stderr: Could not connect to Redis at /var/opt/gitlab/redis/redis.socket: No such file or directory

It should be noted that the /var/opt/gitlab directory has been mapped in /mnt/storage/podman/gitlab/data. GlusterFS is used for /mnt/storage, so the gitlab files resides on a GlusterFS volume.

ERROR 1) Cannot create unix socket.

Checking the /var/log/audit/audit.log reveiled the problem immediately:
Keep on reading!

collectd nginx plugin: curl_easy_perform failed because of selinux

Enabling the Nginx plugin for collectd under CentOS (or any other system using SELinux) might be confusing for a newbie. Most sources on the Internet would just install collectd-nginx:

yum install -y collectd-nginx

and configure it in the nginx.conf and collectd.conf. Still, the statistics might not work as expected, the collectd may not be able to gather statistics from the Nginx.

SELinux may prevent collectd (plugin) daemon to connect to Nginx and gather statistics from the Nginx stats page.

Checking the collectd log and it reports a problem:
Keep on reading!

Dracut boot failed with missing device – exit and continue normal booting!

This issue deserves a much more article, in fact, a straightforward tip:

You may be able to continue a normal boot only by typing “exit” and hitting enter in the “Dracut” console.

Most of the time this Dracut console entering is caused because the system administrator of the server/machine added, replaced or deleted a RAID or similar device and forgot to update the configuration (grub2 probably). And in most of these cases, the raid is not critical for machine normal boot from the root partition, but it may be critical for the services lately. Booting in normal mode, even without some devices, is the main goal because under the normal mode it easier to repair the system.
Check out the two articles on the topic (especially the first one):

SCREENSHOT 1) Just type “exit” and hit enter.

It’s worth noting that if you executed some commands in the console and/or mounted devices to test they are with healthy file system or for whatever reason you did it, the boot process may not continue after typeing exit and probablly a reboot is required. The server will go once more in this mode and then just typing will work.

main menu
type exit

Keep on reading!

CentOS 7 – Your kernel headers for kernel cannot be found at – missing kernel-devel

Getting the following error may be deceiving:

Error! echo
Your kernel headers for kernel 3.10.0-1062.1.1.el7.x86_64 cannot be found at
/lib/modules/3.10.0-1062.1.1.el7.x86_64/build or /lib/modules/3.10.0-1062.1.1.el7.x86_64/source.

Because you may have already installed the kernel-headers package for the current kernel and still to get the same error. So what is missing?

In fact, the kernel headers for compiling a kernel module is in kernel-devel package.

[root@localhost ~]# yum install kernel-devel
Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
 * base: mirror.wwfx.net
 * extras: mirror.wwfx.net
 * updates: mirror.wwfx.net
Resolving Dependencies
--> Running transaction check
---> Package kernel-devel.x86_64 0:3.10.0-1062.1.1.el7 will be installed
--> Finished Dependency Resolution

Dependencies Resolved

============================================================================================================================================================================
 Package                                   Arch                                Version                                           Repository                            Size
============================================================================================================================================================================
Installing:
 kernel-devel                              x86_64                              3.10.0-1062.1.1.el7                               updates                               18 M

Transaction Summary
============================================================================================================================================================================
Install  1 Package

Total download size: 18 M
Installed size: 38 M
Is this ok [y/d/N]: y
Downloading packages:
Delta RPMs disabled because /usr/bin/applydeltarpm not installed.
kernel-devel-3.10.0-1062.1.1.el7.x86_64.rpm                                                                                                          |  18 MB  00:00:02     
Running transaction check
Running transaction test
Transaction test succeeded
Running transaction
  Installing : kernel-devel-3.10.0-1062.1.1.el7.x86_64                                                                                                                  1/1 
  Verifying  : kernel-devel-3.10.0-1062.1.1.el7.x86_64                                                                                                                  1/1 

Installed:
  kernel-devel.x86_64 0:3.10.0-1062.1.1.el7                                                                                                                                 

Complete!

If you have used other Linux distribution the “kernel headers”/”linux headers” package just means what it is named. In the CentOS 7 world there are two packages:

[root@localhost ~]# yum info kernel-devel
Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
 * base: mirror.wwfx.net
 * extras: mirror.wwfx.net
 * updates: mirror.wwfx.net
Installed Packages
Name        : kernel-devel
Arch        : x86_64
Version     : 3.10.0
Release     : 1062.1.1.el7
Size        : 38 M
Repo        : installed
From repo   : updates
Summary     : Development package for building kernel modules to match the kernel
URL         : http://www.kernel.org/
License     : GPLv2
Description : This package provides kernel headers and makefiles sufficient to build modules
            : against the kernel package.

[root@localhost ~]# yum info kernel-headers
Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
 * base: mirror.wwfx.net
 * epel: mirrors.neterra.net
 * extras: mirror.wwfx.net
 * updates: mirror.wwfx.net
Installed Packages
Name        : kernel-headers
Arch        : x86_64
Version     : 3.10.0
Release     : 1062.1.1.el7
Size        : 3.7 M
Repo        : installed
From repo   : updates
Summary     : Header files for the Linux kernel for use by glibc
URL         : http://www.kernel.org/
License     : GPLv2
Description : Kernel-headers includes the C header files that specify the interface
            : between the Linux kernel and userspace libraries and programs.  The
            : header files define structures and constants that are needed for
            : building most standard programs and are also needed for rebuilding the
            : glibc package.

CentOS 7 – Dependency Resolution – Error – Requires: dkms – missing epel repository

Quick not note for those not familiar with the CentOS 7 peculiarity and especially the repository peculiarity.
Receiving the follwoing error:

--> Finished Dependency Resolution
Error: Package: 3:kmod-nvidia-latest-dkms-418.87.00-2.el7.x86_64 (cuda)
           Requires: dkms
 You could try using --skip-broken to work around the problem
 You could try running: rpm -Va --nofiles --nodigest

It means you need a package (or meta-package, which might pull multiple packages and dependencies offering a big framework, for example), which could not be found in the existing repositories. In this very case, we need the DKMS (Dynamic Kernel Module Support) – https://en.wikipedia.org/wiki/Dynamic_Kernel_Module_Support

The DKMS is offered in epel repository and it could not be found in the CentOS 7 official repositories. Just add the epel repository.

[root@localhost ~]# yum install -y epel-release
Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
 * base: mirrors.daticum.com
 * extras: mirrors.daticum.com
 * updates: mirrors.daticum.com
Resolving Dependencies
--> Running transaction check
---> Package epel-release.noarch 0:7-11 will be installed
--> Finished Dependency Resolution

Dependencies Resolved

============================================================================================================================================================================
 Package                                       Arch                                    Version                                Repository                               Size
============================================================================================================================================================================
Installing:
 epel-release                                  noarch                                  7-11                                   extras                                   15 k

Transaction Summary
============================================================================================================================================================================
Install  1 Package

Total download size: 15 k
Installed size: 24 k
Downloading packages:
epel-release-7-11.noarch.rpm                                                                                                                         |  15 kB  00:00:00     
Running transaction check
Running transaction test
Transaction test succeeded
Running transaction
  Installing : epel-release-7-11.noarch                                                                                                                                 1/1 
  Verifying  : epel-release-7-11.noarch                                                                                                                                 1/1 

Installed:
  epel-release.noarch 0:7-11                                                                                                                                                

Complete!

And rerun your first install yum line. Now you won’t receive the DKMS error.

Install CUDA and NVIDIA video driver under CentOS 7

Nvidia CUDA Toolkit supports CentOS 7 and it is relatively simple to install it. Nvidia provides three types of installation – a big setup file, a big rpm file and an official Nvidia repository, which we are going to use it in this article. The Nvidia repository contains the Nvidia video driver for the Nvidia video cards like GeForce, GTX, RTX and so on. You may need CUDA Toolkit if you are a game developer or you want to build yourself some of the mining software like XMR-STAK.
In this article, we are going to use the NVIDIA official repository for CUDA and the video driver module. There are other ways to install CUDA, which are not the purpose of this article. Using an official repository is the best practice for installing software on your system.

STEP 1) Update and install the NVIDIA official repository.

yum update -y
yum install -y yum-utils
yum-config-manager --add-repo http://developer.download.nvidia.com/compute/cuda/repos/rhel7/x86_64/cuda-rhel7.repo

Keep on reading!

How to compile xmr-stak (2.10) under CentOS 7 for CPU mining cryptocurrencies in September 2019

A time to refresh our old article on how to compile xmr-stak for CPU mining with the new version and this time a new GNU GCC version (version 8.3, the last article we used 7.x – How to compile xmr-stak (2.4.5) under CentOS 7 for CPU mining cryptocurrencies). Always use the latest available GNU GCC packages because the latest version of GNU GCC could add some optimizations to the binary compiled code and you may have a CPU miner with better performance!
Thanks to xmr-stak we can have one application capable of mining many different cryptocurrencies based on different algorithms. XMR-STAK is GPU and CPU miner and here we present only the CPU ability under CentOS 7 using our AMD Threadripper 1950X.
The software in this article:

  • CentOS 7 – CentOS Linux release 7.6.1810 (Core)
  • GNU GCC – gcc version 8.3.1 20190311 (Red Hat 8.3.1-3) (GCC)
  • XMR-STAK – 2.10.7

As said many times working with crypto-currency it is mandatory to do the things yourself – do not trust any binary made by someone on the Internet. It is easy to build your miner yourself with the code from the official repository!

So here are the steps to build the XMR-STAK for CPU mining:

STEP 1) Update your system and install the following dependencies

Always start with update command and then install the dependencies in order first install all the new repositories and then the dependency binaries.

sudo yum update -y
sudo yum install -y centos-release-scl epel-release
sudo yum install -y cmake3 devtoolset-8-gcc* hwloc-devel libmicrohttpd-devel openssl openssl-devel make git screen wget

We are going to use GNU GCC 8 to build the XMR-STAK. More on the subject of how to install GNU GCC 8 and what is “devtoolset” here – How to install GNU GCC 8 on CentOS 7.
Keep on reading!