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!

rsync daemon in CentOS 8

Apparently, the team behind the CentOS 8 decided to split the rsync functionality to two packages – one for the client-side and for the server-side, despite the binary rsync is only one and offers the client-size and server-side.
So there two packages in CentOS 8:

  1. rsync – provides the client-side and server-side as usual
  2. rsync-daemon – provides configuration example file and the systemd to start it as a service.

So if you wonder where is your rsync service after installing the rsync package under CentOS 8 you must install additional package “rsync-daemon”.

Of course, you may just create anywhere “rsyncd.conf” (the best place for the configuration file is in /etc, but could be placed anywhere with “–config=PATH/FILE” option) file and start the daemon as usual with “–daemon” option included to have the rsync server-side up and running.

rsync --daemon --config=/etc/rsyncd.conf

Just create yourself the configuration “/etc/rsyncd.conf” file.

Install the rsync program – the client and the daemon

dnf install rsync

Install the configuration and systemd files

dnf install rsync-daemon

rsync and rsync-daemon files

The files included in the two packages:

[root@srv ~]# dnf repoquery -l rsync-daemon
Last metadata expiration check: 0:33:02 ago on Wed 22 Jan 2020 02:57:06 PM UTC.
/etc/rsyncd.conf
/etc/sysconfig/rsyncd
/usr/lib/systemd/system/rsyncd.service
/usr/lib/systemd/system/rsyncd.socket
/usr/lib/systemd/system/rsyncd@.service
/usr/share/man/man5/rsyncd.conf.5.gz
[root@srv ~]# dnf repoquery -l rsync
Last metadata expiration check: 0:33:06 ago on Wed 22 Jan 2020 02:57:06 PM UTC.
/usr/bin/rsync
/usr/lib/.build-id
/usr/lib/.build-id/6e
/usr/lib/.build-id/6e/bdbf5032a966a6293cea003621ba766ab36ff1
/usr/share/doc/rsync
/usr/share/doc/rsync/NEWS
/usr/share/doc/rsync/OLDNEWS
/usr/share/doc/rsync/README
/usr/share/doc/rsync/support
/usr/share/doc/rsync/support/Makefile
/usr/share/doc/rsync/support/atomic-rsync
/usr/share/doc/rsync/support/cvs2includes
/usr/share/doc/rsync/support/deny-rsync
/usr/share/doc/rsync/support/file-attr-restore
/usr/share/doc/rsync/support/files-to-excludes
/usr/share/doc/rsync/support/git-set-file-times
/usr/share/doc/rsync/support/instant-rsyncd
/usr/share/doc/rsync/support/logfilter
/usr/share/doc/rsync/support/lsh
/usr/share/doc/rsync/support/lsh.sh
/usr/share/doc/rsync/support/mapfrom
/usr/share/doc/rsync/support/mapto
/usr/share/doc/rsync/support/mnt-excl
/usr/share/doc/rsync/support/munge-symlinks
/usr/share/doc/rsync/support/rrsync
/usr/share/doc/rsync/support/rsync-no-vanished
/usr/share/doc/rsync/support/rsync-slash-strip
/usr/share/doc/rsync/support/rsyncstats
/usr/share/doc/rsync/support/savetransfer.c
/usr/share/doc/rsync/tech_report.tex
/usr/share/licenses/rsync
/usr/share/licenses/rsync/COPYING
/usr/share/man/man1/rsync.1.gz

Technical details of a default CentOS 8.0.1950 minimal installation

This article is for those of you who do not want to install a whole new operating system only to discover some technical details about the default installation like disk layout, packages included, software versions and so on. Here we are going to review in several sections what is like to have a default installation of CentOS 8.0.
Despite the kernel is 4.18 it detects successfully the new RYZEN/Threadripper AMD and the system is stable (we booted in UEFI mode).

Software

The CentOS 8.0 (8.0.1950) you can have

  • linux kernel – 4.18.0 (4.18.0-80.7.1.el8_0.x86_64)
  • Graphical User Interface
    • Xorg X server – 1.20.3
    • GNOME (the GUI) – 3.28.2
    • K Desktop Environment – NO, it’s depricated and not included in the release.
  • System
    • linux-firmware – version: 20190111, release: 92.gitd9fb2ee6.el8.
    • QT – 5.11.1
    • libc – 2.28
    • GNU GCC – 8.2.1
    • OpenSSL – 1.1.1
    • coreutils – 8.30
    • yum – Depricated and replaced with dnf
    • dnf – 4.0.9.2
    • cups – 2.2.6
    • rsyslog – 8.37.0
  • Servers
    • Apache – 2.4.37
    • Nginx – 1.14.1
    • MySQL server – 8.0.13
    • MariaDB server – 10.3.11
    • PostgreSQL – 10.6
  • Programming
    • PHP – 7.2.11
    • python – 2.7.15 and also includes 3.6.8
    • perl – 5.26.3
    • ruby – 2.5.3
    • OpenJDK – 11.0.4.11 and also includes 1.8.0.222.b10
    • Go – 1.11.5
    • Rust – 1.31.0
    • Subversion – 1.10.2
    • Git – 2.18.1

Note: Not all of the above software comes installed by default.
The installation procedure you can find here – How to do a network installation of CentOS 8 (8.0.1950) – minimal server installation Minimal install with “Standard” Addons selected.
Installed packages are 547 occupying 1.8G space:.

[root@srv ~]# dnf list installed|wc -l
547
[root@srv ~]# df -h /
Filesystem               Size  Used Avail Use% Mounted on
/dev/mapper/cl_srv-root   50G  1.8G   49G   4% /

Note: if you do not select “Standard Addon” the installation occupies less space – 1.6Gbytes and installs only 397 packages.
Keep on reading!

How to do a network installation of CentOS 8 (8.0.1950) – minimal server installation

Minimal net install is useful when a dedicated server is installed from a IPMI KVM or Dell iDRAC, HP iLO, IBM IMM or where the initial client side download of files need to be minimal.
For amd64 CentOS 8 BaseOS the net install bootable media is located here (now the current latest release is 8.0.1950, but you can check the last directory with 8. for the time you follow this howto):

http://mirror.leaseweb.com/centos/8/isos/x86_64/CentOS-8-x86_64-1905-boot.iso

Note there is no minimal CD for offline installation anymore. Boot CD is to just boot and make “netinstall” installation and a big fat DVD of 6.6Gbytes to install offline.
Software details of CentOS 8 minimal install could be found here – Technical details of a default CentOS 8.0.1950 minimal installation

Download it and put it on a cd or usb, the boot from it and follow the steps bellow:

STEP 1) Enter the BIOS of your machine (desktop or server) to change the boot order.

You can try F11 on most servers to have the boot menu. Here we use DEL to enter the UEFI BIOS.

main menu
Enter BIOS – change boot order

Keep on reading!