Tag: dnf

Yum Does Not Work On CentOS

Since this is the fifth time this month that I’ve spun up some CentOS image and been stymied by the inability to install new packages … I’m going to write down the sed commands that magic the default yum repository configuration to something that’s still functional.

cd /etc/yum.repos.d/
sed -i 's/mirrorlist/#mirrorlist/g' /etc/yum.repos.d/CentOS-*
sed -i 's|#baseurl=http://mirror.centos.org|baseurl=http://vault.centos.org|g' /etc/yum.repos.d/CentOS-*

Useful DNF Commands

Beyond basic stuff like “dnf install somepackage” or downloading an rpm and using “dnf install my.package.rpm”, this is a running list of useful dnf commands.

List installed packages (similar to rpm -qa):

dnf list installed

List packages with updates available:

dnf check-update

Update everything but the kernel:
dnf update -x kernel*

Find package that provides something:

[lisa@rhel1 ~/]# dnf whatprovides cdrskin
Last metadata expiration check: 2:35:57 ago on Fri 12 Aug 2022 11:37:43 AM EDT.
cdrskin-1.5.2-2.fc32.x86_64 : Limited cdrecord compatibility wrapper to ease migration to libburn
Repo : fedora
Matched from:
Provide : cdrskin = 1.5.2-2.fc32

cdrskin-1.5.4-2.fc32.x86_64 : Limited cdrecord compatibility wrapper to ease migration to libburn
Repo : updates
Matched from:
Provide : cdrskin = 1.5.4-2.fc32

Package info, including version

[lisa@rhel1 ~/]# dnf info sendmail
Last metadata expiration check: 2:37:19 ago on Fri 12 Aug 2022 11:37:43 AM EDT.
Available Packages
Name : sendmail
Version : 8.15.2
Release : 43.fc32
Architecture : x86_64
Size : 730 k
Source : sendmail-8.15.2-43.fc32.src.rpm
Repository : fedora
Summary : A widely used Mail Transport Agent (MTA)
URL : http://www.sendmail.org/
License : Sendmail
Description : The Sendmail program is a very widely used Mail Transport Agent (MTA).
: MTAs send mail from one machine to another. Sendmail is not a client
: program, which you use to read your email. Sendmail is a
: behind-the-scenes program which actually moves your email over
: networks or the Internet to where you want it to go.
: If you ever need to reconfigure Sendmail, you will also need to have
: the sendmail-cf package installed. If you need documentation on
: Sendmail, you can install the sendmail-doc package.

Show history:

[lisa@rhel1 ~/]# dnf history
ID     | Command line                                                                                                      | Date and time    | Action(s)      | Altered
   102 | remove liberation-fonts                                                                                           | 2021-11-28 18:44 | Removed        |    3
   101 | remove chromedriver                                                                                               | 2021-11-28 18:44 | Removed        |    2
   100 | remove google-chrome-stable                                                                                       | 2021-11-28 18:44 | Removed        |    1  < 99 | install liberation-fonts | 2021-11-28 18:42 | Install | 1 >
    98 | install chromedriver                                                                                              | 2021-11-28 18:38 | Install        |    2
    97 | remove mediainfo                                                                                                  | 2021-11-16 13:31 | Removed        |    4
    96 | install mediainfo                                                                                                 | 2021-11-16 13:29 | Install        |    4


Which brings up an interesting command — you can undo a history step instead of trying to uninstall the list of things you just installed.

dnf history undo 98 -y

DNF — What Provides This File?

“Dependency hell” used to be a big problem — you’d download one package, attempt to install it, and find out you needed three other packages. Download one of them, attempt to install it, and learn about five other packages. Fifty seven packages later, you forgot what you were trying to install in the first place and went home. Or, I suppose, you managed to install that first package and actually use it. The advent of repo-based deployments — where dependencies can be resolved and automatically downloaded — has mostly eliminated dependency hell. But, occasionally, you’ll have a manual install that says “oh, I cannot complete. I need libgdkglext-x11-1.0.so.0 or libminizip.so.1 … and, if there’s a package that’s named libgdkglext-x11 or libminizip … you’re good. There’s not. Fortunately, you can use “dnf provides” to search for a package that provides a specific file — thus learning that you need the gtkglext-libs and minizip-compat packages to resolve your dependencies.