Using grub rescue to boot machine and repair MBR
Use “ls” to find your partition list:
(hd0) (hd0,msdos3) (hd0,msdos2) (hd0,msdos1)
Check the content of each to find your Linux partition:
You want the one with the /boot folder. In our case, this is (hd0,msdos3). The following commands will boot your Linux OS.
<root password for maintenance>
Use “df” or “mount” to figure out which disk holds the Linux partition. In our case, it is /dev/sdb. You don’t want the partition (e.g. /dev/sdb2) but the disk. The following commands install the grub2 bootloader and build a config file.
grub2-mkconfig -o /boot/grub2/grub.cfg
Gimp installed Python 2.7). Which, of course, took over my system so nothing was using Python 3 anymore. We’ve used ‘alternatives’ to manage the Java installation, and I thought that might be a good solution in case I ever need to use Python 2
Add both Python versions to alternatives:
[lisa@fedora ~]# sudo alternatives –install /usr/bin/python python /usr/bin/python3.7 1
[lisa@fedora ~]# sudo alternatives –install /usr/bin/python python /usr/bin/python2.7 2
Select which one you want to use:
[lisa@fedora ~]# sudo alternatives –config python
There are 2 programs which provide ‘python’.
+ 2 /usr/bin/python2.7
Enter to keep the current selection[+], or type selection number: 1
And, of course, repeat the process for PIP:
[lisa@fedora ~]# sudo alternatives –install /usr/bin/pip pip /usr/bin/pip2.7 2
[lisa@fedora ~]# sudo alternatives –install /usr/bin/pip pip /usr/bin/pip3.7 1
[lisa@fedora ~]# sudo alternatives –config pip
Fedora and Red Hat Enterprise Linux have an alias “ll” which uses the long listing format. It’s a quick little tweak that I love, but I generally want to list hidden files too. Seemed easy enough to tweak the alias … but I never had any luck overriding the system setting or finding the source of the alias. Typing “ll -a” gave me what I wanted, although that’s not appreciably easier than typing “ls -al” …
The ll alias is defined in /etc/profile.d/colorls.sh (or colorls.csh if you use the C shell). Add the ‘a’ and “ll” produces a long list format of all files.
lisa@fedora123 ~]# grep “alias ll” /etc/profile.d/colorls.sh
alias ll=’ls -la’ 2>/dev/null
alias ll=’ls -la –color=auto’ 2>/dev/null
Since I’ve got a larger hard drive installed, I have both Fedora and Windows in a dual boot configuration. I have a shared NTFS partition for data, but it’s mounted as read-only under Fedora. Turns out that Fedora sees the file system as not cleanly shut down when Windows Fast Boot is enabled. I disabled fast boot in power management, and the shared data volume is mounted rw as expected.
The graphical interface on a Fedora 28 laptop was unavailable — buggered up video device/driver. Change to what used to be called run level 3, and we could not log in! We know the root password, but it would not take it. Single user is password protected too — and we were unable to log in there.
Normal recovery process:
Get to the grub menu, highlight the kernel you want to boot, and hit ‘e’ to edit it. Scroll down. On line that starts with linux16, change “rhgb quiet” to say “rd.break enforcing=0”
ctrl-x to boot
Once you get a shell:
mount -o remount,rw /sysroot
Voila, you’ve got access to your files. Use vi to edit whatever has the box seriously screwed up (passwd if your problem is that you don’t know the root password) and you’re set. We reset the root password just in case. Aaaand … we still couldn’t log in on init 1 or init 3! And at this point I was feeling stubborn about getting logged into the box.
Now you can tweak up the system so it is not using sulogin when booting into single user mode but that isn’t a good way to install network-sourced packages. For some reason, we had to disable selinux before we could log into anything other than the graphical target. I’m sure there is a policy we could have tweaked, but it was far easier to disable the thing, boot into the multi-user target, sort the video driver, and then boot into the graphical target.
I’ve encountered a few scenarios of late where I couldn’t install an RPM package but needed its content. One is the security config at work where I have sudo access for cp but not install rights. Sigh! But more recently, I needed to compare a library from an updated package to the currently installed one. Listing package content confirms it is the same file name and path.
[root@fedora02 tmp]# rpm -q --filesbypkg -p ./mariadb-libs-10.2.13-2.fc27.i686.rpm
Extracting the rpm allowed me to actually compare the files, swap back and forth to see which worked, etc.
[lisa@fedora tmp]# rpm2cpio mariadb-libs-10.2.13-2.fc27.x86_64.rpm | cpio -idmv
Scott has been setting up our OpenHAB server, and the latest project was controlling our network speakers. You can play Internet radio stations to the speakers, you can stream music from the NAS … but we also want to be able to play announcements. For that, we needed a text to speech engine.
Festival is in Fedora’s yum repository, but everything I’ve read about Festival says the output is robotic. Which is likely fun at first, but tiring after the first three or four times. Even if you have it say “beep, boop” at the end.
SVox (Nuance, which a long LONG time ago was spun off from Stanford Research Labs) has an open-source version of their text to speech product. Not in convenient package form, but close. Someone maintains a shell install script. Download the script:
Then read through it and make sure it’s not doing anything untoward. It wasn’t. Ran the script and a minute later, we can use “pico2wave -w /tmp/ljr.wav “I am your TTS engine”
Quick. Easy. And now we’ve got a wave file to send to the speaker (and remove when we’re done!)