Category: Linux

Find and replace text within a file using sed

Find and replace text within a file using sed

The procedure to change the text in files under Linux/Unix using sed:

  1. Use Stream EDitor (sed) as follows:
  2. sed -i 's/old-text/new-text/g' input.txt
  3. The s is the substitute command of sed for find and replace
  4. It tells sed to find all occurrences of ‘old-text’ and replace with ‘new-text’ in a file named input.txt
  5. Verify that file has been updated:
  6. more input.txt

Resetting the Root Password of RHEL-8

Resetting the Root Password of RHEL-8

Resolution
1) Break the boot sequence by adding ‘rd.break’ at kernel stanza in grub. To do this, restart your system and when the GRUB splash screen comes:

  1. Select/highlight the kernel you wish to boot using the up/down arrow keys.
  2. Press the e key to edit the entry.
  3. Select/highlight the line starting with the word kernel or linux.
  4. Press the e key to edit the line.
  5. Add ‘rd.break’ at the end.
  6. Press ENTER to accept the changes.
  7. Press the ‘ctrl + x’ key to boot the kernel with the modified command line.

2) The system will provide a shell which will be from initramfs:

.
.
Entering emergency mode. Exit the shell to continue.
Type "journalctl" to view system logs.
You might want to save "/run/initramfs/rdsosreport.txt" to a USB stick or /boot
after mounting them and attach it to a bug report.
switch_root:/#

3) Root filesystem will be mounted read-only at ‘sysroot’ directory:

switch_root:/# mount | grep -i sysroot
/dev/mapper/rhel-root on /sysroot type xfs (ro,relatime,attr2,inode64,noquota)

4) Remount it with read-write mode:

switch_root:/# mount -o remount,rw /sysroot

5) Chroot into it:

switch_root:/# chroot /sysroot/
sh-4.4#

6) Change the password:

sh-4.4# passwd
Changing password for user root.
New password:
BAD PASSWORD: The password is shorter than 8 characters
Retype new password:
passwd: all authentication tokens updated successfully.

 
7) Relabel the filesystem:

sh-4.4# touch /.autorelabel

8) Exit from the shell:

sh-4.4# exit
exit
switch_root:/#
switch_root:/# exit

9) The system will continue the paused booting sequence:

.
Starting Relabel all filesystems...
[  OK  ] Started Manage Sound Card St
localhost login:

 

Installing Visual Studio Code on RHEL

RHEL, Fedora, and CentOS based distributions
We currently ship the stable 64-bit VS Code in a yum repository, the following script will install the key and repository:
sudo rpm --import https://packages.microsoft.com/keys/microsoft.asc
sudo sh -c 'echo -e "[code]\nname=Visual Studio Code\nbaseurl=https://packages.microsoft.com/yumrepos/vscode\nenabled=1\ngpgcheck=1\ngpgkey=https://packages.microsoft.com/keys/microsoft.asc" > /etc/yum.repos.d/vscode.repo'
Then update the package cache and install the package using dnf (Fedora 22 and above):
sudo dnf check-update
sudo dnf install code

Or on older versions using yum:
yum check-update
sudo yum install code

Due to the manual signing process and the system we use to publish, the yum repo may lag behind and not get the latest version of VS Code immediately