Are you concerned when some security software flags older kernels as security threats due to known bugs and vulnerabilities? Does leave those outdated kernels installed on a server opens a door for malicious attacks? After upgrading the server or updating the Linux kernel, leaving old kernels installed likely does not open an attacking threat against …
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TBOOT boot crash observed with TPM 2.0 in UEFI mode
When TPM2.0 device is in UEFI mode, booting the kernel through TBOOT hangs. The root cause of this error is because GRUB package included with Alam Linux 8.3 does not implement the complete stack to validate kernel command line parameters. To resolve this issue, upgrade the system to AlmaLinux 8.4/CentOS 8.4. If somehow you cannot …
Devices have inconsistent logical block sizes while adding VDO device
While extending VG on SD or VDO devices, you may get an error: # vgextend vg1 /dev/mapper/vdo2Devices have inconsistent logical block sizes (512 and 4096). In the above output, vgextend fails due to inconsistent block size of physical volume on disk drives. To resolve this issue, enable allow_mixed_block_sizes in lvm.conf to allow the same VG …
VNC session freezes for a few seconds
VNC hangs due to an increased number of VNC sessions initiated by sshd, being under the closing state. # loginctl list-sessions --no-pager | wc -l49290 A session would be in a closing state if a process within the session stayed alive after the session was closed. # loginctl session-status 4509845098 - root (0)Since: Fri 2021-09-04 13:20:15 …
VNC error – Could not connect to session bus:Failed to connect
Your VNC session may give an error as shown below: Could not connect to session bus:Failed to connect to socket /tmp/dbus-xxxxxx:Connection refused The root cause of this error is that the session bus gets multiple dbus-daemon modules in the default path set for the user. A path for /root/anaconda3/bin was exported and set as the …
How to login into VNC without a password
You can remove all types of authentications by configuring the vnc server. As user start a vnc session and “-SecurityTypes none” option while starting a vnc server as below: #vncserver :X -SecurityTypes None In the above command, X is the display number at which the vnc session should start. The “-SecurityTypes none” can be added …
error “Cannot allocate memory” while executing commands
You should increase /proc/sys/kernel/pid_max sysctl. Otherwise, execute the following command to check which app is forking multiple threads. #ps -eLF Error “Cannot allocate memory” indicates that the system is running out of PID (process ids). In other words, the number of threads/processes present on the system has reached the maximum limit, which is delimited by …
How to create local repository distributed through apache on AlmaLinux 8 using DVD ISO
repo creation via ISO DVD image that can be used by local server only Mount the AlmaLinux DVD ISO file to /mnt/iso as the yum destination. mkdir -p /mnt/iso mount -o loop AlmaLinux-dvd.iso /mnt/iso If you are using cdrom/dvdrom, insert cd/dvd and mount it to /mnt/iso as the yum destination. mkdir -p /mnt/iso mount -o …
How to configure multiple instances of Apache HTTPD on the same server in AlmaLinux?
You need to copy instance specific configuration file located at /usr/share/doc/httpd/instance.conf to /etc/httpd/conf/newinstance.conf cp /usr/share/doc/httpd/instance.conf /etc/httpd/conf/newinstance.conf Use the Listen option to change the port to run simultaneously with other httpd.service as below: Listen 81 This configuration will be the default when running httpd@newinstance.service systemctl start httpd@newinstance.service Some changes expected from the default are: The default …
PHP Vs Python – Comparison between both Languages
Scripting Languages Scripting languages are becoming progressively popular in web application programming in the last few years. Now in this article trying to compare popular languages nowadays: PHP and Python. The languages will be compared regarding history, evolution, popularity, syntax, features, security, and enactment in web application locations. A final thought will Conclude and recommends …
How to repair filesystem in rescue environment CentOS 8 & CentOS 7?
Your Linux server may not load after boot and requests fsck of the root filesystem. If this happens server filesystem goes into read-only mode. When prompted for language, and keyboard, provide the pertinent information for the system. Boot your server from CentOS ISO image and select rescue mode at the boot command prompt. When prompted …
How to resolve error resize2fs: Operation not permitted While trying to add group – ext4_group_add: No reserved GDT blocks, can’t resize
The root cause of this error is that the pool of reserved GDT blocks is not available, or the filesystem does not support online resizing. Note that the Ext3 and Ext4 filesystem metadata layout is fixed. mkfs reserves space for future disk resizing, but that is only 1024x the filesystem size during initial disk creation …
Performance testing and benchmarking tools for Linux
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Configure sftp server with restricted chroot users with ssh keys without affecting normal user access
Login on the Linux server (sftp) as root and create a new user account with the following Shell commands: useradd seimaxim-user passwd seimaxim-user On the client system copy the ssh keys to the server: ssh-copy-id seimaxim-user@seimaxim-server On the client system verify the ssh keys so that a password-less login can be made to the server: …
When connecting to VNC either screen is black or icons are shown but no menu or screen background
This issue occurs due to changes in the default service unit file. The changed file which is causing the error is given below; [Service] Type=forking User=<USER> # Clean any existing files in /tmp/.X11-unix environment ExecStartPre=-/usr/bin/vncserver -kill %i ExecStart=/usr/bin/vncserver %i PIDFile=/home/<USER>/.vnc/%H%i.pid ExecStop=-/usr/bin/vncserver -kill %i The correct file is shown below; [Service] Type=forking # Clean any existing …
