CentOS/RHEL 8

Problem /tmp is not automatically mounted after reboot even though an entry is present in /etc/fstab. Below outputs show an example of the issue: # uptime 16:44:11 up 2 min, 1 user, load average: 0.21, 0.55, 0.44 # df -h Filesystem Size Used Avail Use% Mounted on devtmpfs 252G 0 252G 0% /dev tmpfs 252G […]

Question: How to remotely access graphical environment on an CentOS/RHEL 8? The access will be used using a VNC server. Setup VNC Server 1. Install VNC Server and the graphical environment in the server: $ sudo dnf install tigervnc-server $ sudo dnf group install “Server with GUI” 2. Configure the users that will user VNC. […]

The Problem DNF Update fails with the below error: 2018-06-22T14:31:22 DDEBUG Cleaning up. 2018-06-22T14:31:22 INFO The downloaded packages were saved in cache until the next successful transaction. 2018-06-22T14:31:22 INFO You can remove cached packages by executing ‘dnf clean packages’. 2018-06-22T14:31:22 SUBDEBUG Traceback (most recent call last): File “/usr/lib/python3.6/site-packages/dnf/cli/main.py”, line 64, in main return _main(base, args, […]

Question: How To Disable Weak Cipher And Insecure HMAC Algorithms in SSH services in CentOS/RHEL 8? In order to disable weak Ciphers and insecure HMAC algorithms in ssh services in CentOS/RHEL 8 please follow the instructions bellow: 1. Edit /etc/sysconfig/sshd and uncomment CRYPTO_POLICY line: Before: # CRYPTO_POLICY=[Original value] After: CRYPTO_POLICY=[New value] 2. Make sure correct […]

This post will help to disable TLS 1.1 cockpit port 9090. 1. Create file /etc/systemd/system/cockpit.service.d/ssl.conf containing: [Service] Environment=G_TLS_GNUTLS_PRIORITY=NORMAL:-VERS-SSL3.0:-VERS-TLS1.0:-VERS-TLS1.1 2. Reload systemd daemons: # systemctl daemon-reload 3. Restart cockpit service: # systemctl restart cockpit 4. Check protocols tls1_1: # echo test | openssl s_client -connect localhost:9090 -tls1_1CONNECTED(00000003) 139687924594576:error:1408F10B:SSL routines:SSL3_GET_RECORD:wrong version number:s3_pkt.c:365: — no peer certificate available […]

Access to certain ports are blocked or dropped by firewalld unless added to a firewall zone. This post outlines steps to add source, service, and ports to the firewall zones in CentOS/RHEL 7 and 8 systems. Adding Service to Firewall Zone Adding a service to a zone is the simplest way to configure the firewall. […]

Question: How to configure CIFS debug option in Linux servers to provide additional debug information in the client system logs? 1. Take backup of existing debug or to check the default value: # cp /sys/kernel/debug/dynamic_debug/control /root/backup # cat /proc/fs/cifs/cifsFYI # cat /proc/fs/cifs/traceSMB 2. Enable debug chosen options: # echo ‘module cifs +p’ > /sys/kernel/debug/dynamic_debug/control # […]

The Problem When trying to create a VDO disk the procedure fails with the following error: # vdo create –name=vdoTEST2 –device=/dev/sde –vdoLogicalSize=1G –writePolicy=async Creating VDO vdoTEST2 vdo: ERROR – vdoformat: formatVDO failed on ‘/dev/disk/by-id/ata-VBOX_HARDDISK_VBcd2ac7bf-4750ebec’: VDO Status: Out of space The Solution The size of the disk was 4G. # lsblk | grep sde sde 8:64 […]

Question: How to debug/find, changes or failing commands during boot process? During boot process, when seeing grub boot menu press “e” for edit the grub, then scroll down until you see boot entry: echo “Loading Linux… linux16 /vmlinuz-XXX root=XXXro crashkernel=auto rd.lvm.lv=rhel/root rd.lvm.lv=rhel/swap rhgb quiet LANG=en_US.UTF-8 On the line with “linux” remove the following entries if […]

By default, IPv6 is enabled on CentOS/RHEL 8 systems. However, in certain situations, some users may find it desirable to disable IPv6 support. This post outlines steps to enable ipv6 on a CentOS/RHEL 8 system. 1. Edit /etc/default/grub and delete the entry ipv6.disable=1 from the GRUB_CMDLINE_LINUX, as shown below: # vi /etc/default/grub GRUB_CMDLINE_LINUX=”rd.lvm.lv=rhel/swap crashkernel=auto rd.lvm.lv=rhel/root” […]