Cloud Network

Cloud Network

Networking | Support | Tricks | Troubleshoot | Tips

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    Showing posts with label Fedora. Show all posts
    Showing posts with label Fedora. Show all posts

    Monday, November 2, 2020

    RHEL 7 uses system temp files to

    November 02, 2020
    RHEL 7 uses system temp files to

     

    Managing temporary files with systemd-tmpfiles on Red Hat

    Why the files in /tmp directory gets deleted periodically

     

    For CentOS/RHEL7

    cd /usr/lib/tmpfiles.d/tmp.conf

    # cat /usr/lib/tmpfiles.d/tmp.conf
# Clear tmp directories separately, to make them easier to override
v /tmp 1777 root root 10d
v /var/tmp 1777 root root 30d

# Exclude namespace mountpoints created with PrivateTmp=yes
x /tmp/systemd-private-%b-*
X /tmp/systemd-private-%b-*/tmp
x /var/tmp/systemd-private-%b-*
X /var/tmp/systemd-private-%b-*/tmp
     

    For CentOS/RHEL6

    cd /etc/cron.daily/tmpwatch 

    # cat /etc/cron.daily/tmpwatch
#! /bin/sh
flags=-umc
/usr/sbin/tmpwatch "$flags" -x /tmp/.X11-unix -x /tmp/.XIM-unix \
	-x /tmp/.font-unix -x /tmp/.ICE-unix -x /tmp/.Test-unix \
	-X '/tmp/hsperfdata_*' -X '/tmp/.hdb*lock' -X '/tmp/.sapstartsrv*.log' \
	-X '/tmp/pymp-*' 10d /tmp
     
    # man tmpwatch 

     
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    Monday, October 28, 2019

    How to Reset/Recover/Forget Root Password in CentOS/RHEL/Fedora and VM/KVM

    October 28, 2019
    How to Reset/Recover/Forget Root Password in CentOS/RHEL/Fedora and VM/KVM

    Note : Take Backup of your data before you proceed

    Method 1 - (CentOS/RHEL/Fedora)

    Step1 :- Restart the Machine

    Step2 :- Press "e" from keyboard at time when kernel versions presented Press "e" again

    Step3 :- Search for "rd.break" line (last line of Linux16) or write next to rw file (rw init=/sysroot/bin/sh)

    Step4 :- Press Ctrl+X(control+x) to start on single user mode

    Step5 :- Type at command line "mount -o remount, rw /sysimage"
    chroot /sysimage or  chroot /sysroot
    passwd root      or  passwd
    load_policy -i   or touch /.autorelabel
    restorecon /etc/shadow to restore the SELinux settings for the given file
    reboot   or exit

    Method 2 - (CentOS/RHEL/Fedora)

    Step1 :- Boot/Restart the Virtual Machine or Server

    Step2 :- Then Select Troubleshooting see below screenshot

    Step3 :- Then Select Rescue a CentOS system and hit Enter

    Step4 :- Then type 1 and hit enter a couple of times until you get the command prompt (shell).

    Step5 :- Then type in command prompt one by one
    Chroot /mnt/sysimage
    Passwd
    Rm -f /.autorelabel
    Exit
    Exit

    Step6 :- After Reboot Login with New Password

    Method 3 - (CentOS/RHEL/Fedora)

    Step1 :- Boot/Restart the Virtual Machine or Server

    Step2 :- Interrupt while booting at GRUB Stage with any arrow or space bar from keyboard

    Step3 :- Type "e" to edit kernel argument, 'ESC' is used for Cancel or to goback

    Step4 :- Then type 1 after rhgb quiet line hit enter to boot

    Step5 :- Press "b" to boot process then type "runlevel" in command prompt 1S is single user mode

    Step6 :- Type New Password and Again Same Password

    Step7 :- Reboot it
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    Tuesday, October 22, 2019

    How to Generate/Encrypt/Decrypt Random Passwords on CentOS/RHEL & Fedora

    October 22, 2019
    How to Generate/Encrypt/Decrypt Random Passwords on CentOS/RHEL & Fedora
     




     1. Generate a random unique password of length equal to 10 characters
    Step1 :-  yum install pwgen
    Step2 :-  pwgen 10 1
    Step3 :-  pwgen 50
    Step4 :- yum install expect
    Step5 :- yum –y install makepasswd    --- As per choice
    Step6 :- makepasswd                       --- Default is 10
    Step7 :- makepasswd  --char 50
    Step8 :- makepasswd  --char 20  --count 7     --- Generate 7 random password of 20cht.

    2. Encrypt a password using crypt along with salt.

    Salt is a random data which servers as an additional input to one way function in order to protect password against dictionary attack.




    Step9 :-  Yum install mkpasswd
    Step10 :- mkpasswd  cloudnetwork
                    mkpasswd cloudnetwork  -s   tt

    4. Encrypt a string say “cloudnetwork is a video tutorials make in Linux,Ubuntu” using aes-256-cbc encryption using password say “cloudnetwork” and salt.

    Step8 :- echo cloudnetwork-is-a-video-tutorials-make-in-Linux,Ubuntu  | openssl
    enc -aes-256-cbc -a -salt -pass pass:cloudnetwork

    5. Decrypt the above string using openssl command using the -aes-256-cbc decryption.

    Step9 :- echo U2FsdGVkX18Zgoc+dfAdpIK58JbcEYFdJBPM9oXWsgpvpdO/Z | openssl
    enc -aes-256-cbc -a -d -salt -pass pass:cloudnetwork
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