Configuring cups client

Lpstar and lpr commands

Configuring cups client lpstar and lpr commands Check if cups-client or cups-utils # zypper in cups-client # lpstat -p -v # telnet <PrinterIP> 9100 # lpstat -p <printer_name> -l # lpq -a # lpstat -ato From a network printer, print the file and check for idle state of the printer #  ..

Perform fsck for root filesystem

Dryrun fsck

Boot the server in emergency mode with root password. Dryrun will give you information on how many sectors are affected and how may fix will happen. # fsck -N <Device Name> Perform FSCK, handle with care # fsck -p <Device Name> Make you always have backup before performing this activity, reboot the  ..

Extend lv with striped

Extend striped lv

Find the disk with stripes # lvs -o+lv_layout,stripes # lvs +o+devices,lv_layout,stripes # pvs | grep vg_volgroup002 # lsblk | grep '<disks which are present in VG or affected by LV>' All the striped disk must extend equally # pvresize /dev/sdp /dev/sdq # vgs # lvresize -L+200G /dev/vg_volgroup002/lv_mylv # resize2fs /dev/vg_volgroup002/lv_mylv once the disk is  ..

Rsync with hidden files

Copy files using rsync

To copy hidden files, you must include --include # rsync -av --include='.*' /opt/bluff/* /opt/linux/. If you are not using "*" and "." at the end rsync will copy hidden files # rsync -av --include='.*' /opt/bluff/ /opt/linux/ Below are few examples of rsync # rsync -axHAX --progress --stats /opt/bluff/* /opt/linux/. # rsync  ..

Using dracut kver

Build an initramfs using dracut

Please be careful what you are doing, this can break you server or machine sometimes the kernel might have updated but initramfs would have been broken, in such condition dracut -kver can be used # dracut --kver 4.8.x.x86_64 Quick way to build initramfs for a specific kernel version is to invoke dracut  ..

Skip fsck and do fastboot

Avoid entering into fsck during boot

Reboot system and stop auto fsck on-boot # shutdown -rf now During boot press e and add fastboot # /vmlinuz-.xx ro root=LABEL=/ console=tty0 console=ttyS1,19200n8 fastboot press e during server boot and add fastboot at end of the boot kernel to skip fsck or avoid filesystem check during boot. To avoid filesystem check permenantly,  ..

Edit bootgrub2grub config grub2 mkconfig

Grub2-mkconfig is used to regenerate file

When you make changes in /etc/default/grub run below command to update /boot/grub2/grub.cfg # cat /etc/default/grub GRUB_HIDDEN_TIMEOUT=0 GRUB_TIMEOUT=20 Once you change timeout or add any additional parameter in CMDLINE # grub2-mkconfig -o /boot/grub2/grub.cfg why do we edit /etc/default/grub? Changes or edit in grub.cfg will be lost anytime when grub2-mkconfig is  ..

Troubleshooting with dns queries

Simple handy commands for DNS check

check dns using dig or nslookup # dig # nslookup Check the connectivity of a domain or by resolving the domain with DNS Server # nslookup myhostname <DNS-server-IP> # dig @DNSServerIP How to check NS and SOA # dig NS @<DNS-Server-IP> # dig SOA @<DNS-Server-IP>  ..

Azure delete blockdevice

Delete mount volume and detach disk

Before deleting a blockdevice make sure to backup/snapshot of the disk check if the disk is mounted or added in any logical volume. # pvs | grep vg_1-lv-backup # fdisk -l | grep -i /dev/mapper/vg_1-lv-backup # lvremove /dev/mapper/vg_1-lv-backup # vgremove vg_1 # pvremove /dev/sde Finding LUN in azure # vgs # pvs  ..

Add swap disk and remove swap disk

Add swap disk

By using below commands, collect required disk information and mount points # df -hT # fdisk -l # lvdisplay # pvdisplay # lvs # lsblk -o NAME,KNAME,MAJ:MIN,FSTYPE,MOUNTPOINT # lsblk -o NAME,KNAME,MAJ:MIN,FSTYPE,MOUNTPOINT | egrep 'dm-0|dm-1' Once you see new disk visible on OS, create and mount swap disk using swapon  ..

Systemctl service reload

Systemctl daemon reload

Sometime if blockdevice is not visible to OS # systemctl daemon-reload Enable a service on boot # systemctl is-active <servicename> # systemctl is-enabled <service_name> # systemctl enable <service_name>   ..

Zypper and rpm commands

Zypper and rpm handy commands

zypper commands # zypper se -s 'kernel-def' | grep '4.12' # zypper wp libc.s0.6 # zypper se --provides --match-exact '' # zypper in package-name +i installed by user request i installed automatically (by the resolver, see section Automatically installed packages) se - search package in - install package   ..

Network troubleshooting guide

Network troubleshooting commands

Below are few frequently used commands for my application troubleshooting Check IP tables # iptables -t nat -nL Check how many simultaneous connections are present # netstat -auntpl | grep | grep 22 | wc -l Part of active connections # netstat -auntpl | egrep -i "active|proto|" | head -20 Nmap  ..

Route add and delete

Add route and delete

Before making any changes in route always have backup of existing route tables and output. Its always good to proceed it with change, be cautious when you change or add routes. Get route table information # ip route show # ip route show table bond0 # ip route show table main   ..

How to find defunt process on linuxbox

Find and kill all defunct process in linux

how to find defunt process on linuxbox Find and kill all defunct process in linux To find all defunct process # ps axo ppid,pid,stat,comm | grep -w defunct -w, --word-regexp Select only those lines containing matches that form whole words. The test is  ..

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