Recovering MySQL InnoDB after power failure

Once, after the power was turned off, the UPS was discharged, then the generator automatic start did not work because it turned on and off several times, as a result, the server with MySQL was also started and disconnected from the power supply several times, later the tables of different databases were damaged , including the default database with mysql users, as a result, the MySQL daemon did not start.

Continue reading “Recovering MySQL InnoDB after power failure”

WS-SUP720-3BXL does not start Not Applicable Unknown

Once after a power outage, on Cisco Catalyst 6509-E, instead of the main module WS-SUP720-3BXL, only the backup module was launched.
As I found out later, the memory card stopped working and, accordingly, the module could not start the firmware. At this moment on the module all the indicators glowed red.

Continue reading “WS-SUP720-3BXL does not start Not Applicable Unknown”

Recovering file systems using fsck

Fsck (File System ChecK) – checks and restores file systems.

Before starting the scan, unmount the file system with the command:

umount /dev/sda1

An example of starting a scan (where /dev/sda1 is a device or partition to be checked):

fsck -V -C -f /dev/sda1

View brief documentation:

man fsck

I will describe some startup keys:
-C (display progress bar if possible)
-M (do not check mounted file systems)
-p (auto mode)
-y (agree to all questions)
-n (disagree on all questions)
-f (forced check)
-V (more detailed information)

Restoring MikroTik (RouterOS) using NetInstall

NetInstall is used to reinstall RouterOS when it is damaged, the access password is incorrectly set or the access password is not known.

I will describe the basic steps:

1) Download NetInstall from the official site
https://www.mikrotik.com/download

2) Register a static IP address to the computer, for example 192.168.88.254

3) Connect the Ethernet cable to the router through the ETH1 port with the computer using the switch or directly.

4) Run the NetInstall application. Click the “Net booting” button, check “Boot Server” enabled and enter the IP address from the same subnet where the computer is located, for example 192.168.88.200, its NetInstall will temporarily assign it to the router. Any firewall on the computer must be disabled.

5) When the router is disconnected from the mains, press the “reset” button and continue to turn it on, wait for about half a minute until the NetInstall program displays a new device in the device list.

6) In “Packages”, click the “Browse” button and specify the directory with the firmware. In the list of devices (Routers/Drives) select a router, in the bottom of the list, tick the firmware to be downloaded to the router and click “Install”. The firmware is downloaded to the router and the status will be written “Waiting for reboot”, after which, instead of the install button, there will be a reboot button, and you will need to click it.

The router will boot with the new firmware. If there are any problems with the loading of the router, you can try to reset it to the standard settings by holding the reset button, or if there is a display, select “Restore settings” and enter the standard pin code 1234. Alternatively, restore via Netinstall with the tick “Keep Old Configuration” and indicating below your “Configure script”.

Recovering GRUB Linux

Usually on each disk there is an MBR (master boot record) and when the computer is turned on, the BIOS accesses it for information for further download. On Linux systems, GRUB is used as the boot loader, I will write about the recovery options of which below.

You can see the version of GRUB using the command:

grub-install --version

1) First option.
We start the system with LiveCD/USB, for example in the Ubuntu Desktop image, in addition to the installation, it is possible to start the system.
Open the terminal, for this press Alt+F2 and enter the command:

gnome-terminal

Continue reading “Recovering GRUB Linux”