How to run fsck on a Logical Volume in Linux.
I recently had a problem on my laptop running Fedora 11 where my X session just totally froze when trying to bring the laptop back from a hibernate state. Outside of the occasional issues coming out of hibernate (usually X not restoring) I'd say Fedora 11 has been pretty solid. This particular time, my X session restored but everything locked up. I tried switching to another virtual terminal to log in and kill GDM but some sort of inode error just streamed down the console. My only option was a hard reboot and after that I couldn't boot Fedora with any kernel. To fix my problem I booted off the Fedora install CD into rescue mode without mounting / . I then performed the following:
# lvm pvscan # lvm vgscan # lvm lvchange -ay /dev/VolGroup00/LogVol_home # lvm lvscan # fsck -yfv /dev/VolGroup00/LogVol_home
Connect to Cisco routers using screen
screen is a Linux utility that I use to connect to the console on Cisco routers. If your router is plugged in to a serial port on a Linux box, you can use the following command to connect to it:
[dacaprice@FedoraBox ~]$ screen /dev/ttyS0
Changing sdiff column width in Linux
I use sdiff pretty often to do a side-by-side comparison of config files on my Linux box. The thing that annoys me the most is the default column width; often whatever it is I am comparing, gets cut short because the width is too narrow. I like use the -w ColumnWidth to set a wider width and the -s to supress any common lines.
[dacaprice@fedora]$ sdiff -s -w 150 file1 file2
Using script to record a terminal session.
script is a useful utility in Linux that records everything that is printed to stdout to a specified file.
[dacaprice@fedora10 ~]$ script filename.txt
I find script particularly useful for capturing a large amount of output from a router or firewall that I need to save it to a file.
The ssh_config file.
Working in an environment with hundreds of SSH servers, one appreciates the value a good ssh_config file. I use an ssh_config file to specify specific usernames for certain hosts, as well as specifying a keepalive interval, to prevent my session from timing out.
I use the following options:
Host hostname HostName hostname (can be an IP) User username ServerAliveInterval 60 (sends keepalive every 60 seconds)
For further info check out the good old man ssh_config.