Downloading and using kernel source on Ubuntu
There may come a time when you need the kernel source code, usually to build kernel headers, compile a module etc. To work with the kernel source once you have it, you’ll want some development tools installed on your server.
sudo aptitude update
sudo aptitude install build-essential
To check the version right on the server. Just run:
root@laptop:~# uname -r
2.6.28-11-generic
Searching for kernel source.
# apt-cache search linux-source
linux-ports-source-2.6.28 - Linux kernel source for version 2.6.28 with Ubuntu patches
linux-source - Linux kernel source with Ubuntu patches
linux-source-2.6.28 - Linux kernel source for version 2.6.28 with Ubuntu patches
Initial RAM disk image ( initrd )
Once the second stage boot loader has determined which kernel to boot, it locates the corresponding kernel binary in the /boot/ directory. The proper binary is the /boot/vmlinuz-2.6.x-xx file that corresponds to the boot loader’s settings.
Next the boot loader places the appropriate initial RAM disk image, called an initrd, into memory. The initrd is used by the kernel to load any drivers not compiled into it that are necessary to boot the system. This is particularly important if you have SCSI hard drives or are using the ext3 file system.
Debugging on part(s) of the bash script
Using the set Bash built-in you can run in normal mode those portions of the script of
which you are sure they are without fault, and display debugging information only for troublesome zones.
Say we are not sure what the `uptime` command will do in a script, then we could enclose it in the script like this:
set -x # activate debugging from here
uptime
set +x # stop debugging from here
How to find IPs and IP networks behind each interface
To find the IPs of your network interfaces use ip addr show and to find the IP networks behind each interface use ip route show.
$
ip addr show
1: lo: mtu 16436 qdisc noqueue state UNKNOWN
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
2: eth0: mtu 1500 qdisc pfifo_fast state UNKNOWN qlen 1000
link/ether 00:08:74:22:5c:61 brd ff:ff:ff:ff:ff:ff
inet 192.168.1.2/24 brd 192.168.1.255 scope global eth0
inet 192.168.1.4/24 brd 192.168.1.255 scope global secondary eth0:1
#
ip route show
192.168.52.12 dev ppp0 proto kernel scope link src 117.114.119.119
192.168.1.0/24 dev eth0 proto kernel scope link src 192.168.1.1
169.254.0.0/16 dev eth0 scope link metric 1000
default dev ppp0 scope link
How can I force fsck on next boot
You can force an automatic full check by changing the check interval using tune2fs (-c and/or -i).
-c max-mount-counts
Adjust the number of mounts after which the filesystem will be checked by e2fsck(8). If max-mount-counts is 0 or -1, the number of times the filesystem is mounted will be disregarded by e2fsck(8) and the kernel.
-i interval-between-checks[d|m|w]
Adjust the maximal time between two filesystem checks. No postfix or d result in days, m in months, and w in weeks. A value of zero will disable the time-dependent checking.
It is strongly recommended that either -c (mount-count-dependent) or -i (time-dependent) checking be enabled to force periodic full e2fsck(8) checking of the filesystem.
The above command would tell the init scripts to run fsck on hda2 at every boot.
# tune2fs -i 1d /dev/hda2
The above command would tell the init scripts to run fsck on hda2 after 1 day.
If you only want to run fsck on the next boot, please execute the following as the root user.
This will only run the file system check on the next reboot. By touching the file “forcefsck” in the / directory, it will force the system to perform a full file system check.
The file “forcefsck” will be deleted automatically after fsck is finished.
