Posts Tagged ‘server boot’

How to Remove / Add SuSE Linux start service command

Thursday, July 2nd, 2015

opensuse-remove-add-new-service-geeko-suse-linux-mini-logo
If you happen to administer SUSE LINUX Enterprise Server 9 (x86_64) and you need to add or remove already existing /etc/init.d script or custom created Apache / Tomcat .. etc. service and you're already familiar with Fedora's / RHEL chkconfig, then the good news chkconfig is also available on SuSE and you can use in same way chkconfig to start / stop / enable / disable boot time services.

To list all available boot time init.d services use:
 

suse-linux:/etc # chkconfig –list

SuSEfirewall2_final       0:off  1:off  2:off  3:off  4:off  5:off  6:off
SuSEfirewall2_init        0:off  1:off  2:off  3:off  4:off  5:off  6:off
SuSEfirewall2_setup       0:off  1:off  2:off  3:off  4:off  5:off  6:off
Tivoli_lcfd1.bkp          0:off  1:off  2:off  3:off  4:off  5:off  6:off
activate_web_all          0:off  1:off  2:off  3:on   4:off  5:on   6:off
alsasound                 0:off  1:off  2:on   3:on   4:off  5:on   6:off
apache2                   0:off  1:off  2:off  3:off  4:off  5:off  6:off
apache2-eis               0:off  1:off  2:off  3:on   4:off  5:off  6:off
atd                       0:off  1:off  2:off  3:off  4:off  5:off  6:off
audit                     0:off  1:off  2:off  3:off  4:off  5:off  6:off
autofs                    0:off  1:off  2:off  3:off  4:off  5:off  6:off
autoyast                  0:off  1:off  2:off  3:off  4:off  5:off  6:off
boot.clock                0:off  1:off  2:off  3:off  4:off  5:off  6:off
boot.crypto               0:off  1:off  2:off  3:off  4:off  5:off  6:off
boot.device-mapper        0:off  1:off  2:off  3:off  4:off  5:off  6:off
boot.evms                 0:off  1:off  2:off  3:off  4:off  5:off  6:off
boot.idedma               0:off  1:off  2:off  3:off  4:off  5:off  6:off
boot.ipconfig             0:off  1:off  2:off  3:off  4:off  5:off  6:off
boot.isapnp               0:off  1:off  2:off  3:off  4:off  5:off  6:off
boot.klog                 0:off  1:off  2:off  3:off  4:off  5:off  6:off
boot.ldconfig             0:off  1:off  2:off  3:off  4:off  5:off  6:off
boot.loadmodules          0:off  1:off  2:off  3:off  4:off  5:off  6:off
boot.localfs              0:off  1:off  2:off  3:off  4:off  5:off  6:off
boot.localnet             0:off  1:off  2:off  3:off  4:off  5:off  6:off
boot.lvm                  0:off  1:off  2:off  3:off  4:off  5:off  6:off
boot.md                   0:off  1:off  2:off  3:off  4:off  5:off  6:off
boot.multipath            0:off  1:off  2:off  3:off  4:off  5:off  6:off
boot.proc                 0:off  1:off  2:off  3:off  4:off  5:off  6:off
boot.restore_permissions  0:off  1:off  2:off  3:off  4:off  5:off  6:off
boot.rootfsck             0:off  1:off  2:off  3:off  4:off  5:off  6:off
boot.sched                0:off  1:off  2:off  3:off  4:off  5:off  6:off
boot.scpm                 0:off  1:off  2:off  3:off  4:off  5:off  6:off
boot.scsidev              0:off  1:off  2:off  3:off  4:off  5:off  6:off
boot.shm                  0:off  1:off  2:off  3:off  4:off  5:off  6:off
boot.swap                 0:off  1:off  2:off  3:off  4:off  5:off  6:off
boot.sysctl               0:off  1:off  2:off  3:off  4:off  5:off  6:off
boot.udev                 0:off  1:off  2:off  3:off  4:off  5:off  6:off
coldplug                  0:off  1:on   2:on   3:on   4:off  5:on   6:off

To then stop the service:
 

suse-linux:/etc # chkconfig gtiweb off


If you prefer to do it the SuSE way and learn a bit more on SuSE boot time process check out:

suse-linux:/etc # man insserv


Removing already existing SuSE start-up script from init.d start up with insserv is done with:

suse-linux:/etc # cd /etc/init.d/
suse-linux:etc/init.d # insserv -r gtiweb
insserv: script ipmi.hp: service ipmidrv already provided!
insserv: script boot.multipath.2008-10-29: service boot.multipath already provided!


To install a new custom written and placed into /etc/inti.d/ on SuSE's server boot time with insserv:

suse-linux:/etc/init.d/ # insserv your_custom_script_name

How to configure manually static IP address on Debian GNU/Linux / How to fix eth0 interface not brought up with error (networking restart is deprecated)

Friday, July 29th, 2011

I’ve recently had to manually assign a static IP address on one of the servers I manage, here is how I did it:             

debian:~# vim /etc/network/interfaces

Inside the file I placed:

# The primary network interface
allow-hotplug eth0
auto eth0
iface eth0 inet static address 192.168.0.2 netmask 255.255.255.0 broadcast 192.168.0.0 gateway 192.168.0.1 dns-nameservers 8.8.8.8 8.8.4.4 208.67.222.222 208.67.220.220

The broadcast and gateway configuration lines are not obligitory.
dns-nameservers would re-create /etc/resolv.conf file with the nameserver values specified which in these case are Google Public DNS servers and OpenDNS servers.

Very important variable is allow-hotplug eth0
If these variable with eth0 lan interface is omitted or missing (due to some some weird reason), the result would be the output you see from the command below:

debian:~# /etc/init.d/networking restart
Running /etc/init.d/networking restart is deprecated because it may not enable again some interfaces ... (warning).
Reconfiguring network interfaces...

Besides the /etc/init.d/networking restart is deprecated because it may not enable again some interfaces … (warning). , if the allow-hotplug eth0 variable is omitted the eth0 interface would not be brough up on next server boot or via the networking start/stop/restart init script.

My first reaction when I saw the message was that probably I’ll have to use invoke-rc.d, e.g.:
debian:~# invoke-rc.d networking restart
Running invoke-rc.d networking restart is deprecated because it may not enable again some interfaces ... (warning).

However as you see from above’s command output, running invoke-rc.d helped neither.

I was quite surprised with the inability to bring my network up for a while with the networking init script.
Interestingly using the command:

debian:~# ifup eth0

was able to succesfully bring up the network interface, whether still invoke-rc.d networking start failed.

After some wondering I finally figured out that the eth0 was not brought up by networking init script, because auto eth0 or allow-hotplug eth0 (which by the way are completely interchangable variables) were missing.

I added allow-hotplug eth0 and afterwards the networking script worked like a charm 😉

How to reboot remotely Linux server if reboot, shutdown and init commands are not working (/sbin/reboot: Input/output error) – Reboot Linux in emergency using MagicSysRQ kernel sysctl variable

Saturday, July 23rd, 2011

SysRQ an alternative way to restart unrestartable Linux server

I’ve been in a situation today, where one Linux server’s hard drive SCSI driver or the physical drive is starting to break off where in dmesg kernel log, I can see a lot of errors like:

[178071.998440] sd 0:0:0:0: [sda] Result: hostbyte=DID_BAD_TARGET driverbyte=DRIVER_OK,SUGGEST_OK
[178071.998440] end_request: I/O error, dev sda, sector 89615868

I tried a number of things to remount the hdd which was throwing out errors in read only mode, but almost all commands I typed on the server were either shown as missng or returning an error:
Input/output error

Just ot give you an idea what I mean, here is a paste from the shell:

linux-server:/# vim /etc/fstab
-bash: vim: command not found
linux-server:/# vi /etc/fstab
-bash: vi: command not found
linux-server:/# mcedit /etc/fstab
-bash: /usr/bin/mcedit: Input/output error
linux-server:/# fdisk -l
-bash: /sbin/fdisk: Input/output error

After I’ve tried all kind of things to try to diagnose the server and all seemed failing, I thought next a reboot might help as on server boot the filesystems will get checked with fsck and fsck might be able to fix (at least temporary) the mess.

I went on and tried to restart the system, and guess what? I got:

/sbin/reboot init Input/output error

I hoped that at least /sbin/shutdown or /sbin/init commands might work out and since I couldn’t use the reboot command I tried this two as well just to get once again:

linux-server:/# shutdown -r now
bash: /sbin/shutdown: Input/output error
linux-server:/# init 6
bash: /sbin/init: Input/output error

You see now the situation was not pinky, it seemed there was no way to reboot the system …
Moreover the server is located in remote Data Center and I the tech support there is conducting assigned task with the speed of a turtle.
The server had no remote reboot, web front end or anything and thefore I needed desperately a way to be able to restart the machine.

A bit of research on the issue has led me to other people who experienced the /sbin/reboot init Input/output error error mostly caused by servers with failing hard drives as well as due to HDD control driver bugs in the Linux kernel.

As I was looking for another alternative way to reboot my Linux machine in hope this would help. I came across a blog post Rebooting the Magic Wayhttp://www.linuxjournal.com/content/rebooting-magic-way

As it was suggested in Cory’s blog a nice alternative way to restart a Linux machine without using reboot, shutdown or init cmds is through a reboot with the Magic SysRQ key combination

The only condition for the Magic SysRQ key to work is to have enabled the SysRQ – CONFIG_MAGIC_SYSRQ in Kernel compile time.
As of today luckily SysRQ Magic key is compiled and enabled by default in almost all modern day Linux distributions in this numbers Debian, Fedora and their derivative distributions.

To use the sysrq kernel capabilities as a mean to restart the server, it’s necessery first to activate the sysrq through sysctl, like so:

linux-server:~# sysctl -w kernel.sysrq=1
kernel.sysrq = 1

I found enabling the kernel.sysrq = 1 permanently in the kernel is also quite a good idea, to achieve that I used:

echo 'kernel.sysrq = 1' >> /etc/sysctl.conf

Next it’s wise to use the sync command to sync any opened files on the server as well stopping as much of the server active running services (MySQL, Apache etc.).

linux-server:~# sync

Now to reboot the Linux server, I used the /proc Linux virtual filesystem by issuing:

linux-server:~# echo b > /proc/sysrq-trigger

Using the echo b > /proc/sysrq-trigger simulates a keyboard key press which does invoke the Magic SysRQ kernel capabilities and hence instructs the kernel to immediately reboot the system.
However one should be careful with using the sysrq-trigger because it’s not a complete substitute for /sbin/reboot or /sbin/shutdown -r commands.
One major difference between the standard way to reboot via /sbin/reboot is that reboot kills all the running processes on the Linux machine and attempts to unmount all filesystems, before it proceeds to sending the kernel reboot instruction.

Using echo b > /proc/sysrq-trigger, however neither tries to umount mounted filesystems nor tries to kill all processes and sync the filesystem, so on a heavy loaded (SQL data critical) server, its use might create enormous problems and lead to severe data loss!

SO BEWARE be sure you know what you’re doing before you proceed using /proc/sysrq-trigger as a way to reboot ;).

How to enable AUTO fsck (ext3, ext4, reiserfs, LVM filesystems) checking on Linux boot through /etc/fstab

Tuesday, July 12th, 2011

How to auto FSCK manual fsck screenshot

Are you an administrator of servers and it happens a server is DOWN.
You request the Data Center to reboot, however suddenly the server fails to boot properly and you have to request for IPKVM or some web java interface to directly access the server physical terminal …

This is a very normal admin scenario and many people who have worked in the field of remote system administrators (like me), should have experienced that bad times multiple times.

Sadly enough only a insignifant number of administrators try to do their best to reduce this down times to resolve client stuff downtime but prefer spending time playing the ztype! game or watching some porn website 😉

Anyways there are plenty of things like Server Auto Reboot on Crash with software Watchdog etc., that we as sysadmins can do to reduce server downtimes and most of the manual human interactions on server boot time.

In that manner of thougts a very common thing when setting up a new Linux server that many server admins forget or don’t know is to enable all the server partition filesystems to be auto fscked during server boot time.

By not enabling the auto filesystem check options in Linux the server filesystems did not automatically scan and fix hard drive partitions for fs innode inconsistencies.
Even though the filesystems are tuned to automatically get checked on every 38 system reboots, still if some kind of filesystem errors are found that require a manual confirmation the boot process is interrupted and the admin ends up with a server which is not reachable remotely via ssh !

For the remote system administrator, this times are a terrible times of waitings, prayers and hopes that the server hardware is fine 😉 as well as being on hold to get a KVM to get into the server manually and enter the necessery input to fsck prompt.

Many of this bad times can be completely avoided with a very simple fix through /etc/fstab by enabling all server partitions containing any filesystem to be automatically checked and fixed in case if inconsistencies or errors are found by fsck.ext3, fsck.ext4, fsck.reiserfs etc. commands.

A very typical default /etc/fstab file you will find on many servers should look something like:

/dev/sda8 / ext3 errors=remount-ro 0 1
tmpfs /dev/shm tmpfs defaults 0 0
devpts /dev/pts devpts gid=5,mode=620 0 0
sysfs /sys sysfs defaults 0 0
proc /proc proc defaults 0 0
/dev/sda1 /home ext3 defaults 0 0

Notice the line:
/dev/sda1 /home ext3 defaults 0 0

The first column in the example contains the device name, the second one its mount point, third its filesystem type, fourth the mount options, fifth (a number) dump options, and sixth (another number) filesystem check options. Let’s take a closer look at this stuff.

The ones which are interesting to enable auto fsck checking and error resolving is provided usually by the last sixth variable (filesystem check option) which in the above example equals 0 .

When the filesystem check option equals 0 this means the auto fsck and repair for the respective filesystem is disabled.
Some time in the past the dump backup option (5th option in the example) was also used but as far as I can understand today it’s not that important in modern GNU/Linux distributions.

Now having the above sample crontab in order to enable the fsck file checking on Linux boot for /dev/sda1 , we will need to modify the above line’s filesystem check option be 2, e.g. the line would afterwards look like:

/dev/sda1 /home ext3 defaults 0 2

Setting the 2 as an option for filesystem check is necessery for every filesystem which is not mounted as a root filesystem /

In above example /etc/fstab you already see that auto filesystem fsck is enabled for root partition:

/dev/sda8 / ext3 errors=remount-ro 0 1
(notice the 1 in the end of the line)

Finally a modified version of the default sample /etc/fstab which will check the extra /dev/sda1 /home partition would look like so:

/dev/sda8 / ext3 errors=remount-ro 0 1
tmpfs /dev/shm tmpfs defaults 0 0
devpts /dev/pts devpts gid=5,mode=620 0 0
sysfs /sys sysfs defaults 0 0
proc /proc proc defaults 0 0
/dev/sda1 /home ext3 defaults 0 2

Making sure all Linux server partitions has the auto filesystem check option enabled is something absoultely necessery!
Enabling the auto fsck on servers always makes me sleep calmer 😉
Hope it helps your too. 🙂