Posts Tagged ‘acpi’

Ubuntu 9.04 (Jaunty) on Toshiba Satellite L40 14B ACPI problem ACPI loading problem and workaround

Thursday, September 10th, 2009

As you have noticed in my previous posts I'm playing a bit with Toshiba Satellite L40 14B updates this days. I've came across an ugly problem with ACPI on Ubuntu Jaunty. It's really a big issue because acpi stalls and keeps loading the system on 100% leaving it with 0% idle all the time. The solution I’ve found is suggested on the following Ubuntu bug launchpad . As it describes the solution comes to this:

1. rm -f /etc/acpi/events/asus-wireless-on

2. rm -f /etc/acpi/events/asus-wireless-2

the next two steps are added by meto prevent some problems caused by acpidupgrades.

3. touch /etc/acpi/events/asus-wireless-2

4. touch /etc/acpi/events/asus-wireless-on

Disable bluetooth on Linux IBM / Lenovo Thinkpad laptops

Thursday, February 14th, 2013

bluetooth gnu linux disable bluetooth linux how to tux logo bluetooth thinkpad

I have a Debian GNU / Linux squeeze with bluetooth and bluetooth is started automatically on system boot. This is pretty annoying, cause I use bluetooth quite rarely.
 disable / enable bluetooth via terminal is controlled via Linux sysfs virtual filesystem. The command to disable bluetooth one time is:

debian:~# echo 0 > /sys/devices/platform/thinkpad_acpi/bluetooth_enable

It is efficient in terms of energy saving especially if you use often your notebook on battery to turn off bluetooth permanently and only enable it when needed with:

debian:~# echo 1 > /sys/devices/platform/thinkpad_acpi/bluetooth_enable

To permanently disable bluetooth on Linux boot use:

# service bluetooth stop

In /etc/rc.local before exit 0 line place:

echo 0 > /sys/devices/platform/thinkpad_acpi/bluetooth_enable

An alternative method to permanently disable bluetooth (on other non-Thinkpad – any brand laptops) is via rfkill (bluetooth device control interface), on Ubuntu rfkill is installed by default but Debian users has to explicitly install it via apt:

debian:~# apt-get install –yes rfkill

Once rfkill is installed on host put a line before exit 0 in /etc/local:

rfkill block bluetooth

How to disable ACPI on productive Linux servers to decrease kernel panics and increase CPU fan lifespan

Tuesday, May 15th, 2012

Linux TUX ACPI logo / Tux Hates ACPI logo

Why would anyone disable ACPI support on a server machine??
Well  ACPI support kernel loaded code is just another piece of code constantly being present in the memory,  that makes the probability for a fatal memory mess up leading to  a fatal bug resulting in system crash (kernel panic) more likely.

Many computers ship with buggy or out of specifications ACPI firmware which can cause a severe oddities on a brand new bought piece of comp equipment.

One such oddity related to ACPI motherboard support problems is if you notice your machine randomly powering off or failing to boot with a brand new Linux installed on it.

Another reason to switch off ACPI code will would to be prevent the CPU FAN rotation from being kernel controlled.

If the kernel controls the CPU fan on  high CPU heat up it will instruct the fan to rotate quickly and on low system loads it will bring back the fan to loose speed.
 This frequent switch of FAN from high speed to low speed  increases the probability for a short fan damage due to frequent changes of fan speed. Such a fan damage leads often to  system outage due to fan failure to rotate properly.

Therefore in my view it is better ACPI support is switched off completely on  servers. On some servers ACPI is useful as it can be used to track CPU temperature with embedded motherboard sensors with lm_sensors or any piece of hardwre vendor specific software provided. On many machines, however lm_sensors will not properly recognize the integrated CPU temperature sensors and hence ACPI is mostly useless.

There are 3 ways to disable fully or partially ACPI support.

- One is to disable it straight for BIOS (best way IMHO)
- Disable via GRUB or LILO passing a kernel parameter
- Partial ACPI off-ing - /disabling the software that controls the CPU fan/

1. Disable ACPI in BIOS level

Press DEL, F1, F2, F10 or whatever the enter bios key combination is go through all the different menus (depending on the vios BENDOR) and make sure every occurance of ACPI is set to off / disable whatever it is called.

Below is a screenshot of menus with ACPI stuff on a motherboard equipped with Phoenix AwardBIOS:

BIOS ACPI Disable power Off Phoenix BIOS

This is the in my opinon best and safest way to disable ACPI power saving, Unfortunately some newer PCs lack the functionality to disable ACPI; (probably due to the crazy "green" policy the whole world is nowdays mad of).

If that's the case with you, thanksfully there is a "software way" to disable ACPI via passing kernel options via GRUB and LILO boot loaders.

2. Disabling ACPI support on kernel boot level through GRUB boot loader config

There is a tiny difference in command to pass in order to disable  ACPI depending on the Linux installed  GRUB ver. 1.x or GRUB 2.x.

a) In GRUB 0.99 (GRUB version 1)

Edit file /etc/grub/menu.lst or /etc/grub/grub.conf (location differs across Linux distribution). Therein append:


to the end of kernel command line.

Here is an example of a kernel command line with ACPI not disabled (example taken from CentOS server grub.conf):

[root@centos ~]# grep -i title -A 4 /etc/grub/grub.conf
title Red Hat Enterprise Linux Server (2.6.18-36.el5)
root (hd0,0)
kernel /vmlinuz-2.6.18-36.el5 ro root=/dev/VolGroup00/LogVol00 console=ttyS0,115200n8
initrd /initrd-2.6.18-36.el5.img

The edited version of the file with acpi=off included should look like so:

title Red Hat Enterprise Linux Server (2.6.18-36.el5)
root (hd0,0)
kernel /vmlinuz-2.6.18-36.el5 ro root=/dev/VolGroup00/LogVol00 console=ttyS0,115200n8 acpi=off
initrd /initrd-2.6.18-36.el5.img

The kernel option root=/dev/VolGroup00/LogVol00 means the the server is configured to use LVM (Logical Volume Manager).

b) Disabling ACPI on GRUB version 1.99 +

This version is by default installed on newer Ubuntu and Debian Linux-es.

In grub 1.99 on latest Debian Squeeze, the file to edit is located in /boot/grub/grub.cfg. The file is more messy than with its predecessor menu.lst (grub 0.99).
Thanks God there is no need to directly edit the file (though this is possible), but on newer Linuces (as of time of writting the post), there is another simplied grub config file /etc/grub/config

Hence to add the acpi=off to 1.99 open /etc/grub/config find the line reading:


and append the "acpi=off" option, e.g. the line has to change to:


On some servers it might be better to also disable APIC along with ACPI:

Just in case you don't know what is the difference between ACPI and APIC, here is a short explanation:

ACPI = Advanced Configuration and Power Interface

APIC = Advanced Programmable Interrupt Controllers

ACPI is the system that controls your dynamic speed fans, the power button behavior, sleep states, etc.

APIC is the replacement for the old PIC chip that used to come imbedded on motherboards that allowed you to setup interrupts for your soundcard, ide controllers, etc.

Hence on some machines experiencing still problems with even ACPI switched off, it is helpful  to disable the APIC support too, by using:

acpi=off noapic noacpi

Anyways, while doing the changes, be very very cautious or you might end up with un-boot-able server. Don't blame me if this happens :); be sure you have a backup option if server doesn't boot.

To assure faultless kernel boot, GRUB has ability to be configured to automatically load up a second kernel if 1st one fails to boot, if you need that read the grub documentation on that.

To load up the kernel with the new setting, give it a restart:

[root@centos ~]# shutdown -r now

3. Disable ACPI support on kernel boot time on Slackware or other Linuxes still booting kernel with LILO

Still, some Linux distros like Slackware, decided to keep the old way and use LILO (LInux LOader) as a default boot loader.

Disabling ACPI support in LILO is done through /etc/lilo.conf

By default in /etc/lilo.conf, there is a line:

append= acpi=on

it should be changed to:

append= acpi=off

Next to load up the new acpi disabled setting, lilo has to be reloaded:

slackware:~# /sbin/lilo -c /etc/lilo.conf

Finally a reboot is required:

slackware:~# reboot

(If you don't have a physical access or someone near the server you better not 🙂 )

4. Disable ACPI fan control support on a running Linux server without restart

This is the most secure work-around, to disabling the ACPI control over the machine CPU fan, however it has a downside that still the ACPI code will be loaded in the kernel and could cause kernel issues possibly in the long run – lets say the machine has uptime of more than 2 years…

The acpi support on a user level  is controlled by acpid or haldaemon (depending on the Linux distro), hence to disable the fan control on servers this services has to be switched off:

a) disabling ACPI on Debian and deb based Linux-es

As of time of writting on Debian Linux servers acpid (Advanced Configuration and Power Interface event daemon) is there to control how power management will be handled. To disable it stop it as a service (if running):

debian:~# /etc/init.d/acpid stop

To permanently remove acpid from boot up on system boot disable it with update-rc.d:

debian:~# update-rc.d acpid disable 2 3 4 5
update-rc.d: using dependency based boot sequencing
insserv: Script iptables is broken: incomplete LSB comment.
insserv: missing `Required-Start:' entry: please add even if empty.
insserv: warning: current start runlevel(s) (empty) of script `acpid' overwrites defaults (2 3 4 5).
insserv: warning: current stop runlevel(s) (2 3 4 5) of script `acpid' overwrites defaults (empty).
insserv: missing `Required-Start:' entry: please add even if empty.

b) disabling ACPI on RHEL, Fedora and other Redhat-s (also known as RedHacks 🙂 )

I'm not sure if this is safe,as many newer rpm based server system services,  might not work properly with haldaemon disabled.

Anyways you can give it a try if when it is stopped there are issues just bring it up again.

[root@rhel ~]# /etc/init.d/haldaemon stop

If all is fine with the haldaemon switched off (hope so), you can completely disable it to load on start up with:

[root@centos ~]# /sbin/chkconfig --level 2 3 4 5 haldaemon off

Disabling ACPI could increase a bit your server bills, but same time decrease losses from downtimes, so I guess it worths its costs 🙂


How to mount directory in memory on GNU / Linux and FreeBSD / Mount directory in RAM memory to increase performance on Linux and BSD

Tuesday, October 11th, 2011

One of the websites hosted on a server I currently manage has a cache directory which doesn’t take much space but tens of thousands of tiny files. Each second a dozen of files are created in the cache dir. Hence using a hard disk directory puts some serious load on the server consequence of the many fopen and fclose HDD I/O operations.

To get through the problem, the solution was obvious use a directory which stores its information in memory.
There are of course other benefits of using a memory to store data in as we all know as access to RAM is so many times faster.

GNU/Linux is equipped with a tmpfs since kernel version 2.4.x, primary usage of tmpfs file system across many G / Linux distributious is the /tmp directory.

Some general tmpfs information about tmpfs is explained in mount’s manual e.g.: man mount, a good other reading is the tmpfs kernel documentation file

An implementation of tmpfs is /dev/shm .

/dev/shm is a standard memory device used among Linuces, its actually an ordinary directory one can list with ls . /dev/shm is used as a “virtual directory” memory space. Below is an output of /dev/shm from my notebook, one can see few files stored in memory which belong to the pulse audio linux architecture:

linux:~$ ls -al /dev/shm
ls -al /dev/shm/total 7608drwxrwxrwt 2 root root 160 Oct 10 18:05 .
drwxr-xr-x 16 root root 3500 Oct 10 10:57 ..
p-w------- 1 root root 0 Oct 10 10:57 acpi_fakekey
-r-------- 1 hipo hipo 67108904 Oct 10 17:20 pulse-shm-2067018443
-r-------- 1 hipo hipo 67108904 Oct 10 10:59 pulse-shm-2840042043
-r-------- 1 hipo hipo 67108904 Oct 10 10:59 pulse-shm-3215031142
-r-------- 1 hipo hipo 67108904 Oct 10 18:05 pulse-shm-4157723670
-r-------- 1 hipo hipo 67108904 Oct 10 18:06 pulse-shm-702872358

To measure the size of /dev/shm across different Linux distriubtions one can use the usual df cmd, e.g.:

[root@centos: ~]$ df -h /dev/shm
Filesystem Size Used Avail Use% Mounted on
tmpfs 16G 0 16G 0% /dev/shm

Above I show a df -h /dev/shm output from a CentOS server equipped with 32 GB of memory, as you can see CentOS has reserved half of the size of the system memory (16GB) for the purposes of creating files in memory through /dev/shm. The memory is dynamically assigned, so if its not use the assigned memory by it can still be used for the purposes of the services running (which by the way is very nice).

Accoring to what, I’ve read in wikipedia about tmpfs, tmpfs defaults in Linux to half of the system physical memory.
However I’ve noticed Debian Linux hosts usually reserve less memory for /dev/shm, on my personal notebook Debian /dev/shm is only 1 Giga, where on a Debian running server, Debian automatically has set it to the humble 2GB. Setting less by the way as with the Debian example, is a rather good idea since not many desktop or server applications are written to get actively advantage of the virtual /dev/shm directory.

One can directly drop files in /dev/shm which will immediately be stored in memory, and after a system reboot the files will disappear.
Let’s say you zip archive file, and you like to store the file in memory to do so, just copy the file in /dev/shm.

linux:~$ cp -rpf /dev/shm

You don’t even need to be root to copy files in the “virtual memory directory”. This is a reason many crackers (script kiddies), are storing their cracking tools in /dev/shm 😉

A rather funny scenario, I’ve witness before is when you list /dev/shm on some Linux server and suddenly you see a tons of brute forcing tools and all kind of “hack” related stuff belonging to some system user. Sometimes even this malicious script tools belong to the root user…

Now as I’ve said a few words on how linux’s tmpfs works here is how to mount a directory which cache content will be stored in volatile memory:

linux:~# mount -t tmpfs -o size=3G,mode=0755 tmpfs /var/www/site/cache

As you can see the above command will dynamically assign a tmpfs directory taking up from the system RAM mem which could expand up to 3GB within the system memory.

Of course before mounting, its necessery to create the /var/www/site/cache and set proper permissions in the above example I use /var/www/site/cache with a default permissions of 755 which is owned by the use with which the Apache server is running, e.g.:

linux:~# mkdir -p /var/www/site/cache
linux:~# chown -R www-data:www-data /var/www/site/cache
linux:~# chmod -R 755 /var/www/site/cache

Using a tmpfs is very handy and have many advantages, however one should be very careful with the data stored inside a tmpfs dir resource, all data will be lost in case of sudden system restart as the data is stored in the memory.
One other problems one might expect with tmpfs would be if the assigned virtual disk space gets filled with data. It never happened to me but, I’ve red online some stories that in the past this led to system crashes, today as the dox I’ve checked prescribed overfilling it will start swapping make the system terribly sluggish and eventually afred depleting the reserver swap space will start killing processes.

Using tmpfs as a cache directory is very useful on servers running Apache+PHP/Perl/Python/Ruby etc. as it can be used for stroring script generated temorary data.

Using a tmpfs can signifantly decrease server i/o created disk overheads.

Some other application I can think of though, I haven’t tested it would be if tmpfs mounted directory is used to store scripting executable files, copied after restart. Executing the script reading it directly from the “virtual directory” could for sure have very good impact especially on huge websites.
One common service which takes advantage of the elegancy of tmpfs nowdays almost all modern GNU/Linux has is udevd – The Linux dynamic device management. By the way (man udev) is a very good and must read manual especially for Linux novices to get a good basic idea on how /dev/ mamagement occurs via udev.

To make permenant directory contained in memory on Linux the /etc/fstab file should be used.

In order to mount permanently a directory as a memory device of a size of 3GB with 0755 permissions in /var/www/site/cache, as shown in the earlier example, one can use the command:

linux:~# echo 'tmpfs /var/www/site/cache/ tmpfs size=3G,mode=0755 0 0' >> /etc/fstab

This will assure the directory stored in memory would be recreated on next boot.

Nowdays the use of tmpfs is constantly growing, I’ve seen it to be used as a way to substitute ordinary disk based /tmp with a tmpfs directory contained in memory in Cloud Linux OS.
The applications of tmpfs is pretty much to the imagination of the one who wants to get advantage of it. For sure using tmpfs will be seen by the Linux GUI programs.

Going to FreeBSD and the BSD world, tmpfs is also available, however it is still considered a bit experimental. To get use of tmpfs to gain some performance, one should first enable it via bsd’s /etc/rc.conf:

freebsd# echo 'tmpfs_load="YES"' >> /etc/rc.conf

Mounting a directory permanently using tmpfs persmanently it again is doable via /etc/fstab to add a new directory inside memory with tmpfs: is done with adding:

freebsd# echo 'tmpfs /var/www/site/cache tmpfs rw 0 0' >> /etc/fstab

The native equivallent of tmpfs in FreeBSD is called mdmfs.
As I said it is slower than tmpfs but rock solid.

To mount a 4gigabyte size mdmfs “ram directory” on BSD from csh:

freebsd# mdmfs -s 4g md /var/www/site/cache

Mounting a directory permanently using tmpfs persmanently it again is doable via /etc/fstab to add a new directory inside memory with tmpfs: is done with adding:

freebsd# echo 'tmpfs /var/www/site/cache tmpfs rw 0 0' >> /etc/fstab

The native equivallent of tmpfs in FreeBSD is called mdmfs.
As I said it is slower than tmpfs but rock solid.

To mount a 4gigabyte size mdmfs “ram directory” on BSD from csh:

freebsd# mdmfs -s 4g md /var/www/site/cache

Mounting a directory permanently using tmpfs persmanently it again is doable via /etc/fstab to add a new directory inside memory with tmpfs: is done with adding:

freebsd# echo 'md /var/www/site/cache mfs rw,-s4G 2 0' >> /etc/fstab There are some reports of users who presumable use it to increase the ports / kernel compile times, but I haven’t tried it yet so I don’t know for sure

In huge corporations like Google and Yahoo tmpfs is certanly used a lot as this technology can dramatically can improve access times to information.I’m curious to know for some good ways to get use of tmpfs to improve efficiency.
If someone has some readings or has some idea please shar with me 😉