Mdthbs

Looking for Correct Greek Translation for Heraclitus

Button changing it's text & action. Good or terrible?

Can one be advised by a professor who is very far away?

Why was M87 targetted for the Event Horizon Telescope instead of Sagittarius A*?

Resizing object distorts it (Illustrator CC 2018)

Why is the Constellation's nose gear so long?

Why can Shazam fly?

Falsification in Math vs Science

What tool would a Roman-age civilization have for the breaking of silver and other metals into dust?

Can you compress metal and what would be the consequences?

Why isn't the circumferential light around the M87 black hole's event horizon symmetric?

Did Section 31 appear in Star Trek: The Next Generation?

What to do when moving next to a bird sanctuary with a loosely-domesticated cat?

Is "plugging out" electronic devices an American expression?

Does a dangling wire really electrocute me if I'm standing in water?

Return to UK after having been refused entry years ago

Pokemon Turn Based battle (Python)

Apparent duplicates between Haynes service instructions and MOT

Time travel alters history but people keep saying nothing's changed

How to type this arrow in math mode?

Why didn't the Event Horizon Telescope team mention Sagittarius A*?

How to support a colleague who finds meetings extremely tiring?

How to check whether the reindex working or not in Magento?

Can we generate random numbers using irrational numbers like π and e?

“echo 3 > /proc/sys/vm/drop_caches” - Permission denied as root

.everyoneloves__top-leaderboard:empty,.everyoneloves__mid-leaderboard:empty,.everyoneloves__bot-mid-leaderboard:empty{ margin-bottom:0;
}

20

3

I am currently having some issues with the cache. It is a little too much right now so I wanted to clear it. I googled and found this little command: sync && echo 3 > /proc/sys/vm/drop_caches.

I am logged in as root over SSH (not using sudo). These are the attempts I made:

root@server: ~ # ll /proc/sys/vm/drop_caches

-rw-r--r-- 1 root root 0 15. Jan 20:21 /proc/sys/vm/drop_caches



root@server: ~ # echo 3 > /proc/sys/vm/drop_caches

-bash: /proc/sys/vm/drop_caches: Permission denied



root@server: ~ # sudo su -c "echo 3 > /proc/sys/vm/drop_caches"

bash: /proc/sys/vm/drop_caches: Permission denied



root@server: ~ # echo 3 | sudo tee /proc/sys/vm/drop_caches

tee: /proc/sys/vm/drop_caches: Permission denied

3

It is a remote machine running Debian. As far as I know there are some vCores in this machine and it uses Virtuozzo for the virtualization.

I really just want to clear the cache (So I can only access it using SSH).

I also tried registering this as a cronjob. But it simply fails too!

linux permissions virtualization proc openvz

share|improve this question

edited Jun 30 '14 at 18:36

Tshepang

26.5k72187265

asked Jan 15 '14 at 19:42

BrainStoneBrainStone

1,07371943

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  Are you running this as root or are you using sudo?
  
  – terdon♦
  Jan 15 '14 at 19:52
  

  
  
  
  


• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  
  I am running this as root. But sudo also fails.
  
  – BrainStone
  Jan 15 '14 at 19:53
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Does not work either. Already tried it. Same error message.
  
  – BrainStone
  Jan 15 '14 at 19:55
  
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  See the slm's A on this question, it might help.
  
  – Risto Salminen
  Jan 15 '14 at 19:58
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  This is extremely unlikely, but you never know, does /proc/sys/vm/drop_caches actually exist?
  
  – terdon♦
  Jan 15 '14 at 20:02
  

  
  
  
  

 | 
show 4 more comments

20

3

I am currently having some issues with the cache. It is a little too much right now so I wanted to clear it. I googled and found this little command: sync && echo 3 > /proc/sys/vm/drop_caches.

I am logged in as root over SSH (not using sudo). These are the attempts I made:

root@server: ~ # ll /proc/sys/vm/drop_caches

-rw-r--r-- 1 root root 0 15. Jan 20:21 /proc/sys/vm/drop_caches



root@server: ~ # echo 3 > /proc/sys/vm/drop_caches

-bash: /proc/sys/vm/drop_caches: Permission denied



root@server: ~ # sudo su -c "echo 3 > /proc/sys/vm/drop_caches"

bash: /proc/sys/vm/drop_caches: Permission denied



root@server: ~ # echo 3 | sudo tee /proc/sys/vm/drop_caches

tee: /proc/sys/vm/drop_caches: Permission denied

3

It is a remote machine running Debian. As far as I know there are some vCores in this machine and it uses Virtuozzo for the virtualization.

I really just want to clear the cache (So I can only access it using SSH).

I also tried registering this as a cronjob. But it simply fails too!

linux permissions virtualization proc openvz

share|improve this question

edited Jun 30 '14 at 18:36

Tshepang

26.5k72187265

asked Jan 15 '14 at 19:42

BrainStoneBrainStone

1,07371943

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  Are you running this as root or are you using sudo?
  
  – terdon♦
  Jan 15 '14 at 19:52
  

  
  
  
  


• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  
  I am running this as root. But sudo also fails.
  
  – BrainStone
  Jan 15 '14 at 19:53
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Does not work either. Already tried it. Same error message.
  
  – BrainStone
  Jan 15 '14 at 19:55
  
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  See the slm's A on this question, it might help.
  
  – Risto Salminen
  Jan 15 '14 at 19:58
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  This is extremely unlikely, but you never know, does /proc/sys/vm/drop_caches actually exist?
  
  – terdon♦
  Jan 15 '14 at 20:02
  

  
  
  
  

 | 
show 4 more comments

I am currently having some issues with the cache. It is a little too much right now so I wanted to clear it. I googled and found this little command: sync && echo 3 > /proc/sys/vm/drop_caches.

I am logged in as root over SSH (not using sudo). These are the attempts I made:

root@server: ~ # ll /proc/sys/vm/drop_caches

-rw-r--r-- 1 root root 0 15. Jan 20:21 /proc/sys/vm/drop_caches



root@server: ~ # echo 3 > /proc/sys/vm/drop_caches

-bash: /proc/sys/vm/drop_caches: Permission denied



root@server: ~ # sudo su -c "echo 3 > /proc/sys/vm/drop_caches"

bash: /proc/sys/vm/drop_caches: Permission denied



root@server: ~ # echo 3 | sudo tee /proc/sys/vm/drop_caches

tee: /proc/sys/vm/drop_caches: Permission denied

3

It is a remote machine running Debian. As far as I know there are some vCores in this machine and it uses Virtuozzo for the virtualization.

I really just want to clear the cache (So I can only access it using SSH).

I also tried registering this as a cronjob. But it simply fails too!

linux permissions virtualization proc openvz

share|improve this question

edited Jun 30 '14 at 18:36

Tshepang

26.5k72187265

asked Jan 15 '14 at 19:42

BrainStoneBrainStone

1,07371943

root@server: ~ # ll /proc/sys/vm/drop_caches

-rw-r--r-- 1 root root 0 15. Jan 20:21 /proc/sys/vm/drop_caches



root@server: ~ # echo 3 > /proc/sys/vm/drop_caches

-bash: /proc/sys/vm/drop_caches: Permission denied



root@server: ~ # sudo su -c "echo 3 > /proc/sys/vm/drop_caches"

bash: /proc/sys/vm/drop_caches: Permission denied



root@server: ~ # echo 3 | sudo tee /proc/sys/vm/drop_caches

tee: /proc/sys/vm/drop_caches: Permission denied

3

share|improve this question

edited Jun 30 '14 at 18:36

Tshepang

26.5k72187265

asked Jan 15 '14 at 19:42

BrainStoneBrainStone

1,07371943

share|improve this question

edited Jun 30 '14 at 18:36

Tshepang

26.5k72187265

asked Jan 15 '14 at 19:42

BrainStoneBrainStone

1,07371943

edited Jun 30 '14 at 18:36

Tshepang

26.5k72187265

edited Jun 30 '14 at 18:36

Tshepang

26.5k72187265

asked Jan 15 '14 at 19:42

BrainStoneBrainStone

1,07371943

asked Jan 15 '14 at 19:42

BrainStoneBrainStone

1,07371943

6 Answers
6

active

oldest

votes

24

I am logged in as root over SSH...It is a remote machine running Debian.

Is it actually a remote machine, or a just a remote system? If this is a VPS slice somewhere, (at least some forms of) OS virtualization (e.g. openVZ) won't permit this from within the container. You don't run the machine, you just run your slice.

share|improve this answer

edited Jan 15 '14 at 20:12

answered Jan 15 '14 at 20:06

goldilocksgoldilocks

63.4k17157213

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  There is like no way???
  
  – BrainStone
  Jan 15 '14 at 20:09
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  Probably not, since there wouldn't be much point in not permitting it if there were alternate methods that worked.
  
  – goldilocks
  Jan 15 '14 at 20:11
  

  
  
  
  


• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  
  @BrainStone - I use OpenVZ, it's not possible!
  
  – slm♦
  Jan 15 '14 at 21:42
  

  
  
  
  

add a comment | 

28

sudo has to cover whole the redirection so it can be completely executed by root:

$ sudo sh -c "/usr/bin/echo 3 > /proc/sys/vm/drop_caches"

share|improve this answer

edited Jan 15 at 14:58

Wrzlprmft

1035

answered Aug 5 '14 at 6:50

rasty.grasty.g

40346

• 
  
  
  

  
  5
  

  
  
  
  
  
  

  
  
  this actually worked for me (with the right binary location for echo)
  
  – orm
  Nov 5 '14 at 19:59
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  in OpenVZ not work
  
  – shilovk
  Mar 3 '15 at 16:03
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  alternatively, you could use tee instead: echo 3 | sudo tee /proc/sys/vm/drop_caches
  
  – mchid
  Dec 23 '15 at 0:09
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  @mchid, consider adding your comment as an answer. It also worked for me on Azure VM.
  
  – Erik Shilts
  Jan 26 '17 at 22:04
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  It's root already, see # at the beginning of line. Issue with sudo is worth noting, but for another question.
  
  – Alexei Martianov
  Mar 18 '18 at 7:31
  

  
  
  
  

add a comment | 

11

This is normal behavior under OS-level virtualization. This can only be executed by someone with root access to the hardware node.

With for example OpenVZ, you don't get your own kernel instance and as such, are restricted from performing commands like this.

All share the same page cache, so to drop caches of only your instance, the kernel must check if the page belongs to you and if the other instances aren't using this page too.

With another virtualization technique like KVM or Xen this might be working.

share|improve this answer

edited Jan 15 '14 at 22:06

terdon♦

134k33269449

answered Jan 15 '14 at 20:14

chaoschaos

36.2k977120

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  So I could/should/must contact my hoster to clear the cache for me? And how do I find out what "virtualisation technique" my system is on?
  
  – BrainStone
  Jan 15 '14 at 20:15
  
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Yes, you may not come around this...
  
  – chaos
  Jan 15 '14 at 20:18
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  I am not shure if this is right. I am running some vm's at aws and Xen and i am able to drop_caches.
  
  – user55518
  Jan 15 '14 at 20:51
  

  
  
  
  


• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  
  The difference is between OS virtualization (OpenVZ, LXC) and platform virtualization (QEMU, Xen), both of which have advantages and disavantages vs. the other.
  
  – goldilocks
  Jan 15 '14 at 21:52
  
  
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  @bersch Xen uses an own kernel for VMs. OpenVZ does not. You can think of OpenVZ like a better "chroot".
  
  – Nils
  Jan 20 '14 at 11:49
  

  
  
  
  

 | 
show 2 more comments

7

You can use echo piped to sudo tee to allow the proper permission needed when you need to echo as root.

echo 3 | sudo tee /proc/sys/vm/drop_caches

Use tee --help to list more options.

share|improve this answer

answered Jan 29 '17 at 16:59

mchidmchid

8391917

add a comment | 

1

sudo sh -c "echo 3 > /proc/sys/vm/drop_caches"


This command work for me without /usr/bin/echo in mchid answer. It was giving error sh: 1: /usr/bin/echo: not found . So used only 'echo'

share|improve this answer

answered Oct 16 '18 at 11:47

ascii_walkerascii_walker

1113

add a comment | 

0

I had the same problem when I tried to use sudo like this:

sudo echo 1 > /proc/sys/vm/overcommit_memory

My solution was to temporarily switch to root. Obiously, that permission has to be enabled on your system:

sudo su -  #temporarily switch to root user

echo 1 > /proc/sys/vm/overcommit_memory

exit # Exit as root.  

share|improve this answer

edited 21 hours ago

muru

37.4k589164

answered Dec 4 '18 at 16:31

thebiggestlebowskithebiggestlebowski

1011

add a comment | 

protected by Stephen Kitt 14 hours ago

Thank you for your interest in this question.
Because it has attracted low-quality or spam answers that had to be removed, posting an answer now requires 10 reputation on this site (the association bonus does not count).



Would you like to answer one of these unanswered questions instead?

24

I am logged in as root over SSH...It is a remote machine running Debian.

Is it actually a remote machine, or a just a remote system? If this is a VPS slice somewhere, (at least some forms of) OS virtualization (e.g. openVZ) won't permit this from within the container. You don't run the machine, you just run your slice.

share|improve this answer

edited Jan 15 '14 at 20:12

answered Jan 15 '14 at 20:06

goldilocksgoldilocks

63.4k17157213

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  There is like no way???
  
  – BrainStone
  Jan 15 '14 at 20:09
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  Probably not, since there wouldn't be much point in not permitting it if there were alternate methods that worked.
  
  – goldilocks
  Jan 15 '14 at 20:11
  

  
  
  
  


• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  
  @BrainStone - I use OpenVZ, it's not possible!
  
  – slm♦
  Jan 15 '14 at 21:42
  

  
  
  
  

add a comment | 

24

I am logged in as root over SSH...It is a remote machine running Debian.

Is it actually a remote machine, or a just a remote system? If this is a VPS slice somewhere, (at least some forms of) OS virtualization (e.g. openVZ) won't permit this from within the container. You don't run the machine, you just run your slice.

share|improve this answer

edited Jan 15 '14 at 20:12

answered Jan 15 '14 at 20:06

goldilocksgoldilocks

63.4k17157213

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  There is like no way???
  
  – BrainStone
  Jan 15 '14 at 20:09
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  Probably not, since there wouldn't be much point in not permitting it if there were alternate methods that worked.
  
  – goldilocks
  Jan 15 '14 at 20:11
  

  
  
  
  


• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  
  @BrainStone - I use OpenVZ, it's not possible!
  
  – slm♦
  Jan 15 '14 at 21:42
  

  
  
  
  

add a comment | 

I am logged in as root over SSH...It is a remote machine running Debian.

Is it actually a remote machine, or a just a remote system? If this is a VPS slice somewhere, (at least some forms of) OS virtualization (e.g. openVZ) won't permit this from within the container. You don't run the machine, you just run your slice.

share|improve this answer

edited Jan 15 '14 at 20:12

answered Jan 15 '14 at 20:06

goldilocksgoldilocks

63.4k17157213

share|improve this answer

edited Jan 15 '14 at 20:12

answered Jan 15 '14 at 20:06

goldilocksgoldilocks

63.4k17157213

answered Jan 15 '14 at 20:06

goldilocksgoldilocks

63.4k17157213

answered Jan 15 '14 at 20:06

goldilocksgoldilocks

63.4k17157213

28

sudo has to cover whole the redirection so it can be completely executed by root:

$ sudo sh -c "/usr/bin/echo 3 > /proc/sys/vm/drop_caches"

share|improve this answer

edited Jan 15 at 14:58

Wrzlprmft

1035

answered Aug 5 '14 at 6:50

rasty.grasty.g

40346

• 
  
  
  

  
  5
  

  
  
  
  
  
  

  
  
  this actually worked for me (with the right binary location for echo)
  
  – orm
  Nov 5 '14 at 19:59
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  in OpenVZ not work
  
  – shilovk
  Mar 3 '15 at 16:03
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  alternatively, you could use tee instead: echo 3 | sudo tee /proc/sys/vm/drop_caches
  
  – mchid
  Dec 23 '15 at 0:09
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  @mchid, consider adding your comment as an answer. It also worked for me on Azure VM.
  
  – Erik Shilts
  Jan 26 '17 at 22:04
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  It's root already, see # at the beginning of line. Issue with sudo is worth noting, but for another question.
  
  – Alexei Martianov
  Mar 18 '18 at 7:31
  

  
  
  
  

add a comment | 

28

sudo has to cover whole the redirection so it can be completely executed by root:

$ sudo sh -c "/usr/bin/echo 3 > /proc/sys/vm/drop_caches"

share|improve this answer

edited Jan 15 at 14:58

Wrzlprmft

1035

answered Aug 5 '14 at 6:50

rasty.grasty.g

40346

• 
  
  
  

  
  5
  

  
  
  
  
  
  

  
  
  this actually worked for me (with the right binary location for echo)
  
  – orm
  Nov 5 '14 at 19:59
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  in OpenVZ not work
  
  – shilovk
  Mar 3 '15 at 16:03
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  alternatively, you could use tee instead: echo 3 | sudo tee /proc/sys/vm/drop_caches
  
  – mchid
  Dec 23 '15 at 0:09
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  @mchid, consider adding your comment as an answer. It also worked for me on Azure VM.
  
  – Erik Shilts
  Jan 26 '17 at 22:04
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  It's root already, see # at the beginning of line. Issue with sudo is worth noting, but for another question.
  
  – Alexei Martianov
  Mar 18 '18 at 7:31
  

  
  
  
  

add a comment | 

sudo has to cover whole the redirection so it can be completely executed by root:

$ sudo sh -c "/usr/bin/echo 3 > /proc/sys/vm/drop_caches"

share|improve this answer

edited Jan 15 at 14:58

Wrzlprmft

1035

answered Aug 5 '14 at 6:50

rasty.grasty.g

40346

$ sudo sh -c "/usr/bin/echo 3 > /proc/sys/vm/drop_caches"

share|improve this answer

edited Jan 15 at 14:58

Wrzlprmft

1035

answered Aug 5 '14 at 6:50

rasty.grasty.g

40346

edited Jan 15 at 14:58

Wrzlprmft

1035

edited Jan 15 at 14:58

Wrzlprmft

1035

answered Aug 5 '14 at 6:50

rasty.grasty.g

40346

answered Aug 5 '14 at 6:50

rasty.grasty.g

40346

11

This is normal behavior under OS-level virtualization. This can only be executed by someone with root access to the hardware node.

With for example OpenVZ, you don't get your own kernel instance and as such, are restricted from performing commands like this.

All share the same page cache, so to drop caches of only your instance, the kernel must check if the page belongs to you and if the other instances aren't using this page too.

With another virtualization technique like KVM or Xen this might be working.

share|improve this answer

edited Jan 15 '14 at 22:06

terdon♦

134k33269449

answered Jan 15 '14 at 20:14

chaoschaos

36.2k977120

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  So I could/should/must contact my hoster to clear the cache for me? And how do I find out what "virtualisation technique" my system is on?
  
  – BrainStone
  Jan 15 '14 at 20:15
  
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Yes, you may not come around this...
  
  – chaos
  Jan 15 '14 at 20:18
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  I am not shure if this is right. I am running some vm's at aws and Xen and i am able to drop_caches.
  
  – user55518
  Jan 15 '14 at 20:51
  

  
  
  
  


• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  
  The difference is between OS virtualization (OpenVZ, LXC) and platform virtualization (QEMU, Xen), both of which have advantages and disavantages vs. the other.
  
  – goldilocks
  Jan 15 '14 at 21:52
  
  
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  @bersch Xen uses an own kernel for VMs. OpenVZ does not. You can think of OpenVZ like a better "chroot".
  
  – Nils
  Jan 20 '14 at 11:49
  

  
  
  
  

 | 
show 2 more comments

11

This is normal behavior under OS-level virtualization. This can only be executed by someone with root access to the hardware node.

With for example OpenVZ, you don't get your own kernel instance and as such, are restricted from performing commands like this.

All share the same page cache, so to drop caches of only your instance, the kernel must check if the page belongs to you and if the other instances aren't using this page too.

With another virtualization technique like KVM or Xen this might be working.

share|improve this answer

edited Jan 15 '14 at 22:06

terdon♦

134k33269449

answered Jan 15 '14 at 20:14

chaoschaos

36.2k977120

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  So I could/should/must contact my hoster to clear the cache for me? And how do I find out what "virtualisation technique" my system is on?
  
  – BrainStone
  Jan 15 '14 at 20:15
  
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Yes, you may not come around this...
  
  – chaos
  Jan 15 '14 at 20:18
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  I am not shure if this is right. I am running some vm's at aws and Xen and i am able to drop_caches.
  
  – user55518
  Jan 15 '14 at 20:51
  

  
  
  
  


• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  
  The difference is between OS virtualization (OpenVZ, LXC) and platform virtualization (QEMU, Xen), both of which have advantages and disavantages vs. the other.
  
  – goldilocks
  Jan 15 '14 at 21:52
  
  
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  @bersch Xen uses an own kernel for VMs. OpenVZ does not. You can think of OpenVZ like a better "chroot".
  
  – Nils
  Jan 20 '14 at 11:49
  

  
  
  
  

 | 
show 2 more comments

This is normal behavior under OS-level virtualization. This can only be executed by someone with root access to the hardware node.

With for example OpenVZ, you don't get your own kernel instance and as such, are restricted from performing commands like this.

All share the same page cache, so to drop caches of only your instance, the kernel must check if the page belongs to you and if the other instances aren't using this page too.

With another virtualization technique like KVM or Xen this might be working.

share|improve this answer

edited Jan 15 '14 at 22:06

terdon♦

134k33269449

answered Jan 15 '14 at 20:14

chaoschaos

36.2k977120

share|improve this answer

edited Jan 15 '14 at 22:06

terdon♦

134k33269449

answered Jan 15 '14 at 20:14

chaoschaos

36.2k977120

edited Jan 15 '14 at 22:06

terdon♦

134k33269449

edited Jan 15 '14 at 22:06

terdon♦

134k33269449

answered Jan 15 '14 at 20:14

chaoschaos

36.2k977120

answered Jan 15 '14 at 20:14

chaoschaos

36.2k977120

7

You can use echo piped to sudo tee to allow the proper permission needed when you need to echo as root.

echo 3 | sudo tee /proc/sys/vm/drop_caches

Use tee --help to list more options.

share|improve this answer

answered Jan 29 '17 at 16:59

mchidmchid

8391917

add a comment | 

7

You can use echo piped to sudo tee to allow the proper permission needed when you need to echo as root.

echo 3 | sudo tee /proc/sys/vm/drop_caches

Use tee --help to list more options.

share|improve this answer

answered Jan 29 '17 at 16:59

mchidmchid

8391917

add a comment | 

You can use echo piped to sudo tee to allow the proper permission needed when you need to echo as root.

echo 3 | sudo tee /proc/sys/vm/drop_caches

Use tee --help to list more options.

share|improve this answer

answered Jan 29 '17 at 16:59

mchidmchid

8391917

echo 3 | sudo tee /proc/sys/vm/drop_caches

share|improve this answer

answered Jan 29 '17 at 16:59

mchidmchid

8391917

answered Jan 29 '17 at 16:59

mchidmchid

8391917