How to keep transparent hugepages config after reboot? - centos

I used the below way to disable transparent hugepages. But they are restored (enabled again) after reboot.
echo never > /sys/kernel/mm/redhat_transparent_hugepage/defrag
echo no > /sys/kernel/mm/redhat_transparent_hugepage/khugepaged/defrag
How to keep those modified after reboot?

resolved^_^ Add them to the end of /etc/rc.local

In /etc/grub.conf.
Add:
transparent_hugepage=never
to the "kernel" line.

Related

$PATH messed up. How did this happen and how to change back to default

My $PATH comes up as:
/Library/Frameworks/Python.framework/Versions/3.8/bin:/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin:/usr/local/share/dotnet:~/.dotnet/tools:/Library/Apple/usr/bin:/Library/Frameworks/Mono.framework/Versions/Current/Commands
I'm not sure how this happened but how do I change it back to the default PATH?
What is your system?
Ubuntu default path is
/usr/lib/lightdm/lightdm:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games
if you want to change this back to the default, you need to opne your .bashrc file on your home and change it in there:
vim ~/.bashrc

How can I fix "/etc/cron.daily/logrotate: gzip: stdin: file size changed while zipping"?

in last days i get daily mail from cron's logrotate task:
/etc/cron.daily/logrotate:
gzip: stdin: file size changed while zipping
How can I fix it?
Thanks,
Gian Marco.
Here's a blog post in French which gives a solution.
In English, you can read this bug report.
To summarise:
First you have to add the --verbose option in the script /etc/cron.daily/logrotate to have more information the next time it runs to identify which rotation log cause the problem.
#!/bin/sh
test -x /usr/sbin/logrotate || exit 0
/usr/sbin/logrotate --verbose /etc/logrotate.conf`
Next you have to add the delaycompress option in logrotate configuration.
Like exemple, I add the nginx's logrotate configiguration in /etc/logrotate.d/nginx:
/var/log/nginx/*.log {
daily
missingok
rotate 14
compress
delaycompress
notifempty
create 0640 www-data adm
sharedscripts
...
}
upstart will close (and reopen) its log file when it notices that the file is deleted. However, if you look at what gzip does, you see that it doesn't delete the file until after it's one writing the output file. That means that there always is a race condition where log lines might be lost for lines logs being written gzipping.
You can disable the warning using gzip --quiet, but really that doesn't hide the fact that you might still loose log lines.
This means that delaycompress is not a generic fix to this. It's a specific fix to a specific problem.
The real solution for this is probably a combination of delaycompress and being able to send a signal to the process. It will make the race condition go away in practise (unless you rotate multiple times per second :) ).

How to empty a file in fish?

In bash shell scripting, I would typically run :> file to empty a file.
Now using fish, things are slightly different and the above command doesn't work.
What is fish equivalent?
Although it's not as short as :, true is a command that will work everywhere and produces no output:
true > file
Probably the easiest way that will be work in both Fish and Bash is to do echo "" > file
EDIT: Commenter was absolutely right echo "" > file produces a file with a newline, the correct command I was thinking of to create an empty file is cat /dev/null > file.
There is, and always was the magic method called touch which set change time to actual or create non-existent file. For compatiblity I suggest you to use this way in all scripts that you write (even if you write bash code).

Delete App (.apk) in emulator?

I know of two ways of deleting an app under development from the emulator:
Using the emulator GUI: Settings >
Applications > Manage Applications >
Uninstall
Using ADB: adb uninstall
I may have discovered a third way, using 'adb shell':
rm /data/app/<package>.apk
It seems, however, that this isn't really a good way to delete apps because there may be additional information associated with it (registration?).
What is that information and where can it be found?
It's interesting you mention this. I ran a quick home made test to shed some light onto your question.
Generally, when you install a .apk file, Android creates an internal storage area for it located at /data/data/< package name of launching activity>. This is mainly used as an internal caching area that cant be accessed by other apps or the phone user. You can read up about that in a little bit more detail in the Internal storage chapter of Androids data storage section. It is an area exclusively used by your app and you can write private data there.
Once you uninstall an app theoretically, this internal storage area is also deleted. The first 2 ways which you outlined indeed does that: the .apk file in /data/app/ is deleted aswell as the internal storage area in /data/data/.
However if you used adb shell and run the rm command, all that is removed is the .apk file in /data/app/. The internal storage area in in /data/data/ is not deleted. So in essence you are correct that additional information with the app is not necessarily deleted. But on the flip side, if you reinstall the app after running the command, then the existing internal storage area gets overwritten as a fresh copy of it is being installed.
adb uninstall com.example.test
com.example.test may vary acording to your app.
I was having a problem with this too. I have Link2SD on my phone, but the ext4 partition on my SD card corrupted, so I reformatted, but all of the linked files were still in the /data/app folder. So I created a script to delete all broken links, and ran into the same problem as you, the app manager said they were still installed! so I made another script to fix that, using the pm program on your phone.
heres my code to remove broken links from the app folder:
fixln.sh
#!/system/bin/sh
#follow and fix symlinks
appfolder="/data/app/"
files=`ls ${appfolder}*`
fix=$1
badstring="No such file or directory"
for i in $files
do
if [ -h $i ]
then
if [ -a `readlink $i` ]
then
echo -e "\e[32m$i is good\033[0m";
else
if [ $fix == "fix" ]
then
`rm $i`
echo -e "\e[31m$i is bad, and was removed\033[0m";
else
echo -e "\e[31m$i is bad\033[0m";
if
fi
else
echo -e "\e[36m$i is not a symlink\033[0m";
fi
done
and heres my code to uninstall apps that have no apk:
fixmissing.sh
#!/system/bin/sh
#searches through a list of installed apps, and removes the ones that have no apk file
appfolder="/data/app/"
fix=$1
installed=`pm list packages -f -u`
for i in $installed
do
usefull=${i#*:}
filename=${usefull%=*}
package=${usefull#*=}
if [ -a $filename ]
then
echo -e "\e[32m$package ($filename) is good\033[0m"
else
if [ "$fix" == "fix" ]
then
uninstall=`pm uninstall $package`
if [ "$uninstall" == "Success" ]
then
echo -e "\e[31m$package ($filename) is bad, and was removed\033[0m"
else
echo -e "\e[31m$package ($filename) is bad, and COULD NOT BE REMOVED\033[0m"
fi
else
echo -e "\e[31m$package ($filename) is bad\033[0m"
fi
fi
done
copy these files to your phone, and run them with no arguments to see what they find, or add fix onto the end (fixmissing.sh fix) to make them fix what they find. Run at your own risk, and back up your files. I am not responsible if this code in any way wrecks anything.
If anyone wants to update/merge these scripts together, thats fine. these were just made to fix my problem, and they have done so, just thought I'd share them.
I believe any files the app has created on the sdcard would not be deleted.
There is another way - using the emulator like a real device -
locate the app in the emulator and drag it up to uninstall it.

MongoDB log file growth

Currently my log file sits at 32 meg. Did I miss an option that would split the log file as it grows?
You can use logrotate to do this job for you.
Put this in /etc/logrotate.d/mongod (assuming you use Linux and have logrotate installed):
/var/log/mongo/*.log {
daily
rotate 30
compress
dateext
missingok
notifempty
sharedscripts
copytruncate
postrotate
/bin/kill -SIGUSR1 `cat /var/lib/mongo/mongod.lock 2> /dev/null` 2> /dev/null || true
endscript
}
If you think that 32 megs is too large for a log file, you may also want to look inside to what it contains.
If the logs seem mostly harmless ("open connection", "close connection"), then you may want to start mongod with the --quiet switch. This will reduce some of the more verbose logging.
Rotate the logs yourself
http://www.mongodb.org/display/DOCS/Logging
or use 'logrotate' with an appropriate configuration.
Using logrotate is a good option. while, it will generate 2 log files that fmchan commented, and you will have to follow Brett's suggestion to "add a line to your postrotate script to delete all mongod style rotated logs".
Also copytruncate is not the best option. There is always a window between copy and truncate. Some mongod logs may get lost. Could check logrotate man page or refer to this copytruncate discussion.
Just provide one more option. You could write a script that sends the rotate signal to mongod and remove the old log files. mongologrotate.sh is a simple reference script that I have written. You could write a simple cron job or script to call it periodically like every 30 minutes.