Docker-alpine: Issue with supported formatting commands for "ps"

[kabudu]

I've run into a problem on one of my containers built using alpine 3.3.

When I run the following command:

ps

Sample output:

PID   USER     TIME   COMMAND
    1 root       0:00 /bin/bash /entrypoint.sh
  20 nginx      0:00 php-fpm: pool www

and then proceed to run the following command:

ps -A -o pid,command | grep [f]pm 

I get the following error:

ps: bad -o argument 'command', supported arguments: user,group,comm,args,pid,ppid,pgid,etime,nice,rgroup,ruser,time,tty,vsz,stat,rss

I understand what the error means and how to solve my problem, but I want to understand why it doesn't work. I've carried out the same steps on a VM based on CentOS 7 and it does work.

Is it simply down to different implementations of "ps" or is there something more to it?

Thanks,

[andyshinn]

The default ps in the image is a BusyBox command. You need to install procps to get the ps you are expecting:

apk --no-cache add procps

[wanghy8166]

make