SOA Checking

RHEL Subscription

Register a new system and attach a subscription to it. Then execute the following commands to obtain the registration and subscription data using newly registered system UUID:

subscription-manager register --consumerid=UUID
subscription-manager subscribe --auto

Edit /etc/yum.repos.d/redhat.repo to enable or disable additional repositories.

Non-root Process Listening on Priviledged Ports

Allow a user application to bind to a port below 1024 using POSIX File Capabilities:

setcap cap_net_bind_service=+eip /path/to/the/executable

Disabling CPU Cores

Disable all CPU cores except the first one which does not honor online attribute:

for i in /sys/devices/system/cpu/cpu*/online; do echo 0 > $i; done

There Are Too Many Ways To Do It

Benchmark of Perl text replacing subroutines as taken from There are too many ways to do it presentation: My own results (the table is split for better readability):

                      Rate delpoint8 elim_last pack01 count_and_replace sexeger
delpoint8           9237/s        --      -58%   -73%              -82%    -86%
elim_last          22232/s      141%        --   -36%              -58%    -67%
pack01             34855/s      277%       57%     --              -34%    -49%
count_and_replace  52466/s      468%      136%    51%                --    -23%
sexeger            68259/s      639%      207%    96%               30%      --
two_parts          72359/s      683%      225%   108%               38%      6%
delpoint2          80775/s      774%      263%   132%               54%     18%
via_split          90009/s      874%      305%   158%               72%     32%
delpoint1         101626/s     1000%      357%   192%               94%     49%
rindex01          145985/s     1480%      557%   319%              178%    114%
look_ahead        163399/s     1669%      635%   369%              211%    139%

                      Rate two_parts delpoint2 via_split delpoint1 rindex01 look_ahead
delpoint8           9237/s      -87%      -89%      -90%      -91%     -94%       -94%
elim_last          22232/s      -69%      -72%      -75%      -78%     -85%       -86%
pack01             34855/s      -52%      -57%      -61%      -66%     -76%       -79%
count_and_replace  52466/s      -27%      -35%      -42%      -48%     -64%       -68%
sexeger            68259/s       -6%      -15%      -24%      -33%     -53%       -58%
two_parts          72359/s        --      -10%      -20%      -29%     -50%       -56%
delpoint2          80775/s       12%        --      -10%      -21%     -45%       -51%
via_split          90009/s       24%       11%        --      -11%     -38%       -45%
delpoint1         101626/s       40%       26%       13%        --     -30%       -38%
rindex01          145985/s      102%       81%       62%       44%       --       -11%
look_ahead        163399/s      126%      102%       82%       61%      12%         --

SSH Agent Forwarding for "sudo su"

Exporting of SSH_AUTH_SOCK environment variable when using sudo su enables forwarding of user's SSH agent connection to root environment

(umask 0440; echo 'Defaults env_keep += "SSH_AUTH_SOCK"' > /etc/sudoers.d/ssh-auth-sock)

Example of using /etc/sudoers.d/ssh-auth-sock on host machine. The example assumes that the user copied already their public SSH key to the destination machines under root user:

$ ssh -A user@host
[user@host]$ sudo su
[root@host]# ssh remote
[root@remote]#

dos2unix & unix2dos

Convert file with Windows line endings to UNIX and vice versa, all in Perl:

perl -i -pe 's/\r//g' dos2unix
perl -i -pe 's/\n/\r\n/g' unix2dos