Written by Simone

I'll update this post whenever I see fits, A.K.A. when I have other bits of information which don't require a whole post.

Operations on files and directories

Move files and directories to the current/parent directory in Linux

Current dir

find . -type f -exec mv {} . \;

Parent dir

find . -type f -exec mv {} .. \;

Recursive chmod on files and dirs

To change all the directories to 755 (-rwxr-xr-x):

find /var/www/blog -type d -exec chmod 755 {} \;

To change all the files to 644 (-rw-r--r--):

find /var/www/blog -type f -exec chmod 644 {} \;

Certbot common commands

Register single domain:

certbot certonly --standalone -d domain.tld --dry-run

Renew single domain:

certbot renew --cert-name domain.tld --dry-run
  • Remove “–dry-run” when ok.

Revoke certificate:

certbot revoke --cert-path /etc/letsencrypt/archive/${YOUR_DOMAIN}/cert1.pem

Check certificate's expiry date:

cat /etc/letsencrypt/live/domain.tld/cert.pem | openssl x509 -noout -enddate


To reset your git repository to given commit id, do:

git reset --hard <commit-id>
git push origin master --force

Ignoring files that are already tracked

git update-index --assume-unchanged <your file here>

Delta Chat Mail sieve

require ["fileinto"];
# rule:[DeltaChat]
if header :contains "Chat-Version" "1.0"
	fileinto "DeltaChat";

Postfix mail queue

To view postfix mail queue in case of problems and remove a particular message from it, do as follows:

# mailq

-Queue ID-  --Size-- ----Arrival Time---- -Sender/Recipient-------
6DCF32201B*    4824 Thu Oct 19 22:54:44

-- 4 Kbytes in 1 Request.
# postsuper -d 6DCF32201B

postsuper: 6DCF32201B: removed
postsuper: Deleted: 1 message

Check Preferred Outgoing IP (when multiple are set on <interface>)


The correct command to add a new Linux user (in this case without a shell)

adduser --shell /usr/sbin/nologin <username>

I always forget which command is the complete one, useradd or adduser


  1. supersquirrel said:

    Hi, Your find commands often need the { } escaped as well. find . ....... -exec \{\} \;
  2. supersquirrel said:

    Oh, now I get it: the code quotes remove the backslashes. Chyrp!!!! Ahhh!!! Disregard my comment.
  3. Simone said:

    Hi supersquirrel, thanks for your comments and excuse the late reply but chyrp didn't send mail notifications until latest upgrade, so I never read these.

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