To merge multiple pdf files using the most current qpdf (instead of the older pdftk) you can use the following:
qpdf --empty --pages file1.pdf file2.pdf file3.pdf -- output.pdfMerge multiple pdf documents using qpdf
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Managing print jobs in linux command line
Some useful commands to manage print jobs
| lpstat -p -d | To get a list of available printers, along with their status |
| lpstat -a | To check the status of all connected printers, including job numbers |
| cancel job-id or lprm job-id | To cancel a print job |
| lpmove job-id newprinter | To move a print job to new printer |
Taken from Introduction to Linux course (LFS101) from Linux Foundation here
List loaded modules in NGINX
To list the currently loaded modules in NGINX you can use the following:
nginx -V 2>&1 | grep -oP '(?<=--with-http_)[a-zA-Z0-9_]+'
Get the monitor resolution in linux command line
You can use the following xdpyinfo command
xdpyinfo | grep dim
dimensions: 3840x3673 pixels (1016x971 millimeters)
ldapsearch on a json attribute.
Problem
You have an LDAP entry with an attribute that consists of json entries, and you would like to use ldapsearch to filter on a json item condition.
So having the attribute
mobileIDAuthenticator: {“creationDateTime”:”2023-08-28T14:53:29.061Z”,”state”:”ENABLED”,”mobileNumber”:”+411111111″,”mobileSerialNumber”:”AAAAAAAAAAAAA”}
you would like to filter on the state item.
Solution
you can use the following syntax:
ldapsearch -LLL -H "ldaps://domain.com:1636" -D "cn=Directory Manager" -w $LDP -o ldif_wrap=no -c -vvvv -b "ou=persons,dc=domain,dc=com" -s sub "(mobileIdAuthenticator=state eq 'ENABLED')" uid mobileIDAuthenticator Return results from LDAP without a line wrap (attribute)
Problem
You have an attribute in LDAP that might be a long line (ie a json array that contains many records like logins for example)
loginHistory: [{"lastLoginDate":"20250107094531.782Z","loginModule":"1"},{"lastLoginDate":"20241202075005.298Z","loginModule":"1"},{"lastLoginDate":"20241129143412.785Z","loginModule":"1"},{"lastLoginDate":"20241129103347.029Z","loginModule":"1"},{"lastLoginDate":"20240920105718.171Z","loginModule":"2"}]
But you want to return it in one line for further processing (ie counting the number of times in a year).
Solution
You can use the -o ldif_wrap=no option in your ldapsearch like
ldapsearch -LLL -H "ldaps://ldap.com:1636" -o ldif_wrap=no -D "cn=User" -w $LDP -b "ou=people,dc=domain,dc=com" -s sub "(mail=usernname@domain.com)" uid loginHistory
Return all attributes from LDAP (user and operational)
To return all attributes from LDAP using ldapsearch you can use both “*” for user and “+” for operational attributes
ldapsearch -LLL -H "ldaps://url:1636" -D "cn=Directory Manager" -w $LDP -b "ou=entity,dc=domain,dc=com" -s sub "(&(attr_filter1=SOMETHING)(attr_filter2=ELSE))" "*" "+"
PITR recovery fails when there are no transactions (pgbackrest)
Prolem
You are trying to do PITR recovery for a specific time, but the restore fails with something similar to the following message
FATAL: recovery ended before configured recovery target was reachedSolution
This seems to be caused by a feature/bug that causes this error when there are no transactions between the backups, as explained in more detail here
Displaying the IP address of a gitlab runner in a Gitlab job
To be able to see the job runner IP address in a gitlab job, you can add a script (or add it to an existing one) that uses hostname -I
script:
- hostname -I && your_other_scriptProducing a file C.txt that contains common lines between A.txt B.txt using grep
Problem
You have two files (A.txt, B.txt) that contain records (one line each), and you want to find out the common lines between the two.
For example you have the following two files.
A.txt
one
two
threeand B.txt
two
six
sevenand you want to find or produce a new file (C.txt) that contains only the common record (two) from the two files.
Solution
You can use grep with the -Fx options like
grep -Fxf A.txt B.txt > C.txtthat will produce file C.txt that contains the common line (two) from the two files.
The options for grep have the following meaning:
-F: Interpret the pattern as a list of fixed strings (instead of regular expressions).-x: Only match whole lines.-f fileA.txt: Read the patterns fromfileA.txt.