Archive for the ‘*nix’ Category
Posted by jpluimers on 2020/02/03
A few notes for managing the users that should be allowed to send mail via sendmail using TLS authentication.
Most of it is derived/summarised for [WayBack] SMTP AUTH in sendmail 8.10-8.13 and [WayBack] Creating Users for a Postfix-Based Mail Relay – Scott’s Weblog – The weblog of an IT pro specializing in cloud computing, virtualization, and networking, all with an open source view
- Verify your sendmail allows TLS:
# sendmail -d0.1 -bv | grep SASL
NETUNIX NEWDB NIS NISPLUS PIPELINING SASLv2 SCANF SOCKETMAP
- The list of TLS authentication users differs from the ones in
/etc/passwd
- The tools and files manage if the output is
SASLv2 or older. For SASLv2 they are:
/etc/sasldb2 has the users/passwordssasldblistusers2 lists the userssaslpasswd2 manages users
For instance, this commands creates a new user for use with sendmail:
# saslpasswd2 -c -u example.org firstname.lastname
Password:
Again (for verification):
sasldblistusers2
firstname.lastname@example.org: userPassword
cat /etc/sasldb2
....................firstname.lastname@example.orguserPassword
For future reading:
I thought I needed this so I could add an alias @pluimers.com to my gmail box, as I read only the accepted answer at [WayBack] Add new alias to Gmail without SMTP (forwarding-only address) – Web Applications Stack Exchange pointing to:
I should have read the second answer at [WayBack] Add new alias to Gmail without SMTP (forwarding-only address) – Web Applications Stack Exchange:
As of writing, however, you can simply use the Gmail SMTP server, as long as you use [WayBack] Google two-step authentication.
So just for completeness, the full steps:
- Gmail settings, Accounts and Import tab.
- Add another email address you own
- Type name and email address to be added.
- For SMTP Server, put
smtp.gmail.com
- For Username, your full Gmail address including
@gmail.com
- For password, provide an App Password generated in Google Accounts at https://security.google.com/settings/security/apppasswords
- Leave Secured connection using TLS selected as is.
- Add Account
–jeroen
Posted in *nix, *nix-tools, Power User, sendmail | Leave a Comment »
Posted by jpluimers on 2020/01/29
After years with “missed schedule” posts on (paid!) wordpress.com based sites, WordPress has documented that the scheduler officially does not support more than 100 posts:
[WayBack] Warning: Please do not schedule more than 100 posts. Any posts scheduled beyond that amount will not be published.
In practice this is not fully true, so lets explain that a little.
Background
Imagine the list of scheduled posts as a list of posts to be posted anywhere from the near future (lets call that tail) until far in the future (for now head).
As long as you schedule posts in head to tail order, then there is no problem. You can schedule 100s of posts (usually I’ve between 700 and 1200 posts scheduled that way).
The problems appear when:
Read the rest of this entry »
Posted in *nix, Development, Missed Schedule, Monitoring, Power User, SocialMedia, Software Development, Uptimerobot, Web Development, WordPress, WordPress | Leave a Comment »
Posted by jpluimers on 2020/01/20
When you look at how to find listed cron jobs, usually the answer is cron -l or cron -u username -l.
However, on OpenSuSE systems, cron jobs can be in different places, and the sysconfig settings have influence on them too.
These files and directories all influence cron:
Directories:
/etc/cron.d/
/etc/cron.daily/
/etc/cron.hourly/
/etc/cron.monthly/
/etc/cron.weekly/
Files:
/etc/sysconfig/cron
/etc/init.d/rc2.d/K01cron
/etc/init.d/rc2.d/S14cron
/etc/init.d/rc3.d/K01cron
/etc/init.d/rc3.d/S14cron
/etc/init.d/rc5.d/K01cron
/etc/init.d/rc5.d/S14cron
/etc/init.d/cron
/etc/news/crontab.sample
/etc/pam.d/crond
/etc/systemd/system/multi-user.target.wants/cron.service
/etc/omc/srvinfo.d/cron.xml
/etc/cron.deny
/etc/crontab
Most are available for other Linux distributions as well, but each one might have slightly different configurations (especially for the directories). Some background reading:
Some details:
- The
crontab -l will only list what is in /etc/crontab.
- These directories are influenced by
/etc/sysconfig/cron, especially the DAILY_TIME variable (see below) for the daily jobs.
All of the directories are checked every 15 minutes through /usr/lib/cron/run-crons:/etc/cron.daily/
/etc/cron.hourly/
/etc/cron.monthly/
/etc/cron.weekly/
- That script then uses these files for checking when to run:
/var/spool/cron/lastrun/cron.weekly
/var/spool/cron/lastrun/cron.daily
/var/spool/cron/lastrun/cron.hourly
The DAILY_TIME variable:
## Type: string
## Default: ""
#
# At which time cron.daily should start. Default is 15 minutes after booting
# the system. Example setting would be "14:00".
# Due to the fact that cron script runs only every 15 minutes,
# it will only run on xx:00, xx:15, xx:30, xx:45, not at the accurate time
# you set.
DAILY_TIME=""
–jeroen
Posted in *nix, *nix-tools, cron, Linux, openSuSE, Power User, SuSE Linux, Tumbleweed | Leave a Comment »
Posted by jpluimers on 2019/12/23
Posted in *nix, *nix-tools, Development, Encoding, Google, GoogleWebP, Image Editing, Power User, Software Development, The Gimp, WebP | Leave a Comment »
Posted by jpluimers on 2019/12/20
Cool: Magic SysRq key – Wikipedia
The magic SysRq key is a key combination understood by the Linux kernel, which allows the user to perform various low-level commands regardless of the system’s state. It is often used to recover from freezes, or to reboot a computer without corrupting the filesystem.[1] Its effect is similar to the computer’s hardware reset button (or power switch) but with many more options and much more control.
Sometimes reading fluffy fluff posts teaches you new things, so be sure to read this one:
[WayBack] I just got trolled by my cat, hard. Last night i left my linux laptop open and running while watching TV in the other room. I came back to find Marley … – Stephen Shirley – Google+
…
I started looking through the kernel logs from last night, to see if there was any indication of the issue starting. And then i saw it. One innocent line that said:
Dec 18 21:26:52 x240 kernel: [373001.156356] sysrq: SysRq : Emergency Remount R/O
The fluffy dumbass had somehow hit the Sysrq [0] key combo to mount all filesystems read-only. This is an old, low-level when-all-else-fails facility for dealing with an linux unresponsive system, and fluff-for-brains Marley had somehow hit alt+fn+s+u.
Sigh.
[0] https://en.wikipedia.org/wiki/Magic_SysRq_key
Via: [Archive.is] I just got trolled by my cat, hard. Last night i left my linux laptop open and running while watching TV in the other room. I came back to find Marley … – Kristian Köhntopp – Google+
–jeroen
Posted in *nix, *nix-tools, Keyboards and Keyboard Shortcuts, Linux, Power User | Leave a Comment »
Posted by jpluimers on 2019/12/16
The answers at [WayBack] CHMOD – Applying Different Permissions For Files vs. Directories – Server Fault describe various ways to do this. Depending in why/when you want to change them you’d probably favour different ones, so be sure to read the answers.
I mostly use these combinations:
find . -type d -exec chmod 700 {} \;
find . -type f -exec chmod 600 {} \;
and
find . -type d -exec chmod 775 {} \;
find . -type f -exec chmod 664 {} \;
And since I forget how to do ocatal too often:
commonly used permissions:
Permission COMMAND
--------- ------------------
rwxrwxrwx chmod 777 filename
rwxrwxr-x chmod 775 filename
rwxr-xr-x chmod 755 filename
rw-rw-rw- chmod 666 filename
rw-rw-r-- chmod 664 filename
rw-r--r-- chmod 644 filename
permissions are divided into 3 divisions. The first rwx is for the owner. The next 3 is for the group. The last 3 is for everyone else.
rwx------ owner permissions - read, write, executable
---rwx--- group permissions - rwx
------rwx other permissions - rwx
Source: [WayBack] Title
–jeroen
Posted in *nix, Power User | Leave a Comment »
Posted by jpluimers on 2019/12/03
Many unix tools that report sizes in bytes can convert them to either IEC or SI readable formats.
For github.com/jpluimers/btrfs-du/blob/master/btrfs-du I wrote about last week, I also wanted that kind of behaviour. So I did some research and came up with the code and test cases below.
Note that depending on the bitness of your system, bash integer numeric values are limited in size; see [WayBack] What is the maximum value of a numeric bash shell variable? – Super User.
So I wrote a small bash script for that too, which needed also gave me the opportunity to show how a perpetual while loop as explained by [WayBack] bash – “while :” vs. “while true” – Stack Overflow.
Two things that always bite me with these short scripts are expressions (done through [WayBack]Arithmetic Expansion) and comparisons (through[WayBack] Other Comparison Operators).
The IEC suffixes contain one extra i to indicate binary and – next to the ISO notation that were already ISO defined – made it into the ISO 80000 standard since 2008. Here is a comparison list from [WayBack] Binary prefix – Wikipedia:
Prefixes for multiples of
bits (bit) or bytes (B) |
|
|
|
Most tools nowadays default to binary IEC suffixes for byte sizes, though disk manufacturers still use SI suffixes because, well then they appear bigger but aren’t. Just for comparison, look at the numbers from [WayBack] File size – Wikipedia and [WayBack] IEC and SI Size Notations – AN!Wiki where I got the test cases from:
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Posted in *nix, *nix-tools, bash, bash, Development, Power User, Scripting, Software Development | Leave a Comment »
The Wiert Corner - irregular stream of stuff 