[rbdr/txt] / learning.md

2024-01-29: You can't have CNAME and TXT records on the same subdomain!
2024-01-27: If you accidentally rewind a whole 35mm film, you can get it back by wetting the end of a new film and putting it inside the cartridge. It's a pain to do but it's better than losing a whole cartridge.
2024-01-24: When AppleTalk is enabled you can't use the printer port for a modem in a Macintosh SE/30. You need to disable it in Chooser first.
2024-01-23: AWS Glue has some very inefficient ways of composing queries, so it's sometimes easier to embed the query itself. In postgres it doesn't let you but you can add sources for each table and then run the query. This seems to work a lot faster.
2024-01-22: ssl_early_data on; can mess up your responses in safari if you set it in more than one place. What's worse, because of the caching it uses it can be annoying to revert.
2024-01-21: You can inject HTML and CSS to gitweb without modifying the default files by using $home_text and pointing it to a variable, and push @stylesheets.
2024-01-20: App groups can let you share application data, but they will create a new container, so unless you have a remote data source it will erase your data. It's better to start new mac or ios projects with a group
2024-01-19: You can rename the classes in xcdatamodel in order to avoid collisions, in case you named an entity something too generic.
2024-01-18: MacPPP with modem initialization options works much better than ZTerm + FreePPP, and allows 115200 baud. You just have to set the modem to initialize with AT, and then dial PPP.
2024-01-17: Mastodon will NOT auto-clean the media directory, which can quickly bubble in size, and you can't ask sidekiq to deal with this so you need to set a cron job. A systemd.timer can handle both cases.
2024-01-16: With dnsmasq + tailscale you can easily combine your home lab with a remote server and make management a lot easier without exposing some services to the web. A local dnsmasq running on raspberry pi can make sure all local services have a nice name, and then can point an internal url to the vps. In firewalld you need to block connections unless they come from your 100.0.0.0/8 block.
2024-01-16: You don't actually need the users in unix in some situations, you can use an arbitrary number of the id and if the other system expects it, then it will work. In fact, you can "sudo" into that if runas_allow_unknown_id (then run sudo -u \#9999 <your_command>)
2024-01-15: SELinux provides restrictions to files I wasn't aware of, and can prevent execution in some contexts. With eza you can view it with -Z.
2024-01-14: On linux you can see logical volumes inside a partition with lsblk, they're shown as lvm. If you resize a partition, you still need to resize the lvm (eg. with `lvresize -l +100%FREE` to take all remaining free space), AND the filesystem (eg. using resize2fs). This is important eg when installing an OS from an image as you might not be using your whole disk.
2024-01-14: On fedora rather than ufw or nftables, you use firewalld. You can create services (eg. gopher with port tcp 70 goes in /etc/firewalld/services/gopher.xml), attach them to zones with `firewall-cmd --zone=<YOURZONE> --add-service=gopher --permanent`
2024-01-14: User systemd files are expected in /etc/ and not /lib/
2024-01-14: You can use @ and %i in systemd to have multiple instances (eg myfile@.service, and then executable=blabla %i) where %i will be what comes after @. (So in myfile@howdy, %i will expand to howdy)
2024-01-13: PPP Connections stay alive in the old net router, so you don't need to run ATDTPPP again, but just the connection.
Commit	Line	Data
1122f78a RBR	1	2024-01-29: You can't have CNAME and TXT records on the same subdomain!
1122f78a RBR	2	2024-01-27: If you accidentally rewind a whole 35mm film, you can get it back by wetting the end of a new film and putting it inside the cartridge. It's a pain to do but it's better than losing a whole cartridge.
0e8741be	3	2024-01-24: When AppleTalk is enabled you can't use the printer port for a modem in a Macintosh SE/30. You need to disable it in Chooser first.
d4c5d4d7 RBR	4	2024-01-23: AWS Glue has some very inefficient ways of composing queries, so it's sometimes easier to embed the query itself. In postgres it doesn't let you but you can add sources for each table and then run the query. This seems to work a lot faster.
d4c5d4d7 RBR	5	2024-01-22: ssl_early_data on; can mess up your responses in safari if you set it in more than one place. What's worse, because of the caching it uses it can be annoying to revert.
8a96796c RBR	6	2024-01-21: You can inject HTML and CSS to gitweb without modifying the default files by using $home_text and pointing it to a variable, and push @stylesheets.
	7	2024-01-20: App groups can let you share application data, but they will create a new container, so unless you have a remote data source it will erase your data. It's better to start new mac or ios projects with a group
	8	2024-01-19: You can rename the classes in xcdatamodel in order to avoid collisions, in case you named an entity something too generic.
c57b0f38 RBR	9	2024-01-18: MacPPP with modem initialization options works much better than ZTerm + FreePPP, and allows 115200 baud. You just have to set the modem to initialize with AT, and then dial PPP.
c57b0f38 RBR	10	2024-01-17: Mastodon will NOT auto-clean the media directory, which can quickly bubble in size, and you can't ask sidekiq to deal with this so you need to set a cron job. A systemd.timer can handle both cases.
1260b987	11	2024-01-16: With dnsmasq + tailscale you can easily combine your home lab with a remote server and make management a lot easier without exposing some services to the web. A local dnsmasq running on raspberry pi can make sure all local services have a nice name, and then can point an internal url to the vps. In firewalld you need to block connections unless they come from your 100.0.0.0/8 block.
e1293d89	12	2024-01-16: You don't actually need the users in unix in some situations, you can use an arbitrary number of the id and if the other system expects it, then it will work. In fact, you can "sudo" into that if runas_allow_unknown_id (then run sudo -u \#9999 <your_command>)
2e8c5fee	13	2024-01-15: SELinux provides restrictions to files I wasn't aware of, and can prevent execution in some contexts. With eza you can view it with -Z.
cca2c219	14	2024-01-14: On linux you can see logical volumes inside a partition with lsblk, they're shown as lvm. If you resize a partition, you still need to resize the lvm (eg. with `lvresize -l +100%FREE` to take all remaining free space), AND the filesystem (eg. using resize2fs). This is important eg when installing an OS from an image as you might not be using your whole disk.
76ed347e	15	2024-01-14: On fedora rather than ufw or nftables, you use firewalld. You can create services (eg. gopher with port tcp 70 goes in /etc/firewalld/services/gopher.xml), attach them to zones with `firewall-cmd --zone=<YOURZONE> --add-service=gopher --permanent`
2e8c5fee RBR	16	2024-01-14: User systemd files are expected in /etc/ and not /lib/
	17	2024-01-14: You can use @ and %i in systemd to have multiple instances (eg myfile@.service, and then executable=blabla %i) where %i will be what comes after @. (So in myfile@howdy, %i will expand to howdy)
	18	2024-01-13: PPP Connections stay alive in the old net router, so you don't need to run ATDTPPP again, but just the connection.