Monthly Archives: October 2025

CLI

Increment modified date of files in a directory based on first file

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I had an issue in Immich where it was sorting pictures by their modified date. The modified dates are random, but the filenames are not. I wanted the album to sort by filename, and to do that I needed to get each filename to have a modified time in the same order. This was my solution (run within the directory in question) :

date=$(date -r $(ls | head -1) +%s); for file in *.jpg; do touch -m -d "@$date" $file; ((date+=1)); done

This bash one-liner does the following:

  • Sets a date variable by taking the modified date of the first file in the directory and converting it to epoch time
  • Goes through each JPG file in the directory and executes a touch command to set the date of that file to the date variable
  • Increments the date variable by 1 before processing the next file

The end result is now the order the files are in by modified date match their filename order.

CLI

Rename directory contents with prefix of directory

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Quick snippet to rename every file within a directory to have a prefix of the directory they reside in as part of the file name. If the directory name has a space in it, replace spaces with underscores for the file name. Run from within the directory in question.

base=$(basename "$PWD"| tr ' ' '_'); for file in *; do [ -f "$file" ] && mv "$file" "${base}_$file"; done

It does the following:

  • Gets the name of the current directory, replacing spaces with underscores, and saves into the variable base
  • Iterates through everything in the directory in a for loop
  • If the item is a regular file, execute the mv command to rename the file to include the contents of the base variable as a prefix
    • It uses BASH substitution to prepend the directory name to the new file name

This was helpful when dealing with a scanning project where many files had the same filename in different directories, which confused stacking images within Immich.

Networking

Wireguard client full tunnel no internet

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I tried to set up a wireguard full tunnel VPN on my Debian Bookworm server and ran into issues with internet connectivity. LAN / VPN connectivity was fine, just no internet.

My first realization was that when making changes to your config, be sure to wg-quick down & wg-quick up (if you’re using wg-quick.) Simply editing the files and reloading the service doesn’t pick up the changes.

I followed this guide to get it up, and it simply wasn’t working:

https://wiki.debian.org/WireGuard#Step_2_-Alternative_A-_Manual_Configuration

I did eventually realize I need to enable the following in /etc/sysctl.conf

net.ipv4.ip_forward = 1

Then reload settings with:

# sysctl -p

In the wireguard server config I added these iptables commands:
PostUp = iptables -A FORWARD -i %i -j ACCEPT; iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE
PostDown = iptables -D FORWARD -i %i -j ACCEPT; iptables -t nat -D POSTROUTING -o eth0 -j MASQUERADE

I discovered that allowed IPs on the server side are simply the IP address(es) of the wireguard clients, nothing more.

For full tunnel, set Client’s allowed IP to 0.0.0.0/0

I did all this and it still didn’t work. Then I stumbled upon https://www.ckn.io/blog/2017/11/14/wireguard-vpn-typical-setup

which mentioned to enable conntrack with iptables:

iptables -A INPUT -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT
iptables -A FORWARD -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT

When I enabled conntrack, internet connectivity worked. I decided to reboot without making the above iptables commands persistent. But it worked after reboot!

Lesson learned: try rebooting the host as a wireguard troubleshooting step, especially if all the configs look like they should be working but simply aren’t.

Here are my working configs:

Server:

[Interface]
Address = 10.10.1.1/24
SaveConfig = true
PostUp = iptables -A FORWARD -i %i -j ACCEPT; iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE
PostDown = iptables -D FORWARD -i %i -j ACCEPT; iptables -t nat -D POSTROUTING -o eth0 -j MASQUERADE
ListenPort = 51820
PrivateKey = <server_private_key>

[Peer]
PublicKey = <client_public_key>
AllowedIPs = 10.10.1.5/32

Client:

[Interface]
Address = 10.10.1.5/32
PrivateKey = <private key>
DNS = 10.10.1.1 10.10.1.2

[Peer]
PublicKey = <server public key>
Endpoint = mx.jeppson.org:54137
AllowedIPs = 0.0.0.0/0
PersistentKeepalive = 21