Troubleshooting
5 pagesjournalctl: Filtering and Formatting systemd Logs
Logs disappeared. Server rebooted, and the familiar less /var/log/syslog returns nothing. On modern distros with systemd, logs are collected by journald and read with journalctl. Without knowing its filters, system debugging turns into guesswork. Why …
Logs disappeared. Server rebooted, and the familiar less /var/log/syslog returns nothing. On modern distros with systemd, logs are collected by journald and read with journalctl. Without knowing its filters, system debugging turns into guesswork. Why …
lsof: which processes listen on port and hold file
Service won’t start — port 8080 is already bound. You dig into who’s holding it, and discover the same process has your config file open while you’re trying to edit it. lsof answers both questions: which processes opened which files and sockets. …
Service won’t start — port 8080 is already bound. You dig into who’s holding it, and discover the same process has your config file open while you’re trying to edit it. lsof answers both questions: which processes opened which files and sockets. …
strace: System Call Tracing for Diagnosing Hangs and Leaks
When a service hangs, standard tools like top, htop, and ps show the state but not the cause. If a process is in state D (uninterruptible sleep), it’s waiting on a syscall. strace attaches to a live process and outputs every system call in real time. …
When a service hangs, standard tools like top, htop, and ps show the state but not the cause. If a process is in state D (uninterruptible sleep), it’s waiting on a syscall. strace attaches to a live process and outputs every system call in real time. …
ss: socket statistics instead of deprecated netstat
When netstat hangs on a server with tens of thousands of connections, it’s time to switch to ss. Part of the iproute2 package, ss queries the kernel directly via netlink instead of parsing /proc/net/*. The result is instant output with minimal …
When netstat hangs on a server with tens of thousands of connections, it’s time to switch to ss. Part of the iproute2 package, ss queries the kernel directly via netlink instead of parsing /proc/net/*. The result is instant output with minimal …
SSH Escape Sequences: Reviving a Frozen Terminal
SSH session froze, Ctrl+C does nothing, Ctrl+D spits out garbage — familiar situation. Before closing the terminal and losing the session, try built-in escape sequences. They operate at the SSH client level before data reaches the remote host. How to …
SSH session froze, Ctrl+C does nothing, Ctrl+D spits out garbage — familiar situation. Before closing the terminal and losing the session, try built-in escape sequences. They operate at the SSH client level before data reaches the remote host. How to …