setup-zswap.fish

gistfile1.txt

#!/usr/bin/env fish
# =============================================================================
# setup-zswap.fish
# Disables zram and switches to zswap on CachyOS (Limine + LUKS btrfs)
# - Backs up files before changes
# - Verifies each step
# - Rolls back everything on failure
# =============================================================================

# ── Configuration ─────────────────────────────────────────────────────────────
set -g LUKS_DEVICE      /dev/mapper/sda1_crypt
set -g BTRFS_TMP_MOUNT  /mnt/btrfs-root-zswap-setup
set -g SWAP_MOUNT       /swap
set -g SWAP_SUBVOL      @swap
set -g SWAP_FILE        /swap/swapfile
set -g SWAP_SIZE        32g
set -g ZSWAP_COMPRESSOR zstd
set -g ZSWAP_MAX_POOL   30
set -g SWAPPINESS       10
set -g SYSCTL_CONF      /etc/sysctl.d/99-zswap-vm.conf
set -g LIMINE_CONF      /etc/default/limine
set -g MKINITCPIO_CONF  /etc/mkinitcpio.conf
set -g FSTAB            /etc/fstab
set -g UDEV_RULE        /etc/udev/rules.d/30-zram.rules
set -g BACKUP_SUFFIX    ".bak-zswap-"(date +%Y%m%d-%H%M%S)

# ── Rollback stack ────────────────────────────────────────────────────────────
set -g ROLLBACK_STACK

# ── Helpers ───────────────────────────────────────────────────────────────────
function info
    echo (set_color --bold cyan)"[INFO]"(set_color normal)"  $argv"
end

function ok
    echo (set_color --bold green)"[ OK ]"(set_color normal)"  $argv"
end

function warn
    echo (set_color --bold yellow)"[WARN]"(set_color normal)"  $argv"
end

function fail
    echo (set_color --bold red)"[FAIL]"(set_color normal)"  $argv" >&2
end

function die
    fail $argv
    rollback
    exit 1
end

function section
    echo ""
    echo (set_color --bold cyan)"════════════════════════════════════════"(set_color normal)
    echo (set_color --bold cyan)"  $argv"(set_color normal)
    echo (set_color --bold cyan)"════════════════════════════════════════"(set_color normal)
end

function section_red
    echo ""
    echo (set_color --bold red)"════════════════════════════════════════"(set_color normal)
    echo (set_color --bold red)"  $argv"(set_color normal)
    echo (set_color --bold red)"════════════════════════════════════════"(set_color normal)
end

function section_green
    echo ""
    echo (set_color --bold green)"════════════════════════════════════════"(set_color normal)
    echo (set_color --bold green)"  $argv"(set_color normal)
    echo (set_color --bold green)"════════════════════════════════════════"(set_color normal)
end

# Push a rollback action onto the stack.
# Usage: push_rollback "description" "cmd1" ["cmd2" ...]
function push_rollback
    set -l entry (string join "|" $argv)
    set -g ROLLBACK_STACK $ROLLBACK_STACK $entry
end

# Execute all rollback actions in reverse order.
function rollback
    section_red "ROLLING BACK ALL CHANGES"

    if test (count $ROLLBACK_STACK) -eq 0
        warn "Nothing to roll back."
        return
    end

    # Reverse the stack
    set -l reversed
    for entry in $ROLLBACK_STACK
        set reversed $entry $reversed
    end

    for entry in $reversed
        set -l parts (string split "|" $entry)
        set -l description $parts[1]
        info "Undoing: $description"
        for i in (seq 2 (count $parts))
            set -l cmd $parts[$i]
            eval $cmd
            if test $status -ne 0
                warn "Rollback command failed (continuing): $cmd"
            end
        end
    end

    echo ""
    ok "Rollback complete. System should be in its original state."
end

# Backup a file and register its restoration in the rollback stack.
function backup_file
    set -l file $argv[1]
    if test -f $file
        set -l backup $file$BACKUP_SUFFIX
        cp $file $backup
        or die "Failed to back up $file"
        ok "Backed up $file → $backup"
        push_rollback "Restore $file" "cp '$backup' '$file'" "rm -f '$backup'"
    else
        warn "$file does not exist yet — no backup needed."
    end
end

# ── Preflight checks ──────────────────────────────────────────────────────────
function preflight
    info "Running preflight checks..."

    if test (id -u) -ne 0
        die "This script must be run as root (use: sudo fish setup-zswap.fish)"
    end

    if not test -b $LUKS_DEVICE
        die "LUKS device $LUKS_DEVICE not found. Is sda1_crypt unlocked?"
    end

    for cmd in btrfs swapon swapoff mount umount mkinitcpio limine-mkinitcpio udevadm sysctl findmnt
        if not command -q $cmd
            die "Required command not found: $cmd"
        end
    end

    if findmnt --source $LUKS_DEVICE --target / -n &>/dev/null
        ok "LUKS device is the root filesystem — good."
    else
        warn "LUKS device is not mounted at /. Proceeding anyway."
    end

    ok "Preflight checks passed."
end

# ── Step 1: Create @swap btrfs subvolume ─────────────────────────────────────
function step_create_subvolume
    info "Step 1: Creating @swap btrfs subvolume on $LUKS_DEVICE..."

    if test -d $BTRFS_TMP_MOUNT
        die "$BTRFS_TMP_MOUNT already exists. Please remove it first."
    end

    mkdir -p $BTRFS_TMP_MOUNT
    or die "Failed to create temp mount point $BTRFS_TMP_MOUNT"

    mount -o subvolid=5 $LUKS_DEVICE $BTRFS_TMP_MOUNT
    or die "Failed to mount btrfs root of $LUKS_DEVICE at $BTRFS_TMP_MOUNT"

    if btrfs subvolume show $BTRFS_TMP_MOUNT/$SWAP_SUBVOL &>/dev/null
        warn "@swap subvolume already exists — skipping creation."
        umount $BTRFS_TMP_MOUNT
        rmdir $BTRFS_TMP_MOUNT
    else
        btrfs subvolume create $BTRFS_TMP_MOUNT/$SWAP_SUBVOL
        or begin
            umount $BTRFS_TMP_MOUNT
            rmdir $BTRFS_TMP_MOUNT
            die "Failed to create @swap subvolume"
        end

        if not btrfs subvolume show $BTRFS_TMP_MOUNT/$SWAP_SUBVOL &>/dev/null
            umount $BTRFS_TMP_MOUNT
            rmdir $BTRFS_TMP_MOUNT
            die "Verification failed: @swap subvolume not found after creation."
        end

        umount $BTRFS_TMP_MOUNT
        or die "Failed to unmount temp btrfs mount after subvolume creation"
        rmdir $BTRFS_TMP_MOUNT

        # Only register rollback if WE created it
        push_rollback "Delete @swap subvolume" \
            "mkdir -p '$BTRFS_TMP_MOUNT'" \
            "mount -o subvolid=5 '$LUKS_DEVICE' '$BTRFS_TMP_MOUNT'" \
            "btrfs subvolume delete '$BTRFS_TMP_MOUNT/$SWAP_SUBVOL'" \
            "umount '$BTRFS_TMP_MOUNT'" \
            "rmdir '$BTRFS_TMP_MOUNT'"
    end

    ok "Step 1: @swap subvolume ready."
end

# ── Step 2: Mount @swap subvolume at /swap ────────────────────────────────────
function step_mount_swap_subvolume
    info "Step 2: Mounting @swap subvolume at $SWAP_MOUNT..."

    if test -d $SWAP_MOUNT
        die "$SWAP_MOUNT already exists. Please remove it first."
    end

    mkdir -p $SWAP_MOUNT
    or die "Failed to create $SWAP_MOUNT"
    push_rollback "Remove $SWAP_MOUNT mountpoint" "rmdir '$SWAP_MOUNT' 2>/dev/null; true"

    mount -o subvol=$SWAP_SUBVOL,noatime,nodatacow $LUKS_DEVICE $SWAP_MOUNT
    or die "Failed to mount @swap subvolume at $SWAP_MOUNT"
    push_rollback "Unmount $SWAP_MOUNT" "umount '$SWAP_MOUNT' 2>/dev/null; true"

    if not findmnt --target $SWAP_MOUNT -n &>/dev/null
        die "Verification failed: $SWAP_MOUNT is not mounted."
    end
    ok "Step 2: @swap subvolume mounted at $SWAP_MOUNT and verified."
end

# ── Step 3: Create and activate swapfile ─────────────────────────────────────
function step_create_swapfile
    info "Step 3: Creating swapfile ($SWAP_SIZE) at $SWAP_FILE..."

    if test -f $SWAP_FILE
        warn "$SWAP_FILE already exists — skipping creation."
    else
        btrfs filesystem mkswapfile --size $SWAP_SIZE --uuid clear $SWAP_FILE
        or die "Failed to create swapfile at $SWAP_FILE"

        if not test -f $SWAP_FILE
            die "Verification failed: $SWAP_FILE not found after creation."
        end
        set -l actual_size (stat -c %s $SWAP_FILE)
        if test $actual_size -le 0
            die "Verification failed: $SWAP_FILE has zero size."
        end
        ok "Swapfile created ($actual_size bytes)."

        # Only register file removal rollback if WE created it
        push_rollback "Remove swapfile" "swapoff '$SWAP_FILE' 2>/dev/null; true" "rm -f '$SWAP_FILE'"
    end

    # Activate only if not already active
    if swapon --show | grep -q $SWAP_FILE
        warn "$SWAP_FILE already active as swap — skipping swapon."
    else
        swapon $SWAP_FILE
        or die "Failed to activate swapfile with swapon"
        push_rollback "Deactivate swapfile" "swapoff '$SWAP_FILE' 2>/dev/null; true"

        if not swapon --show | grep -q $SWAP_FILE
            die "Verification failed: $SWAP_FILE not showing in swapon --show"
        end
    end

    ok "Step 3: Swapfile ready and active."
end


# ── Step 4: Update /etc/fstab ─────────────────────────────────────────────────
function step_update_fstab
    info "Step 4: Updating $FSTAB..."

    backup_file $FSTAB

    if grep -q "$SWAP_SUBVOL" $FSTAB
        die "fstab already contains a @swap entry. Aborting."
    end

    echo "" >> $FSTAB
    echo "# @swap subvolume (zswap backing store — added by setup-zswap.fish)" >> $FSTAB
    echo "$LUKS_DEVICE  $SWAP_MOUNT  btrfs  subvol=$SWAP_SUBVOL,noatime,nodatacow  0 0" >> $FSTAB
    echo "" >> $FSTAB
    echo "# Swapfile" >> $FSTAB
    echo "$SWAP_FILE  none  swap  defaults  0 0" >> $FSTAB
    or die "Failed to write fstab entries"

    if not grep -q "$SWAP_SUBVOL" $FSTAB
        die "Verification failed: @swap entry not found in $FSTAB after writing."
    end
    if not grep -q "$SWAP_FILE" $FSTAB
        die "Verification failed: swapfile entry not found in $FSTAB after writing."
    end

    ok "Step 4: $FSTAB updated and verified."
end

# ── Step 5: Add zstd to mkinitcpio MODULES ────────────────────────────────────
function step_update_mkinitcpio
    info "Step 5: Adding zstd to MODULES in $MKINITCPIO_CONF..."

    backup_file $MKINITCPIO_CONF

    if grep -qP 'MODULES=\(.*\bzstd\b.*\)' $MKINITCPIO_CONF
        ok "zstd already present in MODULES — skipping modification."
        return
    end

    sed -i 's/^MODULES=(\(.*\))/MODULES=(\1 zstd)/' $MKINITCPIO_CONF
    sed -i 's/MODULES=(  */MODULES=(/' $MKINITCPIO_CONF
    or die "Failed to update MODULES in $MKINITCPIO_CONF"

    if not grep -qP 'MODULES=\(.*\bzstd\b.*\)' $MKINITCPIO_CONF
        die "Verification failed: zstd not found in MODULES after editing $MKINITCPIO_CONF"
    end
    ok "Step 5: $MKINITCPIO_CONF updated and verified."
end

# ── Step 6: Create udev rule override ────────────────────────────────────────
function step_create_udev_rule
    info "Step 6: Creating empty udev override at $UDEV_RULE..."

    set -l udev_existed false
    if test -f $UDEV_RULE
        warn "$UDEV_RULE already exists — backing it up."
        backup_file $UDEV_RULE
        set udev_existed true
    end

    touch $UDEV_RULE
    or die "Failed to create $UDEV_RULE"

    if not $udev_existed
        push_rollback "Remove udev override" "rm -f '$UDEV_RULE'"
    end

    if not test -f $UDEV_RULE
        die "Verification failed: $UDEV_RULE not found after creation."
    end

    udevadm control --reload-rules
    or warn "udevadm reload failed — rules will apply on next boot."

    ok "Step 6: Udev rule created and verified."
end

# ── Step 7: Update /etc/default/limine ───────────────────────────────────────
function step_update_limine
    info "Step 7: Updating $LIMINE_CONF with zswap kernel parameters..."

    set -l new_params "systemd.zram=0 zswap.enabled=1 zswap.shrinker_enabled=1 zswap.compressor=$ZSWAP_COMPRESSOR zswap.max_pool_percent=$ZSWAP_MAX_POOL"

    backup_file $LIMINE_CONF

    if not test -f $LIMINE_CONF
        echo "# Created by setup-zswap.fish" > $LIMINE_CONF
        echo "KERNEL_CMDLINE[default]+=\"$new_params\"" >> $LIMINE_CONF
        push_rollback "Remove created limine config" "rm -f '$LIMINE_CONF'"
    else
        if grep -q "zswap.enabled" $LIMINE_CONF
            die "$LIMINE_CONF already contains zswap parameters. Aborting to avoid duplication."
        end

        # Detect which operator is used on the default cmdline ("+=" or "=")
        if grep -qP 'KERNEL_CMDLINE\[default\]\+=' $LIMINE_CONF
            # Append-style: KERNEL_CMDLINE[default]+="... existing ..."
            # Strategy: add a new += line directly after the existing one
            sed -i '/KERNEL_CMDLINE\[default\]+=/a KERNEL_CMDLINE[default]+="'"$new_params"'"' $LIMINE_CONF
            or die "Failed to insert new KERNEL_CMDLINE[default]+= line in $LIMINE_CONF"
        else if grep -qP 'KERNEL_CMDLINE\[default\]=' $LIMINE_CONF
            # Plain assignment: append inside the existing quotes
            sed -i "s|KERNEL_CMDLINE\[default\]=\"\(.*\)\"|KERNEL_CMDLINE[default]=\"\1 $new_params\"|" $LIMINE_CONF
            or die "Failed to update KERNEL_CMDLINE[default]= in $LIMINE_CONF"
        else
            # No default entry at all — add a new += line at the end
            echo "" >> $LIMINE_CONF
            echo "KERNEL_CMDLINE[default]+=\"$new_params\"" >> $LIMINE_CONF
            or die "Failed to append KERNEL_CMDLINE[default] to $LIMINE_CONF"
        end
    end

    # Verify all params are present
    for param in systemd.zram=0 zswap.enabled=1 zswap.compressor=$ZSWAP_COMPRESSOR
        if not grep -q $param $LIMINE_CONF
            die "Verification failed: '$param' not found in $LIMINE_CONF after editing."
        end
    end
    ok "Step 7: $LIMINE_CONF updated and verified."
end

# ── Step 8: Configure swappiness ─────────────────────────────────────────────
function step_set_swappiness
    info "Step 8: Configuring vm.swappiness=$SWAPPINESS..."

    set -l old_swappiness (sysctl -n vm.swappiness 2>/dev/null)
    if test -z "$old_swappiness"
        set old_swappiness 60
    end
    info "Current vm.swappiness: $old_swappiness → will be set to $SWAPPINESS"

    sysctl -w vm.swappiness=$SWAPPINESS
    or die "Failed to set vm.swappiness=$SWAPPINESS via sysctl"
    push_rollback "Restore vm.swappiness to $old_swappiness" \
        "sysctl -w vm.swappiness=$old_swappiness 2>/dev/null; true"

    set -l current (sysctl -n vm.swappiness)
    if test "$current" != "$SWAPPINESS"
        die "Verification failed: vm.swappiness is '$current', expected '$SWAPPINESS'"
    end
    ok "Runtime vm.swappiness set to $current."

    backup_file $SYSCTL_CONF

    if test -f $SYSCTL_CONF
        if grep -q "vm.swappiness" $SYSCTL_CONF
            die "$SYSCTL_CONF already contains vm.swappiness. Aborting to avoid duplication."
        end
        echo "" >> $SYSCTL_CONF
        echo "vm.swappiness = $SWAPPINESS" >> $SYSCTL_CONF
        or die "Failed to append vm.swappiness to $SYSCTL_CONF"
    else
        echo "# zswap tuning — written by setup-zswap.fish" > $SYSCTL_CONF
        echo "# Lower swappiness is appropriate for zswap (vs 150 used by zram)" >> $SYSCTL_CONF
        echo "vm.swappiness = $SWAPPINESS" >> $SYSCTL_CONF
        or die "Failed to create $SYSCTL_CONF"
        push_rollback "Remove sysctl config" "rm -f '$SYSCTL_CONF'"
    end

    if not grep -q "vm.swappiness = $SWAPPINESS" $SYSCTL_CONF
        die "Verification failed: vm.swappiness not found in $SYSCTL_CONF after writing."
    end

    sysctl --system &>/dev/null
    or warn "sysctl --system reload had warnings — check $SYSCTL_CONF manually."

    ok "Step 8: vm.swappiness=$SWAPPINESS applied (runtime + persistent via $SYSCTL_CONF)."
end

# ── Step 9: Rebuild initramfs ─────────────────────────────────────────────────
function step_rebuild_initramfs
    info "Step 9: Rebuilding initramfs with limine-mkinitcpio..."
    info "(This may take a minute...)"

    push_rollback "Note: initramfs rebuilt — re-run 'limine-mkinitcpio' manually if rollback caused issues"

    limine-mkinitcpio
    or die "limine-mkinitcpio failed. Check output above for errors."

    # CachyOS/Limine stores initramfs under /boot/<machine-id>/<kernel>/
    # e.g. /boot/4bc226dd53f7440e8a8aa50d32838302/linux-cachyos/initramfs-linux-cachyos
    set -l found (find /boot -name 'initramfs-*.img' -o -name 'initramfs-linux-*' 2>/dev/null | grep -v '\.bak' | head -1)
    if test -z "$found"
        die "Verification failed: No initramfs images found anywhere under /boot after rebuild."
    end

    ok "Initramfs verified: $found"
    ok "Step 9: Initramfs rebuilt and verified."
end


# ── Step 10: Runtime zswap activation (no reboot) ────────────────────────────
function step_activate_zswap_now
    info "Step 10: Activating zswap in the running kernel (no reboot)..."

    echo 1 > /sys/module/zswap/parameters/enabled
    or die "Failed to enable zswap via sysfs"

    echo $ZSWAP_COMPRESSOR > /sys/module/zswap/parameters/compressor
    or warn "Could not set zswap compressor via sysfs (may need reboot to take effect)"

    echo $ZSWAP_MAX_POOL > /sys/module/zswap/parameters/max_pool_percent
    or warn "Could not set zswap max_pool_percent via sysfs"

    set -l zswap_enabled (cat /sys/module/zswap/parameters/enabled 2>/dev/null)
    if test "$zswap_enabled" != "Y"
        warn "zswap enabled sysfs shows '$zswap_enabled' — may require reboot to fully activate."
    else
        ok "zswap is active in the running kernel."
    end

    if swapon --show | grep -q zram
        warn "zram swap is still active in this session. Disabling it now..."
        for zram_dev in (swapon --show --noheadings | awk '{print $1}' | grep zram)
            swapoff $zram_dev
            and ok "Disabled zram swap: $zram_dev"
            or warn "Could not swapoff $zram_dev — may need reboot"
        end
    end

    ok "Step 10: Runtime zswap activation complete."
end

# ── Final verification ────────────────────────────────────────────────────────
function final_verify
    section_green "FINAL VERIFICATION"

    set -l all_ok true

    set -l zswap_en (cat /sys/module/zswap/parameters/enabled 2>/dev/null)
    if test "$zswap_en" = "Y"
        ok "zswap enabled:           Y ✓"
    else
        warn "zswap enabled:           $zswap_en (will be Y after reboot)"
    end

    set -l zswap_comp (cat /sys/module/zswap/parameters/compressor 2>/dev/null)
    ok "zswap compressor:        $zswap_comp"

    set -l zswap_pool (cat /sys/module/zswap/parameters/max_pool_percent 2>/dev/null)
    ok "zswap max_pool_percent:  $zswap_pool%"

    if swapon --show | grep -q $SWAP_FILE
        ok "Swapfile active:         $SWAP_FILE ✓"
    else
        fail "Swapfile NOT active:     $SWAP_FILE"
        set all_ok false
    end

    if swapon --show | grep -q zram
        warn "zram still active in this session (will be gone after reboot)"
    else
        ok "zram swap:               not active ✓"
    end

    if grep -q $SWAP_SUBVOL $FSTAB; and grep -q $SWAP_FILE $FSTAB
        ok "fstab entries:           present ✓"
    else
        fail "fstab entries:           MISSING"
        set all_ok false
    end

    if grep -q "zswap.enabled=1" $LIMINE_CONF
        ok "Limine config:           zswap params present ✓"
    else
        fail "Limine config:           zswap params MISSING"
        set all_ok false
    end

    if grep -qP 'MODULES=\(.*\bzstd\b.*\)' $MKINITCPIO_CONF
        ok "mkinitcpio MODULES:      zstd present ✓"
    else
        fail "mkinitcpio MODULES:      zstd MISSING"
        set all_ok false
    end

    if test -f $UDEV_RULE
        ok "udev override:           $UDEV_RULE present ✓"
    else
        fail "udev override:           $UDEV_RULE MISSING"
        set all_ok false
    end

    set -l current_swappiness (sysctl -n vm.swappiness 2>/dev/null)
    if test "$current_swappiness" = "$SWAPPINESS"
        ok "vm.swappiness (runtime): $current_swappiness ✓"
    else
        fail "vm.swappiness (runtime): $current_swappiness (expected $SWAPPINESS)"
        set all_ok false
    end

    if grep -q "vm.swappiness = $SWAPPINESS" $SYSCTL_CONF
        ok "vm.swappiness (persist): $SYSCTL_CONF ✓"
    else
        fail "vm.swappiness (persist): not found in $SYSCTL_CONF"
        set all_ok false
    end

    echo ""
    if $all_ok
        echo (set_color --bold green)"✔ All checks passed! Reboot to fully apply kernel parameters."(set_color normal)
        echo ""
        echo "  Post-reboot, confirm with:"
        echo "    cat /sys/module/zswap/parameters/enabled      # → Y"
        echo "    cat /sys/module/zswap/parameters/compressor   # → zstd"
        echo "    swapon --show                                  # → $SWAP_FILE only"
        echo "    sysctl vm.swappiness                           # → $SWAPPINESS"
    else
        echo (set_color --bold red)"✘ Some checks failed. Review output above."(set_color normal)
        rollback
        exit 1
    end
end

# ── Main ──────────────────────────────────────────────────────────────────────
function main
    section "CachyOS: zram → zswap Setup Script"
    echo ""
    echo "  LUKS device:   $LUKS_DEVICE"
    echo "  Swap mount:    $SWAP_MOUNT"
    echo "  Swap size:     $SWAP_SIZE"
    echo "  Compressor:    $ZSWAP_COMPRESSOR"
    echo "  Pool max:      $ZSWAP_MAX_POOL%"
    echo "  Swappiness:    $SWAPPINESS"
    echo "  Sysctl conf:   $SYSCTL_CONF"
    echo "  Backup suffix: $BACKUP_SUFFIX"
    echo ""

    preflight

    step_create_subvolume
    step_mount_swap_subvolume
    step_create_swapfile
    step_update_fstab
    step_update_mkinitcpio
    step_create_udev_rule
    step_update_limine
    step_set_swappiness
    step_rebuild_initramfs
    step_activate_zswap_now

    final_verify
end

main